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I just thought this was very interesting. I'm not sure how it applies to human 
behavior but I think it has a lot to do with the way we think about the infallibility 
of science which we do try to use to understand human behavior.

Selma

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How Does a Photon Decide Where to Go? That's the Quantum Mystery

April 20, 2002 




 

In Peter Parnell's play "QED," Alan Alda plays the Nobel
Prize-winning physicist Richard Feynman. The action takes
place in his office at the California Institute of
Technology in 1986 when Feynman was 68 and had less than
two years to live before dying of abdominal cancer. Here
are excerpts from his dialogue in the play, which is at the
Vivian Beaumont Theater at Lincoln Center and runs through
June 3. 

What is this prejudice people have against science? When I
won the Nobel Prize, I had to go over to Sweden to get it.
At dinner with the queen of Sweden, that thing that always
happens between me and royalty happened. That thing where
ice forms on the surface of their faces. She asked me what
I won the Nobel Prize for, and when I said "Quantum
physics," she said, "Oh, we can't talk about that because
nobody understands it," and I said: "On the contrary, we
know quite a lot about quantum physics, and that's why we
can't talk about it. It's everything else we don't know
about, like how to solve poverty and lower crime and stop
drugs, that we can talk about!" And then the ice formed on
the surface of her face. 

All of science is about trying to describe Nature, whether
it's biology or the known laws of physics. See, nature is
always out there, she's always doing what she does, and
it's our job to try and trick her into revealing her
secrets to us. It's a dance because nature doesn't always
give up her secrets easily. You have to look closely at
her, you have to experiment, to really find out how she
actually behaves. 

(He jumps up to the blackboard.) 

For instance, you think that light coming at you is
traveling in a straight path, right? 

(He draws a diagram.) 

Here's the surface of mirror.
Here's a ray of light. Common sense tells us that the angle
at which the light hits the surface is equal to the angle
at which it leaves the surface, and therefore the light
travels from its source in a path that takes the least time
to get to your eye. 

And not only common sense tells you this. Schoolbook
physics! This is what they teach! But it's wrong! Well, not
wrong. It's true, but it's not the whole truth! 

Or take this ball. 

(He throws it out to the audience.)


Nice catch! 

If we know the amount of time it took for that ball to
travel and do some other calculations, we can determine the
path it took. There's only one path, the one you just saw! 

But if we were in the quantum world, the world of the very
tiny, and that ball were the size of an atom or a photon of
light, something else would be going on. 

Because the behavior of things on a very tiny scale is
simply different. When we get down to the world of the very
small, to the particles that make up light and matter, that
world behaves like nothing you've ever seen before. Now
this is not just an interesting question. In a way, this is
the question. 

If all of scientific knowledge were destroyed and we had
only one sentence that we could pass on to the next
generation, what do you think that sentence would be? 

I believe it is the simple fact that all things are made of
atoms. Little particles that move around in constant
motion, attracting each other when they are a little
distance apart but repelling when being squeezed into one
another. O.K.? But if all of life, if a stream of water,
can be nothing but a pile of atoms, then I ask you an even
more in-ter-esting question: How much more is possible? 

Is it possible that this thing walking back and forth in
front of you, talking to you, raising and lowering his
chalk, is a great glob of these atoms in a very complex
arrangement, such that the sheer complexity of it staggers
the imagination as to what it can do? 

Know that when we say we are a pile of atoms, we do not
mean that we are merely a pile of atoms, but a pile of
atoms which might well have the possibilities which you see
standing before you! 

Sometimes when you're trying to trick nature into telling
you her secrets, she ends up surprising you. And that!
Suddenly that is the most interesting thing of all. 

For instance. Light. At first it was believed that light
behaves like a shower of particles. Then, with further
research, it was declared it behaves like waves. Light
emanating out from a source might travel like waves on
water. But then, even later, it was decided that it
actually does behave like particles. 

So which is it? Waves or particles? "Photons of light
behave like waves." No, they don't exactly. "They act like
particles." No, they don't exactly. Rather both light and
matter behave in their own inimitable manner. They are both
screwy, but at least they're both screwy in exactly the
same way. 

Look, you want to see an example of screwy? Take a surface
of glass. You see me because light is coming through the
glass and hitting my face, but you also see yourself
because some of the light is reflecting back. At this
angle, for every 100 photons hitting the glass, 96 go
through the glass and 4 hit the glass and go back to you.
How does any individual photon make up its mind which way
to go? 

Already, it's a mystery! Try as we might to explain how a
photon makes up its mind, it is actually impossible to
predict which way a given photon will go. 

Does this mean that physics, a science of great exactitude,
has been reduced to calculating only the probability of an
event and not predicting exactly what will happen? 

Yes. Nature permits us to calculate only probabilities.


This is the horrible condition of our physics today.
Outside the nucleus, we seem to know a lot. This includes
the domain of the very large, the planets and stars and
galaxies, the universe as a whole. In this area gravitation
is the dominant force and Einstein's general relativity the
triumphant theory. What we understand also includes the
second domain, everything in size between the planets and
the nucleus, all of which come under the theory of quantum
electrodynamics, QED, a theory of which we are justly
proud. But the world of the very small - the tiny particles
inside the nucleus - that world we lack a complete
understanding of. Will we ever understand it? 

We don't know. But not knowing is much more interesting
than believing an answer which might be wrong. 

We're lucky to live in an age in which we are still making
discoveries. It's like discovering a new country - like
trying to get to a strange, foreign place - a country
almost beyond our imagining.

http://nytimes.com/2002/04/20/arts/theater/20TANK.html?ex=1020311219&ei=1&en=4a98d8eccf2eb2ed



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