Microgravity

Microgravity is the condition in which objects experience extremely small net accelerations, producing an appearance of weightlessness. It is not true zero gravity; gravity remains present, but the motion of objects in free fall cancels the effective weight. In orbital spaceflight, a spacecraft and everything inside are continually falling toward Earth while traveling forward fast enough to maintain its orbit, so occupants and experiments seem to float.

The microgravity environment is not perfectly uniform. Residual accelerations arise from gravity gradients (tidal forces across a craft), atmospheric drag, thruster firings, crew movements, and mechanical vibrations. These small accelerations, typically measured in micro-g (10^-6 g) to milli-g (10^-3 g), can vary over time and location within a vessel or facility.

Microgravity can be produced or studied using several approaches. Long-duration microgravity is provided by spaceborne platforms such as the International Space Station and former space stations. Shorter episodes are obtained on aircraft in parabolic flight, which generate brief periods of microgravity, and in ground-based drop towers that allow free fall over a few seconds.

Its key applications span many fields. Scientists study fluids, combustion, and material processing under microgravity to reveal phenomena obscured by Earth’s gravity. Biological and medical research investigates how living systems develop and function without normal gravity. Human spaceflight requires countermeasures to mitigate muscle and bone loss and fluid redistribution, while researchers continue to refine methods for experiments and manufacturing that exploit microgravity.