The Universe is expanding - into what exactly?

a giant hob-nob

The heavenly realms are outside of it: the place from which the mass came .001 seconds prior to the big bang.

Yes there must be something beyond the universe that's allowing it to expand- I believe this is where the answers lie to all existence. But we will never truly know because its a mystery. May be its expanding to a point where it will no longer be able to get bigger- it will reverse in to the so called "Big crunch". I just wish we knew the truth!

It's expanding into more memory locations in the Great Mainframe of Existence.

most people assume the edge of the unierse has a clear defined border, like where a lake meets the shore but its more gradual than that. outside the universe there is no matter, energy or time and its into this nothingness the universe expands. It expands by becoming looser and this is why we need blackholes to button it togeather (excuse the anaolgy).

Great question.. Despite the apparent consensus of scientific opinion that the universe has no "boundry" per se between its own outside edge and the nothingness it must be expanding into, this seems to defy logic which lends credence to the validity of your question to which, unfortunately , I do not have an answer.

It'll expand, expand... and expand some more, until it goes POP!

This is all cosmological gobbledy **** that is pure theory and no physical reality. When they say the universe is expanding, all they mean is that they can now measure that things are farther apart than they apparently used to be.

Its just not space expanding: its space-time. It means it would take you longer to get to the "edge" than it did before. Exanding into what? Maybe nothing (when you get to the edge you are just back where you started). Maybe into a higher dimension.