A weightless world
Any celestial body with sufficient mass exerts an attractive force on the objects on its surface. However, the force exerted by gravity varies depending on where it is measured: for example, it is six times lower on the Moon than on Earth.
Scales are ideal for weighing a body on Earth. We often wrongly express weight in kilograms. In fact, weighing scales measure in newtons and the graduations are calculated to give the equivalent mass, which is deduced with respect to the force of Earth’s gravity (see box).
Scales are ideal for weighing a body on Earth. We often wrongly express weight in kilograms. In fact, weighing scales measure in newtons and the graduations are calculated to give the equivalent mass, which is deduced with respect to the force of Earth’s gravity (see box).
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Weight, mass and gravity are in fact three separate but related notions.
As the name suggests, an object in weightlessness has no weight, but its mass remains constant: and if the force of gravity is zero, then the weight will be zero. That is why weighing scales are of no use to us in space.
Crédits : NPO Energia
On Earth, we feel as though we are very agile and free to move as we wish. But all our movements are in fact dependent on gravity. However, the absence of weight does not make things any easier in space, as any astronaut performing the same tasks we are used to performing on Earth will tell you.
Water from a fountain follows the same parabolic trajectory as an object thrown into the air. If we look closer, we see that it in fact breaks up into more or less spherical droplets—much like those astronauts swallow in the weightless environment of space.
