Weightlessness
Weightlessness
Weightlessness (pronounced: /ˈweɪtlɪsnəs/) is a condition experienced by people or objects when they are free-falling in a gravitational field, such as that of the Earth.
Etymology
The term "weightlessness" is derived from the English words "weight" and "less", indicating a state where the force of gravity is not felt.
Definition
In physics, weightlessness is a state of being where gravity is perceived not to be acting (a state of zero gravity). This can occur in the absence of external forces, when the gravitational forces are balanced by equal and opposite forces from the inertia of an object in motion (for example, in free fall), or in the inertial motion of an object in orbit.
Related Terms
- Gravity: The force that attracts a body towards the centre of the earth, or towards any other physical body having mass.
- Free Fall: Any motion of a body where gravity is the only force acting upon it.
- Orbit: The gravitationally curved trajectory of an object.
- Inertia: The resistance of any physical object to any change in its velocity.
Effects of Weightlessness
Weightlessness has several effects on the human body. The most immediate effect is a feeling of euphoria, often described as "floating". Over time, however, prolonged exposure to weightlessness can lead to muscle atrophy and deterioration of the skeleton, or spaceflight osteopenia.
Experiencing Weightlessness
Weightlessness can be experienced in several ways, including space travel, free-falling, and being in a state of orbit. Astronauts in space experience weightlessness because they are in continuous free-fall towards the Earth.
See Also
External links
- Medical encyclopedia article on Weightlessness
- Wikipedia's article - Weightlessness
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