NASA's Earth Minute: Scale in the Sky

Gravity. It’s everywhere! It’s the force that keeps our feet on the ground and the moon orbiting Earth.

But where does it come from? Mass! That’s simply the amount of “stuff” that makes up an object.

The more mass something has, the more gravity it has.

Earth’s gravity is constantly changing because something with a lot of mass is moving around all the time.

What’s moving? Water and ice!

If you’ve ever picked up a bucket of water, you’ve felt just how much mass it has. It creates a lot of gravity.

Using satellites, NASA can measure Earth’s gravity, like a scale in the sky. By comparing one month to the next, we can track where the water and ice is going.

Weaker gravity means there’s less water in that spot.This can tell us where a glacier is melting or a severe drought is drying up lakes.

And stronger gravity? More water, such as in the rainforest in the Amazon.

Our scale in the sky even lets us measure water deep underground.

Knowing where the water and ice is moving helps us improve weather models, forecast droughts, floods and wildfires.

It also helps us get water where people need it.

Measuring gravity from space helps NASA better understand the entire water cycle here on Earth. And that can come in handy next time you want a glass of the stuff.