Why are most of the planets in our solar system round?

Question

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Answer 1

"Most?" All the planets are round, and so is the sun. And so are all the planets and suns we know about. The "why" answer is not so easy. First, there is no good explanation as to why there are planets at all. The sun's gravity should pull everything into it.

Second, since the only decent explanation for planetary formation is accretion, and the particles that accrete form a disk, not a blob, circling the planet (like planetary rings), again, it is not clear why planets are round. We have to assume protoplanets heat up enough to melt the accretions and, rather than throwing off drops (like a spinning umbrella), they form a round object due to local gravity. Most planets are slightly distorted towards their sun or even moon(s), if large enough, and their spin produces a slight flattening at the poles and enlargement around the circumference (equator).

A new theory proposes that protoplanetary blobs push against the solar "wind", making them round and causing them to not fall into the sun. That's entirely computer-generated, of course - a simulation.

Answer 2

It's becuase of the planets' own gravity. Gravity doesn't like "pointy bits"--If something on a planet sticks way up (like a mountain), gravity tends to pull it down over time. If there's a big, empty hole somewhere, gravity tends to fill it up over time. This causes the terrain to be more or less "flat" over large scales. And the only 3-dimensional shape whose surface is "flat" everywhere, and where everything is the same distance from the center, is a sphere.

On small scales (over a few dozen miles, say), the gravity is not as strong as the internal strength of rocks (and concrete and steel, and so on). So on those scales, a planet is "bumpy." But when you look at it over large scales, the bumps seem pretty smooth. If you could reduce the earth to the size of a billiard ball, its surface, even with all the mountains, would actually feel SMOOTHER than a real billiard ball. That's gravity smoothing everything out.

If you've seen pictures of asteroids (and very small moons), you've probably noticed they're distinctly NOT round--they may be shaped like a potato or a dumbbell, for example. Because they're so small (only a few miles across), their gravity is not strong enough to overcome the internal strength of the rock; so they maintain their odd shapes.

Answer 3

It would be an anomaly if all masses in the Unverse were structured into a the shape of a cube.
The mass structures of the Planets in Solar system are in the form of a sphere because the Power that is locked into the Substance of Space(Dark Matter) surrounds a mass and envelops it with a pressure from all directions at the same time which keeps into a containment.

Gravity influence can be compared to the formation of a pizza dough. There is nothing into the dough to pull it together into a sphere. However if an external pressure on to the dough occurs ,we have a gravitational phenomena.
The Pizza Maker causes the gravity by pushing the dough together from all directions and forms it into a spherical volume=a Ball.
Note there was nothing inside the dough to pull it together into a ball.

This is sort of an Unproof that Gravity is a pull. It is more plausible to understand that gravity is an external phenomenon.
That means that , there is nothing inside a Mass that causes Gravity as a pull.

Answer 4

Most of the planets in our solar sysem are round in shape because,sphere has the least surface area and all particles try their best to attain a sherical shape in order to reduce their surface area.It is for the same reason that when you pour any liqiud in space,they attain a sherical shape.
For example,place a drop of mercury on a smooth surface.It attains a sherical shape.This phenomena is due to the cohesive forse(force of attraction between the molecules of same element) which brings the molecules together.
Similarly, when a new star (our sun is a star) is born,the gas clouds around it condenses to form planets..The dense gas passes through the three states which are the gaseous state,the molten liquid state and finally the rigid solid state.When a planet is in the first two states,it attains a spherical structure due to the cohesive force as mentioned above.Later the planet solidifies into a rigid planet like earth.

Answer 5

That's how they formed over time. Gases became liquids and liquids became solids, all the time being pulled towards the centre. A sphere is natures smallest form... maximum volume with a minimum surface area.

In other words, the planets are round for the same reason that bubbles in water are round.

Answer 6

i do no longer pick to assert it back yet sure, GRAVITY!!! All that rotation and Gravitational rigidity from the middle is what supplies them a extra or less around shape...yet u can no longer sense the earth could be a acceptable sphere, or the different planets, bulging out or huge craters, yet then that's the dimensions that extra provides to the around shape... i ask your self how the main suitable answer could be chosen here. all and sundry seems to assert a similar component...I burrowed some techniques, gave some o' my own, created the simplest answer to ur question...if u get the choose the flow... And its no longer in our image voltaic equipment purely...

Answer 7

Because when large amounts of dust and rock get pulled together by gravity, gravity forces them into a round shape - the pull of gravity is equal in all directions.

And all of the planets in our solar system are round. That's part of the definition of a planet: Big round thing.

Answer 8

The force of gravity pulls them into the shape with the smallest area for the largest volume ( like a soap bubble)

Answer 9

Only planets/rocks/stars/moons that have an orbit, are "round". This is due to the circulatory orbit that the sole called object takes. By spinning over and over, and revolving, this "shapes" the object.

This is also why asteroids/meteors don't appear to be "circular", because they aren't in an orbit.

Answer 10

Aren't they all?