Magical Physics

Heisenberg, Schrödinger and Ohm

Heisenberg, Schrödinger and Ohm are in a car.

They get pulled over. Heisenberg is driving and the cop asks him “Do you know how fast you were going?”

“No, but I know exactly where I am” Heisenberg replies.

The cop says “You were doing 55 in a 35 miles per hour zone.” Heisenberg throws up his hands and shouts “Great! Now I’m lost!”

The cop thinks this is suspicious and orders him to pop open the trunk. He checks it out and says “Do you know you have a dead cat back here?”

“We do now, thanks to you!” shouts Schrödinger.

The cop moves to arrest them. Ohm resists.

  • Heisenberg’s Principle of Uncertainty: Werner Heisenberg said that in the study of subatomic particles, the position(where the particle is) and momentum(where and how fast it is going) cannot be known at the same time. When Heisenberg knew exactly where he was, he could not have simultaneously know how fast he was driving.On the other hand, when the cop told him how fast he was driving, he did not know where he was. In practical situations, this only happens with subatomic particles. Heisenberg was uncertain where he was, on principle.

For an analogy, I’ve always imagined taking a photograph of a ball thrown in the air, where you can change your shutter speed. With a very fast shutter speed there’s almost no blur, so you can tell very well exactly where the ball is. However, it’s just hanging there in the photo, so you can’t really tell how fast it’s moving or in what direction. On the other hand, if you take a longer shot, you’ll get a photo of a blur, letting you tell (if you backtrack from your shutter speed and the length of the blur) very much how fast the ball was moving, but not where it was at that instant.

  • Schrödinger’s Cat: A thought experiment by Erwin Schrödinger, which had a cat in a sealed box, with a barrel of poison gas set to randomly release the gas. Schrödinger said that the state of the cat – dead or alive – cannot be known unless we open the box. Until the box is opened, the cat can be said to be both dead and alive at the same time, and it is the opening of the box which causes the state.

This thought experiment was itself an analogy to one of the basic principles in quantum mechanics, which says that an undisturbed particle exists in all possible states until it is observed. It is the observation which causes it to take one state. Hence, when Schrödinger shouts back at the cop, “We do now, thanks to you!”, it has a double meaning in that the cat is dead because the cop opened the trunk as well as they now know that they have a dead cat there.

  • Ohm: Ohm is the unit of resistance to electrical current. Not wanting to face strong “charges”, both the electrical and the legal kind, Ohm resists.

To summarise:

  • Heisenberg: Position and momentum of a subatomic particle cannot both be known definitely at the same time.
  • Schrödinger: The cat is both alive and dead till the box/trunk is opened.
  • Ohm: The unit of resistance to current.
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