Is the shape of the Earth a perfect circle?

Question

I just want to know why planets/moons are circles and not any other shape.

Answer 1

Nope--It's not even a perfect sphere. :-)

Things bigger than a hundred miles or so across tend to be spherical because of their strong gravity, which acts to level out any pointy bits. Over large enough stretches, even solid rock behaves almost like a fluid, and gets squished down by gravity. That's why there's a limit to how tall a mountain can be on the earth--if nature tried to build (say) a 20-mile high mountain, it would just collapse under its own weight.

Planets that spin, "bulge out" a little at the equator, because of the centrifugal force of the spin. That makes the planets not quite perfectly round. On the earth, for example, the diameter across the equator is about 26 miles greater than the diameter from the north pole to the south pole.

If a planet is very big and spins very fast, the bulge can be quite noticeable. For example, Jupiter (which is much larger than the earth) rotates very quickly, in only about 10 hours. It bulges so much that you can easily see in a small telescope that it is not perfectly round.

Answer 2

No, the Earth is a little bit thicker at the equator (due to rotation when the planet was molten). Also Mt. Everest is 28,000 feet above sea level while the Mariana trench is almost 6 miles deep. So it not a perfect circle or a sphere.

Neither are the other planets. For example mars has Olympus Mons which is 16 miles high. Venus has trenches and canyons, etc.

They appear circular because gravity pulls from all directions when the planets formed and clumped together in the smallest state they could while other forces (tectonic, volcanic, impact, erosion) reshaped them.

Answer 3

They are spherical (or almost) You have to think 3-dimensional if you want to understand space.

What shape would you expect them to be? A sphere is the perfect shape. Everything is trying to be a sphere – hey, you don’t get cubic rain drops, do you?

A spherical body, like a planet or a star, has its surface equi-distant from its center. That is the way gravity works.

With smaller bodies like asteroids, their gravity is not large enough to squeeze them into the perfect shape. SO, they are not in equilibrium and roll and turn and twist through space. Planets rotate very smoothly because of their spherical shape.

However, no planet is a perfect sphere because their rotation causes them to bulge at their equators. That is very evident in Jupiter because it is so large and it is gaseous. However, Earth bulges about 11 kms at the Equator. That may sound a lot but being 13000 kms wide, makes it almost a perfect sphere.

Answer 4

Earth isn't a perfect circle - it's more of an eliptical shape. And the reason why all the planets are spherical in shape is because of their rotation.

Asteroids and comets aren't spherical because they don't rotate.

That's what I can recall from all the documentaries I've watched anyway.

Answer 5

The earth is not a perfect sphere. It is actually distorted a little due to its rotation. All celestial bodies are spherical because a the surface of a sphere is a minimal surface area per volume.

Answer 6

It's not a perfect circle (and not even a perfect sphere) It's thicker along the equator and flatter at the poles.

Answer 7

Spheres are what I think you meant. They are this way because of gravity. Gravity comes from all directions pushing it into like a little ball. Think of a soap bubble for example. This is another reason why bubbles are spherical and not square/triangular/etc. Gravity comes from all directions jamming it into a sphere.

Answer 8

Not a perfect circle. It bows out in the middle.

Answer 9

Earth is an oblate spheroid due to it's spinning on it's axis. Spherical because we have always had (esp during our molten stage) enough mass/gravity for everything to pull together evenly due to gravity.

Answer 10

yes lke a bubble