Was looking at a NASA image of the sun and thought, huh, why wouldn’t it just be a chaotic blob? Pls help
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Gravity is pretty strong for these large planets. Every bit of gas is pulling on every other bit of gas, this has the net effect of pulling everything towards the middle of the object. The shape where all the mass is closest to the centre is a sphere. So the gas forms a sphere.
For small objects like pluto or comets, they are very irregular in shape due to very little gravity.
A larger objects, the force is great enough to shift rocks and gases and turn planets and stars into perfect spheres.
Ever notice that you can’t pile sand straight up really high? Eventually it just collapses into a pile. Well, thinks like trees and building manage to get higher because they’re stronger materials than sand, but if they get big enough, they still can’t hold up their own weight, and collapse into a pile. It happens to everything.
And out in space, what things collapse into are spheres. Gravity makes everything want to get to the center of the pile, and a sphere is the most efficient way to get everything as close to the center as it can get.
Think how water acts in space – it wants to stick together. If you let it float, it forms into a ball.
Other material likes to do the same thing. At the size of a planet the math is different, but the way it behaves is basically the same.
Here’s Chris Hadfield doing a neat experiment showing how water likes to stick to itself (and his hands) in space. https://youtu.be/o8TssbmY-GM
The way I explain it to my students: gravity pulls towards the center of mass. If you have a big pile of stuff and you pull towards the middle from every direction, what shape do you get?
A relatively famous planet known as WASP-12b is so close to its sun that it is egg shaped, literally being torn apart by its sun. I believe this happens because a day and a year are the same on that planet, so one side always has more gravity pulling it, which the planet’s own gravity isn’t able to resist. So not all planets are spherical.
Because laws of physics like spheres.
Put a drop of oil in the water. It will form a circle. Maybe not a perfect one but you can clearly see a circle.
Water droplets on the table will also form a half-circle while the bottom touching the table is flat. Even if the shape is irregular, you can always see rounded edges if you look close enough.
Freely suspended liquids always form a sphere if not affected by other forces.
The reason for this is quite simple, yet fascinating to me – out of all geometrical shapes in the world, the sphere has the smallest volume and surface given the same width and height.
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