Astronauts Are Not Zero-Gravity

Here is a misconception that even smart people hold: astronauts on the International Space Station experience zero gravity. They do not. At 400 km altitude, Earth's gravity is still about 90 percent as strong as on the surface.

They float because the ISS is in free fall — falling toward Earth constantly but moving forward fast enough that the surface curves away beneath it. Astronauts and station fall together, producing permanent weightlessness.