2007-05-25 08:28:14 · 13 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
actually they are not actual spheres; due to the rotation rate and pull of external gravitational forces, the planets are actually fatter around the center and flatter at the poles. but that merely distorts the actual shape of the planet, which as you know, is sphere-ish.
Gravity is in fact a 4-dimensional force, tugging on objects in the 3 space dimensions and the 1 time dimension (hence those sci-fi stories of bending gravity waves to time-travel across it). let's focus on the 3 spatial dimensions (call them x, y, and z): if i were to tug on each with equal force, then the response would be that of a sphere. in fact, the equation for a sphere is : x^2+y^2+z^2, showing that a sphere is made from three dimensions of equal magnitude. it is derived because of the property of gravity being a 4D force.
2007-05-25 08:29:57 · answer #1 · answered by Tarvold 3 · 3⤊ 1⤋
Because that's the shape that gravity pulls them into. If it were a cube, for example, the corners would be further from the centre and have a higher gravitational potential than the middle of the flat edge. If the mass is large enough the matter will be unable to support its own weight against this gravitational field and will collapse into a sphere. In a sphere every point is the same distance from the centre, so there is no variation in gravitational potential.
2007-05-25 15:34:11 · answer #2 · answered by Jason T 7 · 2⤊ 0⤋
I'm not exactly sure on this, but I'm guessing it probably has something to do with the gravitational pull of the planets. Everything is pulled towards the center, which would eventually make a planet round or a sphere.
2007-05-25 15:31:44 · answer #3 · answered by Anonymous · 1⤊ 0⤋
It's own central gravity pull has through millenia made the planets in that shape,the stronger it's gravity the more perfect sphere is the shape,the earth because of it's rotation has a bulge on the equator,there are stars in the universe that because of their immense gravity are perfect spheres
2007-05-25 16:47:30 · answer #4 · answered by Anonymous · 0⤊ 0⤋
All planets are spheres, or close to them. It has to do with the way a planet comes together when it first starts to form and when it starts to have a gravitational pull.
2007-05-25 15:32:53 · answer #5 · answered by alee522 2 · 0⤊ 0⤋
Because our planets have slow rotation along their axis. If it was faster, due to centrifugal force, our planets would be elliptical in nature, but we'd probably be thrown off of them, ALSO due to centrifugal force.
Consider the planets as a viscus liquid. Let's say syrup. Swing a syrup bottle around you at arm's length but at a level angle. It should flatten out on the bottom of the bottle where the lable is, right? No. It will gather at the bottom (Where the expiration date is) (assuming you hold it by the top.) due to centrifugal force. It dictates that a spinning object has the tendancy to move outwards.
2007-05-25 15:33:58 · answer #6 · answered by jonathan k 1 · 0⤊ 0⤋
the force of gravitation pulls all of the matter into one mass, and as the planet continues to spin, it forms a sphere
take, for example a potter's wheel. you have a chuck of clay on the wheel. That is your mass. This mass spins on the wheel as planets spin, and when you put your hands around the clay, it applies pressure to the mass as gravitation does to planets, and forms the clay into a circular shape.
Sorry if that doens't make enough sense... I hope I helped! ;)
2007-05-25 15:33:11 · answer #7 · answered by Anonymous · 0⤊ 1⤋
Because gravity pulls the matter in all directions so it then pulls it in to a spherical shape.
2007-05-25 16:12:19 · answer #8 · answered by Flintstoner 4 · 0⤊ 0⤋
To turn easily
2007-05-25 15:47:00 · answer #9 · answered by hanibal 5 · 0⤊ 0⤋
Pyramids were still under copyright when they were constructed.
2007-05-25 15:38:49 · answer #10 · answered by BobbyD 4 · 0⤊ 0⤋