At one time or another, you’ve probably been grounded for doing something you weren’t supposed to be doing. Not good! But, that’s not exactly the kind of grounding we’re talking about today, even though both kinds are about staying put!

The Earth rotates on its axis every day — once every 24 hours. The Earth also flies through space at about 67,000 miles per hour as it travels around the Sun. And yet you’re able to stand still with your feet planted firmly on the ground. Have you ever wondered why you don’t simply fly off into space?

You can thank gravity for the fact that you’re firmly grounded on the Earth. When you consider the alternative, being grounded by gravity isn’t so bad, is it?

But what exactly is gravity? Believe it or not, it’s still a bit of a mystery. Scientists from Isaac Newton to Albert Einstein have studied it and come up with different theories to explain it. However, exactly how gravity works still cannot be fully explained.

So what do we know about gravity? We know that gravity is an invisible force that attracts all objects towards each other. It has been around since the beginning of the universe, and it works the same way everywhere in the universe on all kinds of objects of all different sizes.

We know that gravity keeps the Moon in orbit around the Earth. It also holds the planets in orbit around the Sun. Most importantly to you, it’s what keeps you on the ground and causes objects to fall toward the Earth.

Isaac Newton first described gravity as a force. Later, Albert Einstein theorized that gravity is a result of the curvature of space and time. Sound complicated? It is! And no one truly understands WHY gravity works. However, we can see its results and learn some things about it.

Scientists have learned that anything that has mass also has a gravitational pull. The more massive an object is, the stronger its gravitational pull will be. Also, the closer you are to an object, the stronger its gravitational pull will be on you.

For example, large, heavy objects, like airplanes, need lots of power to counteract gravity. That’s why airplanes have such large engines.

Likewise, astronauts who have traveled to the Moon have experienced the feeling of weighing less on the Moon. This is the result of the Moon being less massive than the Earth. As a result, its pull on a human being is much less than that of the Earth.

When in space, astronauts may also experience the feeling of being weightless. You’ve probably seen pictures of astronauts and objects floating inside of space vehicles. Is this because there is no gravity in space? Absolutely not!

There is gravity everywhere. However, the farther from the Earth that the astronauts get, the weaker the gravitational pull on them will be. It never gets to zero, but it can get too small to matter. As a result of extremely weak gravitational forces acting in space, the astronauts can float around inside their space vehicles!

22 Join the Discussion

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  1. Dear Wonderopolis,

    You tricked us to think that this article was about being grounded by our parents in our room.

    We had fun searching through your article. We did the experiment with the paper and shoe. It was fun to see the difference that gravity makes on objects.

    Thanks,
    Mrs. Johnson’s Third Grade

    • Happy Monday, Mrs. Johnson’s Third Grade! We think it’s AWESOME that you guys tried the experiment and learned some new things! We’re sorry for tricking you…we like to keep our friends WONDERing what each new Wonder will bring! :-)

  2. Dear Wonderopolis,

    We had fun testing out gravity by jumping into the air and realizing that we always land due to a gravitational pull. We are wondering if other planets have gravity?

    We love reading wonders!

    Thanks, Mrs. Meyer’s Third Grade Class

    P.S. We are excited to read tomorrow’s wonder after reading the clue…

    • That’s a GREAT question, Mrs. Meyer’s Third Grade Class! We will have to do a bit more WONDERing about that one! Thank you SO MUCH for leaving us this comment and letting us know that you like visiting Wonderopolis and reading the Wonders of the Day®! :-)

    • Hi, Tyler! We’re proud of you for thinking ahead and trying to guess the next Wonder of the Day®! You were…RIGHT! Way to go! Be sure to visit Wonder #373 to learn all about Jack-O’-Lanterns! :-)

    • Thanks for sharing your point of view on being grounded, Evan! It stinks to be grounded, but maybe it’s a good thing in a way, because we can use that time to reflect on why we are grounded in the first place and also try to figure out a way to keep from getting grounded again! :-)

    • Well, we think YOU are a pretty amazing Wonder Friend, Noah! Thanks for leaving us this comment and sharing what you think about being grounded! :-)

  3. Hi my name is Brooke and I’m in 6th grade.. thanks for sharing this video, I got bored of watching it though… I wanted some help… how do you make a website like this, that doesn’t require money to use? Me and my cousin wanted to know. :P

    • Hello, Brooke! Thank you for letting us know what you thought about the video for this Wonder of the Day®! We bet your parents, teacher, librarian, or computer lab instructor would have some GREAT resources for creative kids like you who want to start their own website! :-)

  4. I think that this article is very interesting and it is so amazing that gravity is everywhere in the universe! Then without gravity the human race would probably be all dead by now because of floating up into the sun or to close to it and die. But even if that did not happen all the food and water would disappear!

    • Thanks for telling us about your favorite part of this Wonder, B! We sure are glad you learned something new with us! Doesn’t science make you smile?! :)

  5. We loved the amazing video. We learned that space does not have zero gravity. We learned there are two different types of being grounded. We like the grounding mentioned in this article. Instead of walking on the moon you almost float while leaping. We are wondering if gravity can be taken away from objects?

    • Hello, Mrs G’s WONDERful Third Grade Class! We are so happy to have you all WONDERing with us today! It sounds like you learned a lot from this Wonder! We agree with you that we prefer to be grounded by gravity than by our parents. ;-) Keep WONDERing with us, Wonder Friends! :-)

    • Thanks for letting us know you thought the video was WONDERful, Amaria! Thanks for WONDERing with us today! :)

    • We have a hard time thinking of what to comment here in Wonderopolis too, Sian Pi! We hope you try WONDERing and commenting again tomorrow! Maybe it will be a bit easier! :)

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Have you ever wondered…

  • When is being grounded good?
  • How does gravity work?
  • Is there gravity in space?

Wonder Gallery

hDefying GravityAirplane enginehfive-friends-jumping_shutterstock_15812149 (Custom)Vimeo Video

Try It Out

Ready to learn about gravity firsthand? Great! Let’s get going. Grab a friend or family member to help you explore one or more of the following activities:

  • First, make sure that there is indeed gravity where you are right now. You can do this with a simple test. Jump and see what happens. If you jump into the air and keep flying off into space, we have a problem. If you jump into the air and return to the ground, we’re all set. Gravity is present and working. Have you ever thought to be thankful for the force of gravity? It might be fun to fly around without gravity from time to time, but life would get pretty hard if you weren’t able to walk around, wouldn’t it? What kinds of things do you enjoy doing that would be impossible without gravity? For example, think about what it would be like to try to swim, kick a soccer ball or throw a football without gravity!
  • We’ll assume that the gravity test worked and you’re still grounded here on Earth. Whew! That’s a relief! To test out gravity, you’ll need a shoe and a piece of notebook paper. Hold the shoe in your left hand and the piece of notebook paper in your right hand. Before doing this first experiment, make a guess about which item — the shoe or the piece of paper — will hit the ground first. Now, drop both items at the same time from the same height. What happens? Did you guess correctly? The shoe should have hit the ground first. Why? The force of air pushing up on the piece of notebook paper prevented it from falling as rapidly as the shoe. We call this air resistance. Think of some other items that you could drop at the same time, such as bowling balls, feathers, pillows and tacos. Which of these items would hit the ground first? Do some tests with other items you have around the house to see if you can guess correctly. (Note: Get your parents’ permission before dropping tacos on the floor!)
  • Up for a challenge? Do what scientists would do and make some modifications to see what effect they have on the results of your first gravity test. For example, crumple up the piece of notebook paper into a tight ball. Before dropping the crumpled paper ball and the shoe again, make another guess about which item will hit the ground first. When you’re ready, drop both items at the same time from the same height. What happened this time? How was it different from the first experiment? Did you guess correctly again? The paper ball should’ve hit the ground at about the same time as the shoe, since you reduced the amount of air resistance by crumpling up the piece of paper into a ball. Isn’t science cool? Can you do anything else to the paper to make it fall faster? What happens if you soak it in water? Isn’t gravity fun to experiment with?

Still Wondering

Explore Science NetLinks’ Gravity Launch lesson to explore how the Earth’s and the moon’s gravity affects the path of a rocket launched into space.

 

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