I was wondering.....

If you go through the crack your entire history vanishes etc etc. Like a big black void of nothingness where you don't and never have exisited.

How come in episode 1 - Prisoner Zero came out of the crack, as did the Atraxi...And then (i assume) back into the crack.

And if they did go back into the crack...Why could folk still remember them?

Ahhh, whatever I guess. Artistic License. Still a crackin series!!!

I think some cracks were stronger than others.

The one on the Bizantium was huge, and wiped out groups of people. A medium sized one took out just Rory. The one in Amy's room was small, and 'nibbled' away at her life over many years. It didn't even seem to attempt to take the Doctor. He had to willingly give himself to it.

In vampires of venice wasn't it said "through some we saw worlds"

Are the cracks not okay until they release that time vortex energy? Hence why the Doctor could put his hand inside and pull out a piece of the Tardis, but then the energy got Rory.

I knew there would be an explanation somewhere!!