Weightlessness

Weightlessness is the experience (by people and objects) during freefall, of having no apparent weight. This condition is also known as microgravity (see below).

Health effects

Following the establishment of orbiting stations that can be inhabited for long durations by humans, exposure to microgravity has been demonstrated to have some deleterious effects to health. Humans have evolved for life on the surface of the Earth. When the constraint of gravity is removed, certain physiological systems begin to function to the detriment of the overall system.

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The most common initial condition experienced by humans in weightless conditions is commonly known as space sickness. The symptoms include general queasiness, nausea, vertigo, headaches, lethargy, vomiting, and an overall malaise. The first case was reported by cosmonaut Gherman Titov in 1961. Since then roughly 45% of all people to experience free floating under zero gravity have also suffered from this condition. The duration of space sickness varies, but in no case has it lasted more than 72 hours. By that time the astronauts have grown accustomed to the new environment.

Related Topics:
Space sickness - Nausea - Vertigo - Headache - Lethargy - Vomit - Cosmonaut - Gherman Titov - 1961

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The most significant adverse effects of long-term weightlessness are muscle atrophy and deterioration of the skeleton; these effects can be minimized through a regimen of exercise. Other significant effects include fluid redistribution, a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include weight loss, nasal congestion, sleep disturbance, excess flatulence, and puffiness of the face. These effects are reversible upon return to Earth.

Related Topics:
Muscle - Atrophy - Skeleton - Cardiovascular system - Red blood cell - Immune system - Flatulence - Earth

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Many of the conditions caused by exposure to weightlessness are similar to those resulting from aging. Scientists believe that studies of the detrimental effects of weightlessness could have medical benefits, such as a possible treatment for osteoporosis and improved medical care for the bed-ridden and elderly.

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