| 1. A condition in which no acceleration, whether of gravity or other force can be detected by an observer within the system in question. 2. A condition in which gravitational and other external forces acting on a body produce no stress, either internal or external, in the body. Any object falling freely in a vacuum is weightless, thus an unaccelerated satellite orbiting the earth is "weightless" although gravity affects its orbit . Weightlessness can be produced whitin the atmosphere in aircraft flying a parabolic flight path.
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