Ingravity poses a series of physiological limitations to humans exploring the Universe,or at least, the vecinity of Earth: first the osteoporosis (decalcification of the bones) and the second is muscular atrophia (the degrading of the muscles). Other limitation is disorientation, there is no left or right nor up or down. You are in an ambiance where there are no walls, no ceiling, and no floor. The floor may be any surface on which the person is standing.
Furthermore, equilibrium is affected you may feel dizzy or sick in the stomach.

There is also, according to Einstein, the time paradox: on Earth a longer time may have elapsed than the one thought to elapse on the space vehicule

• Meeting travellers' physiological & psychological needs - quiet - March 9, 2005 - 19:31 UTC
  • Use the movies - kurushio95 - June 16, 2005 - 22:34 UTC