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Comment on Would a disk shaped planet have uniform gravity like earth or would it vary depending on whether you're near the center or edges?

sbeak@sopuli.xyz ⁨1⁩ ⁨day⁩ ago

A planetary mass disc would collapse into a sphere. Gravity works towards the centre of mass, so it makes sense that it becomes a sphere once the force is great enough, where the distance from said centre of mass is nearly equal from all points on the surface. it’s the reason why smaller objects are usually oblong and weird shaped (e.g. asteroids) while larger objects are close to spherical (e.g. Pluto!)

And what do you mean by “uniform gravity”? If you mean for a theoretical person on the planet, it would not be uniform on the edges as you have an imbalance of forces towards either side (while on a symmetrical spherical planet, it would all add up to a downward force), while in the centre it is symmetrical, an equal amount of mass on either side

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sbeak@sopuli.xyz ⁨1⁩ ⁨day⁩ ago
One interesting note, some planets like Jupiter and Saturn spin so fast they bulge in the equator, making them a little less spherical than normal!

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- hansolo@lemmy.today ⁨1⁩ ⁨day⁩ ago
  Earth, too. By about 43 km.
  
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- RichardDegenne@lemmy.zip ⁨23⁩ ⁨hours⁩ ago
  uwu whats this?
  
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Skullgrid@lemmy.world ⁨1⁩ ⁨day⁩ ago

A planetary mass disc would collapse into a sphere

… but galaxies are “flat”?

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- meco03211@lemmy.world ⁨1⁩ ⁨day⁩ ago
  A galaxy isn’t a planet. Planets themselves are rarely perfect spheres. Earth is actually an oblate spheroid. Solar systems also exhibit planar geometry. They all spin. The angular momentum is enough to overcome the gravitational pull. If that momentum was not enough to overcome gravity, all that mass would collapse into a spherical object. Depending on how much mass would determine what kind of celestial body it is.
  
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- hansolo@lemmy.today ⁨1⁩ ⁨day⁩ ago
  Not all galaxies are flat, and the stars in galaxies are sperated by enormous distances.
  
  It’s the difference between Saturn and its rings. Saturn the plantet collapsed into a spheroid. The rings are pieces of stuff, not solid. Of all the stuff in the rings were thrown together into one solid clump, it would be a spheroid, too.
  
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  - bjoern_tantau@swg-empire.de ⁨1⁩ ⁨day⁩ ago
    And I think we’re pretty lucky to see Saturn’s rings. Wait a few million years and they will collapse into a moon.
    
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- ada@lemmy.blahaj.zone ⁨1⁩ ⁨day⁩ ago
  Yep, as are solar systems. But when they collapse in to single objects, those objects end up spherical once they’re about a third the size of our moon (or even less than that if they’re icy/gaseous).
  
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- sbeak@sopuli.xyz ⁨1⁩ ⁨day⁩ ago
  In this case, it’s all to do with the conversation of angular momentum! This is also why the solar system is in a plane.
  
  Basically, during formation, the cloud of gas forming the galaxy is spinning super fast, and the difference in rotational forces flattens the cloud closer to a plane.
  
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