not just the photon, but the electron (Score 1)

Re. no. 3,

If you think its kewl that you get an interference
pattern when you send one photon though at a time,
then you'll be delighted that the same thing happens when one sends one electron through at a time. That means the electron goes through both
slits, just like the photon. But since we are more used to thinking of an electron as a single
particle it always struck me a stranger.

In fact, quantum mechanics says that if we would
perform the same experiment with a bowling ball
(and we had a few billion years to perform the
experiment) the same interference pattern would
emerge.

Physicists don't understand the universe. All
they understand is how to approximate some of the
universe with some tough mathematics.