Why the earth rotate on its own axis?

We know, Earth's rotation is the rotation of Planet Earth around its own axis. Earth rotates eastward, in prograde motion. As viewed from the north pole star Polaris, Earth turns counter clockwise.

Earth rotates its own axis but What force makes the earth rotate on its own axis?

There are many views from different scientists. But there is no correct reason of that question. Here, i like to discuss some main views.

1. At the centre of the earth is a huge ball of liquid iron. It is always spinning and causes the earth to spin with it. Every few million/billion years the iron core shifts its direction of spin. When it does, the entire eco-system could be wiped out (if it's a big enough shift). Mega tsunamis, total change of weather systems, etc. Antartica could end up in the tropics.
   -----Johnathan Wilkinson, Surabaya, Indonesia

2. No force is needed because there is no resist