(Thinkstock)
Why are all planets round?

You asked us, "Why are all planets round?" and in a nutshell, it's gravity.

We all know what gravity is, right?

It's what makes apples tumble from trees and people fall flat on their faces, and
well, the bigger an object is, the stronger its gravitational field.

Planets are pretty big, so gravity acts on them as a strong force, pulling 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.

You see, 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?

• briannec-ste
12/04/2015 - 05:47 p.m.

The way the Gravity and the center of the planet pull together. that are arguing over what part of the planet will go where.

• matthewc-pay
12/08/2015 - 10:37 a.m.

I think the gravity had more or less of an effect on the terrain. Maybe some terrain were lighter than others which caused the gravity to not pull down them down as hard as the bigger terrains.

• kaelanr-pay
12/08/2015 - 10:47 a.m.

I really enjoyed this article because, it's very interesting it shows how planets are round and how gravity affects how they are shape. Also I learned that planets are not shaped perfectly round. Throughout this article I have gained a new perspective on planets and their shape and size.

• danellel-pay
12/08/2015 - 11:03 a.m.

This article spoke to me because I was always admired space. Also I always thought the planets were shaped solid, but i i have realized that some are filled with gases. Now it makes sense that 4 of the planets are called gas giants.

• tishelh-pay
12/08/2015 - 11:04 a.m.

Planets are all round because gravity pulls everything in together causing it to be a perfectly round circle If it wasn't for gravity they wouldn't be so round but a lot of things would be different without gravity.

• robertc-pay
12/08/2015 - 11:06 a.m.

This article is interesting. The force of gravity, pulled this molten material inwards towards the planet's center into the shape of a sphere. Later, when the planets cooled, they stayed spherical. Planets are not perfectly spherical because they also spin

• osajis-pay
12/08/2015 - 11:12 a.m.

Its good that schools are finally going into the specifics of things. I learned this from my favorite youtuber, but not every child has the same passion I do for science.

• TehyaWhite-Ste
12/08/2015 - 11:49 a.m.

The spinning of the planets works against the strong gravitational pull and that's why planets have a slight bulge instead of being perfectly round.

• nylae1-pay
12/08/2015 - 12:29 p.m.

I learned that planets aren't perfectly round because of gravity's strong force on larger objects pulling everything together forming a sphere. Also planets aren't perfectly round, they're shape is referred to as a spare tire.

• sydneyd-pay
12/08/2015 - 12:47 p.m.

Gravity is a huge factor because that is what keeps all of the things on the planet from flying off to space. Also, gravity holds all of the planet's objects and surfaces on it.