I'm thinking diarrhea. Or one of these. Yep, that's right. In space, while humans can suffer nausea, vomiting, vertigo, headaches, lethargy, muscular atrophy, bone degeneration, flatulence and lower red blood cell count, among others, our old nemesis, the cockroach, will grow bigger, faster and tougher than it's Earthling brethren. Lovely.
What actually led me to look up the effects of zero gravity was in fact an anime. Planetes (or ΠΛΑΝΗΤΕΣ, or プラネテス, if you like) is set in 2076, a near enough future in which spaceflight is commonplace, the Moon has been colonized, at least 5 manned missions to Mars have been sent successfully and work is underway to prepare the ship that will visit Jupiter, the Von Braun. The anime series follows the story of a bunch of misfits whose job it is to collect space debris, an exceedingly unglamourous yet vital task in an age where a screw travelling at 8 km/s* can send a multibillion dollar spacecraft down the toilet.
Our main protagonists are Hoshino Hachirota, an EVA specialist and Tanabe Ai, the newbie just assigned to work with him. Hoshino is loud, brash and crude, but for all that he's a skilled astronaut with an intense love for space. Tanabe is a bit dim, but she tries very, very hard indeed and has a head full of more high ideals than a university student.
One thing that struck me about this anime was the attention to IRL detail. For instance, astronauts wear diapers under their spacesuits, but in all the glamour and romance of space exploration, we generally don't get that fact pointed out to us quite as explicitly as this:
And that's how I learnt the Japanese word for 'diapers'. One of the more charming aspects of this attention to detail is the existence of Lunarians, that is, children born on the Moon, who are abnormally tall due to the reduced gravity:
Unfortunately for Nono-chan (right), aged 12, this means her body can't actually handle the stresses of Earth's gravity, and she's cut off from Earth for now.
There are a few things that struck me as odd, though. For instance, one of the characters has a serious smoking habit. In space, this means there are very, very few places indeed where she can smoke, i.e. special rooms with all the right filtration and waste disposal systems. So why bother go through the astronomical expense of allowing smoking in space? And I'm not sure if they quite covered all the angles to the growth of a child in space... But, what the hell. Compared with the ridiculous liberties taken with the laws of physics in anime in general, Planetes is an encyclopedia of space exploration and aerospace design.
Of course, like any other anime worth watching, Planetes waxes existential at times, with protagonists, most notably Hoshino, occasionally facing their inner demons against the epic backdrop of space exploration. And of course, there will be those opposed to space exploration. Why expend so much resources on space exploration when there are still nations on Earth torn apart by war, famine and poverty? Thus, a terrorist group exists to try and cause as much low orbit havoc as possible and make the Kessler Syndrome a reality, filling the skies with debris and cutting off humans from space. I leave it to you to find out how it's all resolved in the end. I have to say, it has the best game of shiritori I've ever witnessed.
Long story short, Planetes is 26 episodes of perfection, a triumph of the art of anime and a testament to the epic human journey into space. There's no shortage of adequate torrents out there. Go watch and be amazed.
Edit: On a related note, check out this offering from XKCD. This guy's comic is t3h r0xx0rz.
* Perfectly normal relative velocity for an object in orbit, apparently.