Hmm... that would mean that actually, there's either a wind blowing at 70 mph or you're in a (near-) vacuum, wouldn't it? Now, if all this took place in a vacuum, you'd run into problems anyway because you wouldn't be able to breathe, which would hurt you, no matter if you jump or not.

Also, space isn't infinite. It's still expanding, and there are mainly theories about what will happen in the future, depending on the total amount of mass in the universe: either, it will go on expanding infinitely, till finally through nuclear fusion and fission every single atom has become iron (that being the most stable element of all), or it will collapse into a singularity again. Of course, no one can say where and how the borders of space are, and what lies beyond them, if anything. Perhaps it just sort of wraps around, or something. *That* should give you a headache.

Fuzz"migraine"pilz