Telescope Reviews: Re: What drives an atom?

Hello Dave

Your quest to locate the position of an electron presupposes that an electron has a position. The only electrons that exhibit particle properties are those who have high energy such as an electron beam in a video tube. At lower energies such as the ground state of the hydrogen atom, one can not localize it's position to one side or the other of the atom because there is no evidence that it orbits at all. It's wave function is centered on the nucleus and is non-zero every where in the universe.

Yes, this is non-intuitive. The wave function describes the probability of an observation. An observation does not allow the electron to be undisturbed. In the situation you describe you wish to take a photograph of an electron. If the photon hit’s the electron, the electron will go to a different energy state. If the electron emits a photon later it can not tell you about the position of the electron prior to the high energy state.

An incomplete list of non-intuitive ideas from Quantum Mechanics:

There is no such thing as a beam of light. Light consist of quanta that may not be subdivided.
Electrons are not little balls that can cast a shadow in a beam of light.
Electrons can have smaller wavelength than visible photons. This is why we use electrons for illumination in microscopes and can ‘see’ smaller things. Using visible photons to locate electrons is like using a Am football 10 yard chain set to measure the width of a needle. http://en.wikipedia.org/wiki/Electron_Microscope

If one shrunk a nikon coolpic camera and attempted to photograph an electron one would first observe that electrons are invisible. With no light on you would not see them. When the flash fires a burst of photons come out. If all of the photons miss the electron you would see nothing. You would think that your flash did not work because all of the photons moved away from you and did not return. If one photon interacts with an electron, it would move to a different energy state. You and your camera would still see nothing.

This situation is enshrined in the Feynman diagrams. It shows in infinite variation that when an electron meets a photon, both are changed.

Please do not feel that there is something preventing you from understanding this. This area is one of the reasons that physics has the reputation it has. Just hearing the results without the theory behind it does not facilitate understanding.