The Quantum Mystery


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.

Feynman: 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.