why is the moon round?
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Because gravity works equally in all directions. And gravity wants to pull everything as close to the centre as possible. It’s called the hydrostatic equilibrium. And the only shape in which all points are equally close to the centre and no direction is preferred is a ball.
The caveat to this is that rotation DOES create a preferred direction. It resists gravity through motion. So pretty much all planets and moons (Earth and Moon included) bulge out at the equator, and that why the solar system (and all orbits within it) is flat.
All bodies above a certain size are. If it wasn’t round it’s own gravity would be strong enough to pull the parts that are higher up down until all surface has an equal distance to the center (and a sphere is the only shape that permits that)
Smaller objects can be hard enough to prevent that. But the bigger something is the stronger the gravity gets and then no material can withstand that force.
As an example a cube shaped moon would technically have mountains that have a height of ~1000km. The pressure in the stone would be so big that it simply deforms like a liquid
The moon is round because it was formed by a bunch of rocks and dust coming together. Over time, the rocks and dust pulled on each other and squished together to make a round shape.
same reason any celestial body that is large enough is.
Hydrostatic balance/equilibirum, Aka: any body that is large enough ot have its own gravity well has to balance out its own internal pressure(pushing out) with its own gravity(pushing in) and to achieve this the shape you want to be in is perfectly spherical (as anything different would have gravity pull it into this shape ).
this is one of the criteria that separates planets from asteroids and other smaller celestial bodies.
for reference: https://asterism.org/wp-content/uploads/2019/07/tut38_Hydrostatic_Equilibrium_And_Planetary_Differentiation_pdf__page_2_of_7_-768×534.png
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