What causes the earth to continue rotating on its axis?

@w1z111 (985)
United States
March 6, 2007 4:33pm CST
Ever wonder how or why our planet continues to rotate on its axis, millions & millions of years after it was formed? Information on the net is a bit confusing, unless you understand the "conservation of angular momentum" concept. One site says it's using energy from the original 'big-bang' explosion, which somehow caused EVERYTHING to be put into rotational motion...but never to stop? That's some energy. Wonder who developed that?? Accidental? Natural Selection? Evolution? God?
1 person likes this
2 responses
@bkalafut (49)
• United States
6 Mar 07
Why is this a question? What would make it stop? The notion that motion requires a cause is on the ash heap of history. Linear momentum is conserved in the absence of an external force, and angular momentum is conserved in the absence of external torque. Put in even simpler terms, spinning objects continue to spin until something exerts a force to stop them.
1 person likes this
@w1z111 (985)
• United States
6 Mar 07
Ahhhhhh.....thx for that. But I don't see the answer to "why" it spins in the first place. What started it? Does all rotating matter rotate in the same direction? Why? What is the "force" that got it all going? Thx again.
1 person likes this
• United States
8 Mar 07
Now that you've clarified, that's a very interesting question. The very hot gas that was the early universe had, as gases do, not only density fluctuations, which were amplified into galaxies, galactic clusters, stars, etc. but also velocity fluctuations and, accordingly, angular momentum or vorticity fluctuations. When an object becomes caught in a bound orbit, it will curve one way or the other depending on which way it was going. Chances of it not having an overall tendency one way or the other are small, and over time interactions--collisions between dust, etc.--will cause the tendency to become more homogenous. Once one body has this sort of rotation, it also has a velocity gradient--particles toward the outside are moving faster than particles toward the center. So once the galaxy is spinning, the accreting solar system will pick up its own spin, because the particles that started off toward the outside of the galaxy will be swirlind in their direction faster than those that started off farther toward the inside swirl in theirs. And from that, the earth will pick up its own spin, etc. So an early thermal fluctuation on the scale of a nascent galaxy can be propagated all the way down to the level of the earth!
1 person likes this
• India
7 Mar 07
There is a theory in physics which states that all bodies tend to get into a position of least energy. The lesser the energy of the body, the more stable it is. Now consider a planet in space..if it is static it'll have high potential energy..so it starts rotating. And why does any body rotate with a particular angular velocity.. a planet rotates with that particular velocity at which the sum of its potential and kinetic energy is minimum. And a planet can rotate in any sense.. clockwise or counter clockwise. In our solar system, only venus rotates from east to west..all the others rotate from west to east. And for your information, its not only the planets, the stars also rotate about their own axes..the galaxies rotate about their own axes.. the whole thing is rotating. And nobody need make them rotate. It just happens.
• India
7 Mar 07
And when is the earth going to stop rotating.. its not going to happen. It may change its speed.. For that some serious disturbance has to happen in the neighbourhood of our solar system resulting in a serious disruption in the mass balance. And rest assured it is not happening during the lifetime of yours or mine.
@w1z111 (985)
• United States
7 Mar 07
Thanks for the post(s). I hear you about the laws of physics and all...and I (almost) understand it. But I still can't quite grasp where the original energy came from to get it all going. As you note, ALL matter is in motion, in macro and micro scale. I just don't know how it started in the first place, y'know? Thanks again for the informative response.
1 person likes this
• India
8 Mar 07
For that I think the big bang has to be clearly understood, which it still isnt. The big bang starts off saying that there was this infinitely small, infinitely dense ball of infinitely great energy... now thats a little hard to imagine. And where did that ball come from.. no one's explained it properly till date.