The world of subatomic particles is strange and wonderful. Particles move and interact in ways very different than the way objects move and interact in the larger world. The following conversation is from the novel SUPERPOSITION by David Walton, and it will give you some idea of just how strange quantum physics can be.
“So, tell me about these resonators again,” Terry said. “I’m having trouble remembering why two spinning doodads smaller than a clipped fingernail are so important.”
The question seemed to spark Jeannie’s enthusiasm. “One word,” she said. “Superposition.” She took a deep breath. “Imagine there’s a tennis ball bouncing back and forth between these two walls. It never slows down or falls; it just keeps bouncing back and forth endlessly.”
“Okay,” Terry said.
“We turn off the lights, and you pull out your camera and take a flash picture. What do you see?”
“A green dot, in the air, somewhere between the walls.”
“Is it any more likely to be in one place than another?”
“Not if it’s moving at a constant speed, and assuming the impact with the walls doesn’t slow it down.”
My respect for Terry increased the more time I spent with him. All his answers were precise, and he seemed ready to sit there all day until he understood what Jean was talking about. He could have been a scientist. Though I suppose if he’d gone that route, he wouldn’t be able to bill $400 an hour.
“Let’s say you take a thousand pictures, or a million, and merge them together,” Jean said. “What would you see?”
“A set of green dots stretching from wall to wall,” Terry said. “A solid green line, if I took enough pictures.”
“Right. So now we’ll step into the quantum world. Say this was an electron instead of a tennis ball, though any particle would do. When you look at your million pictures, what you will see is a pattern where some areas have the usual number of green dots, some areas have twice as many dots, and some areas have no green dots at all.”
Terry gave her a skeptical look. “None?”
“So no matter how many pictures I took, I would never catch the ball in those spots.”
“The ball never is in those spots.”
“So how does it get from wall to wall?”
I laughed, enjoying his consternation. I could tell he thought he was missing something, but he wasn’t. The truth is, everyone is confused by quantum physics, no matter how much they’ve studied it. We learn all the technical jargon, and we can do all the math, but nobody really understands it, because it defies all common sense. “It gets worse,” I said. “Trust me, it gets a lot worse.”
“Let’s say you don’t believe this is actually possible,” Jean said, “so you hire one of your interns to hold a tennis racket in the path of the ball, right at one of those blank spots where the ball never appears in your pictures.”
“In the dark,” Terry said.
“And I take some more pictures. Let me guess: the ball keeps bouncing back and forth against the walls, as if the racket wasn’t there.”
“You’ve got it,” Jean said.
“You should have been a physicist,” I said.
“Okay, so what really happens? Does the tennis ball–the electron–fly right through? Or go around? I’m losing the thread here.”
I stepped in. “The point is, electrons and protons and neutrons are very different than tennis balls. The tennis ball is made out of them, but they’re not the same thing at all. The electron isn’t bouncing back and forth, not really. It exists everywhere between the two barriers at the same time, at some probability. This is the probability wave–the chance that it will be in any given spot when you look at it. The tennis ball has a probability wave, too, only its wave averages out to be consistent with how we experience the world. The electron’s probability wave doesn’t make any normal sense at all.”
“That’s the concept of superposition,” Jean said. “Being in more than one place, or more than one state, at the same time. You can overlay multiple probability waves on this poor electron, like overlapping wakes from two different boats on the ocean, changing the probability that it will or will not be in any given place.”
She waited. Terry nodded, but whether it was because he understood or because he’d given up, I wasn’t certain.
“Now, entanglement”–Jean cracked her knuckles loudly–“this is where we really start to blow your mind.”