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By *opinovMan
over a year ago
Point Nemo, Cumbria |
Planets are spherical as a result of gravity squishing into that shape. If it's over a certain size there's enough gravity, if it's smaller it tends to stay whatever potato shape it accumulated in. I think the usual potato radius is around 2-300km. |
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By (user no longer on site)
over a year ago
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"I’m just asking for a friend 
But why ( friend ) has asked are planets round?
I assume they all have different gravitational pull. So why are they all the same ? "
Basically gravity pulls down the mass of the planet equally on all sides so it becomes a sphere. |
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By (user no longer on site)
over a year ago
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"Planets are spherical as a result of gravity squishing into that shape. If it's over a certain size there's enough gravity, if it's smaller it tends to stay whatever potato shape it accumulated in. I think the usual potato radius is around 2-300km. "
Better explanation than mine tbh |
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By (user no longer on site)
over a year ago
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"I’m just asking for a friend
But why ( friend ) has asked are planets round?
I assume they all have different gravitational pull. So why are they all the same ? "
The easiest way to explain it without getting too far into the mechanics of gravity is to imagine a planet consisted purely of a loose material like sand. As the material starts to accumulate it will be in whatever shape it happens to be.
Each particle exerts a "gravitational pull" on each other particle and once there is a sufficient mass as a whole; the combined gravitational pull will have created a "centre of gravity" in the middle of the mass of material. All of the individual particles want to be as close to the centre of mass as they can be. In the example of it being sand each grain would "fall down" towards the centre of the mass and this has the natural effect of organising into a spherical shape.
All stellar bodies we know of have a period of rotation. Again without going into the mechanics of inertia and the subsequent impact on the centre of mass; this rotation produces a slight flattening of the shape at the axis of rotation. The flattening of the earth means at the equator you are about 21km further away from the centre of the earth than if someone either of the poles. Concord flew at 18.3km, so realistically irrelevant but technically it's there. |
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By *hesblokeMan
over a year ago
Derbyshire village |
"Planets are spherical as a result of gravity squishing into that shape. If it's over a certain size there's enough gravity, if it's smaller it tends to stay whatever potato shape it accumulated in. I think the usual potato radius is around 2-300km. "
That'll be why my face is the way it is... |
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