Why the planets are spherical in shape?

Question

Why the planets are spherical in shape?

Answer 1

Dip a finger into a bowl of water and then take it out.Now watch the drop of water as it trickles down the finger and drops down.You will notice that the drop of water acquires a spherical shape.Place a drop of mercury on a smooth surface.It attains a spherical shape;this phenomena is due to the cohesive force(force of attraction between the molecules of same element) which brings the molecules together.

But then,why does it take a spherical shape,why not a cubic one?.This is because, out of all mutidimensional geometric figures,sphere has the least surface area.Thus all particles try their best to attain a spherical shape in order to reduce their surface area.It is for the same reason that when you pour any liquid in space they attain a spherical shape.But this is not the case with solids since their molecules are compactly packed and can not be displaced.

When a new star is born,the gas clouds around it condenses to form planets.The dense gas passes through three states,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 molten planet solidifies into a rigid planet like Earth.

Answer 2

Because thats the way the universe wants them

Answer 3

They are only roughly spherical. The Earth bulges at the Equator for example. The moons of Mars are not spherical at all. But broadly yes large planets are spherical-ish.

It is to do with gravity. All the mass is pulled towards the centre equally, since the attraction is universal and applies to all the components of the planet. Hence the sphere is the best option.

consider if they were cuboid. The corners would be further from the centre which would indicate they were being attracted less strongly to the centre than the edges (from pythagoras theorem the hypotenuse is longer than the side). Since gravity is universal this doesn't happen.

Answer 4

Planets stay basically spherical because any large deviations get crushed.

" Yes, Planets seem to be spheres, not cubes or cylinders or oddball rocky shapes.  Some smaller bodies such as asteroids or Mars moons Phobos and Deimos, do have odd shapes, but larger bodies like the nine planets and most of their moons do look like spheres.  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 5

You spin me right round baby right round. Ever try to spin a square?