The double slit experiment shows that light has properties traditionally associated with waves (as opposed to particles). Can you clarify how this is related to hypothesis 2?
It works when you send electrons one at a time, suggesting they are somehow interfering with themselves. In other words, the electrons are in both slits at once until we check. That might not literally be true, but it's not possible to explain the interference by saying we just don't know which slit they're going through.
