Question about hypothetical planet

[Eidolon]

Say there was a planet, which has all the essential material and physics to support life and is orbiting in a good location, has an adequate moon/tidal influence, and proper tilt. However, the planet is huge. Many times larger than earth, say the size of Uranus (giggity). Would it be possible for this planet to support life given the fact that its immensely larger? If the planet spun much faster than earth, fast enough that the centrifugal force countered the pull of gravity and equaled an earth sized pull could it possible support earth like life but with much more room to spare?

I didn't really put a whole lot of thought into formulating this idea. I was just watching a documentary about the beginning of the solar system and planet formation and it got me to think about it.

 

[Netheralian]

I think you just destroyed your planet with this statement. The force variation between the poles and the equator would flatten this thing into a pancake, if not destroy it completely.

 

[Eidolon]

If the planet spun much faster than earth, fast enough that the centrifugal force countered the pull of gravity and equaled an earth sized pull could it possible support earth like life but with much more room to spare?

I think you just destroyed your planet with this statement. The force variation between the poles and the equator would flatten this thing into a pancake, if not destroy it completely.

[/quote]

But wouldn't the gravity counter the centrifugal force and keep its shape? It would have to be a balance of the gravity vs the CF. Just more gravity would have to = faster spin to equal an earth like gravitational pull.

 

[Netheralian]

But wouldn't the gravity counter the centrifugal force and keep its shape? It would have to be a balance of the gravity vs the CF. Just more gravity would have to = faster spin to equal an earth like gravitational pull.

No - Because you have no CF at the poles. I.e. You would have a high equivalent weight at the poles (No CF), and low weight at the equator (high CF). The same variation in force will occur within the planet and would flatten it out.

 

[MRaverz]

Even without the 'pancake effect', you'd drastically decrease the length of the day so that life as we know it couldn't exist.

 

[Squawk]

Ignoring the physics questions about centripetal forces and grabity, just consider a planet that was such a size.

There is no reason for life not to emerge on such a world. Life forms such as ourselves wouldn't of course, for the simple reason that we are ill adapted to gravity of such magnitude, but that's by the by. Natural selection chooses the forms of life that survive, so whatever does evolve would be suited to the environment in which it found itself.

Going back to the physics, there are limits on what's possible for a planet. AndromedasWake is probably you best bet around here for simply knowing the numbers rather than having to look them up or do calculations (I lack the inclination I'm afraid), but beyond a certain speed of rotation a planet will simply rip itself apart. Take a peak at the wiki page for oblate spheroids to get started

http://en.wikipedia.org/wiki/Oblate_spheroid

 

[Lallapalalable]

but beyond a certain speed of rotation a planet will simply rip itself apart.

True, for the gravity to be counteracted to an earth-like level it would possibly spin itself into an asteroid field. I assume you, Eidolon, are speaking in terms of a humanizable planet, but bear in mind that uranus is methane gas and at that size its gravity is still significantly greater than earths, so for a solid planet of that size (or at least mostly liquid with a solid surface) would have to spin unimaginably fast for the equator to have 1G gravity, so fast that keeping it together would be impossible.

But, in therms of hypotheticallity (is that a word?) there is a possibility that life, perhaps even intelligence, could form on that planet. It would just be completely different in terms of biology from anything we could imagine.

 

[creamcheese]

You could have a planet that is larger than earth but less dense, and hence has the same gravitational pull... smallish variations in planet density exist, but you might have to build it yourself if you want it bigger than a certain amount, as it might never form naturally.

 

[DepricatedZero]

Hmm, what about a "hollow" planet? I don't know what part the core plays, but if one were to expand the size but retain the density by hollowing it out, so that the same mass filled a larger volume basically, would that allow for a larger planet with an earth-like gravity? Or would the hole in the middle cause problems in the formula?

 

[Netheralian]

Hmm, what about a "hollow" planet? I don't know what part the core plays, but if one were to expand the size but retain the density by hollowing it out, so that the same mass filled a larger volume basically, would that allow for a larger planet with an earth-like gravity? Or would the hole in the middle cause problems in the formula?

Simply - no.

1. Accretion would never be able to occur with a hole in the middle (i.e. it can't form)
2. It couldn't be maintained structurally (i.e. it can't stay that way)
3. It is entirely incompatible with a molten core which you will need for a magnetosphere (i.e. no life )

 

[nasher168]

A hollow world would probably need to be constructed deliberately-like a dyson sphere.

 

[Womble]

The simplest get around for increased size and still have an earth like gravity is to decrease the density of the planet. This could feasably work but depending on the density you could have an impact on the planets ability to maintain it's atmosphere. Whilst principly it would have the same pull as our planet with it's increased size you have an increase in the surface area of the planet, so more space for lighter elements to escape from.