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Sun 20 Jun, 2004 12:19 am
I have a question about the behavior of gravity. In all the textbook we are shown a diagram of the 9 planets (or now 10) they are all in line with eachother on what seems to be a centerpoint at which the sun pulls the planets around with its gravity. So if we call this its Y axis that all of the planets move on, why do planets not rotate around the sun on the X axis, or Z axis? Does gravity have the same pull in all directions? Or is it stronger at this hypothetical equator?
The plane and direction of the planets' rotation probably has to do with the fact that the solar system coalesced out of a cloud of gas with a certain direction of rotation. So you could call it an historical accident.
The gravity of the sun doesn't pull them around, it only pulls them towards itself and prevents their velocities from allowing them to escape.
The gravitational field strength of the sun is the same in all directions.
I believe it is not so much the property of gravity as that of the angular momentum (rotation).
Yeah it's to do with the rotation of the original cloud plus the effects of objects within the cloud that formed. Hence not all objects are on the same plane.
Gravity is the same in all directions. There is no inherent property of gravity that explain why all the planets are in the same plane. Other pieces of the puzzle are that they are all orbiting in the same direction and spin the same way (with one exception).
The solar system started out as a cloud of gas and dust. It spins faster and faster and flattens into a disk. The planets are formed out of this disk.
Comets that orbit the Sun were not formed from this disk. They have orbits that are not in this plane.
This link explains this pretty well
http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html
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