What Happens to Your Body in Zero Gravity?

When you stand on Earth, gravity pulls everything down. It keeps your blood in your legs and makes your bones strong because they have to work hard holding you up. In space, there is no heavy pull, so your body forgets how to do all that work.

Imagine if you stopped carrying a heavy backpack for months. Your shoulders would feel much lighter, right? That is what happens to an astronaut's whole body. Because they are floating, they do not need strong leg muscles to walk or strong bones to support their weight.

On Earth, gravity pulls the liquid in your body downward toward your feet. In space, that liquid floats up toward your head. This makes astronauts look like they have puffy faces and chicken legs because their upper bodies get too much fluid while their lower bodies lose some.

Also, without gravity squishing them down, their spines stretch out! You might see an astronaut grow a few inches taller when they are floating in space. When they come back to Earth, the gravity pulls them down again, and they seem shorter for a little while until their bones adjust.

Your body is smart. If you do not use something, it gets weaker. In space, astronauts must exercise two hours every day just to keep their muscles from shrinking and their bones from becoming brittle like old eggshells. Without this hard work, they would struggle to stand up when they land back on Earth.