Why are all planets round? (Thinkstock)
Why are all planets round?
Lexile

You asked us, "Why are all planets round?"
 
In a nutshell? Gravity.
 
We all know what gravity is, right?
 
It's what makes apples tumble from trees and people fall flat on their faces.
 
The bigger an object is, the stronger its gravitational field.
 
And planets are pretty big, so gravity acts on them as a strong force. It pulls everything together towards their center.
 
And the resulting shape is a sphere.
 
Now, planets aren't actually perfectly round - they've got a bit of what you might call a spare tire.
 
Planets spin around their axes and the force generated by the spinning works against gravity and causes a planet to bulge out at its equator.
 
Join the club, planets.

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CRITICAL THINKING QUESTION
Why aren't planets perfectly round?
Write your answers in the comments section below


COMMENTS (214)
  • kyled-2929778-
    12/03/2015 - 03:20 p.m.

    That is really cool to have the planets around that way the sun is not in just one spot.

  • garretts-9868-
    12/03/2015 - 03:29 p.m.

    i liked this passage i love gravity but not falling on my face so good story

  • aidano-1-bar
    12/03/2015 - 04:00 p.m.

    Planets are not perfectly round because "Planets spin around their axes and the force generated by the spinning works against gravity and causes a planet to bulge out at its equator." I found this article interesting because i did not know gravity could be an effect on such a large object, and have so much impact.

  • lukep-6-bar
    12/03/2015 - 04:06 p.m.

    Planets aren't perfectly round because planets spin around their axes and the force generated by the spinning works against gravity and causes the planet to bulge out its equator. Planets are pretty big so gravity has a huge affect on them and pulls towards their center.

  • william1108-yyca
    12/03/2015 - 07:57 p.m.

    WOW! I never knew that is why planets are round. And I never even wondered why they are round. But now that I have read this article I now know why. Because of the planets are sort of big the gravity makes it round. Now I know and maybe I will know even more.

  • simonak-3-bar
    12/03/2015 - 08:02 p.m.

    Planets are not perfectly round because the gravitational pull causes for the equator to budge out a little bit, as stated in the text, "Now, planets aren't actually perfectly round - they've got a bit of what you might call a spare tire.
    Planets spin around their axes and the force generated by the spinning works against gravity and causes a planet to bulge out at its equator." This states that gravity is working against the spinning of the planet, causing for it's middle to come out.
    My opinion on this article is that it is very interesting and I am glad I now know why planets are "round".

  • owenh-ver
    12/03/2015 - 08:15 p.m.

    i think that it is cool that the gravity makes the planets round and how the bigger the objet is the stronger pull it has

  • jennaw-1-bar
    12/03/2015 - 08:25 p.m.

    The reason that planets aren't round is because, they spin. The force of gravity pulls the molten inwards, and it creates the sphere shape.

  • oscarb-1-bar
    12/03/2015 - 08:52 p.m.

    Planets aren't perfectly round because gravity works against their axis. Planets have an axis and when gravity pushes against them it causes the planet to bulge at the equator. I didn't think that planet were that round and smooth but It's cool how the gravity affects it that much to have a round shape.

  • John0724-YYCA
    12/03/2015 - 09:00 p.m.

    Well I learned something today and it is pretty cool how this process works. I never knew that something that is bigger as more gravitational field. So the planets are big so they pull in so that's why they get a shape of an sphere but what I really wonder is that what is gravity didn't work on planets any more. Then i wonder what the planets would have looked like.

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