photons

[Mil P]

how come photons can be in two plces at once or two times at once.

[Clanad]

A good basic explanation here:

http://library.thinkquest.org/C008537/cool/dif fraction/diffraction.html

[mattfox]

Ooh... just been studying a module on quantum mechanics as part of my degree course. Fascinating stuff!

In order to understand how that can happen, you have to forget conventional physics - things on this small a scale comply with entirely different sets of rules! Wikipedia has some good info http://en.wikipedia.org/wiki/Quantum_mechanics .

and

http://en.wikipedia.org/wiki/Schr%C3%B6dinger' s_cat