What Is Microgravity?
Gravity is a force that governs motion throughout the universe. It holds us to the ground and keeps the Earth in orbit around the Sun. Microgravity describes the environment in orbital space flight, which has very weak gravitational effects (one-millionth of what is felt on Earth) and which is sometimes referred to as a state of 'weightlessness.' The condition of microgravity occurs when an object is in 'free fall.' In free fall, an object falls faster and faster, accelerating with exactly the speed of attraction caused by gravity. Objects traveling around the Earth in a state of continuous free fall, or orbit, are essentially weightless even though their mass remains the same.
Conducting research in a microgravity environment gives researchers a unique opportunity to study the true nature of processes and materials without having to consider the effects of Earth's gravity. Thus, physics theories can be tested at levels of accuracy that are impossible on Earth. Microgravity experiments uncover the mystery of how gravity affects processes such as combustion science and fluid physics. This knowledge can then help to improve the way we do things on Earth.
NASA Glenn Research Center