https://www.youtube.com/watch?v=36GT2zI8lVA
For a comedian's take on the same question, here.
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Speaker 1: If you get ahold of two
magnets and you push them, you can feel this pushing between them. Turn it
around the other way, and they slam together. Now, what is it, the feeling
between those two magnets?
Richard
Feynman: What do you mean,
what's the feeling between the two magnets when you hold them?
Speaker 1: Well, there's something
there, isn't there? The sensation is that there's something there when you push
these two magnets together.
Richard
Feynman: Listen to my question.
What is the meaning when you say that there's a feeling? Of course, you feel
it. Now, what do you want to know?
Speaker 1: What I want to know is
what's going on between these two bits of metal.
Richard
Feynman: The magnets repel each
other. The magnets repel each other.
Speaker 1: Well then, but what does
that mean, or why are they doing that, or how are they doing it?
Richard
Feynman: You're asking-
Speaker 1: ... I think that's a perfectly reasonable question.
Richard
Feynman: Of course, it's a
reasonable question. It's an excellent question, okay? But the problem that you're asking
... You see, when you ask why something happens, how does a person answer why
something happens?
For example, Aunt Mini is in the hospital. Why? Because she
slipped. She went out and she slipped on the ice and broke her hip. That
satisfies people. It satisfies, but it wouldn't satisfy someone who came from
another planet and knew nothing about things.
At first, you'd understand why,
when you break your hip do you go to the hospital? How do you get to the
hospital when the hip is broken? Well, because her husband, seeing that she had
the hip was broken up, called the hospital up and sent somebody to get her. All
that is understood by people.
Now
when you explain a why, you have to be in some framework that you allow
something to be true, otherwise you're perpetually asking why. Why did the
husband call up the hospital? Because husband is interested in his wife's
welfare. Not always. Some husbands aren't interested in their wife's welfare
when they're drunk and they're angry.
And so you begin to get a very
interesting understanding of the world and all its complications. If you try to
follow anything up, you go deeper and deeper in various directions.
For
example, if you go "Why did she slip on the ice?" Well, ice is
slippery. Everybody knows that. No problem. But you ask why is ice slippery?
That's kind of curious. Ice is extremely slippery. It's very interesting. You
say, "How does it work?" You see? So you could either say "I'm
satisfied that you've answered me 'Ice is slippery, that explains it'" or
you could go on and say "Why is ice slippery?" And then you're
involved with something because there aren't many things as slippery as ice.
It's
very hard to get greasy stuff, but that's sort of wet and slimy. But a solid
that's so slippery? Because it is in the case of ice, that when you're standing
on it, they say, momentary the pressure melts the ice a little bit so you gotta
sort of instantaneous water surface on which you're slipping. Why on ice and
not on other things? Because water expands when it freezes so the pressure
tries to undo the expansion and melts it, is capable of melting it. But other
substances contract when they're freezing, and when you push them, they're just
as satisfied to be solid. Why does water expand when it freezes and other
substances don't expand when they freeze, all right? I'm not answering your
question, but I'm telling you how difficult a "why" question is.
You'll notice in this example that the more I ask why it gets interesting after
a while. That's my idea, that the deeper a thing is the more interesting in it.
We
could even go further and say, "Why did she fall down when slipped?"
That has to do with gravity, it involves in all the planets and everything
else, but nevermind. It goes on and on. And when you ask for example, why two
magnets repel, there are many different levels. It depends on whether you're a
student of physics or an ordinary person that doesn't know anything or not. If
you're somebody who doesn't know anything at all about it, all I can say is
that there's a magnetic force that makes them repel and that you're feeling
that force. You see, but that's very strange because I don't feel kind of force
like that in other circumstances. When you turn them the other way, they
attract.
There's
a very analogous force, electrical force, which is the same kind of a question.
And you say "That's also very weird." But you're not at all disturbed
by the fact that when you put your hand on the chair, it pushes you back. But
we've found out by looking at it that that's the same force, as a matter of
fact, the electrical force, not a magnetic exactly, in that case. But it's the
same electric repulsions that are involved in keeping your finger away from the
chair because everything's made out of it ... It's electrical forces in minor
and microscope details. There's other forces involved, but it's connected to
electrical forces. It turns out that the magnetic and the electric force, with
which I wish to explain these things, this repulsion in the first place, is
what ultimately is the deeper thing that we can start with to explain many
other things that looked like everybody would just accept them.
You
know you can't put your hand through the chair. That's taken for granted, but
that you can't put your hand through the chair, when looked at more closely,
why, it involves these same repulsive forces that appear in magnets. The
situation you then have to explain is why in magnets it goes over a bigger
distance than in ordinarily, and there it has to do with the fact that in iron,
all the electrons are spinning in the same direction. They all get lined up and
they magnify the effect of the force until it's large enough at a distance that
you can feel it.
If
you were a student, I could go further. I could tell you that the magnetic
forces are related to the electrical forces very intimately, that our
relationship between the gravity forces and electrical forces remains unknown,
and so on. But I really can't do a good job, any job, of explaining magnetic
force in terms of something else that you're more familiar with because I don't
understand it in terms of anything else that you're more familiar with.
There are many books on "how to explain, explanation" but one different entry point than Feynman's is David Deutsch; see his famous Ted Talk or his more recent book "Beginning of Infinity."
