The weightlessness , in the field of the Astronautics as in very other, is the state of a body such as the whole of the forces gravitational and inertial to which it is subjected has a null resultant and a moment resulting. Weightlessness ( weightlessness is a technically incorrect Synonyme) is thus the phenomenon felt in the absence of Pesanteur.

Weightlessness is thus not caused by the distance of with the distance from the Ground: the Accélération due to the Gravité with a 100 km height for example is only of 3% less than on the surface of the Ground.

Actually, weightlessness is felt when the Accélération undergone equalizes the Gravité, which recovers also the case where the field of gravity would be null, which does not arrive since the influence of gravity is everywhere in the Universe.

Usually what we feel as the Poids is not the force exerted by the Ground (or any other star) on ourself, but the reaction of the ground (or any other surface on which we are posed) to this force. Thus, weightlessness is felt for example when we are in Freefall, or on a free Orbite around the Earth (case of the Astronaute S). That is due so that the astronauts and their cockpit are very close from/to each other and fall all with same acceleration, i.e it is a reference frame of inertia.

A situation a little similar to weightlessness can be lived when the effects of the Poussée of Archimedes are opposed to gravity. This type of balance is exploited, for example, to train the astronauts with the operations in space. Immersed with their diving-suit in a swimming pool, the push of Archimedes maintains them in suspension. However, contrary to gravity or an acceleration, the force of Archimedes does not act on the Internal ear, which controls the balance. The astronauts undergoing training in a swimming pool thus continue, in particular, to distinguish the top from bottom, which is not any more the case in space.

The term weightlessness was the French term to indicate this state of absence (A) gravity; however frequent oral confusions between “weightlessness” and “gravity” resulted in using the term weightlessness in place and place. The term microgravity is also misused to indicate the state of weightlessness, in particular by much of professionals. One should speak about microgravity only very far from the Earth, or at the points of Lagrange where fields of gravity " annulent" , between Ground and the Moon for example.

The correspondents term in English are weightlessness , zero gravity , and zero-g .

Reference

Right French: decree of February 20th, 1995 relating to the terminology of sciences and space technology.

See too

• apparent Weight
• Badly of space
• List of the articles relating to astronautics
• Celestial mechanics

External bonds

• international Experiments on the reactions to weightlessness according to the sex.
• life in weightlessness on board an orbit station