weightlessness

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weight·less·ness

(wāt'les-nĕs),
The psychophysiologic effect of zero gravity, as experienced by someone falling freely in a vacuum (for example, astronauts in a stable orbit). A temporary state of simulated weightlessness can be achieved during powered flight within the earth's atmosphere by traversing an inverted parabolic curve where gravitational pull and centrifugal force cancel each other out.
A state in which there is no gravitational effect on a body or material
Physiologic effects Bone mineral loss, altered blood chemistries, weakened immune system, variable heart rate, arrhythmias, loss of skeletal and cardiac muscle mass and strength, increased urinary loss of nitrogen and phosphorus, motion sickness, and redistribution of fluids that are normally pooled in the lower torso and legs, resulting in a ‘fat face’