Why do astronauts float?

An orbit isn't an escape from gravity — it's a fall that misses its target. An object launched horizontally fast enough keeps falling, but the Earth's surface curves away beneath it at the same rate: its path closes into a loop and it keeps circling. The spacecraft and its occupant then undergo the same acceleration, they fall together, and no floor pushes back against their feet. The Moon obeys the same principle around the Earth.

What we call weight in everyday life is actually the reaction of the ground, a seat, or a scale pushing back. Remove that contact and the sensation disappears, even though Earth's pull remains fully present. The same effect occurs during a diver's fall or inside an elevator whose cable has snapped. In orbit, this situation continues indefinitely, which gives it physiological consequences: fluids shift toward the chest and head, the spine relaxes, and weight-bearing muscles stop working.

Specialists prefer the term microgravity, because free fall is never perfect. Drag from the residual atmosphere, orbit corrections, fans, and crew movements introduce small accelerations that some experiments cannot tolerate; these are then mounted on damped platforms. On Earth, this state can only be reproduced briefly: in drop towers, or aboard aircraft that fly repeated parabolic arcs, engines tuned to follow exactly the curve of a projectile.