The Feynman Lectures on Physics Quotes

“One of the most interesting technical problems may or may not
be called psychology. The central problem of the mind, if you will, or the nervous
system, is this: when an animal learns something, it can do something different
than it could before, and its brain cell must have changed too, if it is made out of
atoms. In what way is it different ? We do not know where to look, or what to
look for, when something is memorized. We do not know what it means, or what
change there is in the nervous system, when a fact is learned. This is a very impor-
tant problem which has not been solved at all.”
― Richard Feynman, The Feynman Lectures on Physics

“It is the nuclear "burning" of hydrogen which supplies the energy of the sun;
the hydrogen is converted into helium. Furthermore, ultimately, the manufacture
of various chemical elements proceeds in the centers of the stars, from hydrogen.
The stuff of which we are made, was "cooked" once, in a star, and spit out. How
do we know? Because there is a clue. The proportion of the different isotopes—
how much C12
, how much C13
, etc., is something which is never changed by
chemical reactions, because the chemical reactions are so much the same for the
two. The proportions are purely the result of nuclear reactions. By looking at the
proportions of the isotopes in the cold, dead ember which we are, we can discover
what the furnace was like in which the stuff of which we are made was formed.
That furnace was like the stars, and so it is very likely that our elements were
"made" in the stars and spit out in the explosions which we call novae and super-
novae. Astronomy is so close to physics that we shall study many astronomical
things as we go along.”
― Richard Feynman, The Feynman Lectures on Physics

“One of the most impressive discoveries was the origin of the energy of the
stars, that makes them continue to burn. One of the men who discovered this was
out with his girl friend the night after he realized that nuclear reactions must be
going on in the stars in order to make them shine. She said "Look at how pretty
the stars shine!" He said "Yes, and right now I am the only man in the world
who knows why they shine." She merely laughed at him. She was not impressed
with being out with the only man who, at that moment, knew why stars shine.
Well, it is sad to be alone, but that is the way it is in this world.”
― Richard Feynman, The Feynman Lectures on Physics

“If we had an atom and wished to
see the nucleus, we would have to magnify it until the whole atom was the size of
a large room, and then the nucleus would be a bare speck which you could just
about make out with the eye, but very nearly all the weight of the atom is in that
infinitesimal nucleus. What keeps the electrons from simply falling in? This
principle: If they were in the nucleus, we would know their position precisely, and
the uncertainty principle would then require that they have a very large (but
uncertain) momentum, i.e., a very large kinetic energy. With this energy they
would break away from the nucleus. They make a compromise: they leave them-
selves a little room for this uncertainty and then jiggle with a certain amount of
minimum motion in accordance with this rule.”
― Richard Feynman, The Feynman Lectures on Physics

“When we put an electron in an electric field,
we say it is "pulled." We then have two rules: (a) charges make a field, and
(b) charges in fields have forces on them and move. The reason for this will be-
come clear when we discuss the following phenomena: If we were to charge a body,
say a comb, electrically, and then place a charged piece of paper at a distance and
move the comb back and forth, the paper will respond by always pointing to the
comb. If we shake it faster, it will be discovered that the paper is a little behind,
there is a delay in the action. (At the first stage, when we move the comb rather
slowly, we find a complication which is magnetism. Magnetic influences have to
do with charges in relative motion, so magnetic forces and electric forces can really
be attributed to one field, as two different aspects of exactly the same thing. A
changing electric field cannot exist without magnetism.) If we move the charged
paper farther out, the delay is greater. Then an interesting thing is observed.
Although the forces between two charged objects should go inversely as the
square of the distance, it is found, when we shake a charge, that the influence
extends very much farther out than we would guess at first sight. That is, the effect
falls off more slowly than the inverse square.”
― Richard Feynman, The Feynman Lectures on Physics

“So the chemical
properties of a substance depend only on a number, the number of electrons. (The
whole list of elements of the chemists really could have been called 1, 2, 3, 4, 5,
etc. Instead of saying "carbon," we could say "element six," meaning six electrons,
but of course, when the elements were first discovered, it was not known that they
could be numbered that way, and secondly, it would make everything look rather
complicated. It is better to have names and symbols for these things, rather than
to call everything by number.)”
― Richard Feynman, The Feynman Lectures on Physics

“If we burn the carbon with very little oxygen in a very rapid reaction (for example,
in an automobile engine, where the explosion is so fast that there is not time for
it to make carbon dioxide) a considerable amount of carbon monoxide is formed.
In many such rearrangements, a very large amount of energy is released, forming
explosions, flames, etc., depending on the reactions. Chemists have studied these
arrangements of the atoms, and found that every substance is some type of arrange-
ment of atoms.”
― Richard Feynman, The Feynman Lectures on Physics

“The differ-
ence between solids and liquids is, then, that in a solid the atoms are arranged in
some kind of an array, called a crystalline array, and they do not have a random
position at long distances; the position of the atoms on one side of the crystal
is determined by that of other atoms millions of atoms away on the other side of
the crystal. Figure 1-4 is an invented arrangement for ice, and although it con-
tains many of the correct features of ice, it is not the true arrangement. One of the
correct features is that there is a part of the symmetry that is hexagonal. You can
see that if we turn the picture around an axis by 120°, the picture returns to itself.
So there is a symmetry in the ice which accounts for the six-sided appearance of
snowflakes. Another thing we can see from Fig. 1-4 is why ice shrinks when it
melts. The particular crystal pattern of ice shown here has many "holes" in it,
as does the true ice structure. When the organization breaks down, these holes
can be occupied by molecules. Most simple substances, with the exception of
water and type metal, expand upon melting, because the atoms are closely packed
in the solid crystal and upon melting need more room to jiggle around, but an
open structure collapses, as in the case of water.”
― Richard Feynman, The Feynman Lectures on Physics

“The atoms are 1 or 2 X 10-8
cm in radius. Now 10-8
cm is called an
angstrom (just as another name), so we say they are 1 or 2 angstroms (Å) in radius.
Another way to remember their size is this: if an apple is magnified to the size
of the earth, then the atoms in the apple are approximately the size of the original
apple.”
― Richard Feynman, The Feynman Lectures on Physics

“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only
one sentence passed on to the next generations of creatures, what statement would
contain the most information in the fewest words? I believe it is the atomic
hypothesis (or the atomic fact, or whatever you wish to call it) that all things are
made of atoms—little particles that move around in perpetual motion, attracting
each other when they are a little distance apart, but repelling upon being squeezed
into one another. In that one sentence, you will see, there is an enormous amount
of information about the world, if just a little imagination and thinking are applied.”
― Richard Feynman, The Feynman Lectures on Physics