Round planets

[bischar]

Is there a reason for the round form of the earth and other planets ?

Is it possible that we see one time a planet with a form of potato or something else ? :beer:

[Xerxes314]

Originally posted by bischar
Is there a reason for the round form of the earth and other planets ?Yes, the pressure of the weight of all that rock crushes out any open space and may liquify the core. A plastic material will take on a shape that minimizes its gravitational self-energy: that is, a sphere.

Is it possible that we see one time a planet with a form of potato or something else ?Yeah, but they have to be really light so you don\'t get the effect described above. The largest such object known is Hyperion (http://saturn.jpl.nasa.gov/science/moons/moonDetails.cfm?pageID=6), which is about 300km long.

Or you can spin it really fast. That makes your planet an oblate spheroid, which is like a sphere but squashed.

Xerxes

[nmondal]

In between, only very few planets are parfectly round I presume, earth is a far call from calling a sphere...he he...

[Edited on 7-18-2005 by nmondal]

[Xerxes314]

Originally posted by nmondal
In between, only very few planets are parfectly round I presume, earth is a far call from calling a sphere...he he...
This site details the surface of the earth a bit more: Geoid of the Earth (http://kartoweb.itc.nl/geometrics/Reference%20surfaces/body.htm). The deviations from elliptical are about one part in 15000. Very very small.

Xerxes

[nmondal]

You meant oblet spheroid.
:eureka:
But no way sphere.

[Xerxes314]

Originally posted by nmondal
But no way sphere. The deviation from spherical to elliptical is somewhat larger, but still under a percent. It\'s spherical to high precision.

Xerxes

[nmondal]

A non spinning hole is an example of a sphere, right?
With very high precision?

[bischar]

Yes curious.. why no planet in orbit with a form of portion of tore ? :tumble:

And why should a planet (in orbit or not) spin on itself, it doesn\'t roll on anything ? Would there be a force pushing more on a side than on another due to the move around the central planet ?

[nmondal]

Umm...rolling planets are there...though rare...:lol:

[mayanknagory]

the reason why plannets or any object at the elementary level is sperical is because of a simple fact that nature loves symetry and symetrical operations can be best seen in a sphere

[nmondal]

the reason why plannets or any object at the elementary level is sperical is because of a simple fact that nature loves symetry and symetrical operations can be best seen in a sphere


Who says?
:eyebrow:
Which elementry object is spherical?
An atom? No way.
An elctron? Nobody knows.
Then what?

[bischar]

An eye.
A pearl.
A bubble.
An egg of some animals (fishes and insects).
A cell.
A drop of water in vacuum (maybe, never seen :wink:)
A fire ball (like in Tintin comics).
A track let by something turning around a point.

Why and what else ?

[nmondal]

The talk is about *perfectly* spherical.

[bischar]

I believe those objects are in theory perfectly spherical, don\'t you ?
Now any environment causes the perfection to become unperfect (isn\'t that sad ?).
There is hence probably no perfectly spherical sphere, although in the vacuum maybe ?