Why does astronauts float in space?

Weight is not a property of a body; it is what you feel when something holds you up. Standing still, the ground pushes on your feet and your nervous system reads that push as weight. Remove the push, by stepping off a diving board, and the sensation vanishes even though gravity is doing exactly what it did a second earlier. Astronauts live permanently in that second. Their spacecraft is falling, they are falling inside it at the same rate, and there is nothing to press against.

The fall never ends because of horizontal speed. The International Space Station orbits about 400 km up, where Earth's pull is only slightly weaker than at sea level, and it travels at roughly 28 000 km/h, right around the planet in some 90 minutes. Its path curves downward under gravity at the same rate the surface curves away beneath it. Take the speed away and the station would come down like anything else, which is precisely what a deorbit burn arranges.

The condition has a name, microgravity, and the prefix is honest. Residual forces are small but real: the thin upper atmosphere drags on the structure, parts of the station farther from its centre of mass tend to drift differently, and every thruster firing or crew push shows up in sensitive experiments. The consequences are visible. Water clings in spheres, flames burn round, and blood that normally pools in the legs shifts into the chest and head, which is why newly arrived crews have puffy faces and thin legs.

Floating does not even require an orbit. Passengers on a suborbital hop feel the same thing while their capsule coasts up and back down, because for those few minutes nothing is holding them up either.