Physics
Gravity in Space: The Persistent Pull
Quick fact
The International Space Station is only about 250 miles above Earth—still well within Earth's gravitational pull. Gravity there is about 90% as strong as on the surface.
Why this is interesting
If you could stand on the International Space Station with a scale, would you weigh anything? Surprisingly, the answer is yes—but you'd never get a reading.
Read the full explanation
Understanding Gravity in Space: The Persistent Pull
Many people think gravity disappears in space, but that's not true. Gravity is the force that keeps planets in orbit around the Sun and holds galaxies together. On Earth, we feel gravity as weight because the ground pushes up against us. Astronauts on the ISS float because they and the station are falling towards Earth together—just moving sideways fast enough to keep missing it. This free-fall state is what we call microgravity or weightlessness.
A deeper explanation
Gravity follows an inverse-square law: its strength decreases with distance but never reaches zero. At the altitude of the ISS, gravity is still about 90% of surface gravity. The reason astronauts float is not lack of gravity but that they are in continuous free fall. Their forward velocity (about 17,500 mph) balances the downward pull, creating an orbit. This principle is central to understanding how satellites, the Moon, and planets move. Without gravity in space, orbits wouldn't exist; objects would fly off in straight lines.