Quotes from The Feynman Lectures on Physics

“It doesn't make a difference how beautiful your guess is. It doesn't make a difference how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it's wrong.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“How I'm rushing through this! How much each sentence in this brief story contains. "The stars are made of the same atoms as the earth." I usually pick one small topic like this to give a lecture on. Poets say science takes away from the beauty of the stars—mere globs of gas atoms. Nothing is "mere." I too can see the stars on a desert night, and feel them. But do I see less or more ? The vastness of the heavens stretches my imagina-tion—stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern—of which I am a part—perhaps my stuff was belched from some forgotten star, as one is belching there. Or see them with the greater eye of Palomar, rushing all apart from some common starting point when they were perhaps all together. What is the pattern, or the meaning, or the why ? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it ? What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?”
― Richard Feynman, quote from The Feynman Lectures on Physics

“How can we tell whether the rules which we "guess" at are really right if we cannot analyze the game very well? There are, roughly speaking, three ways.

First, there may be situations where nature has arranged, or we arrange nature, to be simple and to have so few parts that we can predict exactly what will happen, and thus we can check how our rules work. (In one corner of the board there may be only a few chess pieces at work, and that we can figure out exactly.)

A second good way to check rules is in terms of less specific rules derived from them. For example, the rule on the move of a bishop on a chessboard is that it moves only on the diagonal. One can deduce, no matter how many moves may be made, that a certain bishop will always be on a red square. So, without being able to follow the details, we can always check our idea about the bishop's motion by finding out whether it is always on a red square. Of course it will be, for a long time, until all of a sudden we find that it is on a black square (what happened of course, is that in the meantime it was captured, another pawn crossed for queening, and it turned into a bishop on a black square). That is the way it is in physics. For a long time we will have a rule that works excellently in an over-all way, even when we cannot follow the details, and then some time we may discover a new rule. From the point of view of basic physics, the most interesting phenomena are of course in the new places, the places where the rules do not work—not the places where they do work! That is the way in which we discover new rules.

The third way to tell whether our ideas are right is relatively crude but prob-ably the most powerful of them all. That is, by rough approximation. While we may not be able to tell why Alekhine moves this particular piece, perhaps we can roughly understand that he is gathering his pieces around the king to protect it, more or less, since that is the sensible thing to do in the circumstances. In the same way, we can often understand nature, more or less, without being able to see what every little piece is doing, in terms of our understanding of the game.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“...if we were to name the most powerful assumption of all, which leads one on and on in an attempt to understand life, it is that all things are made of atoms, and that everything that living things do can be understood in terms of the jigglings and wigglings of atoms.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“We might like to turn the idea around and think that the true explanation of the near symmetry of nature is this: that God made the laws only nearly symmetrical so that we should not be jealous of His perfection!”
― Richard Feynman, quote from 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, quote from 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, quote from The Feynman Lectures on Physics

“More was discovered about the electrical force. The natural interpretation
of electrical interaction is that two objects simply attract each other: plus against
minus. However, this was discovered to be an inadequate idea to represent it.
A more adequate representation of the situation is to say that the existence of the
positive charge, in some sense, distorts, or creates a "condition" in space, so that
when we put the negative charge in, it feels a force. This potentiality for produc-
ing a force is called an electric field.”
― Richard Feynman, quote from 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, quote from The Feynman Lectures on Physics

“We call the sum of the weights times the heights gravitational potential
energy—the energy which an object has because of its relationship in space, rela-
tive to the earth.”
― Richard Feynman, quote from 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, quote from The Feynman Lectures on Physics

“For example, the force of electricity between two charged objects looks just like the law of gravitation: the force of electricity is a constant, with a minus sign, times the product of the charges, and varies inversely as the square of the distance. It is in the opposite direction-likes repel. But is it still not very remarkable that the two laws involve the same function of distance? Perhaps gravitation and electricity are much more closely related than we think. Many attempts have been made to unify them; the so called unified-field theory is only a very elegant attempt to combine electricity and gravitation; but, in comparing gravitation and electricity , the most interesting thing is the relative strengths of the forces. Any theory that contains them both must also deduce how strong the gravity is.”
― Richard Feynman, quote from 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, quote from The Feynman Lectures on Physics

“The general name of energy which has to do with location relative to some-
thing else is called potential energy.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“Another most interesting change in the ideas and philosophy of science
brought about by quantum mechanics is this: it is not possible to predict exactly
what will happen in any circumstance. For example, it is possible to arrange an
atom which is ready to emit light, and we can measure when it has emitted light
by picking up a photon particle, which we shall describe shortly. We cannot,
however, predict when it is going to emit the light or, with several atoms, which
one is going to. You may say that this is because there are some internal "wheels"
which we have not looked at closely enough. No, there are no internal wheels;
nature, as we understand it today, behaves in such a way that it is fundamentally
impossible to make a precise prediction of exactly what will happen in a given
experiment.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“As an example of something , let us consider the time it takes light to go across a proton, 10 to the negative 24 second. If we compare this time with the age of the universe , 2 times 10 to the tenth power years, the answer is 10 to the negative 42nd power. It has about the same number of zeros going off it, so it has been proposed that the gravitational constant is related to the age of the universe.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“The gravitational attraction relative to the electrical repulsion between two electrons is 1 divided by 4.17 times ten to the 42nd power!

As an example of something , let us consider the time it takes light to go across a proton, 10 to the negative 24 second. If we compare this time with the age of the universe , 2 times 10 to the tenth power years, the answer is 10 to the negative 42nd power. It has about the same number of zeros going off it, so it has been proposed that the gravitational constant is related to the age of the universe.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“The question is, of course, is it going to be possible to amalgamate everything,
and merely discover that this world represents different aspects of one thing?
Nobody knows. All we know is that as we go along, we find that we can amalga-
mate pieces, and then we find some pieces that do not fit, and we keep trying to
put the jigsaw puzzle together. Whether there are a finite number of pieces, and
whether there is even a border to the puzzle, is of course unknown. It will never
be known until we finish the picture, if ever. What we wish to do here is to see to
what extent this amalgamation process has gone on, and what the situation is at
present, in understanding basic phenomena in terms of the smallest set of principles.
To express it in a simple manner, what are things made of and how few elements
are there ?”
― Richard Feynman, quote from The Feynman Lectures on Physics

“All things, even ourselves, are made of fine-grained, enormously
strongly interacting plus and minus parts, all neatly balanced out. Once in a while,
by accident, we may rub off a few minuses or a few plusses (usually it is easier
to rub off minuses), and in those circumstances we find the force of electricity
unbalanced, and we can then see the effects of these electrical attractions.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“If it can be controlled in thermonuclear reactions, it turns
out that the energy that can be obtained from 10 quarts of water per second is equal
to all of the electrical power generated in the United States. With 150 gallons of
running water a minute, you have enough fuel to supply all the energy which is
used in the United States today! Therefore it is up to the physicist to figure out
how to liberate us from the need for having energy. It can be done.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“Thus Kepler's three laws are:

I. Each planet moves around the sun in an ellipse, with the sun at one focus.

II. The radius vector from the sun to the planet sweeps out equal areas in equal intervals of time.

III. The squares of the periods of any two planets are proportional to the cubes of the semimajor axes of their respective orbits : T - a'3/2”
― Richard Feynman, quote from The Feynman Lectures on Physics

“Galileo expressed the result of his observations in
this way: if the location of the ball is marked at 1, 2, 3, 4,... units of time from
the instant of Its release, those marks are distant from the starting point in propor-
tion to the numbers 1, 4, 9, 16, ... Today we would say the distance is propor-
tional to the square of the time”
― Richard Feynman, quote from The Feynman Lectures on Physics

“By extending our techniques—and if necessary our definitions—still further
we can infer the time duration of still faster physical events. We can speak of the
period of a nuclear vibration. We can speak of the lifetime of the newly discovered
strange resonances (particles) mentioned in Chapter 2. Their complete life occupies
a time span of only 10-24
second, approximately the time it would take light
(which moves at the fastest known speed) to cross the nucleus of hydrogen (the
smallest known object).”
― Richard Feynman, quote from The Feynman Lectures on Physics

“Newton proved to himself (and perhaps we shall be able to prove it soon) that the very fact that equal areas are swept out in equal tines is a precise sign post of the proposition that all deviations are precisely radial-that the law of areas is a direct consequence of the idea that all of the forces are directed exactly toward the sun.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“In order to verify the conservation of energy, we
must be careful that we have not put any in or taken any out. Second, the energy
has a large number of different forms, and there is a formula for each one. These
are: gravitational energy, kinetic energy, heat energy, elastic energy, electrical
energy, chemical energy, radiant energy, nuclear energy, mass energy. If we total
up the formulas for each of these contributions, it will not change except for energy
going in and out.
It is important to realize that in physics today, we have no knowledge of what
energy is. We do not have a picture that energy comes in little blobs of a definite
amount. It is not that way. However, there are formulas for calculating some
numerical quantity, and when we add it all together it gives "28"'—always the
same number. It is an abstract thing in that it does not tell us the mechanism or
the reasons for the various formulas.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“What is this "zero mass"? The masses given here are the masses of the
particles at rest. The fact that a particle has zero mass means, in a way, that it
cannot be at rest. A photon is never at rest, it is always moving at 186,000 miles a
second.”
― Richard Feynman, quote from The Feynman Lectures on Physics

“Universal gravitation
What else can we understand when we understand gravity? Everyone knows the earth is round. Why is the earth round? That is easy ; it is due to gravitation. The earth can be understood to be round merely because everything attracts everything else and so it has attracted itself together as far as it can! If we go even further, the earth is not exactly a sphere because it is rotating and this brings in centrifugal effects which tend to oppose gravity near the equator. It turns out that the earth should be elliptical, and we even get the right shape forthe ellipse. We can thus deduce that the sun, the moon, and the earth should be (nearly) spheres just from the law of gravitation.”
― Richard Feynman, quote from 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, quote from The Feynman Lectures on Physics

“To summarize: every reversible
machine, no matter how it operates, which drops one pound one foot and lifts
a three-pound weight always lifts it the same distance, X. This is clearly a universal
law of great utility.”
― Richard Feynman, quote from The Feynman Lectures on Physics

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