and are all different sizes
2007-09-08 06:33:51 · 9 answers · asked by some people are rude 2 in Science & Mathematics ➔ Astronomy & Space
Does a tree falling in the forest make a sound, if no one is there to hear it?
Its a matter of DEFINITION! if you define SOUND as 'something someone hears', then No, a tree makes no sound at all when it falls.
Why are planets round? Because if they weren't they wouldn't be planets. No kidding.
a planet:
"has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (near-spherical) shape"
from Wiki...
this is not the ONLY requirement to be a planet (sorry, Pluto)
2007-09-08 06:44:22 · answer #1 · answered by Faesson 7 · 2⤊ 1⤋
Planets are approximately spherical because they solidified through cooling from an earlier molten state. In so doing they retained the spherical shape they assumed when they were molten (fluid) masses.
A free-floating mass of fluid takes on a spherical shape because of a simple geometric law that states that a sphere is the shape that contains the greatest possible volume within the smallest possible surface area.
This has to do with molecular cohesion, but really does not depend on a certain critical volume or mass from a gravitational standpoint. To see proof of that, look at raindrops and other water droplets of even very small sizes. They naturally take on a spherical or sphere-like shape because of that geometric law.
For another example, drop a few drops of vegetable oil into a bowl of tap water. Notice that they take on a spherical shape under water.
As for why they are all different sizes: It's really not a "why" kind of thing, but something that scientists call an "imponderable." There's no particular reason; they just happen to be the sizes that they are.
2007-09-08 07:55:15 · answer #2 · answered by aviophage 7 · 1⤊ 1⤋
The center of gravity pulls things into an even shape, round.
However, there are no real rules. We might find some heart shaped planets or planets shaped like a T or something.
2007-09-08 07:03:53 · answer #3 · answered by Anonymous · 1⤊ 2⤋
they are round because when they are first very hot, they are soft so the forces of gravity pulls them together from all directions. just like soap bubbles. and yes, it is part of the definition of a planet so if there is something that's not round, it can't be a planet anyway
2007-09-08 08:27:39 · answer #4 · answered by brandon 5 · 0⤊ 0⤋
All molten masses in free fall take on a spherical form due to the nature of gravitational forces. Lead shot and ball bearings are made by dropping molten metal from different heights into a cooling medium.
2007-09-12 05:05:57 · answer #5 · answered by johnandeileen2000 7 · 0⤊ 0⤋
All planets are round , why would u expect another shape .
2007-09-08 09:07:52 · answer #6 · answered by JOHNNIE B 7 · 0⤊ 0⤋
planets are spheres because the center of gravity pulls to the center of a planet so when u take an object like a piece of paper and u squeeze it together u get a sphere.
2007-09-08 06:43:19 · answer #7 · answered by Anonymous · 0⤊ 1⤋
it is because their gravity pulls the material to its core... and their size varies because of their general make up and the occurences during their formation...
2007-09-08 10:05:25 · answer #8 · answered by Lexington 3 · 0⤊ 0⤋
Magic, or if you ReALLY WANN KNOW!!!111 LOLZ! G3T A TEXTBOOKZ!
2007-09-08 06:42:43 · answer #9 · answered by Anonymous · 0⤊ 3⤋