Free Electron Motions

Most recent answer: 03/05/2013

Q:
Say you have a free electron in a vacuum and you let that electron move for 1 picometre. And you where to zoom in and take a picture for every time it moved a little bit, what would you see? Would you see the electron changing into an oval shape to move a little or would you see the electron teleporting to move a little OR something completly else? (more basic question: what is movement on it's most fundamental level instead of energy coming in and moving the particle)
- Frank van Neerbos (age 18)
Netherlands
A:
What happens really depends on what the electron starting state is and how long you wait. If you're interested in picometer movements, I guess you're thinking about an electron whose position is defined to about a picometer or less. That small a wave lump requires a big spread in momenta. In fact, the spread in velocities would only be a bit less than the speed of light. So in a nanosecond it would spread out by centimeters in every direction.

If you then shined some bright light on it to try to see where it was, you'd get a new starting wavefunction confined to some micron-size region somewhere in there. Any picometer shifts wouldn't amount to much against that background spread.

Mike W.

(published on 03/05/2013)