Why are so many objects in the universe spherical in shape?

Question

The earth, the moon, the sun, the planets, millions of stars and other planets throughout the galaxy share this common shape. Why? Galaxies do not. Many other objects observed in the heavens do not. Asteroids and some of the smaller moons for example are not spherical. Why?

Answer 1

Ever tried moulding clay on a potter's wheel? A sphere is the shape that spinning moion tends to produce.

The larger bodies achieve hydrostatic equilibrium through spinning and become more or less spherical (they can be a little oblated (flattened at the poles, bulging at the equator). Schieving hydrostatic equilibrium is now part of the IAU definition of a planet, since 24th August 2006.

Many asteroids are too small to achieve this. The 4th largest, 10 Hygiae, is oblong, and if the dwarf planet definition doe not change and relax the requirement to be spherical, 10 Hygiae will not be granted dwarf planet status.

Answer 2

This is a phenomeonon called hydrostasis, or hydrostatic equilibrium. When an object has sufficient mass, gravity acts to distribute the mass into a sphere. Stars and planets, as well as many moons, have a sufficiently large mass. However, asteroids and small moons are not massive enough, so the force of gravity is not strong enough to pull them into this shape. An entire galaxy has an overall low density and a high rotation, which means that the local strength of gravity is not strong enough to create a sphere. However, the central bulges of many galaxies exhibit a spherical shape, because the center of the galaxy is more densely massive and the translational motion of objects there is not as rapid.

Answer 3

The spherical objects you mention are all the result of gravity acting in opposition to the mutual electromagnetic repulsion of atoms. In other words, atoms are a bit like, say, tiny tennis balls---they can be squeezed, but if you squeeze them a lot, they push back. Atoms are also attracted to each other, but not terribly strongly. So if you have a big lump of atoms, such as a planet or star, their mutual gravity pulls them into a spherical shape until all the atoms are squeezed a little bit. Then the whole thing is stable. The mutual attraction of the atoms can lead to irregularities on the surface, such as mountains.

Actually, if the object is rotating, it bulges out in the middle and is more of an oblate spheroid than a sphere.

Galaxies and galaxy clusters do not get their shape in the same way. In these large objects, the force of gravity is balanced by the kinetic energy of the stars and galaxies zooming around inside them. Each star or galaxy is orbiting around the combined mass of all the others.

Answer 4

that's the shape that minimises the potential gravitational energy, is all. When an object is too small, the gravitational forces are not quite as strong to pull it into a spherical shape (so many asteroids have funny shapes, often the result of collisions). Galaxies are not spherical, but they're not densely packed objects so this is hardly relevant

Answer 5

because the way the nebulae create planets and stars has to do with the condesing of gas and the pull of gravity around the center. you can find out more by studying the physics of heavenly bodies.

Answer 6

i also asked this question to a physicist. look the answer to this is just simple. you look at the asteroids /. what are they. nothing but small bits of pieces for when objects collided . these objects were round. so since , they were pre existing, they are not round. now due toi intense gravitational for due to the centre of gravity. all the debris collects and fights with with its companion particles of the same debris to reach that centre of gravity.

Answer 7

This is because only one creator created everything and made it in such a wonderful way that even if we all had a billion tongues it would not be enough to praise God.

Answer 8

ahhhhhhh spheres are cute