We all dream of exploring strange new worlds and seeking out new life and new civilizations, but traveling that far is expensive, uncomfortable and so time-consuming that it takes more than one generation to get it done. That means procreating, and that's where it gets difficult.
Despite what your favorite sci-fi shows would have you believe, sex in space is tough.
A hard fact of venturing outside our own solar system is that it takes time. Lots of time. It takes so much time that, even if you're placed on board a spaceship as an infant, you probably won't live to see your destination. Until someone invents one of those nifty faster-than-light drives, the only way to travel long distance in space is to create your crew's replacements as you go. That means kids, and kids means ... well, you know.
So what's so hard about that? Well, we also have yet to invent any kind of gravity simulator for our spacecrafts, so anything we do up there—be it eating, showering or getting it on—has to be done while floating. Zero gravity is tough enough on the body even when you're not doing anything but gliding around, but when you want to have sex, things get even hairier.
"Sex is very difficult in zero gravity, apparently, because you have no traction and you keep bumping against the walls," said Athena Andreadis, a biologist at University of Massachusetts Medical School. "Think about it: you have no friction, you have no resistance."
And even if you do manage to have space relations, you then have to suffer through space pregnancy, then space labor, then space raising a baby who doesn't understand why he or she can't stop floating. It sounds like a setup for a really awesome sci-fi sitcom, but biologists still don't know if raising a baby in zero gravity could have serious health consequences. Also, imagine changing a diaper like that.
Maybe one day we'll all be putting the moves on sexy green aliens in another galaxy, but the bottom line is we'll probably have to figure out copulating in Earth orbit first.