Why are all of the planets round?

Answer 1

All of the planets are round because of gravity. When our solar system was forming, gravity gathered billions of pieces of gas and dust into clumps which grew larger and larger to become the planets. The force of the collision of these pieces caused the newly forming planets to become hot and molten. 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. The spinning force acts against gravity and causes many planets to bulge out more around their equators.

Answer 2

That's because of the nature of gravity. You can think of gravity as a force that points inward toward the center of the planet so that every part of the surface is pulled evenly toward the center, resulting in a spherical shape.
Of course, planets are not perfect spheres because mountains and valleys and even skyscrapers are all deviations from the spherical shape. However, as planets get larger, gravity gets stronger, until eventually large objects on the surface are crushed under their own weight. That's why we don't have mountains that are 50 miles high or skyscrapers that are 2,000 stories tall. Planets stay basically spherical because any large deviations get crushed.

Although gravity keeps planets close to spherical, there are other forces that cause deviations from the basic spherical shape. For example, the rotation of the earth once every 24 hours, causes an apparent centrifugal force which creates a bulge at the equator. In fact the earth's diameter at the equator is 7,926 miles while the diameter between the poles is only 7,900.

Answer 3

Actually not all the planets are round. Many have oval type shapes The earth itself is not completely round.

A more accurate question is why do most planets look rather round.

The answer lies with two concepts: a) Planet formation and b) axial rotation

When a planet forms , it probably has an inner rotating core. As the planet ages it gathers debris from space and part of its gas nature condenses ( water for example may become solid ice or liquid oceans).

The axial rotation will spread gas atmospheres and early debris evenly. Planets with dense atmospheres such as Jupiter may look round, but it may take us a few years to find out the shape of the core.

I hope this clarifies the issue.

Answer 4

Planets are not round because they spin, and not because they go around the sun. It is because they experience internal gravity which pulls them down towards their centre. When all the bits are being pulled equally, the shape is a sphere. If they are a cube, for example, then the eight corners would be like 8 giant mountains on a sphere. The weight of these mountains towards the centre would be more than the material of the planet could withstand, so they would collapse and the planet would turn into a sphere.

Answer 5

PLANETS ARE ROUND NOT BEACUSE GOD MADE THEM ROUND. when the planets are made, they are made red hot, as hot as the sun itself. It takes billions of years to cool to what we c like one today.
but there is some gravity stuff, ain't it? this force pulls everything down to the earth,Actually, this force pulls us to the centre of the earth, since this pull is same on all places on earth, all the rock pieces are made compact to whatever form they can.


BUT PLZ , PLZ, ANSWER THIS ONE QUESTION, i'll give u some dough and ask u to make a shape of it, that has the least surface area than all the rest of the possible shapes. U know what, the only such possible shape is the sphere, a round one.
thus with a large gravity pull, planets tend to get shape of one that has the least surface area, hence the shape of a sphere
THIS IS THE REASON WHY THE PLANETS ARE ROUND!.

Answer 6

Gravity tends to pull everything down to the center and everything gets pulled equally from all sides. This results in the rounded shape you see. Planets are actually slightly elliptical due to the fact that they rotate. The Earth has a slightly larger diameter through the equator than through the poles. The centripetal force of the Earth's rotation causes a slight bulge at the equator.

Answer 7

I'm just adding to the answers you already got.

What gives their shape to objects are chemical bonds like strong valence bonds (giving shape to crystals, for example) and weak polarity bonds between molecules.

These bonds can easily be broken by heat. They can also be broken by mechanical forces (like gravity, shaking, crushing, etc).

When you have sufficient material coming together, you get both: the piling up of material (including the sinking of denser material through the lighter material) generates heat by gravitational fall (the loss of potential energy as an object gets closer to the centre of gravity) and by friction. The shaking from impacts, friction and sinking of materials also grinds things down (e.g., sand is ground-up rock)

With objects the size of planets, you get a lot of heat. Earth's core is still a few thousand degrees (say 4,000 C, close to 8,000 F) and most of that is from the gravitational heating (a small portion is from radioactivity).

When it was being formed, there was a lot more activity (gravitational sinking plus the kinetic energy at impact being transformed into heat) so the Earth was much hotter. It is not surprising that the chemical bonds could not hold any shape under these circumstances. Earth took the simplest form it could take (somewhat spherical).

The equatorial bulge is caused by Earth's rotation.

Answer 8

All planets are not completly round, but I know what you're talking about.Spheres are the most efficiant form in relation to volumn vs.surface area.Gravity pulls on the surface of any mass with equal force, therefore you couldn't have a square planet because the corners would be pulled in by gravity to form the object with the most surface area.

Answer 9

Because they are not strong enough to resist the force of their own gravity.

Gravity is a central force (its the same in all directions) and so naturally tends to pull things into a spherical shape. But materials like rock are strong so resist this.

So for asteroids, for instance, the rocks are strong enough to not succumb to gravity. For planets they are not (the strength of the rocks is fixed by the fine structure constant, the force of gravity by the gravitational constant, so its their ratio that matters).

It is now part of the definition of a planet that it is sufficiently large to be pulled into a sphere by its own gravity.

BTW the Earth is indeed very spherical - more spherical than a pool ball.

Answer 10

Because they spin and the other planets exercise a gravitational force in them, the eventually become round. Anyway, not perfectly round. The Earth is flatter in the poles.