Part of that environment is gravity, the characteristic that we probably take for granted most often. The human body is an extraordinary and complex system with all its parts in constant communication. Your brain is the master controller of this system. In space, the human body responds to the new environment.
Astronauts feel and even look somewhat different.
Within hours or sometimes days, astronauts adapt to microgravity. Some body functions, however, do not adapt as quickly, and may prove to cause problems in the Earth-normal environment to which the astronauts return. Crew members from previous missions have routinely experienced a change in how they perceive objects and motions in space. Even something as simple as catching a ball involves complex interactions between the body's sensory and motor systems. Measurer marks off 2 spots, 3.5 meters apart.