Whats Impossible?

im starting this thread coz i thought it would be interesting to see wat comes out of it.
just name things that you would think that could be possible but are actually impossible.

here's one
nobody can think of a new colour coz u can only make colours with other colours we already no.

does anybody have any others sorta like that??

anyone???????? anyone at all????

try walking through a standard revolving door carrying a set of ladders 8ft plus

There is no original thought.
Impossible ?
Think a thought.....is it original? Has no one else thought of your thought?

An atheist cant convince a Christian, and a Christian cant convince an Atheist.!
This is fun..