There's a good reason why astronauts tend not to stay on the International Space Station longer than six months: Microgravity is not kind to human bodies. Among other effects, it can flatten eyeballs and swell up fingers and faces, causing blinding headaches as blood, organs and cells react in ways they wouldn't on Earth.
For the same reasons, though, space may be the perfect place to study cancer — and someday even treat it.
