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Asimov Great ideas of sc;ience
PUBLIC LIBRARY FORT WAYNE AND ALLEN COUNTY,
IND.
Great Ideas of Science
ISAAC ASIMOV Illustrated hy Lee
Ames
1969
HOUGHTON
MIFFLIN
COMPANY BOSTON
To
Eric Berger
who
has always been cooperative
FIRST PRINTING
COPYRIGHT
©
R
1969 BY ISAAC ASIMOV
ALL RIGHTS RESERVED.
NO PART OF
WORK MAY ANY FORM BY ANY
THIS
BE REPRODUCED OR TRANSMITTED IN
MEANS, ELECTRONIC OR MECHANICAL, INCLUDING PHOTOCOPYING
AND RECORDING, OR BY ANY INFORMATION STORAGE OR RETRIEVAL SYSTEM, WITHOUT PERMISSION IN WRITING FROM THE PUBLISHER. LIBRARY OF CONGRESS CATALOG CARD
PRINTED IN THE
U.S.A.
NUMBER
70-82476
^
CONTENTS
1588855
1
Thales and Science
2
Pythagoras and
3
Archimedes and Applied
Itself
Number
1
10
20
Mathematics
4
Galileo and Experimentation
29
5
Democritus and Atoms
36
6
Lavoisier
7
Newton and
8
Faraday and Fields
63
9
Rumford and Heat
71
10
Joule and Energy
80
11
Planck and Quanta
89
12
Hippocrates and Medicine
98
13
Wohler and Organic Chemistry
106
14
Linnaeus and Classification
114
15
Darwin and Evolution
122
16
Russell and Stellar Evolution
129
Index
and Gases Inertia
45 55
13 8
1 Thales and Science
VA^HAT
IS
the universe
About 600 B.C.
composed
the
Itself
of?
Greek thinker Thales
leez) asked himself that important question
with the ivrong answer:
''All things are
Yet
it is
and came up
water."
This statement was not only incorrect, quite original.
(THAY-
it
was not even
one of the most important
state-
Great Ideas of Science
2
ments in the history of science. Without thing Hke
it
— there would be no
The importance
we
it
— or some-
science.
of Thales' answer will
become
clear
how he happened to hit upon it. Not surprisingly, this man who said that all things were water lived in a seaport. The city, Miletus (migh-LEE-tus) lay on the eastern coast of the Aegean Sea, in what is now if
first
examine
,
part of Turkey. Miletus it
no longer
was the most prosperous
exists,
but in 600 B.C.
city in the Greek-speaking
world.
On
Ancient Shores
Perhaps Thales pondered the nature of the universe the seashore, as he gazed at the Aegean.
the
Aegean opened southward
called the Mediterranean,
miles westward.
narrow
strait
into a
still
Strait
rocky prominences the
He knew
that
larger sea,
now
which stretched hundreds of
The Mediterranean
(the
at
of
passed through a
Gibraltar)
Greeks
called
between two the
Pillars
of
Hercules.
Beyond tic),
the Pillars of Hercules lay an ocean (the Atlan-
and the Greeks thought
land on
all sides.
like a disk a
it
surrounded the world's
Thales thought that the land was shaped
few thousand miles
across and that
it
floated
in an endless ocean.
I
Thales and Science
Itself
3
But he knew even the land Rivers crossed
lakes dotted
it,
Water
beneath.
itself
dried
was riddled with water. springs welled
it,
up and disappeared
up from
into the
air,
occasionally turning back into water and falling as rain.
There was water above, water below, water on
Land Made The very
of
Water?
solids of the land, so it
seemed to Thales, were
formed from water. Thales thought he had seen pen with
own
his
Egypt he had seen
eyes in his youth.
was
left
When
sea,
there
Egypt where the Nile River
was an area of deep,
soft soil that
(It
shape, like the letter "delta" of the
Greek
him
Of
was
had
triangular in
alphabet.
For
reason the region was called the Nile Delta.)
Having thought of to
traveling in
behind.
been formed by the flood waters.
this
hap-
the waters receded, fresh fertile
Indeed, in the north of
met the
While
this
the Nile River rise in a flood that spread
out over the land. soil
all sides.
all this,
Thales came to what seemed
to be a logical conclusion: "All things are water."
course, he
was wrong, for not
all
is
not water, and while water vapor
it
does not become
of earth
may
air.
Solid earth
things are water. Air
may
is
mingle with
air,
not water. Particles
be carried by rivers from the mountains to
the plains, but those particles are not
made
of water.
Great Ideas of Science
Thales
vs,
Babylon
Thales' idea was not quite his own.
It
originated in
Babylonia, another country he had visited as a
The
young man.
ancient civiUzation of Babylonia had reached certain
important conclusions about astronomy and mathematics that
must have fascinated
The
Babylonians considered the solid land to be a disk
the land was
But
salt
isn't this
Wasn't Thales
Not
quite!
set
This water rose to the surface here
in a pit of fresh water.
and there to form
a serious thinker such as Thales.
and
springs.
All around
the same picture presented
by Thales?
rivers, lakes,
water.
just repeating
Babylonian theories?
Unlike Thales the Babylonians did not think
of water as water, but as a collection of supernatural beings.
The
fresh water
was the god Apsu, while the
salt
water was the goddess Tiamat. Together they gave birth to a large
Greeks had
number
a similar notion:
ocean, Okeanos,
(The
of other gods and goddesses.
they thought the god of the
was the father of the gods.)
Eventually, according to Babylonian mythology, there
was war between Tiamat and her descendants. After gigantic battle one of the
and
split
her in two.
new gods, Marduk,
With one
half of
killed
a
Tiamat
Tiamat he made
the sky and with the other half, the solid earth.
That was the Babylonian answer
to the question,
"Of
Thales and Science
what
is
Itself
5
the universe composed?"
same answer from
Thales approached the
a different angle.
universe was different because
it
His picture of the
did without gods and
goddesses and without great battles between supernatural beings.
He
simply
said,
Thales had pupils in
"All things are water."
his
own city of Miletus and in neigh-
boring communities on the Aegean shore. Twelve
on
made
this shore
and
his pupils are
The
a region called Ionia.
known
as the
cities
Thus, Thales
"Ionian school."
lonians continued to try to explain the universe
without resorting to gods and goddesses. In established a tradition that has lasted
down
this
way
they
to the present
day.
Importance of the Ionian Tradition
Why was
it
so important to interpret the universe with-
out falling back on
without such
Suppose
a tradition?
a universe
is
made by gods and
them. Then, they can do If is
Could science have developed
deities?
some goddess
is
as
is
in a
angry because the temple
built to her If
some war-
bad spot and prays to
a god, promising to sacri-
may
send a cloud to hide him
fice cattle to
from
by
they wish with the universe.
not large enough, she might send a plague.
rior
controlled
him, that god
his enemies.
One cannot count on
the universe's
Great Ideas of Science
6
behaving in any certain way: Everything depends on the
whim
of some deity.
In the view of Thales and his pupils, however, no deities interfered with the workings of the universe.
verse behaved only in accordance with
The
own
its
uni-
nature.
Plagues arose and clouds appeared only out of certain natural causes.
plague
Only
arise
if
those natural causes existed,
would
a
or a cloud appear. Thus, Thales and his fol-
lowers had arrived at a basic assumption:
The
haves in accordance with certain "laws of
miiverse benature'''
that
cannot be altered or changed. Is
such a universe better than one that behaves according
to the
who
whims
of the gods?
If the deities
do
as
they please,
can foretell what might happen tomorrow? Even the
sun might not something.
rise if
Men who
natural could see
the ^'sun god" were annoyed about
had
no point
ings of the universe.
their
minds fixed on the super-
in trying to figure out the
Instead, they
would
work-
rather devise
methods for pleasing the gods or for soothing them when they grew angry. temples and
altars, to
special prayers, to
Nor
would be more important
work out methods
mold
idols
a
to build
of sacrifice and
and make magic.
could anything prove
Suppose there was ritual.
It
this
system to be wrong.
drought or a plague despite
left
the
men had something out. They
This would mean only that the medicine
done something improper or
all
Thales and Science
Itself
would simply have
7
to try again, sacrifice
more
and
cattle,
pray more carefully.
But right
the basic assumption of Thales and his pupils was
if
—
if
the universe did
nature that did not change
One
study the universe.
moved, the clouds
One
work according
— then
it
to laws of
was worthwhile
could observe
how
to
the stars
drifted, the rains fell, the plants
grew.
could be certain that those observations would hold
good always and would never change suddenly because
One
of some god.
could then
work out
a set of simple
laws describing the general nature of the observations.
Thus, the
first
assumption of Thales and
led to a second: It
is
possible for
human
his followers
reason to njoork
out the nature of the laws gover?iing the universe.
Idea of Science
These two assumptions, that there and that
man
can work them out by reason, make up the
"idea of science."
Mind you,
these assumptions are just
assumptions; they cannot be proved.
Thales there have always been belief in
The the
fall
are laws of nature
Nevertheless, since
men who
clung firmly to
them.
idea of science nearly faded out in
of the
Roman Empire
— but not
Europe
quite.
after
In the
six-
Great Ideas of Science
8
grow
teenth century the idea suddenly began to
Now,
in the last half of the twentieth century,
strong.
it is
at a
peak of power.
To be sure, the universe is far more complex than Thales could possibly have imagined.
some laws of nature
Still,
can be expressed very simply and
are, as far as
we now
know, unshakable. Perhaps the most important of
these
is
the "law of conservation of energy," which, stated simply,
''The total energy of the universe
is:
is
constant."
The Certain Uncertain Science has learned there are limits to knowledge, too. In the 1920's a
worked out that
German
Werner Heisenberg,
the ''principle of uncertainty."
was impossible
it
physicist,
He
stated
to determine precisely both the posi-
tion and velocity of an object at a particular instant of time.
We can determine one or the other as precisely as we
please,
but not both
at the
same time. Does
the second assumption of science
is
this
mean
that
wrong? That man can-
not gather knowledge with which to reason out the riddle of the universe?
No, not
at
a natural law.
we
all,
for the principle of uncertainty
There
is itself
are limits to the exactness with
which
can measure the universe, yes, but the extent of those
limits
can be worked out by reason.
Indeed, through
Thales and Science
9
Itself
proper understanding of uncertainty, learned about the universe that
much more
can be
would be puzzling without
that understanding. Thus, Thales' great ''idea of science"
holds as well
now
as
it
did
when he advanced
twenty-five hundred years ago.
it
some
ggS^^
'j
x - ".i3^'
•
Pythagoras and Not
long after
Number
the time that Thales was pondering the
mysteries of the universe, around twenty-five hundred years ago, another
Greek
Like Thales (see Chapter
THAG-oh-ras)
1 )
,
was playing with
strings.
the scholar Pythagoras (pih-
lived in a coastal city
ton, in southern Italy.
ordinary man.
scholar
— the
city of
Cro-
Like Thales, Pythagoras was no
Pythagoras and
And
Number
1
"playthings" were no ordinary strings, but
his
tough cords Uke those used in such musical instruments
as
Pythagoras had prepared cords of different
the lyre.
them
lengths, held
and plucked each one to produce
taut,
a musical note.
Musical Numbers Finally, he
found two cords that sounded notes
octave apart. That
is,
just
one sounded low do (pronounced
"doe"), the other high do.
What
was
low do was exactly twice
long
that the cord producing
of the
He
two cords was tried again
notes that
fascinated Pythagoras
The
one producing high do.
as the
sol.
2 to
as
ratio of lengths
1
and obtained two cords which sounded
made up
and the other
an
a "fifth."
That
is,
one note
w^as
do
This time the cord producing the lower
note was just one and a half times as long as the cord pro-
ducing the higher one. If
The
one cord was one and
a "fourth"
ratio of lengths
fa.
Here the
3
to
2.
a third times as long as another,
was produced. That
the other was
was
is,
one note was do and
ratio of lengths
was 4
to
3.
Certainly, musicians in Greece and in other lands also
knew how and
how
goras,
to
to prepare cords that
make them
however, was the
sounded certain notes
into musical instruments. first
man known
to
Pytha-
ponder not
2
Great Ideas of Science
1
over the music, but ove;: the ratio of lengths that produced the music.
Why 3
to
2,
should these ratios of small numbers
4
to
3
— produce
—
2
to
especially agreeable sounds?
1,
If
Pythagoras took two cords of more complicated ratios of length, say 23
to
the sound combination
13,
was un-
pleasant.
Perhaps
at this point
Pythagoras snapped his
Numbers were not merely
tools for counting
fingers.
and measur-
they controlled music and perhaps they controlled
ing;
all
the universe. If
numbers were
so important, then
to study
them for
to begin
by thinking
men
or
two
apples or
evenly divided by ber
3
own
their
of the
two
number
stars.
have in
Now
properties
common? What about
The number
2
could be
did all
2; it all
was an odd
even numbers
One
odd numbers?
with the fact that the sum of two even numbers
could
start
or of
two odd numbers
sum
not of two
2 itself,
was an even number. The num-
2; it
what
became important
For example, one had
could not be evenly divided by
number.
the
sake.
it
of an even
is
And
always an even number.
number and an odd number
is
always
an odd number.
Or drew
suppose one drew each number six dots; for 23,
as dots.
For
6,
twenty-three dots, and so on.
one If
one spaced the dots equally, he would find that some
Pythagoras and
numbers,
Number
known
form orderly
13
as triajigular
triangles.
numbers^ could be made to
Others,
known
as
square numbers^
could become neat squares.
Triangular
knew
Pythagoras
could be made to figure.
gular
The
fit
smallest
number
Numbers
that only certain into a triangle,
was one
numbers of dots
which
is
a three-sided
dot, representing the trian-
1.
Larger triangles could be made by placing additional lines of dots parallel to a side of a smaller triangle.
For
example, a three-dot triangle, representing the number
3,
could be made by placing two dots next to a side of the
one-dot triangle. Similarly, a six-dot triangle, representing the
number
6,
was formed by adding three dots
to the
three-dot triangle.
The
next triangles in the series were
made up
of ten dots
(the six-dot triangle plus jour dots), fifteen dots (ten dots
plus five), twenty-one dots (fifteen dots plus six), and so on. Thus, the series of triangular
numbers was
1, 3, 6,
10,
15,21,...
As Pythagoras dots,
built
up the
series of triangles
he became aware of an interesting
from smaller
to large triangles, the
fact.
number
by adding
As he moved of dots that
Great Ideas of Science
14
had to be added kept increasing by one. (You can verify
by looking
this
for the itahcized
words
in the previous
three paragraphs.)
In other words, he could build up the triangles, or angular numbers,
by
tri-
sums of consecutive num-
a series of
= 1; = + 2; 6=1 + 2 + 3; 10=1 + 2 + 3+4; 15 = 1+2 + 3+4+5; 21 = 1+2 + 3+4+5+6; and so on.
bers.
Thus,
1
3
1
Square Numbers Unlike the three-sided
triangle, the square
had four
sides
(and four right, or 90-degree, angles). Therefore, Pythagoras could expect the series of square numbers to turn
out to be quite different from the triangular ever,
one isolated dot would
into a triangle.
the
number
fit
series.
How-
into a square as easily as
Thus, the square
began with
series, too,
1.
Larger squares were built up by placing additional dots
around two adjacent
sides of
dots were spaced along
two
another square.
lines that
formed
The new
a right angle.
For example, three dots were added to the one-dot square to 4.
form
A
a four-dot square,
nine-dot square was
which represented the number
made
similarly,
by
placing five
dots around the four-dot square.
The
series
continued with squares of sixteen dots (the
Pythagoras and
Number
15
nine-dot square plus seven dots), twenty-five dots (sixteen (twenty-five dots plus
dots plus nine), thirty-six dots eleveii),
and so on. The outcome was the
numbers:
1,
4, 9, 16, 25, 36,
Since the triangles had
.
.
series of
square
.
grown
larger in a regular
way,
Pythagoras was not surprised to see the squares behaving similarly.
The number
of dots added to each
was always an odd number. greater than the
And
number added
it
new
square
was always two dots
to the previous square.
(See the italicized words in the previous paragraphs.)
by
In other words, square numbers could be built up series of
= 1; 25 = + + 5+7 +
sums of consecutive odd numbers. Thus,
4=1 + 3; 9=1 + 3 + 5; 16=1 + 3 + 5+7; 9;
1
1
3
and so on. Squares could also be
triangular numbers:
made by adding two consecutive
4=1 + 3; 9=3+6; 16=6+10;
10+15; ... Or by multiplying
1X1;4=2X2; 9=3X3;. The last method is a
.
the square of is
3.
say that the smaller
by
example, of 16.
itself 3 is
—
number by
is
5,
itself:
particularly important
9=3X3, we
In the same way, 16
the square of
plied
a
25 1
= =
.
forming square numbers. Since
25
a
and so on.
number
—
On
that
9,
say that 9
the other hand,
is,
the one
and 4
of is
the square of 4,
is
the square root of
the square root of
way
its is
we
we
multi-
product.
For
the square root
Great Ideas of Science
16
Right Triangles Pythagoras' interest in square numbers led him to consider right triangles
right angle. that
is, if
A
—
right angle has
one of the
sides
two perpendicular
which runs from one
the other.
This third
A
—
side of the right angle to
If
sides.
is
sides.
a right triangle at
measured the lengths of the
whole number of
a
right triangle adds a
always longer than either of the other
into a
sides
called the "hypotenuse,"
side,
Suppose Pythagoras drew
is
held perfectly horizontal, the
is
other will be perfectly vertical. third side
which one angle
triangles in
random and
he divided one side
units, the other
two
sides usually
did not consist of whole numbers of the same units.
There were triangle in
exceptions, though. Suppose he had a right
which one
side
was
the other just four units long.
just three units long,
and
turned out that the hy-
It
potenuse would then be exactly five units long.
Why triangle? 2,
should the numbers
The numbers
3,4, nor almost
3, 4,
and
5
make up
a right
1,2,3 did not, nor did the numbers
any other combination.
Suppose Pythagoras considered the squares of the numbers. Instead of 3, 4, 5,
he
now had
thing interesting showed up, for
9, 16, 25.
Now some-
9+16=25. The sum
the squares of the sides of this particular right triangle
equal to the square of the hypotenuse.
of
was
Number
Pythagoras and
1
Pythagoras went further.
He
noticed that the differ-
ence between successive square numbers was always an
odd number:
4-1 = 3; 9-4=5; 16-9=7; 25-16=9;
so on.
Every once
would
itself
same
as
in a while that
be a square,
9+16=25). When
instance, Pythagoras
cessive square
144=25.
It
this
— 16=9
difference
(which
is
the
happened, another right
up from whole numbers.
triangle could be built
For
as in 25
odd-number
and
might have subtracted the suc-
numbers 144 and 169
169—
as follows:
happens that the square roots of these num-
bers are 13, 12, and
5,
since
169=13X13, 144=12X12,
and 25=5X5. Therefore, he could form a right triangle with
sides equal to five
and twelve units and
hypotenuse
a
equal to thirteen units.
Pythagorean Theorem
Pythagoras that
now
had
a large
number
of right triangles
were made up of hypotenuses whose squares were
equal to the
sum
of the squares of the other
he soon proved that
this situation
two
sides.
was true for
all
And right
triangles.
Many
hundreds of years before Pythagoras' time the
Egyptians, the Babylonians, and the Chinese had that such a relationship applied to the fact, the
3, 4, 5
known
triangle.
In
Babylonians and others probably had been sure
8
Great Ideas of Science
1
that
the
it
applied to
first
He
we know
stated:
of the sides
is
known
he prove
of
who
proved
But Pythagoras was
it.
In any right triangle the
sum
of the squares
equal to the square of the hypotenuse. Be-
cause he was the it is
right triangles.
all
first
as the
to succeed in proving this statement,
"Pythagorean theorem." But
how
did
it?
Proof of Deduction
To
answer that question,
who was
thinker Thales,
we must go back
Greek
to the
discussed in Chapter
1.
Tradi-
tion holds that Pythagoras studied under Thales.
Thales had worked out an orderly system of proving the truth of mathematical statements, or theorems,
One began with
reasoning.
From
"axioms."
accepted statements called
these axioms, one could reach a certain
With
conclusion.
this
conclusion accepted, a second con-
clusion could be obtained, and so on.
Thales' system,
known
gorean theorem.
by
And
as
Pythagoras used
"deduction," to prove the Pytha-
deduction has been used ever
since.
Perhaps Thales did not actually invent the system of proof by deduction. Perhaps he learned lonians and the
But even duction,
if
it
name
it
from the Baby-
of the true inventor
is
unknown.
Thales was the inventor of mathematical de-
was Pythagoras who made
it
famous.
Pythagoras and
Number
19
Geometry
Birth of
The Greeks were goras, especially
by
inspired
by
the teachings of Pytha-
his great success in finding a
proof for the Pythagorean theorem.
As
deductive
a result they
went
even further. In the next three hundred years, they built a
complex structure of mathematical proofs that
marily with lines and shapes. This system
is
deal pri-
called
"geom-
etry" (see Chapter 3).
We
have gone far past the Greeks in the thousands of
we moderns have done in mathwe have penetrated its mysteries,
years since. Yet, whatever
ematics and however far all rests
on two foundations. There
is, first,
the study of
the properties of numbers and, second, the use of the
method of deduction. The
first
began with Pythagoras,
and the second was popularized by him. It
was not simply musical notes
plucked out of mathematics.
his cords,
that Pythagoras
had
but the whole vast world of
w
M^ [M
^
l^tfe
Ml m
3 Archimedes and Applied Mathematics You
MIGHT think
that an aristocrat in one of the greatest
and richest of the Greek ter to
do with
crowbars.
his
cities
would have something
time than to study the workings of
Apparently the
aristocrat
thought so too, for
he was embarrassed to have such a "low-bred"
The
aristocrat
bet-
interest.
was Archimedes (ahr-kih-MEE-deez)
of Syracuse, a city on the eastern shore of Sicily. Archi-
Archimedes and Applied Mathematics
medes was born about 287 B.C.
2
He
was the son of
a dis-
tinguished astronomer and was probably a relative of
Hiero
king of Syracuse.
II,
An
Inventor of Gadgets
In Archimedes' day
it
was
felt that
no gentleman should
involve himself with engineering devices.
were
fit
life
But Archimedes
only for slaves and laborers.
couldn't help
it.
Machinery
he worked out
many
Such matters
interested him,
and during
his
gadgets for use in both peace
and war.
He ever.
"low"
didn't give in entirely to these
For
up
instance, he didn't write
mechanical devices
— he was ashamed
tastes,
how-
descriptions of his to.
We
know
of
them only through the inaccurate and perhaps exaggerated tales
of other men.
The one
exception
is
Archimedes' de-
scription of a device that imitated the heavenly motions
of the sun, moon, and planets. But then, that was an in-
strument devoted to the science of astronmy and not to base mechanical labor.
Engineering
—
or
Math?
Machines were not Archimedes' only
youth he had gone to Alexandria,
in
interest.
In his
Egypt, the home of
Great Ideas of Science
22
the great sity
Museum. The Museum was
where
the learned Greeks
all
came
like a large univer-
and teach.
to study
There Archimedes had studied under Conon (KOH-non) of Samos, a great mathematician. Archimedes himself be-
came an even
greater mathematician; he invented a
form
of calculus two thousand years before modern mathematicians finally
worked out
all
the details.
Thus, Archimedes had an
However,
well as in engineering. fields
had
little
in his time the
as
two
common.
in
true that the
It is
mathematics
interest in
Greek and
earlier engineers,
such
as
the Babylonians and Egyptians, had to use mathematics to
achieve
what they
great pyramids
The
ancient Egyptians had built
which were already ancient
With only
time.
did.
The tures,
raise
them
Archimedes'
the most primitive tools the Egyptians
dragged immense blocks of granite aged to
in
many
then man-
miles,
to great heights.
people of Babylon also had built imposing struc-
and the Greeks themselves had done well.
engineer
A Greek
named Eupahnus (yoo-puh-LIGH-nus)
built a
tunnel on the island of Samos three centuries before Archi-
He
medes' time. sides of a hill,
directed
do
of diggers at opposite
and when they reached the
walls of the tunnel
To
two teams
all this,
met almost
^
how
center, the
exactly.
the engineers of Egypt, Babylonia, and
Greece must have used mathematics. understood
hill's
lines
were
They must
related to each other,
have
and
Archimedes and Applied Mathematics
how
23
the size of one part of a structure determined the
of another.
size
Yet Archimedes was not famihar with
this
mathematics,
but with an abstract kind the Greeks had begun to develop in Eupalinus' time.
Pythagoras had popularized the system of mathematical deduction (see Chapter 2). In a
few simple
this
system one began with
by
notions, readily accepted
men, and
all
reached complicated conclusions by proceeding one step time according to the principles of deduction.
at a
Beautiful
Theorem
Other Greek mathematicians followed Pythagoras and gradually built up a large and beautiful system of theorems
(mathematical statements) about angles, parallel angles, squares, circles,
how
to
show
angle size
out
how
two
that
— or
in
and other figures
figures.
were equal
both area and angle
lines, tri-
They
learned
in area or in
size.
They found
to determine ratios of numbers, size,
and
area.
Although the marvelous structure of Greek mathematics
went
civilizations,
triangles
beyond the mathematics system of
far it
was
entirely theoretical.
were imaginary ones
finitely thin
The
earlier
circles
built of lines that
were
and in-
and perfectly straight or that were curved
with perfect smoothness. to practical use.
The mathematics was
not put
Great Ideas of Science
24
Consider
about the Greek philosopher Plato
this story
(PLAY-toe).
He
founded
Athens
a school in
a
century
before Archimedes was born and taught mathematics at the school.
One day
during a mathematical demonstration
"But master, of what practical use
a student asked Plato, is
this?"
Plato was outraged.
He
the student a small coin so that he
had some use
after
ordered a slave to give
would
find his learning
and then expelled him from the
all,
school.
An
important figure in the development of the Greek
mathematics was the great mathematician EucUd
kHd)
.
One
of EucHd's pupils was
At
medes' teacher.
Conon
of Samos, Archi-
Alexandria, shortly before Archi-
medes' birth, Euclid brought together
made by
(YOO-
He
earUer thinkers.
order, demonstration
all
the deductions
organized them in beautiful
by demonstration. And he began
with a small handful of generally accepted statements, called "axioms."
Axioms were
so obvious, in the
view, that they required no proof. are "a straight
Hne
is
Examples of axioms
the shortest distance between
points" and "the whole
is
equal to the
All Theory,
No
since.
Still,
in
all its
sum
of
its
two
parts."
Practice
EucHd's book was so neatly done that
book ever
Greek
it
has been a text-
marvelous structure there
Archimedes and Applied Mathematics
was no hint
handy
that
any of the conclusions might come
work
in the ordinary
Greeks put
their
25
of mankind.
Indeed, the
mathematics most thoroughly to use in
working out the movements of the planets and theory of harmony. After fit
in
all,
in the
astronomy and music were
occupations for aristocrats.
So Archimedes excelled in two worlds
—
a practical
world of engineering without the clever mathematics of the Greeks and a world of to
no
His
practical use.
tunity to combine the
do
Greek mathematics
abilities
that
was put
provided a perfect oppor-
two worlds. But how would he
it?
A
Marvelous Device
Consider the crowbar!
Here
but a marvelous one!
vice,
is
a simple
mechanical de-
Without the crowbar
a
huge
boulder can be lifted only by the straining muscles of
many men. But rest
man
it
on
a pivot (such as a smaller rock),
can easily
a single
similar devices are types of levers.
"lever" comes
Anything
and
raise the boulder.
Crowbars and
word
place a crowbar under the boulder and
from
relatively long
a Latin
and
rigid,
or a rod, can be used as a lever. device that even prehistoric
word meaning
men
such
A
used
"to raise."
as a stick, a
lever it.
is
The
board,
such a simple
But they didn't
Great Ideas of Science
26
know how
worked, and neither did the clever Greek
it
The
philosophers.
great Aristotle (AR-is-TOT-1),
had been a pupil of
Plato's,
down and
lever pushed
traced out circles in the
noted that
as
one
who
side of the
the other pulled up, both ends
air.
He
decided that the lever had
wonderful properties because the
had
circle
a
wonderful
shape.
Archimedes had experimented with that Aristotle's explanation
was
ments Archimedes had rested as to
balance
it.
If
the lever, that end
by
a
levers,
incorrect.
and he knew
In his experi-
long lever on a pivot so
he placed a weight on only one end of
went down.
He
could balance the lever
placing weights on both sides of the pivot.
If the
weights were equal, he could balance the lever by placing
them
in certain positions. If the weights
were unequal, the
balance came in other positions.
Language of Math Archimedes found that larity.
ity? tion,
Why
levers
behaved with great regu-
not use mathematics to explain
According
this regular-
to the principles of mathematical deduc-
he would have to begin with an axiom, that
is,
something to be accepted without argument.
The axiom
he used was based on the chief result of
experiments with levers.
It
went: Equal weights
his
at equal
Archimedes and Applied Mathematics
from the pivot
distances
27
will balance the lever.
If equal
weights are at unequal distances from the pivot, the side
with the weight
at the greater distance will
Archimedes then went on
to use mathematical
tion to reach conclusions based
showed
clusions
that the
down on
Suppose
a lever
it is
and
on
this
deduc-
axiom. These con-
most important factors
workings of any lever are the pressing
go down.
size of the
their distances
in the
weights or forces
from the
pivot.
balanced by unequal weights on oppo-
of the pivot. According to Archimedes' findings
site sides
those unequal weights will have to be at different distances
from the
The
pivot.
greater in order to
distance of the small weight will be
make up
for
its
smaller force.
For ex-
ample, a ten-pound weight twenty feet from the pivot will balance a
one hundred-pound weight two feet from
the pivot.
The ten-pound weight
distance
ten times greater.
is
how
This explains a lever.
When
one
man
can
is
ten times lighter, so
lift
a
its
huge boulder with
he places the pivot very near the boulder,
his small force at a great distance
from the pivot
will bal-
ance the boulder's great weight at a small distance from the pivot.
Archimedes saw that
if
a
man's force were applied
at
an
extremely great distance from the pivot, an extremely huge
weight could be is
lifted.
reported to have
But
his
work on
"Give me
said, ''and I
a place to stand on,"
he
can move the world."
the lever had already
moved
the world.
Great Ideas of Science
28
Archimedes was the
practical engineering. In
plied mathematics
He
thus
lit
to apply
first
Greek mathematics
to
one stroke he had pioneered ap-
and founded the science of mechanics.
the fuse of a scientific revolution that was to
explode eighteen centuries
later.
...,:*',',«
4 Galileo and Experimentation
A YOUNG MAN of Seventeen was attending
services at the
Cathedral of Pisa one Sunday in the year 1581.
He
was
devoutly religious and no doubt tried to concentrate on his prayers.
But he was
hung nearby. and
set it
As
it
An
air
distracted
by
a chandelier that
current had caught the chandelier
swinging.
moved with
the current, swinging gently at times
Great Ideas of Science
30
and through
wider arc
swung through
it
Wasn't
that strange!
through
a
At
at others, the
The chandeher seemed
something.
whether
a
young man noticed
to keep steady time
wide arc or
a
Shouldn't
a
narrow one.
take longer to pass
it
wide arc?
this point the
young man, whose name was GaUleo
(gal-ih-LEE-oh), must have forgotten the service com-
His eyes fastened on the swinging chandeher and
pletely.
the fingers of his right hand stole to his left wrist.
While
the organ music swelled about him, he counted his pulse
So many for one swing, so many for the next, and
beats.
The number
so on.
of pulse beats
was always the same,
whether the swing was narrow or wide. In other words, the chandelier took just as long to swing through a narrow arc as through a wide one.
Galileo could hardly wait for the service to end. it
did,
he rushed
Timing from
a
home and hung weights from
their swings, he
found that
a
long string took a longer time to
when
strings.
weight suspended
move back and
forth than a weight suspended from a short string. ever,
When
How-
he studied each weight singly, he found
it
always took the same time to complete one swing, whether the swing was narrow or wide. Galileo had discovered the principle of the pendulum!
But he had done more than self in a
that.
He
had involved him-
problem that had puzzled scholars for two thou-
sand years
—
the problem of
moving
objects.
Galileo and Experimentation
3
Ancient Theories The
ancients had observed that living things could
themselves and could also
move
nonliving objects.
other hand, nonHving things usually could not
moved them. But
a living being
many all
exceptions
— the
moved without
tion that did not
sea,
On
move
the
unless
the ancients had observed
the wind, the sun, the
the help of living things.
depend on the
move
living
moon
Another mo-
was the motion of
falling bodies.
The Greek tion
philosopher Aristotle
was natural for
all
heavy
felt that a falling
things. It
the heavier the falling object was, the
A
pebble
fell faster
than a
leaf,
and
mo-
seemed to him that
more rapidly
it fell.
a large pebble faster
than a small one.
A
century
later
Archimedes applied mathematics
to
physical situations, but only to motionless ones (see Chapter 3).
He
applied
The problem
it
to a lever in balance, for example.
of rapid motion was beyond even his great
mind. For the next eighten centuries no one challenged Aristotle's ideas of motion,
and physics was
at a standstill.
Slowing Falling Objects By 1589
Galileo had finished his university training and
was already famous for
his
work in mechanics. Like Archi-
Great Ideas of Science
32
medes he had appHed mathematics
However, he longed If
to motionless situations.
back to the problem of motion.
to get
only there were some sure way, he thought, to slow
down falling bodies so and study
their
entist sets
up
that he
motion
might experiment with them (In an experiment a sci-
in detail.
him
special conditions that will help
to study
and observe phenomena more simply than he could
in
nature.)
Galileo
remembered
pended from starts falling. it
from
is
down.
a freely falling
fall in a straight line.
tions.
How
weight
string attached to
— and slowly enough
Unlike
If a
sus-
pulled to one side and released,
However, the
falling straight
slantwise
not
a string
pendulum.
his
could Galileo
Instead, the so that
body
a
it
it
it
prevents
weight
falls
can be timed.
pendulum weight does
This fact introduced complicaset
up an experiment
he could make a body move slantwise in
in
which
a straight line?
Of course! Simply prepare a wooden board with a long, straight polished groove. Set balls rolling down that groove, and they will move in a straight line. And if the board
is
slanted nearly horizontal, the balls will roll quite
slowly and one can study their motion in
detail.
Galileo set balls of different weights rolling
down
the
groove and timed them by counting the drops of water falling
from
bottom.
He
a water-filled vessel
with a small hole in the
found that except for very
light objects.
Galileo and Experimentation
3 3
weight made no difference
at
All solid balls covered
all.
the length of the groove in the same time.
Aristotle Left Behind
All objects, Galileo decided, had to push the the
way
with
as
they
difficulty
fell.
Very
light objects could
air
out of
do so only
and were slowed by the resistance of the
Heavier objects could do so
easily
and were not slowed.
In a vacuum, where there was no feathers and snowflakes
air.
air resistance
would drop
as
quickly
at
all,
as pellets
of lead. Aristotle had stated that the speed of falling objects de-
pended on
only for exceptional
And
cases, that
only because of
Aristotle
Galileo proved that this was true
their weight.
is,
for very light objects.
air resistance.
He
was
right,
and
was wrong.
Next, Galileo marked off divisions of equal length.
He
his
long groove into small
found that any
covered each successive division in to cover the one before.
accelerated as
it fell.
It
was
less
rolling ball
time than
it
took
clear than an object
In other words
it
moved
faster
with
each unit of time. Galileo was able to tionships
work out
which he used
simple mathematical rela-
to calculate the acceleration of a
Great Ideas of Science
34
Thus, he apphed mathematics to moving
body.
falling
bodies as Archimedes had once apphed
to motionless
it
ones.
With gained
appHcation and with the knowledge he had
this
in
his
experiments with rolling
achieved astonishing
how
exactly
For
results.
instance, he
would move
a cannonball
Galileo
balls,
worked out
after
it
left
the
cannon. Galileo
was not the
first
to experiment, but his dramatic
with the problem of
results
falling bodies
made
mentation more popular in the world of science.
were
scientists
stead,
experi-
No longer
content merely to reason from axioms. In-
they began to design experiments and make measure-
They
ments.
could use experiments to check their reason-
ing and to serve as starting points for 1589, then,
we
date the beginnings of experimental science.
For experimental science
to succeed, however, accurate
measurements of change had to be the passage of time
Even
new reasoning. From
itself
Most of
possible.
all,
had to be measured accurately.
in very ancient times
mankind had learned
to
measure large units of time by means of astronomical changes.
The
steady march of the seasons marked off the
year, the steady shift of the
moon's phases marked
month, the steady rotation of the earth marked
For
units of time smaller than the day,
turn to
less
accurate methods.
the mechanical clock had
off the
off the day.
mankind had
to
During the Middle Ages
come
into use.
Hands were
1000oll>0
Galileo and Experimentation
moved around
a dial
by suspended
trolled
35
by geared wheels which were conweights.
As
the weights slowly
fell,
they turned the wheels.
But
it
make
was hard
to regulate the fall of the weights and
the wheels turn smoothly and evenly.
such clocks always ran so
fast
Therefore,
or slow that none could be
trusted to give the time closer than to the nearest hour.
Timekeeping Revolutionized What was would
needed was some very steady motion that
regulate the turning wheels.
years after Galileo's death) the
Dutch
Huygens (HIGH-genz) thought
The pendulum
beat out
its
In 1656
(fourteen
scientist Christian
of the pendulum.
swing
in regular intervals.
Suppose, then, that a pendulum was attached to a clock so that
gears
it
controlled the gears.
would then become
The movement
as regular as the
of the
swing of the
pendulum.
Huygens managed
to invent such a
grandfather's clock, as ciple discovered
was mankind's
by first
experimental science.
it is
the
pendulum
clock, or
often called. Based on a prin-
young
Galileo,
Huygens' clock
accurate timepiece and a
boon
to
Democritus and Atoms They called him the
"Laughing Philosopher" because he
always seemed to be laughing bitterly
at the foolishness of
mankind.
His name was Democritus (dee-MOK-rih-tus) and he
was born about 470 B.C. fellow citizens
may
in the
Greek
have thought
city of Abdera.
His
his laughter the result of
Democritus and Atoms
madness
— one
37
tradition says they considered
him
a lunatic
and called in doctors to try to cure him.
To tions.
be sure, Democritus did seem to have peculiar no-
For
instance, he worried about
You
water could be divided.
so small that
it
were too small
Did you eventually get
a limit?
far a
drop of
could produce smaller and
smaller drops of water until they
was there
how
a
to see, but
drop of water
could be divided no more?
An End
to Splitting ?
Democritus' teacher, Leucippus (lyoo-SIP-us), had suspected there was a limit to division. Democritus continued thinking along these lines and finally announced his conviction that
no
further.
all
substances could be divided only so far and
The
smallest bit, or particle, of
substance was indivisible.
He
called that smallest particle
atomoSj a Greek
word meaning
said the universe
was made up of such tiny
cles.
the
There was nothing
"indivisible."
Democritus
invisible parti-
in the universe but particles
and
empty space between them.
According
to Democritus, there
these particles.
They combined
and each arrangement formed substance iron rusted
—
any kind of
it
was because
that
different types of
in various arrangements,
a specific substance.
is,
If
became the substance
the rust
different kinds of particles in iron rear-
ranged themselves.
wood burned and
—
were
If
ore turned to copper, the same. If
turned to ash, again the same.
3
Great Ideas of Science
8
Most Greek philosophers laughed
A
could anything be indivisible? didn't take
up
space. If
it
at
Democritus.
particle either did or
took up space, then
capable of being broken in two, with each
taking up
up no
less
How
it
had to be
new
particle
space than the original. If the particle took
space, then
it
was
indivisible.
But
a particle taking
up no space was nothing, and how could substances be built
from nothing?
Either way, the philosophers decided, the notion of
No wonder people looked at Democ-
atomos was nonsense. ritus suspiciously
and wondered
didn't even think
it
if
he was sane.
They
worthwhile to make many copies of
Democritus wrote more than seventy books,
his books.
but not one has survived.
To
be sure, some philosophers did pick up the idea of
indivisible particles.
Democritus
In 306 B.C., nearly a century after
died, a philosopher
KYOO-rus) founded lar teacher
was
named Epicurus (EP-ih-
a school in Athens.
and had many
called Epicureanism,
pupils.
and
it
His
He was a popu-
style of
philosophy
remained important for
centuries. Part of this philosophy consisted of the particle
theories of Democritus.
Nevertheless, even Epicurus couldn't convince his contemporaries, and his followers found themselves in a minority. Like the
works of Democritus, none of the many
books written by Epicurus has survived.
About 60 B.C. something fortunate happened.
A Roman
Democritus and Atoms
39
poet named Lucretius (loo-CREE-shus) became interested in the
He
Epicurean philosophy.
the Nature of Things^ in
a
On
long poem,
which he described the universe
composed of Democritus'
as
wrote
indivisible
particles.
The
book proved very popular and enough copies were made so that
it
one book the world learned in
this
Through
survived ancient and medieval times. detail of
Democritus'
views.
In ancient times, books were hand-copied and expensive.
As
a result,
only a few volumes of even the greatest works
could be made and only the wealthy could afford to buy
A great change occurred about
them.
1450 A.D. with the
invention of the printing press, which could turn out expensive books to be printed
by
the thousands.
was Lucretius'
On
One
the
of the
Nature of
first
less
works
Thijigs.
Gassendi to Boyle Thus, even the poorest scholars of early modern times could read the views of Democritus.
who
Some
did so were greatly impressed.
A
of the scientists
seventeenth-cen-
tury French philosopher, Pierre Gassendi (ga-san-DEE),
became
a
confirmed Epicurean.
He
argued strongly in
favor of the theory of tiny indivisible particles.
One
of Gassendi's pupils
was an Englishman named
Robert Boyle. In 1660 Boyle was studying
air
and won-
40
Great Ideas of Science
dered
and
why
it
could be compressed, or made to take up
less
less space.
He
supposed that
air
was made up of tiny
would mean pushing the
made
tact.
particles
more
air
closely together.
empty space between
particles.^i
That
sense.
On the that
less
with
between them. Compressing the
a great deal of space
There would be
particles
were
other hand, water might be
made up
close together, so close that they
For that reason,
it
were pulled
water vapor, a thin
So Boyle
also
were
in con-
seemed to Boyle, liquid water
could not be compressed any further. particles
of particles
far apart, the
However,
if
the
water would become
air-like substance.
became
a follower of Democritus.
Thus, for two thousand years there was an unbroken chain of believers in a theory of indivisible particles: Democritus, Epicurus, Lucretius, Gassendi, and Boyle. ertheless, their
"What! cles?
Nev-
views were never accepted by the majority.
A particle that can't be broken into smaller parti-
Nonsense!"
Weight Watchers However,
in the eighteenth century, chemists
way in which chemical compounds were They knew that other substances combined to
reconsider the
formed.
began to
Democritus and Atoms
form
these
41
compounds. For example, copper, oxygen, and
carbon combined to form the compound copper carbonate.
For the
first
time, however, they
began to measure the
weights of the combining substances.
relative
Toward the end
(PROOST), went
Louis Proust in great detail. per, oxygen,
of the century a French chemist, Joseph
He found,
into such measurements
for instance, that
whenever cop-
and carbon formed copper carbonate, they
always combined in the same proportion by weight.
The
proportion, or ratio, was five units of copper to four units
of oxygen to one unit of carbon. In other words,
used up
would
five,
if
Proust
ounces of copper to form the compound, he
have to use up four ounces of oxygen and one
also
ounce of carbon. It
wasn't as though he were baking a cake, where he
could increase the flour a the milk.
There was no way
copper carbonate.
was always
He
5 to
4 to
1
recipe.
of these results
law" or "the law of
"Odd!" thought
change the
By
down on
''recipe" for
did, the proportion
and never anything
else.
and he found the same
1799 he announced
effect
his results.
as "Proust's
definite proportions."
the English chemist results.
Dalton thought of the if
to
came what we now know
Proust announced his
What
he chose, or cut
Whatever Proust
tried other substances
— always one Out
bit, if
John Dalton when
"Why should this be?"
possibility of indivisible particles.
an oxygen particle always weighed four times
as
42
Great Ideas of Science
much
carbon particle and a copper particle always
as a
weighed
much
five times as
as a
carbon particle? Then,
you made copper carbonate by combining cle,
an oxygen
have the ratio If
4 to
5 to
you wanted
slightly,
and
particle,
a
carbon
a
copper
particle,
if
parti-
you would
1.
to alter the ratio of copper carbonate
you would have
to chip a piece off one of the
three particles.
Since Proust and other chemists were
showing that the
ratio of a
it
meant the
they were
compound
couldn't be changed,
particles couldn't be chipped.
indivisible, just as
Democritus had thought.
Dalton searched for more evidence.
compounds
He
found different
were made up of the same
that
However, the proportion of
pound was
Dalton decided
substances.
the substances in each
For example, carbon dioxide was
different.
composed of carbon and oxygen
in the ratio
by weight
the ratio of
3
also
made up
of carbon and oxygen, but in
to 4.
This was interesting. units
of
Carbon
three units of carbon to eight units of oxygen.
monoxide was
com-
was the same
in
monoxide and three might be one carbon
The number
both
ratios
of carbon weight
— three
units in carbon
units in carbon dioxide. particle
So there
weighing three units in each
compound.
At the same
time, the eight units of
oxygen
in the
carbon
dioxide ratio exactly doubled the four units in the carbon
monoxide
ratio.
If
an oxygen particle weighed four
units.
Democritus and Atoms
43
Dalton thought, then perhaps carbon monoxide was partly
composed of one oxygen
and carbon dioxide of
particle
two.
Then Dalton may have remembered the copper carbonate. The weight ratio of carbon to oxygen had been 1 to 4 (which
is
the same ratio as
plained
if
you assumed
to
3
1
2)
.
This
ratio
that copper carbonate
of one carbon and three oxygen particles.
could cles
work out
a
was made up
Always you
system whereby whole numbers of parti-
were involved, never
By
could be ex-
fractions.
1803 Dalton had announced his theory of indivisible
particles.
This time, however, the statement differed from
those previously proclaimed.
merely a
belief.
No
longer was the theory
Dalton had a whole century's worth of
chemical experimentation to back him up.
Atoms by Experiment The change its
worth
(see
in science
brought about by Galileo proved
Chapter 4).
Argument
convinced mankind of the existence of
alone had never
indivisible particles,
but argument plus experimental results did so almost
at
once.
Dalton recognized that
his
view dated back to the
Laughing Philosopher, and he humbly made use of Democritus'
word atomos
to
show
this recognition.
In En-
44
Great Ideas of Science
glish the
word became -atom." Dalton had
estabhshed the
atomic theory. All of chemistry was revolutionized as a result. In 1900, physicists used
methods no one had previously dreamed of
to discover that the cles,
atom was made up of
still
smaller parti-
and the science of physics was revolutionized. Then,
when energy was drawn from
within the atom to produce
atomic power, the course of
human
revolutionized.
history began to be
Lavoisier and Gases
It's see it
hard it
to believe that air
is
and normally you don't
moves quickly enough,
wreck
ships
and blow
it
really something. feel
it,
becomes
down
trees.
and yet a
storm
Its
You
it's
can't
there.
blast that
If
can
presence can't be
denied. Is air
the only substance that can't be seen?
The alchem-
46
Great Ideas of Science
ists
of the Middle Ages seemed to think
so.
When
their
concoctions gave off colorless bubbles or vapors, they re-
corded that they had formed
''an air."
If alchemists existed today,
their findings seriously.
science that
was more
After
some
all,
not take
alchemy was
knowledge of matter.
In this way, they
contributed to
made important
About
with the notion that ''airs"
For
worked
discoveries that
of these talented alchemists was Jan Baptista van
in alchemy.
didn't
How-
Able Alchemist
Helmont. Actually, he was
The
a false
modern chemistry.
An One
of
able alchemists observed and studied the be-
havior of the metals and other substances they with.
many
interested in converting other metals
to gold than in adding to our ever,
we would
a physician
Helmont
1630, van all
colorless vapors
he found bubbling out of
seem to be instance,
and only dabbled felt dissatisfied
were
his
really air.
mixtures just
air at all.
when
he placed
bits
of silver into a strong
chemical called nitric acid, the silver dissolved and a red
vapor bubbled up and curled into the space above the surface of the liquid.
red
air?
Was
this air?
Who
had ever heard of
Who had ever heard of air that could be seen?
Then, when van Helmont added limestone
to vinegar.
Lavoisier and Gases
47
bubbles rose to the top of the Hquid again. These at
were
colorless
and looked
But
just like air bubbles.
least if
he
held a lighted candle above the liquid's surface, the flame
went
out.
What kind of air was it in which a candle would The same
not burn?
flame-quenching vapors rose from
fermenting fruit juice and from smoldering wood. So, the so-called airs that van
Helmont and
chemists produced were not really
much
like air that
example of a group of
He
al-
But they were
they fooled everyone
one but van Helmont.
decided that
—
that
air
is,
was
so
every-
just
one
airlike substances.
These substances were harder materials,
air.
other
which could
easily
to study than ordinary
be seen and
Ordinary
felt.
substances had definite shapes and took up definite amounts
of room.
They came
in pieces
sugar, half a glass of water.
They seemed no
and quantities
The
—
a
lump of
airlike substances did not.
to spread out thinly
everywhere and
to have
structure.
From
A
new group
mont knew
the
''Chaos'' to ''Gas"
Van
of substances needed a name.
Greek myth
that the universe
Hel-
began with
thin matter without structure that spread out everywhere.
The Greeks a
called that original matter chaos.
good word! But van Helmont was Flemish
There was
—
that
is,
he
48
Great Ideas of Science
lived in
old
what
now Belgium
is
Greek word
he pronounced
in
it,
— and he pronounced the
good Flemish
fashion.
and the word became
He
spelled
it
as
"gas.''
Van Helmont was the first to realize that air was but one kind of gas and that there also were other kinds of
Nowadays, we
call his
gas.
red gas nitrogen dioxide and his
flame-quenching gas carbon dioxide.
Van Helmont found
I
,
it
difficult to
study the gases be-
cause as soon as they formed, they mixed with air and
faded away. However, about one hundred years later an '
English minister, Stephen Hales, thought of a
way
to pre-
vent that diffusion. I
Hales
the gas bubbles
let
opening was the
mouth
a bent pipe.
form
The
in a vessel
whose only
pipe led under water, into
The
of an upside-down water-filled bottle.
bubbles traveled through the pipe and up into the bottle, forcing out the water, giving Hales a bottle full of some particular gas, with
which he could then experiment.
Priestley's
New Drmk
Unfortunately, some gases could not be collected in a water-filled bottle because they dissolve in water.
How-
ever, about 1770, another English minister, Joseph Priestley, substituted
in
mercury, so
mercury for water. Gases did not it
could be used to collect any
gas.
dissolve
Lavoisier and Gases
49
Priestley collected
mercury.
He was particularly interested in carbon dioxide.
Once he had some
van Helmont's two gases by using
in water
collected the gas over mercury, he dissolved
and found that
a pleasant drink resulted.
He
had invented soda water. Priestley also collected the gases chloride,
ammonia, hydrogen
and sulfur dioxide and he discovered oxygen.
Obviously, there were dozens of different gases.
A About
Burning Issue
the same time that Priestley
gases, in the 1770's, the
Lavoisier
was discovering
French chemist Antoine-Laurent
(lah-vwah-ZYAY) was wrapped up
lem of combustion. Combustion rusting of substances in air
—
— was
that
is,
in the prob-
the burning or
a process that
nobody
really understood.
Of tion.
course, Lavoisier wasn't the
first
But he had an advantage over
to study
combus-
his predecessors:
He
firmly believed that accurate measurements were important in an experiment.
surements was not new.
The It
idea of
making
careful
had been introduced two hun-
dred years before by Galileo (see Chapter 4) it
mea-
was Lavoisier who extended the idea
.
However,
to chemistry.
Therefore, Lavoisier didn't just watch substances burning and examine the ash that was left behind.
And
he
50
Great Ideas of Science
didn't just is,
rust, that
the dull or crumbly substance that formed on their sur-
Before a substance burned or rusted, he carefully
face.
measured it
watch metals rusting and examine the
its
And
weight.
combustion he weighed
after
again.
At
first
Wood
these measurements brought only confusion.
burned and the ash
A
than the original wood. altogether; nothing at
some
friends
also burned.
much
was
That vanished, all
of
its
left
behind.
Lavoisier and
Did burning
too.
was heavier than the
tional solid material
it
until
it
a material
substance?
when
metals
original metal.
Addi-
the other hand, Lavoisier found that
rusted, the rust
lighter
candle burned and was gone
bought a small diamond and heated
destroy part or
On
all
behind was
it left
seemed to come from nowhere.
Why
should rusting add matter, while burning seemed to destroy
it?
A
Weighty Problem
Earlier chemists had not worried very
much
about such
things because they weren't acustomed to weighing their chemicals.
Lighter?
Heavier?
What
difference did
it
make? But Lavoisier worried about
it.
Did burned material
vanish into thin air? Ah, perhaps that was
formed
gases
when they
it.
If substances
burned, wouldn't those gases do
Lavoisier and Gases just that?
into
5
Wouldn't they mix with the
and vanish
air
it?
Van Helmont had shown
that burning
wood produced
carbon dioxide. Lavoisier had obtained the same gas from his
burning diamond. Thus,
could produce it
enough
to
gas.
But
make up
it
was
certain that combustion
how much
gas
was formed?
Was
for the loss of weight?
Lavoisier thought that might be the case.
About
twenty-
years earlier a Scottish chemist, Joseph Black, had heated
limestone (calcium carbonate) and found that
The
carbon dioxide.
it
released
limestone lost weight, but the weight
of the gas produced equaled that lost weight.
"Well then," Lavoisier thought, "suppose substance loses weight because
about metals?
it
releases a gas.
a
burning
Then what
Did they gain weight when they
rust be-
cause they combine with a gas?" Black's
work
He
again provided a clue.
had bubbled
carbon dioxide gas through limewater (a solution of
cal-
cium hydroxide), and the gas and calcium hydroxide combined to form powdered limestone.
If
calcium hydroxide
could combine with a gas to form another substance, Lavoisier thought, then perhaps metals did the same.
Locking Air Out Thus, Lavoisier had good reason to suspect that gases
were behind the weight changes
that resulted
from com-
Great Ideas of Science
52
But
bustion.
how would
he prove
Weigh-
his suspicion?
ing ashes and rusts was not enough; he also would have to
weigh the
gases.
However, the wide blanket of created a problem.
How
air that encircles
could he weigh gases that
caped from burning objects into the hand,
how
The
its
the other
air
left
would rush
place?
all
but a definite amount of
both by conducting
gases,
when more
es-
answer, Lavoisier realized, was to lock in the gases
and lock out
tainer.
On
air?
could he determine the amount of gas that
the air to combine with a metal, in to take
the earth
Then,
if
his
He
air.
chemical reactions in a sealed con-
a substance inside
it
burned and released
they would be captured in the container.
stance rusted and
only from the
combined with
air inside
with the
by
solid substance
the enclosed substance
gases,
If a
sub-
they would come
the container.
Weighing Lavoisier began
could do
the Evidence
carefully weighing the container
and
air sealed inside
He
on
heated
it
with a
by building a fire under it.
When
by focusing
large magnifying glass or
it.
sunlight
the substance had burned or rusted, he again weighed the
container with
He
its
contents.
repeated the process with a
number of
different sub-
Lavoisier and Gases
stances. In
every
53
case, regardless of
what
it
was
that
burned
or rusted, the sealed container showed no change in weight.
Suppose, for example, a piece of
which of course weighed of the gas released
by
less
the
wood burned
to an ash,
than the wood.
The weight
wood made up
the missing
weight. Therefore, the weight of the container remained the same.
Suppose
a piece of iron
absorbed gas from the
The
container and changed into rust.
by
the
the
was heavier
However, the weight gained was exactly
than the iron. offset
rust
air in
air's loss
of weight. Again, the weight of the
container did not change.
and measurements had
a great
on the development of chemistry. They
laid the
Lavoisier's experiments
influence
groundwork for terpretation
him
we
his interpretation of still
use today.
The
combustion, the inexperiments also led
to conclude that matter could be neither created nor
destroyed;
it
could only change from one form to another
(for example,
This
is
from soHd substance
to gas)
the famous "law of conservation of matter."
This idea that matter
is
indestructible
made
it
easier to ac-
cept, thirty years later, the theory that matter
is
made up
of indestructible atoms (see Chapter 5).
Both the law of conservation of matter and the atomic theory have been improved and slightly changed in the twentieth century. the
strong
and
On
sturdy
the whole, however, they
platform
on
which
form
modern
Great Ideas of Science
54
:j
chemistry stands. For Lavoisier
is
chemistry."
hi$ part in building this platform,
commonly
called
the
''father
of
modern
Newton and It's
only
two
parts
natural to think that the universe
— the heavens and the
Greek philosopher ate in
Inertia
Aristotle the
earth.
two
And
parts
is
made up
of
to the ancient
seemed
to oper-
completely different ways.
Aristotle observed that everything
decayed
— men
grew old and
on earth changed or
died, buildings aged
and
crumbled, the sea became stormy then calm, winds blew
56
Great Ideas of Science
clouds here and there,
blazed up and
fires
went
out, the
very land shivered with earthquakes. In the sky, however, there seemed to be only serenity
and changelessness. The sun rose and flame never brighter or dimmer.
on schedule,
set
its
The moon went through
phases in regular order, and the stars shone without
its
ceasing.
Aristotle decided that the
two
parts of the universe oper-
ated under different sets of rules or "natural laws." There
one natural law for objects on earth and another for
\\'as
objects in the heavens.
These
different natural laws also
Aristotle considered the if
a stone
was held
On
straight
down.
Left to
itself, all
way
seemed to apply when
objects
in the air
and
a windless day,
moved. For example, released,
smoke
it
dropped
rose straight up.
earthly motion seemed to be either
up or
down.
Not fall
so in the sky.
The sun and moon and
toward the earth or
totle
rise
away from
stars didn't
Instead, Aris-
it.
thought they moved in smoth, steady
circles
around
the earth.
One more
difference.
ally stopped.
A
moving
objects eventu-
A falling rock hit the earth and came to rest.
falling ball
came
On earth,
to rest.
kicked pebble
might bounce
a
few
times, but
A shding block of wood,
—
all
came
eventually tired and stood
to rest. still.
soon
a rolling
Even
a
it
also
wagon,
a
running horse
Newton and Thus, things
Inertia
57
seemed to Aristotle that the natural
it
on earth was
rest.
Anything
in
motion returned to
that natural state of rest as soon as possible.
however, the sun, moon, and
moving forever
at the
same
stars
Aristotle's notions about the
years.
human mind had
Then
Where
Newton way objects move were
to offer for nearly
Galileo began to
the
two thousand
come up with
Aristotle had thought that
more rapidly than jects fell at the
better ones
They were with
They
would
fall as
quickly
About forty
as a
fell
more slowly,
all
ob-
it
was
they were slowed down.
push through the
In a vacuum, he
no longer be slowed by
entist Isaac
why
so light, they could
difficulty.
that
fell
same speed. However, Aristotle was right
But Galileo explained
true.
heavy objects
showed
light ones, Galileo
about very light objects.
ject
never stopped, but kept
Chapter 4)
(see
ject
In the sky,
stately speed.
Galileo to
best the
state of
said,
lump of
even the
air
only
lightest ob-
lead because
it
would
air resistance.
years after Galileo's death the English sci-
Newton examined
could be affected by
the idea that a
air resistance.
He
moving ob-
could think of
other ways in which motion was interfered with.
For example, when
a falling object hit the earth, its
mo-
Great Ideas of Science
58
ground got
tion stopped because the
rock skidded across
was
a
rock moved along
Along
a stretch of ice
What would ject
and
less friction
moved
it
happen,
no
barriers,
still
Newton
words, what
if
friction,
its
its
own surface.
farther before stopping. farther.
thought,
made no contact with anything
were no
got in
a
smooth paved road, there
a
moved
it
still
When
between the un-
friction
even surface of the road and rough spots on
When
way.
its
ground
a dirt road, the
way. The rock was stopped by
in
no
the object were
if
at all?
a
moving ob-
What
air resistance?
if
there
In other
moving through
a vast
vacuum? In that case, there would be nothing to stop or swerve
would
just
it
from
its
path
keep moving
natural state of an object
He
at the
part of
Newton
itself will
remain
slow
The
it,
object
in the
same
decided that the necessarily rest.
it.
Any move
statement which can be
object at rest left entirely to
at rest forever.
entirely to itself will
all.
on earth was not
set forth his conclusions in a
expressed as follows:
at
same speed and
Therefore,
direction forever.
That was only
— nothing
it,
Any
at the
object in motion left
same speed
in the
same
straight line forever.
This statement
called
Newton's
first
law of motion.
Newton,
objects tended to stay at rest or
They seemed
almost too "idle" or "lazy" to
According in motion.
is
to
Newton and Inertia change their
motion ertia" If
is
59
For
state.
comes from
a
Greek word meaning
you can
it,
inertia,
Suppose you want to
beach
touch and off
set a
it sails.
If
ease
so, it
ball
you want to it
as
are
moving, there
quickly moving beach ball by batting
A
it
cannonball
is
motion than
much more
inertia.
object was the
it
cannonball as
you can
You can stop a down with your
would knock your hand
and scarcely be affected
fully to one side
state of
hard
much more is
a
beach
Newton
amount of the
pain-
itself.
reluctant to change
ball.
The
cannonball has
Thus,
object's inertia.
a
can-
ball.
A cannonball also has more weight than a beach ball. heavy objects have considerable mass while
objects have as mass.
sixth as
little
mass.
its
suggested that the mass of an
nonball has more mass than a beach
general,
it
cannonball moving at the same speed had better
not be interfered with, for
The
set a
give
a difference in the
is
with which they can be stopped.
hand.
You
moving.
moves but slowly.
two
the
"idleness.")
or resistance to change.
moving, however, you have to push
Once
law of
see that different objects
have different amounts of
and even
first
sometimes called the principle of "inertia." ("In-
you think about
a light
Newton's
this reason,
However, weight
is
In
light
not the same
On the moon, for instance, any object is only oneheavy
as
The movement
it is
on
earth, but
its
of a canonball on the
mass
is
unchanged.
moon would
be as
60
Great Ideas of Science
hard to
start
and
as
dangerous to stop
as
on
cannonball would seem surprisingly light ing
you were hold-
it.
To make on
aside is
if
earth. Yet, the
its
move
an object
faster,
you must push or
path,
The
called a "force."
quicken or slow
its
rate at
slow down, or turn
pull
wich
motion or to turn
it.
a
A push or a pull body
aside
made
is
is its
to
"accelera-
tion."
Newton
may
also
be stated
put forth a second law of motion, which
as follows:
The
acceleration of a?iy
body
is
equal to the force applied to that body divided by the
body^s mass. In other words, pushing or pulling an object tends to speed
it
up, slow
greater the force, the
or direction. is,
the
tion.
much
amount of
more the object
inertia
a
faster because
its
down, or turn will
it
it
has
—
change
its
has
much more
little
speed
—
that
acts against this accelera-
hard push will make a beach it
The
aside.
the other hand, the object's mass
For example,
applied to the affect
On
it
mass.
ball
go
But the same force
massive cannonball will hardly
movement.
From Apple
to
Moon
Newton then went on to propose a third law of motion, which may be stated: If a body exerts a force on a second body, then that second body exerts an equal force,
in the
Newton and Inertia
61
Opposite direction, on the
book
presses
down on
body. In other words,
a table, the table
the
stays in place, neither sinking through the table
nor
on
the motions and forces
much
The
earth.
not in a straight
Can they
line.
move through
The moon,
also explain
first
law?
No, because
"left entirely to itself." it is
It
doesn't
a
vacuum, but
for instance, follows a
curved path around the earth. Does
because
to explain almost
different motions in the heavens?
objects in the heavens
Newton's
is
air.
Those three laws of motion can be used
the
a
must be pressing up
an equal amount. That
just
bounding into the
all
if
why
on the book by
book
first
this fact contradict
the
moon
move
is
not being
in a straight line
always being pulled to one side
—
in the direc-
tion of the earth.
In order for the
moon
to be pulled to one side like that,
Newton's second law required the plied to the
moon,
a force
existence of a force ap-
always exerted in the direction
of the earth.
The ies.
It
earth does, of course, exert a force
makes apples
fall
downward, for Could
the jorce of gravitation.
moon? Newton
if
that
its
one supposed that
of gravitation in the same
What's more,
instance.
This
is
this force also affect the
applied his three laws of motion to the
moon and showed nicely
on earthly bod-
movements could be explained it is
way
affected as
by
the earth's force
an apple.
a force of gravitation
is
set
up by every
62
Great Ideas of Science
object in the universe.
It is
the gravitation of the sun, for
instance, that keeps the earth
moving around
that large,
glowing body.
Newton was able to use his three laws of motion to show that the size of the force of gravitation
between any two
bodies in the universe depended on the masses of the bodies
and on the distance between them. The greater the masses,
The
the greater the gravitational force.
greater the dis-
tance between the bodies, the smaller the gravitational force.
Newton had worked
out the law of universal gravi-
tation.
Two it
great things
were accomplished by
this law.
explained the motions of the heavenly bodies
almost the finest
detail.
bled very slowly on
It
its axis.
explain
how
from us
circled each other.
pairs of stars
Even more Aristotle sets
explained
Eventually
many
important, perhaps,
was wrong
why it
First,
down
to
our earth wobalso
was used
away
trillions of miles
Newton showed
in concluding that there
to
that
were two
of natural laws, one for the heavens and one for the
earth.
The
three laws of motion explained falling apples
and bouncing
balls, as
Newton proved
well as the circling moon.
that the heavens and the earth
of the same universe.
Thus,
were
parts
8 Faraday and Fields Imagine an iron rod standing on about
it
near the top.
Certainly
you
almost
all
it.
cases a force
end, with a string tied
Can you knock
can. Just push
the string and pull
its
it
The push is
it
over?
with your finger or or the pull
delivered only
is
when
seize
a force.
the
In
two ob-
jects touch.
When
you push
the rod, your finger touches
it.
When
64
Great Ideas of Science
you
pull
it,
your
You might knock
touches the rod.
seeming to touch then you push they touch
it
air
and the string
fingers hold the string
it,
the rod over without
by blowing
just
in
direction.
its
But
molecules in the direction of the rod, and
and push
it.
Newton's three laws of motion explained the behavior of such forces (see Chapter 7).
The
laws could be used to
explain the principles underlying machines in pulleys,
which
levers,
and gears acted by pushing and pulling. In such
machines, objects exerted forces on other objects by making contact.
"Mechanicar' Universe In the 1700's, scientists believed the whole universe ran
by such contact
forces.
This was the mechanical view of
the universe.
Could there be forces without contact?
One was
could.
the force of gravitation,
himself had explained.
kept
it
in
its
orbit,
The
Indeed there
which Newton
earth pulled at the
but the earth did not touch the moon.
There was absolutely nothing between the two even
air;
moon and bodies, not
yet there was a considerable force of gravitation
between them.
We
can observe another kind of force without contact
if
wt
is
a small
return to our iron rod standing on end. All
we need
magnet. Bring that magnet close to the top of the
Faraday and Fields
65
rod and the rod will lean toward the magnet and
magnet doesn't have
to
touch the rod; nor
The
fall.
the air in-
is
volved, for the magnet will pull at the rod in a vacuum.
long magnet
If a thin,
is
allowed to swing in any direc-
end up pointing north and south.
tion, it will
words, the magnet will become
a simple
In other
compass.
With
such compasses, European navigators began to explore the oceans about 1350.
The end
of the magnet that points north
north pole; the other end of one magnet
is
is
come
together.
south and south a strong
between the magnets and they
If like poles
—
are
—
that
is,
Even Thales
it
(see
brought near one another, there
Chapter
how
else
1)
called ''action at
first
black ore attracted iron at
a certain
life in it!"
he exclaimed.
It
was only ordinary loadstone. But
scientists
going to explain the mysterious
of course.
were
apart.
was taken aback when he
"This ore must have
It didn't,
is
is
puzzled scientists from the beginning.
observed that lumps of a distance.
will
north and north or
This kind of force-wichout-touching
and
its
south pole. If the north pole
push and the magnets will move
a distance"
called
brought near the south pole of another,
a strong pull
there
is its
is
force of a magnet, a force
which could
attract
and topple
an iron rod without touching
it?
The
was even more mysterious.
Its
magnetic needle always
pointed north and south because distant polar regions of the earth.
it
action of a compass
was
attracted
by
Here was action
the at a
Great Ideas of Science
(i(i
very great distance!
Here was
a force that could find a
magnetic needle in a haystack! In 1831 the English scientist Michael Faraday attacked
He
the problem of these mysterious forces.
magnets on
a
wooden
table,
with the north pole of one
facing the south pole of the other.
enough
to
The magnets were
to pull at each other, but not close
together.
At
overcome
this distance their force
their friction
two
placed
with the
the force was there, however, for
if
enough
close
come
to
wasn't strong enough table.
Faraday knew
he dropped iron
filings
between the magnets, they moved up to the magnets and clung there.
Faraday decided to vary the experiment. of sturdy paper over the filings
on the paper. The
He laid a piece
two magnets, then dropped
the
friction of the filings against the
paper held them in place and kept them from moving to-
ward the magnets.
Magnetic "Line-up" Then Faraday ings
move
a bit.
tapped the paper lightly to make the
Promptly they twisted
like tiny
fil-
compass
needles and pointed toward one magnet or the other.
Indeed, the filings seemed to take up a position in lines that extended
the other.
from the pole of one magnet
Faraday considered
exactly between the
two
poles
to the pole of
this carefully.
were
straight.
The
A
lines
little
to
Faraday and Fields
one
67
between the magnets the fiHngs
side of the space
lined up, but
were
filings
now they traced out a
to
one
curve.
The
still
farther the
the farther outward was the curve
side,
they traced.
Faraday snapped magnetic
lilies
He
his fingers.
of force passing
had
There were
it!
from the north pole of
a
other
own south pole or to the south pole of anmagnet. And these lines of force could move out-
ward
great distances
magnet
to
its
from the
poles.
This meant that the magnet didn't work by action distance at
object
when
magnet pushed or pulled
Instead, a
all.
its lines
of force approached
lines of force either lines of force that
it.
The
at
at a
some
magnet's
touched the object or approached
came from the object
itself.
Later scientists came to suspect that the same thing probably happened in other kinds of action at a distance. There
had to be gravitational the earth and
moon.
lines of force, for instance,
It
was these touching
lines of force
that enable the
two bodies
too, electrically
charged bodies pushed and pulled
jects, so
there
were
around
to attract each other.
Then, at
ob-
also electrical lilies of force.
New
Generators
Faraday was quickly able to show that when objects
moved
across magnetic lines of force, an electric current
was
up
set
in the
moving
object.
68
Great Ideas of Science
Until then, electric currents could be obtained only
from
which
batteries,
are containers of reacting chemicals.
With
Battery electricity was quite expensive.
new
discovery, electricity could be generated
engine,
which could move objects
force.
Electricity obtained
Thus,
it
by
from such steam
was magnetic
a
steam
across magnetic lines of
was very cheap and could be produced tities.
Faraday's
in
gejierators
enormous quan-
lines of force that electrified
the world in the twentieth century.
Faraday was
a self-taught genius.
He
school past the earliest grades, and he matics.
of
how
He
He
could not
work out
could only trace them with 1860, however,
name
of James Clerk
Maxwell worked out described
how
mathematical description
Scottish
mathematician by
Maxwell tackled the problem.
a set of
mathematical equations which
away from
The force surrounding any magnet
rapidly grows
a
his iron filings.
the strength of force changed as one
farther and farther
field of
knew no mathe-
the lines of force were distributed about a magnet.
About the
a
had not been to
weak
fills
a
a
magnet
magnet
is
any
in
direction.
called a "field."
the entire universe.
as distance increases, so
it
went
The
However,
it
can be meas-
ured only quite close to the magnet. Maxwell showed that a
hne could be drawn through
a particular strength.
The
all
result
parts of the field that
would be one of the
had
lines
of force that Faraday spoke of. Maxwell's equations thus
Faraday and Fields
made
it
69
possible to deal exactly with Faraday's lines of
force.
Maxwell fields
showed
also
that magnetic fields and electric
always existed together. Thus, one could speak only
of an electromag7ietic
field.
"waves" spread out
set of
of such a
field.
in
Under all
certain conditions a
directions
from the center
This was electromagnetic radiation. Such
radiation had to travel at the speed of Hght, according to
Maxwell's mathematics. Thus,
was an electromagnetic
New
seemed that
light itself
radiation.
Years after Maxwell died, rect.
it
his theories
were proved cor-
kinds of electromagnetic radiation, such as
radio waves and
X
were discovered. Maxwell had
rays,
predicted these kinds of radiation, but he did not live to see their existence
proved by experiment.
In 1905 the German-Swiss scientist Albert Einstein be-
gan to revamp man's view of the universe. the mechanical view,
He
abandoned
which had begun with Newton's laws
of motion, and explained the universe in terms of
The two
fields that
gravitational field
were known
at the
and the electromagnetic
fields.
time were the field.
Einstein
tried to find a single set of mathematical equations that
would ever,
describe both
two new
fields,
fields
failed.
Since his time,
how-
have been discovered which apply
to the tiny particles that
the atom. These are
but
make up
known
the nucleus, or core, of
as "nuclear fields."
70
Great Ideas of Science
Electromagnet Push-Pull
Everything that used to be considered is
now
viewed
a push-pull force
as the interaction of fields.
atoms consist of electrons.
When
each other, the electromagnetic electrons push one another.
The
rims of
two atoms approach
fields
surrounding these
The atoms
themselves
move
apart without having actually touched.
Therefore,
when we push
a
rod or pull a
not really making contact with anything
we
are
We
are
string,
solid.
just taking
advantage of these tiny electromagnetic
The moon
circles the earth
and the earth
because of the gravitational
fields
Atomic bombs explode because nuclear
fields.
circles the
sun
about these bodies.
of things that happen to
fields.
The new
field
make advances
view of the universe has helped
that
would have been impossible
of the mechanical view.
in the days
Yet, the field view traces right
back to Faraday's idea that magnetic push or pull an object.
scientists
lines of force
could
^ i m 'i VsNiffll
aH
H ttDDtok31 [Z^ii^^-ffl
Rumford and Heat It
is
difficult to have
Thompson.
He
was
a
much sympathy
for Benjamin
shrewd person whose
concern was for himself.
When
first
and
last
he was only nineteen, for
instance, he escaped the poverty of his childhood
by mar-
widow nearly twice his age. Thompson was born in Woburn, Massachusetts,
rying a rich
in
pnI
Great Ideas of Science
72
In those days, Massachusetts and the other original
1753.
American
states
were
still
Thompson was
after
British colonies.
He
as to
which
attached himself to the British
and served
as a
few years
married, the American Revolution
broke out and he guessed wrong win.
A
spy against the colonial
side
army
in
would Boston
patriots.
When the British left Boston, they took Thompson with them.
He
left his
wife and child behind with no apparent
misgivings and never returned.
In Europe, he served any government that would pay his price
— and got
in trouble
with one after another be-
cause he took bribes, sold secrets, and in general was an
immoral and dishonest man.
Thompson
In 1790, tinent.
He
left
England for the European con-
entered the service of Bavaria
Germany, but then an independent varian ruler granted called himself inal
name
married
him
of Concord,
is
New
had
is
now known
Thompson the orig-
Rumford
that
Benjamin
in history.
one thing to be
a strong
of count.
Hampshire, where he had
It is as
Scientific
There
title
part of
nation), and the Ba-
Count Rumford, "Rumford" being
his first wife.
Thompson
the
(now
Mmd
said in
Rumford's favor:
yearning for knowledge.
From boyhood,
He he
Rumford and Heat
showed an
active
73
and shrewd mind that could pierce to the
core of a problem.
In the course of his teresting experiments
life,
Rumford conducted many
and came to many important conclu-
But the most important of
sions.
in-
all
took place in Bavaria,
after
he had been placed in charge of manufacturing can-
nons.
A cannon was made by casting metal in the proper The
shape.
metal then was hollowed out to form
solid
the interior of the cannon.
was used
Of
and gouge out the
to scrape
course, the
A rapidly turning boring tool interior.
cannon and the boring
tool
grew
hot.
Streams of cold water had to be sprayed on them constantly.
Rumford watched
mind began Just
to
the heat develop and his active
work.
what was heat anyway?
Scientists of the time, including the great ist
Lavoisier, felt that heat
called caloric.
As more
stance, that substance
was
caloric
a weightless fluid
was squeezed
grew hotter and
feel the
at quite a distance.
could be
warmth from
The warmth
felt at a distance
they
into a sub-
hotter. Eventually,
the caloric overflowed and streamed out in
Thus, you could
French chem-
all
directions.
a red-hot object
of the sun, for example,
of 93,000,000 miles.
If a
hot
object was placed in contact with a cold one, caloric
flowed out of the hot object and into the cold. caused the hot object to cool to
warm
up.
down and
The
flow
the cold object
74
Great Ideas of Science
The
theory worked quite well and very few
questioned caloric
it.
But Rumford
did.
He wondered why
was breaking the metal
it
was because the boring cannon
inside the
caloric contained in the metal therefore like
the
was pouring out of the cannon. People who be-
lieved in the caloric theory said tool
scientists
The
to bits.
came pouring out
water from a broken jug.
Rumford looked over
Indeed?
the boring tools and
found one that was completely blunted and worn down.
The workers
''Use that one," he said.
used up, but
Rumford
objected that
repeated his order
was
it
more sharply and
they scurried to their labors.
The blunt borer turned uselessly. the metal at
new
borer.
all,
but
it
It
did not cut through
developed even more heat than a
The workers must
have wondered
why
the
count looked so pleased.
Rumford saw
that caloric
break-up of the metal. In at all?
The
have held
was not
fact,
did
it
released through the
come from
metal was cold to begin with, so
much
caloric.
Yet
caloric
it
the metal
couldn't
seemed to flow out in
unlimited quantities.
Rumford measured
the caloric flowing out of the can-
non by noting how much the water was heated up cooled the boring tool and cannon.
If all that caloric
as
it
were
put back into the cannon, he concluded, the cannon would melt.
Rumford and Heat
75
Particles in
Rumford decided
that heat
Motion
was not
form of motion. As the borer ground
a fluid at
all,
but a
against the metal,
its
motion was converted into quick, tiny motions of the
making up the
particles
metal.
It
didn't matter
whether
the borer cut or did not cut through the metal.
It
was
those quick, tiny particle-motions that resulted in heat.
Naturally, heat
would continue
the boring tool turned.
do with any
For
caloric that
as
Heat production had nothing
to
might or might not be
fifty years afterward,
Scientists
as
in the metal.
Rumford's work was ignored.
were content to deal with
out theories explaining
produced
long
to be
how
it
caloric,
and to work
flowed from one body to
another.
Why?
Part of the reason was that they hesitated to ac-
cept the idea of tiny particles undergoing a quick, tiny
motion that no one could
About ten
see.
years after Rumford's work, however, John
Dalton advanced the atom theory
by
little,
Wasn't ticles
it
scientists
(see
Chapter
5).
Little
were accepting the existence of atoms.
possible, then, that
Rumford's small moving par-
were atoms or molecules (groups of atoms)?
Perhaps. trillions
But
upon
how was
trillions
one to imagine the motion of
of invisible molecules? Did they
all
76
Great Ideas of Science
move
Did some move one way and some an-
together?
some neat pattern? Or did they un-
other, according to
dergo random motion^ each one moving in any direction
and
at
any speed, with no way of telHng the direction and
speed of any particular molecule? If the
molecules did engage in random movement,
how
could one possibly make sense out of such a condition? In the middle 1700's, a
few decades before Rumford's
work, a Swiss mathematician named Daniel Bernoulli had tried to handle the
problem of random motion of
This attempt was well before
in gases.
scientists
particles
accepted
an atomic theory, and Bernoulli's mathematics wasn't quite detailed enough.
Still, it
was
a
good
try.
In the 1860's, James Clerk Maxwell came on the scene (see
Chapter
making up
8).
gases
Maxwell assumed
were engaged
keen mathematical
analysis,
movement provided
in
that the molecules
random movement. By
he showed
how random move-
a neat explanation of the
behavior of
gases.
Maxwell showed how
particles of gas
moving
at
random
could create a pressure against the walls of a vessel that held them.
Furthermore, that pressure would change
the particles
were forced together or
to spread apart. is
known
from
a
if
if
they were allowed
This explanation of the behavior of gases
as the kinetic
theory of
Greek word meaning
Maxwell usually
gases.
("Kinetic" comes
''motion.")
shares the credit for the theory with
Rumford and Heat
77
the Austrian physicist
worked
it
Ludwig Boltzmann. The two men
out independently at about the same time.
Maxwell's Solution One a gas
of the important laws of gas behavior states that
expands
as
temperature goes up and contracts
as
tem-
perature goes down. According to the caloric theory, the
As
explanation for this behavior was simple. up, caloric pours into so the gas expands.
it.
As
More
caloric needs
a gas heats
more room,
a gas cools, caloric leaves
and the
gas contracts.
What
did
Maxwell have
periment must have been in motion. faster
As
a gas
is
heated,
his its
mind. Heat
molecules
and nudge each other farther
expands.
When
Rumford's ex-
to say to that?
is
move
apart.
a
form of
faster
Thus
and
the gas
the temperature drops, the reverse hap-
pens and the gas contracts.
Maxwell worked out an equation which showed the range of speed that gas molecules would have temperature.
at
any given
Some molecules moved slowly and some
quickly, but most
moved
at
an intermediate speed.
these various speeds, one particular speed able at a given temperature.
As
Among
was most prob-
the temperature rose, this
most probable speed increased. This kinetic theory of heat could apply to liquids and
Great Ideas of Science
78 solids, as
well as gases. In a solid, for instance, molecules
might not stead,
fly
about
like bullets, as
they did in
The
they might vibrate about one spot.
this variation
followed Maxwell's equation,
gases.
In-
speed of
as did the
speed
of the bulletlike molecules in gases.
A
Better Explanation
All the properties of heat could be explained just as well
by
the kinetic theory as
by
the caloric theory. Indeed, the
kinetic theory easily accounted for as those described
had
by Rumford)
some properties (such
w^hich the caloric theory
failed to explain adequately.
The
caloric theory
flow of caloric from
a
had described heat transfer
as the
hot object into a cold one. Accord-
ing to the kinetic theory, heat transfer resulted from the
movement
When
of molecules.
contact with a cold one,
its
a hot
body was placed
fast-moving molecules collided
with the slow ones of the cold body. As molecules slowed
down
a bit
up. Thus, heat "flowed"
The
in
a result, the fast
and the slow ones speeded
from the hot body
understanding of heat
as a
to the cold.
form of motion
is
one
of the great ideas of science. Maxwell enlarged this great idea into an even greater one.
He showed how random
motion could be used to explain certain
definite laws of
nature whose effect was totally predictable, not at
all.
random
Rumford and Heat
79
Maxwell's idea has been expanded very century.
dom
Scientists
now
take
it
much
in the past
for granted that the ran-
behavior of atoms and molecules can bring about the
most amazing
results.
Even
life
itself
may
have been
created from the nonliving matter in the oceans through the
random movements
of atoms and molecules.
10 Joule and Energy
From prehistoric times, man has realized that motion can accomplish tasks and do work. Place a rock on a nut and
nothing will happen. But bringing larly,
it
down on
set the
rock in motion by quickly
the nut, and the nut will crack. Simi-
an arrow in rapid
flight
the thick hide of an animal.
can force
And many
its
way through
of us have seen
Joule and Energy
81
wreckers shatter a brick wall by swinging a ponderous steel ball against
The
it.
do work
ability to
is
A
called "energy."
moving
object possesses energy of motion, or "kinetic energy."
When Newton
stated his laws of
motion
in the 1680's,
he maintained that any object in motion would continue
moving
same velocity unless acted on by an outside
at the
moving
force (see Chapter 7). In other words, a kinetic energy
But
would always remain
object's
the same.
in the real world, outside forces are always operating
against
moving
A
appear.
ball rolling
A
to a halt.
objects and kinetic energy seems to dis-
A meteorite
along the ground slows and comes
bouncing marble flashes
through the
finally dribbles to a stop. air
and
is
stopped by the
earth.
What
happens to the kinetic energy in
Some, but not
all,
of
it
may
and
still
their kinetic
these cases?
be converted to work. In
the bouncing marble and rolling ball all
all
fact,
may do no work
at
energy will disappear.
The Answer: Heat The heat as that
it
meteorite offers a hint. it
passes
through the atmosphere
glows white hot.
Heat!
It creates a
—
great deal of so
much
heat
Great Ideas of Science
82
Enter
(JOWL)
an
English
James
scientist,
Prescott
Joule
A rather sickly childhood had left Joule unable
.
to lead an active
life,
world of books
so he retired to the
and became intrigued with science. Fortunately, he was the son of a wealthy brewer the best tutors to his son.
who
could afford to bring
Joule eventually inherited the
brewery, but he always remained more interested in science than in the world of business. Joule's interest centered
tion
between energy and
Rumford's
on the problem of the connec-
heat.
belief that heat
He must have known about
was
a
form of motion. Ac-
cording to Rumford, heat consisted of the rapid motion of tiny particles of matter (see Chapter 9). If this
appear at
were all.
true. Joule saw, kinetic
The motion
tion against the heat.
ground
it
energy did not
dis-
of a rolling ball produced fricFriction produced
rolled on.
Thus, the motion of the rolling
ball
was slowly con-
verted to the motion of myriad particles of the ball and those of the ground
it
— the
particles
touched.
Heat would then be another form of the energy of motion. Joule thought.
Ordinary kinetic energy would be
turned into heat energy, with no
true of other forms of energy, too. sense.
Electricity and
Perhaps
loss.
It
this
was
seemed to make
magnetism could do work, and so
could reactions between chemicals.
Thus
there
were
electrical energy,
magnetic energy,
and chemical energy. All could be turned into
heat.
For
Joule and Energy
instance,
83
magnetism could produce an
would heat
a wire.
And when
electric current that
coal burned, the chemical
reaction of the coal and air could produce a great deal of heat.
Heat was
just
another form of these other kinds of
energy. Joule reasoned.
Therefore, a given quantity of
energy always ought to produce a given quantity of In 1840, as a
make very
heat.
young man of twenty-two, he began
to
careful and accurate measurements to test this
possibility.
Joule stirred water or mercury with paddle wheels and
measured the energy of the moving paddle wheels and the temperature rise in the liquid.
He
compressed
air,
then
measured the energy that had gone into the compression
and the heat that developed through narrow tubes.
He
in the
air.
produced an
a coil of
wire by rotating the
magnet.
He
coil
also passed a current
He
forced water
electric current in
between the poles of
a
through the wire with-
out the help of a magnet. In each case. Joule measured the
energy that was used up and the heat that appeared.
Even on
his
honeymoon he
couldn't resist taking time
out to measure the temperature at the top and bottom of a waterfall, to see
how much
heat had been produced
by
the energy of the f alHng water.
By
1847, Joule
was
satisfied that a
given amount of
energy of any sort always produced a given amount of heat.
(Energy can be measured
in units called ergs,
and
84
Great Ideas of Science
heat
is
measured
orie of heat
in calories.)
was produced whenever about 41,800,000
ergs of energy of any kind
between energy and heat
were used up. This
is
established in Joule's honor.
we
relationship
called the "mechanical equiva-
Later, a unit of energy called a joule
lent of heat."
ergs;
Joule showed that one cal-
A joule
is
was
equal to 10,000,000
can then say that one calorie equals 4.18
joules.
Reluctant Listeners
Joule had trouble announcing his discovery, for he was neither a professor nor a
He
was
not
listen.
in
and the
just a brewer,
few months
later,
They would
except that a young
make
son, rose to
tific
a
Manchester news-
he managed to make the same scientists,
but they listened
have dismissed the whole subject,
man
in the audience,
points in
comments were
so
William
sympathy with
shrewd and clever
Joule.
Thomson became one Thus,
He it
is
was
better
ThomThom-
that the scien-
audience could not help but take notice.
century.
day would
his lecture in full.
speech before an audience of
son's
scientists of the
— and then convinced
paper to publish
coldly.
of any learned society.
Finally, Joule decided to give a public lecture
Manchester
A
member
(In later
life
of the great scientists of the 19th
known by
established that
the
title
Lord Kelvin.)
any form of energy could
Joule and Energy
85
be turned into only a fixed amount of heat. But heat
was
a
form of energy. Might
it
itself
not be that energy could
never be destroyed or created? Might
it
not be that energy
could only be converted from one form to another?
Misplaced Credit In 1842, this idea occurred to a Julius
German
scientist
named
Robert Mayer. At that time, however. Joule's work
had not been heard of and Mayer himself had made very
few measurements. Mayer's plucked out of thin
air,
belief
seemed
like
something
and no one would pay any atten-
tion to him.
Another German
Hermann Ludwig Ferdinand
scientist,
von Helmholtz made the same statement parently without
ready to
It is
1847, ap-
of Mayer's prior work.
work had been
time Joule's last
knowing
in
published.
Scientists
By
this
were
at
furthermore, to be impressed.
listen and,
Helmholtz, therefore,
who
is
usually given credit
known as "the law of conservation of energy." The simplest way of stating this law is as follows: The total for
what
is
energy of the universe
Mayer
tried to
same thing
is
constant.
remind the world that he had
in 1842, but
said the
everyone had forgotten or had
never heard. Poor Mayer was accused of trying to credit.
He was in such
despair that he tried to
kill
steal
himself
86
Great Ideas of Science
by jumping out
window.
of a
more
lived in obscurity for thirty
the end of his
life
He
survived, however, and
years. It
was only toward
that Julius Mayer's importance
was
realized.
The law first
of conservation of energy
is
often called "the
law of thermodynamics." Ever since the early part
of the nineteenth century, scientists had been investigating the jflow of heat called
from one object
to another. This study
is
"thermodynamics" (from Greek words meaning
"motion of heat"). Once the law of conservation of energy was accepted, studies of
it
had to be taken into account in
all
thermodynamics.
Carnot's Engine
At
the time that the law of conservation of energy was
established, students of
thermodynamics already
realized
that energy could not always be completely turned into
work. Some of
it
always dribbled away
how they tried to stop it. The first to show this by a
young French
physicist,
as heat,
no matter
careful scientific analysis
was
Nicholas Leonard Sadi Carnot.
In 1824, he published a small book on the steam engine. In
it
he presented arguments to show that the heat energy
turned out by a steam engine could not produce more than a certain
amount of work. The amount of work depended
Joule and Energy
on the
87
difference in temperature
between the
of the steam engine and the coldest. it
— no matter how much heat
built up.
it
the entire steam
If
engine were at one temperature,
hottest part
would produce no work
Once Helmholtz had announced
the law of conserva-
tion of energy, scientists turned back to Carnot's proofs
of the limited
Why
work they could
was the work usually
so
get out of a steam engine.
much
less
than the energy
produced by the engine? Temperature differences affected the
work
that this
obtained, yes
was
so
— Carnot
had shown
brilliantly
— but why? Clausius' Ratio
In 1850, the Clausius
German
physicist
Rudolf
(KLOW-zee-oos) worked out
of the phenomenon.
He
did that
Julius
Emmanuel
the mathematics
by means
of the concept
of absolute temperature^ or the temperature above absolute zero.
No
heat
is
present at absolute zero, that
degrees Fahrenheit or Clausius found that
of a system
by
its
—273 if
he divided the total heat energy
any natural process
was the burning of
The more
—460
degrees centigrade.
— whether
coal in a steam-engine sys-
tem or hydrogen and helium exploding tem."
at
absolute temperature, he obtained a ratio
that always increased in
the process
is,
in the sun's "sys-
rapidly that ratio increased, the
less
work
88
Great Ideas of Science
could be obtained from heat. this ratio
1865 Clausius had named
"entropy."
Does entropy For example,
when
By
increase in every natural process? It does.
it
increases
hot objects cool,
iron rusts,
when meat
when
warm up, downhill, when
cold objects
when water
pours
decays, and so on.
fact that entropy always increases
is
Nowadays
the
called "the second
law of thermodynamics." This law can be expressed more simply
as follows:
The
total
entropy of the universe
is
always increasing.
The
first
and second laws of thermodynamics are per-
haps the most fundamental statements yet made by scientists.
No
ever will.
one has ever found exceptions; perhaps no one
As
nearly as
entire universe,
we
from the
can
tell,
the laws apply to the
largest collections of stars to the
smallest subatomic particles
known.
Despite the revolutions that scientific thinking has un-
dergone in the have held firm.
last
century, the laws of thermodynamics
They remain
of physical science.
a secure foundation for all
KIICMHGI'I
11 Planck and Quanta
In the mid-nineteenth century light
science discovered that
provided each chemical element with a "set of finger-
prints."
How
could light be used to distinguish one
ele-
ment from another? If
an element
will be
is
heated until
made up of waves
it
glows, the light
of various lengths.
it
emits
The group
90
Great Ideas of Science
wave
of
from
lengths the element produces will be different
any other element.
that of
Each
individual
on the eye and
is
wave length produces
thus seen as a different color. Suppose
from
that the light
lengths should then
But
up
how
element
a given
The
various waves.
a different effect
is
separated into
element's unique group
show up
as a
of
its
wave
unique pattern of colors.
can the light from a glowing element be broken
into individual waves?
One answer
is
to pass
it
through a
slit
a triangular piece of glass called a prism.
and then through
The
prism bends
each wave by a different amount, according to In this way, the prism forms images of the
slit
its
length.
in the par-
ticular colors associated
with the element's wave lengths.
The
(plural, spectra) of colored lines
result:
spectrum
a
whose pattern
is
different
from
that of
This procedure was worked out in
German hof).
physicist,
He
detail in
Gustav Robert Kirchhoff
1859 by a
(KIRKH-
and the German chemist Robert Wilhelm von
Bunsen invented the spectroscope scribed above
elements.
any other element.
— and used
They
— the
instrument de-
it
to study the spectra of various
discovered
two new elements when they
found patterns unlike the spectrum of any known element. Later, other scientists
found the patterns of earthly
ments in the spectra of the sun and the
stars.
On the
ele-
other
hand, the element helium was discovered in the sun in 1868,
many
years before
it
was detected on
earth.
These
Planck and Quanta
91
spectra studies finally demonstrated that the same matter
made up
all
the universe.
Kirchhoff' s most important finding was
given element was heated until
this:
When
gave off light of certain
it
wave
lengths, the element tended to absorb those
wave
lengths of light
when
Black
If
appear black.
was
same
a bit cooler.
Body Concept
an object absorbed
would be none
it
a
all
the light that
For
left to reflect.
fell
on
this reason,
Such an object could be
it,
it
there
\\'ould
called a "black
body."
What ought to happen when such a black body is heated until
it
glows? According to Kirchhoff's finding
give off light of every possible
absorbed them
all.
It
wave
it
should
length, since
it
has
happens that there are far more wave
lengths in the invisible ultraviolet end of the electromagnetic spectrum (the system of
energy) than in
all
possible
all
of the visible spectrum
lengths that produce visible light).
seem that lengths,
if a
black
most of the
ultraviolet
In the
wave lengths of
body could light
It
(the
wave
\\-ould therefore
radiate light of
would come from
all
wave
the violet and
end of the spectrum. 1890's
an English physicist. Lord Raylcigh,
worked out an equation based on
the
way
light
was then
92
Great Ideas of Science
His
thought to behave. shorter the
The
wave
shortest
ultraviolet
come
But not?
—
light should be emitted.
lengths of light were in the violet and
end of the spectrum.
off a black
ultraviolet
more
length, the
wave
seemed to show that the
results
body
Thus, the
one quick
in
light should
flash of violet
and
a "violet catastrophe."
had never been observed.
a violet catastrophe
Why
Perhaps because no ordinary object truly absorbs
the light that
on
falls
no object can be
If so,
it.
true black body, although physicists in theory. Perhaps
if
a true black
all
called a
work with such bodies
body
really existed, the
violet catastrophe could be observed.
About worked
the same time
German
the
out,
equation was
that Rayleigh's
physicist
Wilhelm
Wien
(VEEN) thought he knew a way to produce a black body. He used a chamber with a small hole in it. Light of any wave length entering
the hole, he thought,
would be ab-
sorbed by the rough inner wall of the chamber. the light
was
reflected,
it
would
If part of
strike another portion of
the inner wall and be absorbed there.
Once again
the light entered,
from the
hole.
it
The
and would therefore act
should not survive to emerge
hole
would be
as a true
ber was then heated until
its
a total absorber
black body. If the cham-
interior glowed, the light
that radiated out of the hole should be black
Did the
body radiation.
light radiate as a violet catastrophe?
Unfortunately,
it
didn't.
Wien
studied the radiation
Planck and Quanta that did
wave
93
emerge and found that
it
grew more
intense as the
lengths shortened (just as Rayleigh's equation pre-
There was always some
dicted).
where
was most
radiation
intense.
would
tensity of radiation
But
The
after that, the in-
although the wave
decline,
lengths continued to shorten.
hotter
wave length
the chamber, the shorter the
wave length
particular
Wien
after
decline of radiation intensity began, but there
heated
which the
was never
a
violet catastrophe.
Wien
tried to
work out an
the short and long his "black
wave
lengths of light were radiated
body," but the
were
results
Max
German
Planck. Perhaps light was radiated only in
fixed amounts, he supposed.
He
didn't
those amounts might be, so he called lar,
by
unsatisfactory.
In 1899 the problem was tackled by another physicist.
how
equation that described
quantwn), from
Up until then,
all
a Latin
know how
them quanta
large
(singu-
word meaning "how much?"
forms of energy, including
light,
were
believed to exist in quantities as small as could be imagined.
But Planck was suggesting that
this
was not
so.
He
sug-
gested instead that energy, like matter, existed only as particles
of certain
size.
There could not be smaller
quantities
of energy than those he called quanta. Thus, quanta were
"packets" of energy, just as atoms and molecules were "packets" of matter.
Planck supposed that in size according to the
a
quantum of energy would vary
wave length
of the light
— the
94
Great Ideas of Science
shorter the
wave
plied this idea to the
them It
to
would be easy for
small quanta.
a short
for a black
body
it.
It
enough energy
could easily radiate
radiated unless large
would be much more
It
difficult
to gather these large quanta.
at
in a large store
would be easy for you
But you would have
impossible to carry so
and were told
provided you paid cash in
all,
to
buy
a ten-cent
a great deal of trouble
a thousand-dollar item because it
it
wave length could not be
you could buy anything coin for
to gather
which required smaller quanta.
though you were
It is as
body
Therefore,
light,
quanta were gathered.
item.
waves in the form of quanta.
a black
long wave lengths of
But
ap-
problem of black bodies and supposed
to be radiating light
make
He
length, the larger the quantum.
many
buying
you probably would
find
coins.
Planck succeeded in working out an equation to describe
body
black
radiation in terms of quanta.
The
equation
backed up Wien's observation that there w^s some length at which radiation would be most intense.
wave
lengths shorter than that, the black
difficulty in
But,
if
producing the larger quanta
the black
temperatures, shorter
more
wave
lengths
would be
made up of
For
body would have necessar\'.
body chamber were heated energ>'
\v2LVt
available.
to higher
Therefore,
larger quanta could be
produced.
However, was too
there
short,
would always be
even for
a
a \\'ave length that
strongly heated black body. It
Planck and Quanta
95
would then be impossible
Therefore, there could never be
required.
In
trophe.
to emit the very large quanta
much
the same way, there
a violet catas-
would always be
something too expensive for the amount of coins you could carry.
Planck's it
did not
cists
"quantum theory" was announced
make much
were already
of a splash at
first.
in 1900,
but
However, physi-
setting the stage for such a ''splash" as
they began to study the peculiar behavior of particles smaller than atoms (subatomic particles).
Some existing
of this behavior could not be explained \\ith
knowledge. For instance,
tain metals,
why
fell
on
cer-
did tiny subatomic particles, called "elec-
way
The
was
able to
from atoms on the surface of the
metals.
wave
lengths
trons," behave the eject electrons
when hght
they did?
But these electrons were ejected only
if
light
the
of light falling on the metals were shorter than a certain value.
How
That value depended on were
which was
the nature of the metal.
physicists going to explain this
phenomenon,
called the ''photoelectric effect"?
In 1905 Albert Einstein came up with the answer.
He
used the quantum theory to explain the photoelectric effect.
When
long wave lengths of light
metal, the quanta of these to
knock out any
as the
wave
lengths
large
grew
on
a
would be too
electrons, Einstein suggested.
lengths
would become
wave
fell
given small
However,
shorter and shorter, the quanta
enough
to eject electrons.
96
Great Ideas of Science
why
Thus, Einstein explain^ed until the
wave length
was shorter than
The answer
electrons weren't ejected
of the light shining
a certain critical
on the metal
amount.
to the puzzle of the photoelectric effect
a great victory for the
was
quantum theory, and both Planck
and Einstein eventually were awarded Nobel prizes for their
work.
The quantum
theory again proved
on the structure of the atom. the
atom consisted of
its
value in research
Physicists had decided that
a relatively massive central nucleus
around which one or more electrons moved in circular paths, or orbits.
time,
According
to the physical theories of the
the electrons should have radiated light as they
and collapsed into the nucleus of the
circled, lost energy,
atom. But electrons kept on circling the nucleus and did
not collapse into
it.
It
was obvious
that the older theories
could not explain the motion of electrons. In 1913, however, the Danish physicist Niels Bohr
(BAWR) Bohr
applied the
said that
amounts, that
quantum theory
to atomic structure.
an electron could emit energy only in fixed is,
in
emitted, the electron
whole quanta.
would
the nucleus of the atom.
take up a
As
the energy
new
orbit closer to
Correspondingly, the electron
could absorb only whole quanta, taking up a farther
new
from the nucleus. The electron could never
lapse into the nucleus, for
the closest orbit permitted
was
it
orbit col-
could never come closer than
by
its
energy
state.
Planck and Quanta
97
Answers and Understanding By
considering the different orbits allowable, physicists
were
able to understand w^hy each element radiated only
certain
wave
lengths of Hght, and
was always the same Kirchhoff 's
Then in
rule,
why
the Hght absorbed
In
as the light emitted.
which
started
it all,
was
this
way
finally explained.
1927 the Austrian physicist Erwin Schrodinger
(SHROI-ding-er) worked out the mathematics of the
atom according
to
quantum mechanics.
Schrodinger's
explanation took in practically every aspect of the study of the atom, and his
In fact, even the
way
work in
is
crucial to atomic research.
which the atom
stores
and
energy couldn't possibly be understood without
Quantum mechanics physics
is
is
now
it.
modern
considered to date only from Planck's announce-
ment of the quantum theory is
so important that
releases
called classical physics.
in 1900. Physics before 1900
Planck's relatively simple idea
succeeded in changing completely the direction of the science of matter and motion.
Hippocrates and Medicine How WONDERFUL the miraclc of life Hving things complicated,
are!
The
more
is,
and
how amazing
smallest plant or animal seems
intriguing,
more
than the largest mass of
nonliving matter imaginable.
NonHving
matter, after
most of the time. Or a
if it
all,
seems to do nothing
does do something,
mechanical and rather uninteresting way.
it
at all
does so in
Consider a
Hippocrates and Medicine
99
rock lying in the road. lie
there forever.
stop.
Kick
throw
it
you kick
If
harder and
it
up
nothing disturbs
If
in the
air, it
will
it
will
move
shape and
come down. And
hammer,
will break.
With will
it
a little experience
happen to
You
a
rock
it
it,
will just
farther.
you
If
in a curve of a particular
you
if
it
move and then
will
move
it,
hit
it
with a sledge
you can predict exactly what
when any
given thing
is
done
to
it.
can describe what happens in terms of cause and
effect.
If a particular thing
happen
particular thing will
The
effect).
is
belief that the
done to
a
rock (a cause),
a
to the rock as a result (an
same cause will bring about
the same effect every time leads to a view of the universe, called
the
"mechanical
view,"
or
"mechanism"
(see
Chapter 8).
Predictable Universe
Even something
as
remarkable
mechanically every morning and evening.
If
dict exactly
you watch
when
as well as exactly
ancients
it
it
as the set
carefully,
will rise
and
set
you can
rules to predict the
were never broken.
learn to pre-
every day of the year,
and the other heavenly bodies, and the lated
rise
mechanically every
what part of the sky
worked out
sun seems to
it
will cross.
The
motion of the sun rules they
formu-
100
Great Ideas of Science
About 600 B.C.
Qreek philosopher Thales and
the
his
followers stated their belief that the "natural law" of cause
was
and
effect
(see
Chapter
suppose that
But could
Weren't
1 )
all .
was needed
that
Such natural law made
spirits
this natural
fail
it
unnecessary to
or demons ruled the universe.
law be applied to
to follow the
living things?
unto themselves, and didn't
living things a rule
they often
to understand nature
law of cause and
effect?
Uncertain Result
Suppose you push
a friend.
might manage to keep
his balance.
him he might laugh or turn
He
call
at all or
and try to get back thing
may
at
respond to
fall
down
or he
After you had pushed
you names, or push you
— or he might angrily try
even do nothing
might
to strike you.
He
in re-
might
he might do nothing for a while
you
later.
In other words, a living
a particular cause
with any number
of eif ects. This belief that living creatures don't obey the rules that
Then,
Why
govern the nonliving universe too, consider that
is it
that one
another cannot?
is
called "vitalism."
some men have unusual
man can
Why
is
abilities.
write beautiful poetry while
one
man
a clever leader, or
an
inspiring speaker, or a brave warrior, while others are not?
On
the other hand,
all
men seem
to be basically alike.
Hippocrates and Medicine
All have arms and
101
legs, ears
Then what makes
and eyes, hearts and
brains.
the difference between an unusual and
an ordinary man?
To
man might
the ancients, a
favored by some personal
Greeks
be unusual because he was or guardian angel.
spirit
called such spirit a daimon^
We
word "demon."
great deal seems to be "possessed
word
Similarly, the
great
meaning "possessed by
work
is
said to
word meaning self
an
invisible spirit.
And
Latin version of the Greek Naturally, these
work
evil for
man
ancients said he
comes from
spirits
the
that
is,
a
Greek
A man who
a god."
—
a
which means "un-
be "inspired," which
"to breathe in"
who works
by demons."
"enthusiastic,"
usually interested in something," pression
and that became our
say that someone
still
The
to
is
from
draw
word "genius"
is
ex-
does
a Latin
into one-
from the
word davmon. and demons were expected to
as well as
good.
man became ill, the evil spirit. The belief
If a
was possessed by an
seemed most valid when a man began to say and do foolish things.
No man
would
willingly act foolish, so people
blamed "the demon within him." Therefore, societies the
and
respect.
mentally
ill
in primitive
were sometimes treated with awe
The madman was
considered to have been
touched by the finger of some supernatural being (and
we still use the word who seems not quite in
"touched" to described someone his right
mind).
102
Great Ideas of Science
The "Sacred The
disease epilepsy,
Disease"
which we now know
to be a dis-
order of the brain, also seemed to be caused by a
spirit.
Occasionally, a person with this disorder loses control of his
body
reason,
for a
the
few minutes.
disease
was
thrash about, and so on. little
of
He
called
might the
fall
down
"falling
(for this
sickness"),
Afterward, he remembers very
what happened. People watching such an occur-
rence in ancient times were sure they saw a
body and throw
the stricken person's
Greeks therefore referred t6 epilepsy
demon
enter
about.
The
it
"sacred dis-
as the
ease."
As long the
as illness
method of
tific.
was looked on
treating
it
in this unscientific
was bound
way,
to be just as unscien-
To coax or frighten away the demons was considered
the proper
method of treatment. Primitive
"witch doctors" to cast supposed to make the
spells
tribes
and perform
still
rites that are
evil spirits leave a sick person.
people believe that the sick person will get well as the evil spirits
have
as
The soon
have been cast out.
The Greeks had
a
god of medicine,
called Asklepios
(as-KLEP-ee-os), and the priests of Asklepios were doctors.
On the
Greek
island of Kos, in the
off the western coast of
Aegean Sea
(just
modern Turkey), stood an im-
portant temple of Asklepios.
About 400 B.C.
the greatest
Hippocrates and Medicine
103
doctor on the island of Kos was a
man named Hippocrates
(hih-POK-ruh-teez). Hippocrates' view point was
new
to the Greeks, for he
beHeved in treating the patient rather than worrying about the
do
demon
The
so.
have had is
inside him.
many
work
name
that
not the
in history to
first
old civiUzations in Babylonia and
a legend that
the
He was
doctors
who
took
Egypt must
this attitude,
and there
But
Hippocrates studied in Egypt.
of Hippocrates that has survived and is
it
it
is
is
his
remembered.
A
Sensible School
Hippocrates established a school that continued for centuries.
The
doctor of his school used
treating patients.
They
didn't have
common
modern
equipment, or theories. But they did have
and the
sense in
medicines,
common
sense
ability to observe things keenly.
Hippocrates' followers believed that doctors should keep their patients
— and
themselves
the sick should have fresh
air,
—
clean.
They thought
comfortable and restful sur-
roundings, and a balanced diet of simple food.
worked out
They
sensible rules for stopping bleeding, for clean-
ing and treating wounds, for setting broken bones, and so on.
All extremes were avoided, and
were ignored.
all
magical
rites
104
Great Ideas of Science
The
Hippocratic school are
writings of the' entire
lumped
together, and
it is
impossible to
wrote a particular part or when
known
as
medical practice,
it is still
''Hippocratic oath''
The
200 A.D.,
six centuries after
best guess
he prepared to enter
it
when they
his
are graduated.
is
that
it
came
Hippocrates
into use about lived.
any Hippocratic writing that we can
to Hippocrates himself?
There
oldest of these writings that
by Hippocrates. deals
an oath taken by
was not written by Hippocrates,
however.
it
is
used as a guide for physicians.
Medical school students recite
there
who
Because the oath upholds the highest ideals of
profession.
Is
exactly
was written. The best
of these Hippocratic writings
each doctor of the school
The
it
tell
It is called
is
one
treatise
attribute
among
the
may well have been written "On the Sacred Disease" and
with epilepsy.
Demons Dismissed This
treatise
strongly maintains that
blame demons for cause,
and
the cause
Every
disease has
is
useless
to
some natural it.
Once
known, the cure may be found. And
this is
it is is
disease.
it
the task of the doctor to discover
true, the treatise states,
ening disease epilepsy. a sickness like
even of that mysterious and frightIt is
any other.
not a sacred disease
at
all,
but
Hippocrates and iMedicine
What and
105
the treatise says, in effect,
is
that the idea of cause
effect apphes to living things, including
living things are so complicated,
and
trace cause
and must
effect relations.
it
may
But
man. Because
not be simple to
in the
end
can
it
—
— be done.
Medicine had to struggle for against the
common
belief in
many more
demons and
against the use of magical rites
and
centuries
evil spirits,
spells as cures.
and
But the
views of Hippocrates were never entirely forgotten. Because of Hippocrates' ideas on the treatment of the often called the "father of medicine." Actually,
sick,
he
he
even more than
is
is
that.
He applied the notion of natural
law to living things and thus took the
Once
vitalism.
natural law
could begin to study therefore
he
may
made
also
it
first
was applied
systematically.
great step against to
life,
scientists
Hippocrates' view
a science of life (biology) possible,
be considered the "father of biology."
and
TWO
AW^INO ACI
MOLECULES
ALANINE NlTROOEM
I.
CARBON
MVOROGCM
OKY6CK
13 Wohler and Organic Chemistry In 1828 A YOUNG German
chemist, Friedrich
(VOL-ler), knew exactly where
his
Wohler
interests lay
—
in
studying metals and minerals. Such substances belonged to the field of inorganic chemistry,
which
dealt with sub-
stances that supposedly had nothing to do with
was
also organic chemistry,
formed
life.
There
deahng with chemicals that
in the tissues of living plants
and animals.
C
1
Wohler and Organic Chemistry
107
Wohler's teacher, the Swedish chemist Jons
J.
Berzelius
(ber-ZEE-lee-us), had divided chemistry into these two
BerzeHus
classifications.
further
insisted
that
organic
chemicals couldn't be formed from inorganic chemicals in the laboratory.
They
could be formed only in living
tissue
because they required some "vital force."
Vitalist Berzelius
was
Chapter 12).
View
a vitalist, a believer in "vitalism"
He believed that living matter followed laws by nonliving
of nature different from those followed
More than two thousand
matter.
(see
years earlier, Hippocrates
had suggested that the same laws of nature held for both.
But that was
hard to believe, since living
still
so complicated
and
its
tissue
was
functions so hard to understand.
Many chemists were therefore sure that the simple methods of the laboratory stances
found
would never do
for the complex sub-
in living organisms.
So Wohler worked with inorganic chemicals, never dreaming he was about to revolutionize the
field
of organic
began with an inorganic chemical called
chemistry.
It all
ammonium
cyanate.
When Wohler
heated
it, it
changed
into another substance. In order to identify the substance,
Wohler
studied
its
properties.
As
factor after factor
checked out, he grew increasingly astonished.
1
Great Ideas of Science
08
To
play
safe,
it
he repeated the experiment again and
again, but the result
Ammonium
was always the same.
cyanate, an inorganic substance, had turned into urea, a
well-known organic compound. Wohler had done something Berzelius considered impossible:
He
had formed an
organic substance from an inorganic one simply
ing
by
heat-
it!
Wohler's pioneering discovery was a revelation, and other chemists tried to inorganic ones.
make organic compounds out
One French
chemist, Pierre E. Berthelot
(behr-teh-LOH), made dozens of such compounds 1850's.
At
of
in the
the same time an English chemist, William
H.
Perkin, was forming a substance that resembled organic
compounds where
in
its
was not
properties, but
in the realm of
life.
formed only also
make
compounds followed.
tissues
now make compounds
in living tissue.
additional
found any-
Thousands and tens of thou-
sands of such synthetic organic
Chemists could
to be
that
nature
Furthermore, they could
compounds of
the same sort that living
could not produce!
However, planations.
these facts did not
vitalistic
ex-
Chemists might be able to produce the same
compounds made by manner, the
wipe out
living tissue, but hardly in the
vitalists said.
Living
tissue
produced
its
same sub-
stances under conditions of mild temperature and with
only the most gentle substances.
The
chemist had to use
considerable heat, or pressure, or strong chemicals.
Wohler and Organic Chemistry
how
But chemists did know at
room temperature
The
with heat.
trick
mixed with
it
to cause certain reactions
that ordinarily
platinum, for instance,
flame as
109
was
would take
Powdered
to use a catalyst.
would cause hydrogen
Without
air.
place only
to burst into
the platinum, heat
was
required to bring on the reaction.
Catalysts of Life
therefore seemed clear that living tissue had to contain
It
catalysts,
but catalysts of no kind
catalysts of living tissue
were extremely
amount would bring about also
known
to man.
efficient.
The
A tiny
They were
a large reaction.
extremely selective. Their presence would cause par-
ticular substances to
substances
Then, action.
undergo changes, while very
would not be
similar
affected.
too, the catalysts of life
were
easily
put out of
Heat, strong chemicals, or small quantities of cer-
tain metals or other substances
would stop
their action,
usually for good.
These
catalysts of life
were
called "ferments."
The
best-known examples were the ferments in the tiny yeast cells.
Since the
dawn
of history,
ments to make wine from puffy breads from
flat
In 1752 a French
man had
fruit juices
used these fer-
and to make
soft,
cakes of dough. scientist,
Rene A.
F. de
Reaumur
Great Ideas of Science
1 1
(ray-oh-MYOOR),
hawk and showed how? The
obtained some stomach juices from a
that the juices could dissolve meat.
juice itself
was not
living.
The answer seemed
Chemists shrugged.
But
easy enough.
There were two kinds of ferments. One kind worked out-
Those were "unor-
side the living cells to digest food.
ganized" ferments.
Then
ments, which could
work only
there were "organized" fer-
ferments in yeast, which broke to
form wine or
inside living cells.
down
The
sugars and starches
were examples of organized
raise bread,
ferments.
By
the middle 1800's the old vitalism had been dis-
credited, thanks to the
But
a
new form
work
of
Wohler and
of vitalism had taken
vitalists said living
its
his successors.
place.
processes could take place only as a
result of the action of organized ferments, exist
only inside living
ments were in fact the In 1876 a
The new
German
cells.
They
which could
said the organized fer-
"life force."
chemist,
Wilhelm Kiihne
(KYOO-
nuh), insisted that the digestive juices not be called unorganized ferments.
with
life, it
The word "ferment" was
might give the impression that
was taking place
outside the
cells.
so associated
a living process
Instead, Kiihne sug-
gested that the digestive juices be said to contain enzymes.
The word "enzyme," from
a
Greek expression meaning
"in yeast," seemed appropriate because the digestive juices
behaved somewhat hke the ferments in
yeast.
Wohler and Organic Chemistry
1 1
Exit Vitalism The new
vitalism
only in living
had to be
If
ferments worked
then anything that killed the
cells,
destroy the ferment. killed,
tested.
To
be sure,
when
cell
should
yeast cells
were
they stopped fermenting. But perhaps they weren't
killed in the right
by strong
heat or
way.
Usually, they were killed
by
Could something
be
chemicals.
else
substituted? It
occurred to a
German
yeast cells might be killed
chemist,
Eduard Buchner,
by grinding them with
The
fine,
cells
and destroy them. But the ferments
that
sand.
hard particles of sand would rupture the tiny
be exposed to heat or to chemicals.
inside
Would
would not
they be de-
stroyed anyway? In
1896 Buchner ground yeast and
filtered
it.
He
studied the juices under the microscope and was certain that not one living yeast cell
"dead"
juice.
He
was present
in
it.
It
was
just
then added a solution of sugar. Bubbles
of carbon dioxide began to
come
off at once,
and the sugar
slowly turned to alcohol.
Chemists
now knew
that "dead" juice could carry out
a process
which they had thought impossible without
liv-
ing
This time vitalism was really smashed. All
fer-
cells.
ments, inside and outside the
cell,
were
alike.
word "enzyme," which he had used only
Klihne's
for ferments
2
Great Ideas of Science
1 1
outside
the
came- to be used for
cell,
all
ferments.
Therefore, by the twentieth century most chemists had
decided that there were no mysterious forces inside living cells.
Whatever
processes took place in tissues were per-
formed by means of ordinary chemicals. Such chemicals could be worked with in
test
tubes
enough laboratory methods were
Isolating an
However, chemicals
scientists
made up
In
delicate
and gentle
used.
Enzyme
had yet to determine exactly what
the enzymes. But
in such small traces that they isolate
if
enzymes were present
were almost impossible
to
and identify. 1926 the American biochemist James B. Sumner
He was working with an enzyme present mashed jack beans. When crystals formed
showed the way. in the juice of in the juice,
duced
a
Sumner
isolated them.
In solution, they pro-
very active enzyme reaction. Anything that de-
stroyed the molecular structure of the crystals destroyed the
enzyme
zyme
action
action.
Nor
from the
Sumner had
could Sumner separate the en-
crystals.
to conclude that the crystals
enzyme. For the
first
time an enzyme had been obtained
in a clearly visible form. Further testing tals to consist
were the
of proteifi. Since then,
proved the crys-
many enzymes have
Wohler and Organic Chemistry
been
113
and without exception they have proved
crystallized,
to be proteins.
A
String of Acids
Proteins have a molecular structure that
understood.
found to
named "amino Fischer,
now
twenty different kinds of smaller
acids."
German
In 1907 a
showed how amino
well
century proteins were
In the nineteenth
consist of
is
units
chemist, Emil
were strung together
acids
in
a protein molecule.
In the 1950's and 1960's a larly
number
an Englishman named Frederick Sanger, succeeded
in pulling protein molecules apart.
able to determine exactly
artificially
formed
In this
which amino
in the molecule. In addition,
were
of chemists, particu-
way
acid
they were
went where
some simple protein molecules
in the laboratory.
Hippocrates' nonvitalistic view has thus been supported
by more than
a
century and a half of painstaking
scientific
work. This careful search for truth has uncovered the processes of a cell and has
shown
that cell
only chemicals, not "ferments" or other
Thus, from Wohler to Sanger,
scientists
life
components are vitalistic forces.
have proved that
the natural laws of the universe govern living, as well as
nonliving, matter.
^f
•^•••^^^^^^^^^^^^^^^^^^^^^Pp»P»P^"^i"i^pPWP^^^^^
ARISTOTLE
LINNAEUS
14 Linnaeus and Classification
Perhaps the most influential
scientific
of the world was that of the
Greek philosopher
mind
in the history
Aristotle
(384 B.C. to 322 B.C.). Aristotle
Academy
was probably the
in Athens.
A
best
known
few years
pupil at Plato's
after Plato's death in
347 B.C., Aristotle went to the kingdom of Macedon, in
Linnaeus and Classification
115
northern Greece, where
There he spent
cian.
his father
had been court physi-
several years as tutor to the
Macedonian prince Alexander, who was
to
young
become Alex-
ander the Great.
When Alexander left on his carer of conquest,
Aristotle
returned to Athens and established a school of his own.
His teachings were collected into what was almost
man
encyclopedia of ancient thought and knowledge.
Many last
one-
a
of these books survived and were considered the
word
in scientific thinking for nearly
two thousand
years.
Influential
The
—
but
influence of Aristotle's ideas
considerable, particularly his views universe,
on the movement of
Wrong on
later scientists
was
on the nature of the and so on
objects,
(see
Chapters 4 and 7). In the area of physical science, however, he
\V2LS
usually wTong.
Aristotle's views ential,
on
biological subjects
but he was actually strongest in
science
was
his favorite subject,
ing the animals of the Aristotle
was not
less influ-
this area.
Natural
and he spent years study-
sea.
satisfied
simply to look
With
his clear
he went further and
classified
describe them.
were
mind and
at animals
and
his love of order,
animals into groups.
Such
6
Great Ideas of Science
1 1
classification
is
now called
"taxonomy," which comes from
Greek words meaning "a system of arrangement."
We can see
All of us have a tendency to classify things. that lions
and
tigers closely
resemble each other, that sheep
resemble goats, that houseflies resemble Aristotle
was not content with such
He listed more than five hundred and carefully grouped
all
more, he arranged these
But
casual observations.
different kinds of animals
them
of
horseflies.
What's
into classes.
from the very
classes in order,
simplest to the most complex.
He
noted that some animals did not belong to the
which they seemed everybody took It lived in
totle
it
to resemble most.
For
instance, almost
for granted that the dolphin was a
the water and was shaped like a
observed that the dolphin breathed
forth living young, and that
it
class
air,
fish.
But Aris-
fish.
that
brought
it
nourished the young before
birth with an organ called a "placenta." In these respects
the dolphin resembled the four-legged beasts of the dry land,
and Aristotle therefore considered
rather than a Aristotle his
right,
but naturalists ignored
conclusion for two thousand years.
fated to be believed
Naturalists
mammal
fish.
was absolutely
when he was
a
it
when
he was
Aristotle
wrong and
seemed
disbelieved
right.
who came
after Aristotle did not carry
his efforts to classify animals.
on
In ancient and medieval
times books describing animals arranged
them
in
any order
Linnaeus and Classification
and ignored the
117
possibility of
grouping together animals
with similar structures. In the 1500's, however, naturalists
tempts
at
made
the
first at-
But these
such classification since Aristotle.
attempts were not very thorough. For example, one writer
might group together
plants with
all
another might do the same for
all
narrow
leaves while
plants with big yellow
flowers.
The totle
first naturalist
to
do
thorough
as
a job as Aris-
was an Englishman named John Ray. Ray traveled
through Europe, studying plants and animals. In 1667 and for thirty-five years thereafter he published books that
described and classified the plants and animals he had studied.
He
began to
two main groups
Then
mammals by
classify
— those with
toes
dividing
them
into
and those with hooves.
he went on to subdivide these classifications accord-
ing to the
number of hooves or
the toes bore claws or
nails,
toes,
according to whether
and according to whether a
hooved animal had permanent horns or horns that were shed. Thus,
Ray
restored the sense of order that Aristotle
had brought to the realm of
Once Ray had shown beyond
Aristotle.
life.
the way, naturalists soon
In 1735 a
young Swedish
named Carl von Linne published listed different creatures
(He
is
better
a small
book
in
naturalist
which he
according to a system of
known by
went
his
own.
the Latin version of his name,
8
Great Ideas of Science
1 1
Carolus Linnaeus [li-NEE-us].)
based his
work on
Europe (including northern
extensive travel throughout
Scandinavia,
He
which had never before been adequately
ex-
plored).
Linnaeus briefly and clearly described each kind, or species
(plural,
also species),
grouped each collection of (plural, genera)
.
Then he
mal two Latin names
He
of plant and animal.
similar species into a genus
gave each kind of plant or ani-
— one for
its
genus and one for
its
species.
For example, the are very
and
much
cat
alike,
and the lion are two species that
even though one
is
much
genus, the genus Felis (Latin for "cat").
A second Latin
serves to distinguish the ordinary cat
from the
and from other species of the genus. Thus, the cat domesticuSy while the lion Similarly, the
Canis ("dog"). is
is
is
is
lion Felis
Felis leo.
dog and the wolf
The dog
larger
Hence, both are in the same
fiercer than the other.
name
so
are both in the genus
Canis familiaris and the wolf
Cajiis lupus.
Linnaeus even gave human beings such a Latin name.
He placed man in the genus Homo ("man") and called the human species Homo sapiens ("man, wise"). Linnaeus' system Actually,
we
is
known
as
"binomial nomenclature."
use a similar system to identify ourselves.
In America, everyone in the same family has a particular family name, but diiferent
first
names. Thus, one brother
Linnaeus and Classification
might be
listed in the
George," and another
119
telephone directory as
time, naturalists the
world over had
useful.
a
uralist
spoke of Canis lupus, other naturalists a wolf.
It
made no
first
system of
Whenever any
to identify different creatures.
meant
For the
common
names
diately he
"Anderson,
"Anderson, William."
work was tremendously
Linnaeus'
as
nat-
knew imme-
difference
what
language they spoke or what familiar name "wolf" might
own
have in their naturalist
meant one
particular kind of wolf, the
The American
gray wolf.
knew
language. What's more, they
the
European
timber wolf, for example, was
a different species, Canis occidentalis.
This
common
system of identification was a very im-
portant step forward.
new
covered
continents, he
the earth and dis-
found more and more
Aristotle had listed only about five
of animals. species,
As man explored
species
hundred
but by Linnaeus' time tens of thousands were
known. Linnaeus' book of animal classification started off with
only seven pages in thousand
five
its first
edition, but
hundred pages by
its
expanded to two
tenth. If naturalists
had
not adopted a standard classification system, they could
not have been certain naturalists
were
would have
discussing.
group
which
The
plants or animals other
study of natural history
collapsed in chaos.
From genus and to
as to
species classification, Linnaeus
similar genera into orders,
and
went on
similar orders into
120
Great Ideas of Science
Linnaeus recognized
classes,
mammals,
mals:
six different classes
birds, reptiles, fish, insects,
His work was carried
further
still
Georges Cuvier (koo-VYAY) four classes
— mammals,
vertebrates; that
all
He
is,
"phylum"
French
naturalist
a
birds, reptiles,
all
and worms.
French
biologist,
Cuvier saw that the
.
and
fish
first
— were
had internal skeletons of bone.
grouped these animals into
called a
by
of ani-
a
still
larger classification
"phyla").
(plural,
Cuvier and the
Jean Baptiste de Lamarck divided the
invertebrates J or animals without internal skeletons, into a
number of
phyla.
Cuvier moved taxonomy in another direction, too. After
1800 naturalists began studying rocks with stony impressions or
remnants that seemed to have been living creatures.
They called these impressions or remnants "fossils." recognized that although
any
Cuvier
did not closely resemble
fossils
existing species, they did fall
somewhere
into the
scheme of taxonomy.
For
instance,
when Cuvier
studied a fossil that had
all
the earmarks of a reptile skeleton, he concluded that the
animal had been a its
member
skeleton he could also
had thus reptiles.
tell
of the class of reptiles. that
it
identified the first of a
Because each of
its
once had wings. Cuvier
group of extinct flying
wings had been supported by
a single long finger bone, he
dactyl" ("wing-finger").
From
named
the creature "ptero-
Linnaeus and Classification
121
Pathway
to Evolution
Cuvier's followers continued to improve the system of classification.
Linnaeus had often grouped animals to-
gether on the basis of outward appearances.
Instead,
Cuvier's followers began to use internal structures,
which
were more important for grouping purposes.
By
the middle 1800's a system for classifying
things had been
begun
worked
out.
The work
so long ago had finally
all
living
that Aristotle had
been completed.
Every
creature, alive or extinct, could be placed in a particular
category. details,
There might be
of
taxonomy
must be certain
true for
creatures,
all
Thus, the
set naturalists thinking.
biological principles that held
however
different they
might appear.
classification of life
gave
rise to
were involved
some
single
living things
This
fine
fact that life could be classified so neatly suggested
that there
all
some of the
but the general plan was accepted.
The development The
disputes about
idea, in turn,
was
in
to lead to
"great ideas of science"
the idea that
phenomenon.
one of the overwhelming
— evolution
(see
Chapter 15).
wood pecker 'like
warbler-like
ground finches
insectivorous
cactus- feeding
vegetarian tree finches
seed-eating ground finches
15 Dar\vin and Evolution
There's something rose
— something
Each one
Only
is
lions
kittens,
a
special about being a lion, a cat, or a
that
unique
no other animal or plant can
species, or kind, of animal or plant.
can give birth to baby
and only rose seeds
can come up
roses.
share.
lions,
only cats can have
— and not dandelion
seeds
—
Darwin and Evolution Still,
it
Lions are
much
jackals are
two
possible for
is
similarities.
123
like
only lions and not
much
like tigers, for
coyotes
tigers,
and
show
different species to
example, and
— even though
lions breed
and not
jackals breed jackals
coyotes.
In fact, the whole realm of
life
can be conveniently or-
ganized into groups of similar creatures (see Chapter 14).
When
scientists first
became aware of
this,
many
felt that
Were
these similarities could not be just a coincidence.
two
species alike because
members
changed into the other? Could
it
of one species had
be that different species
resembled each other simply because they were closely related?
Some
of the
Greek philosophers had suggested the
bility of relationship
between
had seemed too outlandish and
species, fell
possi-
but their suggestion
on deaf
ears.
It
seemed
unlikely that some lions had once turned into tigers or vice versa, or that
lions
and
some
tigers.
Therefore,
if it
catlike creature
had given
rise to
both
No one had ever seen such a thing happen. happened
at
all, it
must have been
a
very
slow process. In early the earth
modern
was only about
there simply
changed
times most people were convinced that six
thousand years
was not enough time for
their nature.
The whole
idea
old.
Thus,
species to have
was dismissed
as
absurd.
But was the earth
really only six thousand years old?
In
1
24
Great Ideas of Science
the 1700's scientists studying the structure of the rocky layers of the earth's crust
were beginning
to suspect that
those layers could be formed only over long periods of
About 1760
time.
a
French
(byoo-FONG), was Then,
Georges de Buff on
daring enough to suggest that the
much
earth might be as
naturalist,
as seventy-five
in 1785, a Scottish physician
ton went further. Hutton,
who had
thousand years
old.
named James Hut-
developed
his
hobby
of studying rocks into a full-time occupation, published a
book
The Theory
called
together
show
much
evidence and
that the earth
He
years old.
beginning
at
of the Earth.
In
it
he brought
many good arguments
to
might actually be many millions of
said firmly that he
saw no sign of any
all.
The Door Opens For the
first
evolution of there
time
life.
it
seemed possible to
If the earth
was
talk about the
millions of years old,
would have been enough time for animals and
to change very slowly into fact, that
man
why
species
could not have noticed
few thousand years of But
new
—
plants
so slowly, in
this evolution in the
his civilized existence.
should a species change at
all?
And why
change in one particular direction and not in an-
should
it
other?
The
first
person to attempt to answer that question
Darwin and Evolution
was the French
125
Jean Baptiste de Lamarck.
naturalist
In 1809 he presented his theory of evolution in a book
The
Zoological Philosophy.
entitled
changed because they
that creatures
theory suggested
tried to change, with-
out necessarily knowing what they were doing.
Lamarck hypothesized,
for example, that a certain ante-
lope was fond of browsing on the leaves of trees. stretch leaves too.
its
neck upward with
could.
it
It
would
The
its
antelope
its
would then have young
body
proportions.
turn lengthen their bodies little,
over
would reach
new
tongue and life
would all
the
its legs,
would cause
neck, and tongue to lengthen slightly.
those longer
a
stretch
might to reach
All this stretching throughout
its legs,
by
all its
It
many
— the
would
offspring
more by
inherit
would
stretching.
in
Little
thousands of years, the stretching
the point
species
still
The
that
where
that line of antelopes
became
giraffe.
Lamarck's theory depended on the concept of inheritance of acquired characteristics.
body changed during
its
passed on to the young.
lifetime, this
not be
so.
if a
creature's
change could be
Indeed, as the possibility was
began to seem more and more that
it
could
Lamarck's idea had to be abandoned.
In 1831 a
win joined
it
is,
However, there was no evidence
to support such a concept. investigated,
That
young English
the
crew of
naturalist
named Charles Dar-
a ship sent out to explore the world.
Just before leaving, he had read a
book on geology by an
126
Great Ideas of Science
The book
Englishman, Charles Lyell.
discussed and ex-
plained Hutton's theories about the age of the earth. Dar-
win was impressed.
As
the ship passed distant coasts and explored
known
islands,
creatures
still
Darwin had
unknown
little-
a chance to study species of
He
to Europeans.
larly interested in the animal life of the
was particu-
Galapagos
Islands,
located in the Pacific about 650 miles off the coast of
Ecuador.
Darwin found fourteen those obscure islands. other,
and from
coast.
The
different species of finches
on
All differed slightly from one an-
similar finches
on the South American
beaks of some finches were well designed for
eating small seeds, and those of others for eating large ones.
Other finches had beaks made for eating
Darwin suspected from
An
a
common
that
all
ancestor.
insects.
the different finches originated
What
had made them change? Perhaps some
idea flashed through Darwin's mind.
had been born with sHght changes
in their beaks
and had
passed such inborn characteristics on to their young. Dar-
win wasn't
sure,
though.
Would
such accidental changes
be enough to account for the evolution of different species? In 1838
Darwin found an answer
Vrinc'iple of Population, a
English clergyman
its
An
book published
Essay on the
in
1798 by an
named Thomas R. Malthus. Malthus
human
population always increased
food supply.
Therefore, the number of
maintained that the faster than
in
Darwin and Evolution
127
people eventually would be reduced by famine,
not by
if
disease or war.
Nature's
Way
Darwin was impressed by Malthus' arguments,
made him
see
how
not only on the
for they
powerful a force nature could exert
human
—
population, but on the population
of any species.
Many
creatures multiply in great numbers, but only a
small proportion ever survives. in general those that
It
were more
seemed to Darwin that efficient in
way
one
or
another were the ones that survived. For example, those finches born with slightly stronger beaks
would survive
because they were better able to eat tough seeds. Those that could digest an occasional insect
would have an even
better chance of survival.
Generation after generation, slightly
more
efficient in
expense of the slightly
number
of
ways
in
the
finches
any way would survive
less efficient ones.
were
that
at the
There were
which they might be more
a
efficient.
Therefore, in the end there would be a number of widely different species, each specializing in a different It
seemed to Darwin that
this process of natural selection
held true not only for finches, but for ral selection
way.
all
creatures.
Natu-
determined which creatures would survive by
1
Great Ideas of Science
28
starving out those that did not have
some
little
edge of
superiority.
Darwin worked on
his
theory of natural selection for
Finally, in 1859, he published his views in a
years.
On
entitled
the Origin of Species by
Selection, or the Preservation of
Means
book
of Natural
Favoured Races
in the
Struggle for Life.
At
first,
Darwin's views created
a
storm of controversy.
But more and more evidence gathered through the years has supported the central point of his theory
change of species through natural
The
idea of evolution,
first
losophers and finally nailed revolutionized
all
— the slow
selection.
glimpsed by the Greek phi-
down by
thinking in biology.
It
Charles Darwin,
was undoubtedly
the most important single idea in the history of biology.
modern
16 Russell and Stellar Evolution
Aristotle thought
by
that the earth
different laws (see Chapter 7).
there
was
erratic
and decay.
On
change
and the heavens ran
On
— sunshine
earth,
he observed,
and storm, growth
the other hand, he beUeved that the
heavens never changed.
The sun, moon, and planets circled
the heavens so mechanically that their position at any given
Great Ideas of Science
1 3
moment
The
could be predicted long in advance.
stars
remained always in place, always the same.
To
be sure, there were objects which seemed to be
falling stars,
heavens. air
but to Aristotle they did not
They were
just
phenomena
belonged to the earth.
fall
in the
(We know
air,
The
friction
produced
as
they
fall
atmosphere causes them to burn and give off Aristotle
He
was both wrong and
and the
that falling stars
are rocks that enter the earth's atmosphere space.
from the
from outer through the
Thus,
light.
right about falling stars.
was wrong because they do come from the heavens,
but right because they become ''things in the falling stars are also called "meteors,"
meaning
from
a
air."
In fact,
Greek word
''things in the air.")
In 134 B.C.,
two
centuries after Aristotle's death, the
Greek astronomer Hipparchus (hih-PAHR-kus) noted
new
star in the constellation Scorpio.
think?
Could
after all?
stars
What was
a
he to
be "born"? Could the heavens change
But perhaps
observation was wrong, he
his
thought. Perhaps the star had always been there.
To make fooled,
sure that
no future astronomer would be
Hipparchus prepared
sand bright
stars.
It
was the
a
first star
the next sixteen hundred years. stars
were reported for many
In 1054 A.D. a
new
star
map
of
more than
a thou-
map, and the best for
However, no more new
centuries.
appeared in the constellation
Taurus, but only Chinese and Japanese astronomers noted
Russell and Stellar Evolution
it.
131
In Europe, science was at a
that
—
low ebb
no astronomer reported the new
weeks
it
so low, in fact,
although for
star,
blazed brighter than any object in the sky except
for the sun and
moon.
In 1572 a bright
new
star blazed
up once
By
in the constellation Cassiopeia.
again, this time
this time, science
was
again beginning to flourish in Europe and astronomers
were watching the heavens a
Among them was (BRAH-uh). He
carefully.
young Dane named Tycho Brahe
observed the star and wrote a book about
entitled
it
De
Nova Stella ("Concerning the New Star"). Ever since, a new star in the heavens has been called a "nova." There was no denying
it
now.
Aristotle had been
wrong. The heavens were not changeless.
More Evidence More was
in store.
of
Change
In 1577 a comet appeared in the
heavens, and Brahe tried to calculate earth. stars
He
—
did this
by having
at as nearly the
The
should seem to shift position places.
The
closer
it
was
were
observatories
Brahe
when
— from two
as possible
— one was
other in Czechoslovakia.
from the
position noted against the
same time
different observatories. siderable distance apart
its
distance
its
in
Denmark and
knew
that the
seen from
to earth, the
a con-
more
two
it
the
comet
different
should
shift.
Great Ideas of Science
132
However, the comet instead.
the
didn't shift at
shifted
This meant that the comet was farther away than
moon. Therefore,
was
moon
the
all;
despite
its
erratic motion, the
comet
a part of the heavens.
Then
Dutch astronomer David
in 1596 the
(fuh-BRISH-us) discovered
The
tion Cetus.
Sometimes
it
not be seen.
star
was
It
a strange star in the constella-
was always changing
was very
its
bright, sometimes so
a "variable star"
The
other kind of change.
Fabricius
star
brightness.
dim
it
could
and represented an-
came
to be called
Mira
("wonderful"). Still
other changes were observed. In 1718, for example,
the English astronomer stars
Edmund
had indeed changed
Without
were they
An
just
was
it
physicist
this
possible to
make
them or
question became possible after the
any
or spectrum, of colors. its
sense of
in
Gustav R. Kirchhoif invented the spec-
a device that splits
light has
times.
were many kinds of changes
troscope on 1859 (see also Chapter 11). is
Greek
random changes?
answer to
German
their positions since
a doubt, there
the heavens. But
Halley showed that some
own
light falling
on
A it
spectroscope
into a pattern,
Each chemical element emitting
spectrum.
Therefore, the spectroscope
can identify the elements in a source of light and has been used to determine those elements present in the sun and in other
stars.
Different stars produce different "light spectra."
In
Russell and Stellar Evolution
133
1867 an Italian astronomer, Pietro A. Secchi (SAYK-kee), divided stars into four different "spectral classes."
astronomers divided them more finely, into ten
This was an exciting development, for could not be ties, just as
classified in
plants
it
Later
classes.
meant
that stars
groups according to their proper-
and animals could be
classified
according
to their characteristics (see Chapter 14).
In 1893 the
how
German
the light emitted
physicist
by any source
Wien's work made
perature.
temperature of a
Wilhelm Wien showed
star just
its
tem-
possible to tell the surface
it
from
varied with
its
spectral class. It turned
out that the temperature seemed to be related to the color
and
size
of the
star.
The Danish astronomer Ejnar Hertzsprung
(in 1905)
and the American astronomer Henry N. Russell (in 1914)
compared the temperatures of various 720sity
(the
amount of
stars to their
light given off).
graphs of the results and found that almost into a straight line
which came
They all
lumi-
plotted
the stars
to be called "the
fell
main
sequence."
There were
cool, red stars
— huge
bodies
known
as
"red giants." Although each part of their surface was dim,
they gave off
a lot of light
because the total surface was
very great.
Then
there
Although giants."
were yellow
smaller,
they
There were
still
stars, still
hotter than the red giants.
could be called "yellow
smaller and hotter stars
— hot
134
Great Ideas of Science
enough
to be blue-white!
have the
maximum
Blue-white
temperature.
both smaller and cooler.
stars
After
appeared to
that, stars
were
There were "yellow dwarfs"
(such as our sun) and very cool, dim stars called "red dwarfs."
Evolution of Stars?
For the
first
time,
mankind glimpsed
a pattern of steady
change in the heavens. Perhaps the heavens grew old as the earth did;
perhaps the
had
a life cycle like that
Perhaps there was
of living creatures.
evolution of the
stars
stars, just as
there
just
stellar evolution,
was evolution of
life
on
earth.
Russell suggested that stars cool, thin gas that shone
were born
with a dim red
as
huge masses of
heat.
As they aged,
they contracted and grew hotter and hotter until they
maximum now growing
They
continued to con-
reached a
temperature.
tract,
cooler and cooler, and finally became
blackened burnt-out cinders.
Our
sun,
it
seemed, was well
past middle age.
This theory, however, was too simple.
Actually, at
the beginning of the twentieth century, astronomers didn't
know what made
a star shine, or radiate light.
In the
Russell and Stellar Evolution
1880's
had been suggested that the energy for
it
came from
radiation tional
135
its
a star's
slow contraction and that gravita-
energy was converted to
light.
(This meshed nicely
with Russell's notions.) However, such a process couldn't supply enough energy, so the idea had to be abandoned. In the 1890's scientists had discovered that the center of the atom,
its
larger than
American
"nucleus," contained a store of energy far
had been imagined. In the 1930's
physicist,
a
German-
Hans A. Bethe (BAY-tuh), worked
out a scheme of nuclear reactions that could go on within the sun's interior and supply
it
with the energy to form
light.
In these reactions, Bethe hypothesized, atoms of hydro-
gen (the simplest of slightly
all
atoms)
converted to the
are
more complicated atoms of helium. The
enormous hydrogen supply has allowed
it
to shine for five
or six billion years, with enough left over for billions of years. It is still a
young
Thus, the sun
is
sun's
many more
not in decline after
all.
star.
Astronomers have continued to study the nature of the nuclear reactions going on within a
star.
As hydrogen
turns to helium, they believe, the helium collects at the
center as a "helium core."
It
continues to
grow
hotter as
the star ages, until the helium atoms begin to interact and
form
still
more complicated atoms.
believed to take place, too.
Other changes are
1 3
Great Ideas of Science
6
Tremendous Explosion Eventually, the
below
The
a certain level.
hydrogen supply
original
star's
temperature and brightness of
the star change so drastically that
quence.
It
pulsate as
The
it
main
leaves the
se-
expands enormously and sometimes begins to
its
star
structure
may
grows
less stable.
then explode.
remaining "fuel" ignites
at
If
so,
once and the
ceedingly bright for a short period. these
sinks
virtually star
all
its
becomes ex-
Explosions such as
formed the novas observed by Hipparchus and
Tycho
Brahe.
In short, astronomers have developed the idea of heav-
— which Hipparchus two thousand years ago — the point of debating how enly change
first startled
stars are
to
born, grow, age, and
die.
Astronomers can go
still
Some
further.
universe was born in a huge explosion still
flying apart.
billions of stars.
Each fragment
is
Perhaps the day will come
have exploded, and
verse
perhaps, as is
whose fragments
a vast galaxy of
galaxies will have spread out of sight,
Or
theorize that the
when
all
when all the
some other astronomers
all
the
stars will
Perhaps,
think, the uni-
new
always being formed very slowly, and from arise as the old
many
the universe will be dead.
constantly being reborn.
and galaxies
when
are
ones
die.
it
matter
new
is
stars
Russell and Stellar Evolution
137
Indeed, the idea of change in the heavens gives us theories
not merely of
tioji
—
to
stellar evolution,
but of a cosmic evolu-
a ''great idea of science'' almost too vast in scope
comprehend.
INDEX
Croton, 10 Cuvier, Georges, 120 Dalton, John, 41-44, 75 Darwin, Charles, 125-128 Deduction, 18 Definite proportions, law Democritus, 36-38 Diamond, 50 Digestion, 110 Dolphins, 116
Abdera, 36 Acceleration, 60 Air, 45-54
compression of, 39-40 Air resistance, 33 Alexander the Great, 115 Alexandria, 21
Amino
acids, 113
Ammonium
cyanate, 107
Animals, classification
of,
Archimedes, 20-23, 25-28,
Earth, age of, 123-124
116-120 31, 34
Egypt, 21 Einstein, Albert, 69, 95-96 Electric generators, 68
Aristotle, 26, 31, 54-57, 114-117, 121,
129-130 Asklepios, 102
Atoms,
Electromagnetic
Babylon,
69
Energy, 81
structure of, 96-97
Axioms,
field,
Electrons, 96
37
18,
conservation of, 8 quanta of, 93-94
24
Entropy, 88 4,
22
Enzymes, 110-113
Bernoulli, Daniel, 76 Berthelot, Pierre E., 108
isolation of, 112
Epicurus, 38 Epilepsy, 102, 104 Euclid, 24 Eupalinus, 22
Berzelius Jons J., 107 Bethe, Hans A., 135 Black, Joseph, 51 Black body, 91-92
Even numbers,
Bohr, Niels, 96 Boltzmann, Ludwig, 77 Boyle, Robert, 39-40 Brahe, Tycho, 131 Buchner, Eduard, 111 Buff on, Georges de, 124 Bunsen, Robert Wilhelm von, 90
Experimental science, 34 Experimentation, 32 Fabricius, David, 132
Fallingbodies, 31-34, 57 Faraday, Michael, 66-68 Ferments, 109-111 Fields, 68-69 Fischer, Emil, 113 Force, 60, 63 Fossils, 120
Caloric, 73 Carbon dioxide, 48-49, 51
Carnot, Nicholas L.
S.,
86-87
Catalyst, 109
Cause and Chaos, 47
effect,
12
Evolution, 124-128 stellar, 134-137
99
Classes, 120
Galapagos
Rudolf J. E., 87 Clock, pendulum, 35 Combustion, 49-53 Comets, 131-132 Compass, 65 Conon, 22, 24
Galileo, 29-35, 57
Clausius,
Islands, 126
Gases, 48-49 kinetic theory of, 76-79
Gassendi, Pierre, 39
Genus, 118 Geometry, 19 Gods, 4
Conservation of energy, 85 Conservation of matter, 53
life
138
and, 101
of, 41
Index
139
Grandfather's clock, 35 Gravitation, 64 universal, 61-62 Hales, Stephen, 48 Halley, Edmund, 132
Heat, 73-79
energy and, 82-84 kinetic theory, 77-78 Heisenberg, Werner, 8 Helium, 90 Helmholtz, Hermann von, 85 Hertzsprung, Ejnar, 133
Hiero
II,
Magnetism, 64-67 Malthus, Thomas R., 126 Mass, 59 Mathematics, applied, 28 Matter, composition of, 37-44 Maxwell, James Clerk, 68, 76-78 Mayer, Julius R., 85-86 Mechanical view, 64, 99 Meteors, 130 Miletus, 2 Mira, 132 Moon, 61
Motion, laws
21
Hipparchus, 130 Hippocrates, 103, 107 Hippocratic oath, 104 Hutton, James, 124, 126
Huygens, Christian, Hypoteneuse, 16
35
31
of,
58-61
random, 75-76
Museum,
22
Natural selection, 127
Newton,
Isaac, 57-62
Nile River,
3
Nitrogen dioxide, 48 Notes, musical, 11
Illness, 102
Inertia, 59
Inheritance of acquired characteristics,
125
Inorganic chemistry, 107 Invertebrates, 120 Ionia, 5
Joule,
James
P.,
82-84
Kelvin, Lord, 84 Kinetic energy, 81 Kinetic theory of gases, 76-79 Kinetic theory of heat, 77-78 Kirchhoff, Gustav R., 90-91, 132 Kiihne, Wilhelm, 110
Lamarck, Jean B.
de, 120, 125
Lavoisier, Antoine-Laurent, 49-54
Laws
of nature, 6
Leucippus, 37 Lever, 25
Nova, 131 Numbers, 12-17
Odd
numbers,
12
Orders, 119 Organic chemistry, 107
Pendulum, 30, 35 Perkin, William H., 108 Photoelectric effect, 95 Phyla, 120 Planck, Max, 93-95 Platinum, 109 Plato, 24, 114 Priestley, Joseph, 48-49 Prism, 90 Proust, Joseph L., 41 Pterodactyl, 120 Proteins, 112-113 Pythagoras, 10-19, 23
Pythagorean theorem,
17
Life, 98 ff
Quanta, 93-94
Light, 89-93
Quantum
Limestone, 51 Lines of force, 66-67 Linnaeus, Carolus, 118-120 Linne, Carl von, 117
Radiation, electromagnetic, 69 Random motion, 75-76
Lucretius, 39 Lyell, Charles, 126
theory, 95-97
Ray, John, 117 Rayleigh, Lord, 91 Reason, 7
4
Index
140 Reaumur, Rene A. Right
F. de, 109-1 IQ
triangles, 16
Rumford, Count, 71-75, 82 Russell,
Henry
N., 133-135
Sanger, Frederick, 113 Schrodinger, Erwin, 97 Science, idea of, 7-8 Secchi, Pietro A., 133 Soda water, 49 Species, 118
Spectral classes, 133 Spectroscope, 90, 132 Spectrum, 90
Thermodynamics, 86 second law of, 88 Thompson, Benjamin. See Rumford, Count Thomson, William. See Kelvin, Lord Time, measurement of, 34-35 Triangular numbers,
13
Uncertainty, principle of, 8 Universe, birth of, 136 composition of, 1-4 gods and, Urea, 108
Square numbers, 14 Stars, 133
explosion of, 136 maps of, 130 Steam engine, 86 Stellar evolution, 134-137
Sumner, James
B., 112
Sun, 73 Syracuse, 20
Taxonomy, 115-120 Thales, 1-7,
Theorems,
18, 65,
18
van Helmont, Jan
B., 46, 51
Vertebrates, 120 Violet catastrophe, 92 Vitalism, 100, 107
end
of. 111
Water, 1-4 Wien, Wilhelm, 92-93, 133 Wohler, Friedrich, 106-108
100 Yeast, 110
^