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What is Gravity? | Science for Kids

"Millions saw the apple fall, but Newton asked why." - Bernard Baruch

Does your child have the same curiosity about gravity? Let's learn more about it together!

Gravity is an invisible force, meaning you can’t see it. It’s similar to the wind. You can see gravity work on things, but gravity itself doesn't look like anything. Gravity is what keeps everything on planet Earth from flying off into space. If you've ever thrown something in the air and had it fall back down, you're experimenting with gravity!

How Does Gravity Work?

Gravity is how planets or large objects pull other objects toward their center. Think of it like holding a big sheet. If you put a heavy thing in the center of the sheet, it weighs it down. The heavier something is, the greater the dip in the sheet. Putting another object, like a marble, on the same sheet will roll down toward the bigger object. Gravity works a lot like this. Anything with mass also has gravity, so technically, you have a gravitational pull, but nothing like how strong a planet's gravity is!

Gravity is what makes things weigh anything at all. The planet's mass pulls on your mass, which is what we measure as weight. So you'd weigh less if you were on a planet with less mass. Isn't that cool?

What Does Gravity Do?

Besides keeping us all on the surface of the planet, gravity is what keeps the planets orbiting around the sun. You can thank gravity for a lot of things. If we didn't move around the sun, we wouldn't have seasons. Plus, the moon's gravity pulling against the earth makes the tides go up and down. Gravity also keeps the atmosphere in place, allowing us to breathe.

Gravity also impacts the larger objects in space. For example, gravity forms stars by pulling materials together. You can find one of the strongest instances of gravity in black holes. A black hole packs a ton of mass in a tiny area, making its gravity so strong that even light can't escape it.

How Do Scientists Measure Gravity?

Scientists launched a pair of two satellites into orbit in 2002. These two satellites, part of the Gravity Recovery and Climate Experiment (GRACE), measure the relative gravity of the earth. Since the two satellites are identical, scientists can track when the satellite in front gets pulled away from its twin. These differences are recorded, and scientists can get a good idea of the gravity of that area of the earth. However, these differences in gravity are so minor that scientists need a microwave ranging system to ensure that GRACE is as accurate as possible.

However, when scientists want to measure the gravity of something very far away, like a planet or a star, they have to use another method. One way of doing this is to see how the object interacts with things nearby. Because gravity exists due to the mass of different objects, scientists can get a good idea of how strong their gravity works by figuring out the mass of the object. The same thing goes for bigger objects like galaxies; scientists track how fast the galaxies rotate and figure out their mass and gravity from there.

While gravity might seem like a mysterious force, scientists can measure it very well. Gravity can teach us a lot about space, as once we know how much mass something has, we can use that to figure out the entire system of objects around it. We can also use gravity to slingshot spaceships around a planet or to keep satellites in orbit around the earth. Pretty cool, right?

If you're interested in learning about other cool science projects, check out our other articles!


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