The microgravity that permits what Garriott de Cayeux describes as “joyous, free-feeling” motion we associated with astronauts also takes a serious physiological toll. “Body fluids stop flowing normally, which is why, in space, people’s faces look puffy, and they generally have somewhat bloodshot eyes,” he says. “It feels sort of like lying on a children’s slide, head down. In the first days, you get very stuffed up and have a bit of a headache.” These symptoms can be easily remedied with common drugs, such as aspirin and Sudafed.
Another side effect comes from the floating fluid in your inner ear, which normally helps a person detect motion and stay balanced. In space, of course, it also begins floating. “So if you move your head forward, it will slosh to the back and make you feel like you’re falling backwards,” says Garriott de Cayeux. “There’s a disagreement between what you see that you’re doing and what your body thinks it’s doing—and that often causes sea sickness.”
That perceptual disconnect tends to last for about three days before your brain begins compensating. When you get back to Earth it takes another three days to readjust. This is another downside of space tourism that can be treated with drugs.
Other physical challenges are more difficult to address and also less acute. Humans in space suffer muscle and bone atrophy. Space travel requires exposure to increased levels of radiation, which can lead to surprising visual effects. "All of a sudden you will see this really intense, bright white ... and then it will fade back out," says Garriott de Cayeux. "That is basically you being damaged by radiation, it triggers the impression of light even though there is no light." Bloomberg Read More>>>>>>>Should be obvious - but its not.