What makes the Earth infinitely rotating around its axis I was reading two sites before I posted the question here. One site says something like that the collisions in Universe eventually set the planets rotating, another site says that our planet is formed from some collapsing Nebula or whatsoever and Nebula was rotating when it was about to die and that set the Earth rotating at first place.

The question should be probably better specified. Is Earth rotating because of some continuous force, or because at first place there was some one-time force which set it rotating and the effect lasts until now?

As for the first case, which force is it? As for the second case, that should break our physical laws, because there would be one force, applied a very long time ago which is still in effect and not about to slow down and with a very very long lasting effect. Because thousands or millions of years for rotation is a very long time, isn't it. Or is it slowing down? 

BTW: the infinite movement around orbit is bit mysterious too, because you can say that's because of gravity, but gravity itself attracts the things only to one direction, but orbit movement is like parallel with the gravity emitter, and again it is perpetual.
As for the second case, that should break our physical laws


That is precisely the wrong statement. The fact that the Earth is still spinning matches our physical laws exactly. The physical law I'm specifically referring to is known as Newton's First Law of Motion, which is loosely paraphrased as:


  An object at rest remains at rest unless acted upon by a net, outside force. Conversely, an object in motion remains in motion unless acted upon by a net, outside force.


What this means is that once something starts moving (like the Earth spinning) it will keep moving until something else stops it. The Earth long ago started spinning because of the initial angular momentum of the collapsing cloud which eventually made up the Earth. There is nothing in space to stop the Earth from spinning so it is just going to go on spinning1.

You appear to believe that if you start an object moving by applying some force, it will eventually run down and stop moving of its own accord. This is a common thought, based on everyday experiences. In fact, that was what Aristotle thought (and much of the world up until Isaac Newton's time). But what you're not taking into account is that there's always a force being applied to slow things down. Consider a car rolling along the highway. If you take your foot off the gas pedal, the car starts slowing down. But it isn't because some physical law says it should, it's because a net force is acting on the car to slow it down $-$ that net force being wind resistance on the car. So you see, even common, everyday experiences hold up to Newton's first law.



1Technically there are some small forces acting on the Earth to slow it down but those are nearly negligible and mostly from the Moon. These forces would take billions of years or longer to make the Earth come to a complete stop (if they ever even could).