why are planets all round

[[Tycho?]]

yes but there are massive pressures inside the earth. suddenly theres going to be nothing holding them in. and what happens with high pressures, thats right an explosion(not necessarily a quick and dramatic bomb style one but i couldn't think of a better word.

 

Ahh yes, I guess the heat would certainly provide enough pressure.

[Royston]

The bulk of the earth is molten rock, and so would have very weak cohesion. The core is solid, but only from extreme pressure. Take away gravity, and you take away the force holding it together, and all you're left with is something very very hot and very very compressed, which would explode with unfathomable force and vaporize itself from the heat and sudden absence of pressure.

 

Deerrr, I really should of know that...considering what I've been studying for the last few weeks. Had a moment of stupidity I got swayed a little by Insane_aliens answer about the speed of the explosion...of course it doesn't actually change the result.

[swansont]

The bulk of the earth is molten rock, and so would have very weak cohesion. The core is solid, but only from extreme pressure. Take away gravity, and you take away the force holding it together, and all you're left with is something very very hot and very very compressed, which would explode with unfathomable force and vaporize itself from the heat and sudden absence of pressure.

 

 

But the pressure is due to the gravity, and the solids and liquids are relatively incompressible. I would think that a small amount of expansion would relieve the pressure. It would be the heat that would be the problem, if you had liquids flashing to gaseous form and needing to expand.

[Royston]

But the pressure is due to the gravity, and the solids and liquids are relatively incompressible. I would think that a small amount of expansion would relieve the pressure. It would be the heat that would be the problem, if you had liquids flashing to gaseous form and needing to expand.

 

Sorry, I'm still a little fuzzy on the order of events here. If liquids were free to undergo thermal expansion due to the release of pressure from gravity, would we (if we could hypothetically observe this) see the earth bulge and then the surface area would liquify as the molten rock become gaseous, as this was happening wouldn't anything that's held to the earth by gravity (such as farm animals) just fly off into space. I'm probably being stupid again.

[insane_alien]

yeah if gravity failed we would be pulled away from the earth by the rapidly escapng atmosphere, well... pushed, but anyway. probably wouldn't have much time to worry about it. and then you've got the big highly compressed nuclear fireball a 90 million miles away. the sun would explode.

[Sisyphus]

But the pressure is due to the gravity, and the solids and liquids are relatively incompressible. I would think that a small amount of expansion would relieve the pressure. It would be the heat that would be the problem, if you had liquids flashing to gaseous form and needing to expand.

 

Yeah, that's what I meant. The core of the planet is suddenly under no pressure, but is ridiculously hot. It tries to vaporize and pushes everything outwards.

[swansont]

Yeah, that's what I meant. The core of the planet is suddenly under no pressure, but is ridiculously hot. It tries to vaporize and pushes everything outwards.

 

 

Right. But that wouldn't necessarily be true for all planets, if they didn't already have a hot interior.

 

(is "ridiculously hot" the temperature equivalent of attaining "ludicrous speed"? )

[Sisyphus]

Right. But that wouldn't necessarily be true for all planets' date=' if they didn't already have a hot interior.

 

(is "ridiculously hot" the temperature equivalent of attaining "ludicrous speed"? )[/quote']

 

Yes it is.

 

But wouldn't most planets fly apart from inertia even if they weren't hot? Like, Mars, for example? The acceleration at the equator and at the surface seems like it would have to be much greater than any cohesion of the matter. Or maybe only part of it would fly off, leaving a huge axial pillar....

[swansont]

But wouldn't most planets fly apart from inertia even if they weren't hot? Like, Mars, for example? The acceleration at the equator and at the surface seems like it would have to be much greater than any cohesion of the matter. Or maybe only part of it would fly off, leaving a huge axial pillar....

 

 

I agree. A rotating planet would almost certainly disintigrate (to some degree) and fly apart.

[JesuBungle]

But why is the question of gravity failing even an issue lol. I don't mean to be a party pooper, but we're talking about the things that create gravity, flying into space. I'm thinkin as long as these things are still there, gravity will always be there.

Feel free to slap me if this was just a theoretical discussion of what would happen:-)

[JustStuit]

But why is the question of gravity failing even an issue lol. I don't mean to be a party pooper' date=' but we're talking about the things that create gravity, flying into space. I'm thinkin as long as these things are still there, gravity will always be there.

Feel free to slap me if this was just a theoretical discussion of what [i']would[/i] happen:-)

Party Pooper

I think they took away gravity to create a hypothetical situation to prove/disprove that gravity was the thing holding the earth in a sphere.