Astronauts on the International Space Station look weightless, drifting through the cabin like nothing is pulling on them. It's tempting to assume they've simply left gravity behind. They haven't- gravity up there is still about 90% as strong as it is on Earth's surface.

So why do they float?

The real explanation is that astronauts, and the station itself, are constantly falling ; they're just falling in a very particular way that never actually hits the ground.

Imagine throwing a ball horizontally. Gravity pulls it into a curved path, and eventually it hits the ground. Now imagine throwing it much, much harder. It still curves downward due to gravity, but it also covers so much horizontal distance that by the time it would have fallen, the curve of the Earth has dropped away beneath it. If you throw it fast enough, it never lands, it just keeps falling around the planet. That's an orbit.

Falling together

The ISS is doing exactly this: falling toward Earth constantly, but moving sideways so fast (about 28,000 km/h, or 17,500 mph) that it continuously misses the planet, tracing a circle around it instead. Astronauts inside are falling at the exact same rate as the station around them. Since they and their spacecraft are falling together, there's no relative force pushing them toward the floor , which is what "weightlessness" actually feels like.

This state has a more precise name: microgravity, or free fall. It's the same sensation you get for a brief moment at the top of a rollercoaster drop, or in a falling elevator, just sustained indefinitely, because the station never lands.

A common misconception

A lot of people assume space is simply "outside" gravity's reach. But gravity from Earth (and the Sun, and other planets) extends across the entire solar system and beyond, it just gets weaker with distance. Even satellites much farther out than the ISS are still very much under Earth's or the Sun's gravitational influence; that pull is exactly what keeps them in orbit instead of drifting off in a straight line.

Try it yourself

  • Watch a video of a "vomit comet" training flight, where astronauts experience brief weightlessness in a regular airplane that's put into a controlled dive, it's the same free-fall effect, just for 20–30 seconds instead of months.
  • Next time you're in a fast elevator, notice the brief feeling of lightness right as it starts moving down, that's a tiny, everyday taste of what astronauts feel constantly.

written by: Nazanin Ghulami