Expert: James Gort - 4/8/2005

Question
        My question is going to sound a little crazy but please If u can answer it, Then please do. Even if it is just a prediction.
        What can make earth change it's rotation direction around it self. So that the sun come out of the west. That's it, simple but crazy.

Answer
Hassan,

There are no crazy questions - only crazy answers!  And I hope this isn't one of them.

The earth's rotation carries a LOT of energy, in the form of "angular momentum".  It gained that energy when the planet condensed from the gas and dust forming the early solar system.  To reverse the rotation direction, something would have to somehow get rid of that energy (to stop it) and then to give it additional energy to start it rotating in the opposite direction.

That's not impossible, but it's unlikely we could live through such an event.  In Uranus's early history, astronomers think it collided with a large body that changed its rotation.  It didn't completely reverse it, but it knocked it on "its side".  So Uranus doesn't rotate from west to east, but from north to south!  I suppose if the body would have hit it somewhat differently (rapidly moving objects carry a lot of momentum), the direction of rotation of Uranus could have been totally reversed.

In the case of the earth, nothing internal (like earthquakes or magnetic poles changing) could totally reverse the rotation (although a large earthquake slightly does change the axis of rotation).  But a collision with an earth-sized body could cause it to change its rotation, although that collision could also break up the planet, or otherwise make it uninhabitable.

Hope that answers your question.  It can happen by a collision, but I know of nothing else that can cause it.

Prof. James Gort