Why are the Planets almost round?

[Pete999]

Go on take the Mick not bothered, I couldn't sleep last night so I got up and started watching some NASA documentary's, one described how some Scientists reasoned that the Earth and the Moon, along with other planets within our Solar System, were created by giant collisions millenniums ago, so to my question, how come Planets areas near spherical as you can get for something as big as they are, surely if they were created by collisions they would be ragged in appearance, but most appear to be spherical, what do you all reckon? A bit deep for an early morning thread, but hey ho.

 

[Octopus]

Gravity.

 

[Bob Geldoff1234]

I am no expert but I would think it's something to do with the earth being molten in it's early life and the earth spinning at a very fast speed.Everything gets thrown outwards into a perfect circle as it spins.

 

[Midwest]

They're not round, they're flat

 

[telectrix]

you're all wrong.

 

[Spoon]

you're all wrong.

View attachment 43741

Love minecraft... but that's taking the thread off at a tangent again....

 

[Pete999]

They're not round, they're flat

Right!!!!!!!!!!!

 

[telectrix]

Love minecraft... but that's taking the thread off at a tangent again....

that's the answer to pete's question. it's to provide tangents that makes the planets round. only a circle has tangents.

 

[rsgaz]

Everything gets thrown outwards into a perfect circle as it spins.

More like, these is so much mass, that everything gets crushed into a sphere. Doesn't really matter if it's spinning or not.

If there is enough mass to create enough pressure and heat to turn the middle into liquid, it will squidge* into a sphere under it's own weight.

* squidge = highly technical term!!

 

[Pete999]

More like, these is so much mass, that everything gets crushed into a sphere. Doesn't really matter if it's spinning or not.

If there is enough mass to create enough pressure and heat to turn the middle into liquid, it will squidge* into a sphere under it's own weight.

* squidge = highly technical term!!

Kin Hell a few Nobel Prize winning theories floating about today. Especially the "squidgy " theorem, love it.

 

[Squid]

Mercury and Venus are the roundest, near perfect spheres, now why are planet different colours and what about hypervelocity?

 

[The Ghost]

That's the way God made them.

 

[littlespark]

Not perfectly spherical. Fatter round the equator as the spinning pushes it out.

A bit like a builder after too many times on a merry go round

 

[Midwest]

Right!!!!!!!!!!!

I was listening to the Vine show some time ago. There were several believers explaining their theories. As to the edge of the world issue, apparently there's a massive ice wall, thats stops you falling off. Its located in Antarctica. Thats why the worlds main protagonist won't allow public access there. And the reason you see the curvature of the world from an airliner, is the pin cushion effect of the aircrafts windows

 

[Deleted member 26818]

Planets form by particles attracting each other due to gravity.
They form a sphere because the attraction operates in all directions equally.

 

[telectrix]

but the earth is not a sphere. it's a jagged lump. it's only
round because water has filled most of the holes.

 

[littlespark]

Jagged lumps due to parts of the crust around the planet pressing against each other and being pushed up.
Also volcanic spouts of molten lava solidifying and creating mounds.
All this happens over millions of years and is hard for us to imagine.

A bit like waiting for a plumber to arrive

 

[telectrix]

 

[GeorgeCooke]

Surface tension.

 

[ElectroChem]

@rsgaz has it essentially right.

Any planet/planetoid of larger diameter than ~1000km (IIRC) will form a roughly spherical shape as its own weight is enough to overcome the rigidity of rock/iron-nickel so it 'squidges' together.

@telectrix

The earth is jagged to our perception, but in terms of the surface roughness vs overall diameter it's about as smooth as a billiard ball.