Objects and astronauts appear to float around on International Space Station. Gravity also exists in space, that is the reason why the moon moves around earth or earth is orbiting around the Sun. If a tower is made to height of ISS and any object is thrown, it will definitely hit the ground. Space station and objects in it or satellites are also falling towards the earth. However, since they have huge orbital velocity, they don’t fall on the earth. They are falling around the earth. The circular orbital velocity around earth is 7.9 km/s. Satellites and International Space Station are designed to move around the earth and stay in orbit. Since they are in orbit they are in free fall and is weightless.