Astronauts are not weightless because gravity is gone. They are actually in a constant state of freefall.

The phenomenon of weightlessness in space is scientifically known as microgravity. At the International Space Station (ISS) altitude of approximately 250 miles (400 kilometers), the Earth's gravitational pull is roughly 8.9 meters per second squared. This is only slightly less than the 9.8 meters per second squared we experience at sea level.To stay in orbit, the ISS must maintain a precise orbital velocity of about 17,500 miles per hour (28,000 kilometers per hour). This speed allows the centrifugal force of the station's forward motion to perfectly balance the downward pull of gravity. Because the station and the astronauts are accelerating toward Earth at the same rate, there is no normal force pushing back against their feet, creating the sensation of floating.Sir Isaac Newton first described this concept using the 'Newton's Cannonball' thought experiment in his 1687 work, 'Philosophiæ Naturalis Principia Mathematica.' He theorized that if a cannonball were fired fast enough, the curvature of its falling path would match the curvature of the Earth. This state of perpetual falling is what defines a stable orbit.Without this extreme forward velocity, gravity would pull the ISS straight down into the atmosphere within minutes. NASA and other space agencies use this principle of freefall to conduct experiments that require a low-gravity environment. It allows researchers to study fluid dynamics and crystal growth without the interference of Earth's heavy pull.