reducedgravity

Reduced gravity refers to gravitational acceleration that is lower than Earth's standard surface gravity of 9.81 m/s^2. The term covers both partial gravity on other planetary bodies and the near-weightless conditions known as microgravity, where net accelerations are very small even though Earth's gravity is still present.

Planetary bodies exhibit different fixed levels of reduced gravity determined by mass and radius. For example, the Moon experiences about 0.165 g, Mars about 0.38 g, Venus around 0.9 g, Mercury about 0.38 g, and Jupiter about 2.5 g. In space, objects in orbit around Earth experience microgravity because they are in continuous free fall, effectively reducing apparent weight.

Reduced gravity environments are created and studied through several methods. Parabolic flights use aircraft that fly parabolic arcs to produce brief periods of microgravity (about 0 g for roughly 20 seconds, alternating with higher g during the pull-up and descent). Drop towers provide very short, intense intervals of microgravity as objects are released in free fall. Neutral buoyancy facilities simulate some aspects of reduced gravity for training by offsetting weight with buoyant force, though true microgravity is not achieved. Longer-duration microgravity is available aboard spacecraft and the International Space Station, where experiments can run for weeks or months.

Applications and effects span science and human factors. In reduced gravity, fluids behave differently, surface tension and capillary forces become more influential, and certain mechanical and combustion processes change. For living organisms, reduced gravity can cause fluid shifts, bone density loss, and muscle atrophy, along with sensorimotor adaptations. Designers of spacecraft, habitats, and experiments account for these changes to ensure functionality and safety in environments with diminished gravitational forces.