Why Does The Earth Rotate On Its Axis?

Answer 1

its the effect of gravity on it

Answer 2

It has to do with one of Newton's laws that a body in motion tends to stay in motion. This leads to the principle of the conservation of angular momentum. This principle says that the product of a bodies mass and velocity does not change unless an outside force is applied.

When the solar system formed, a bunch of random mass from very far away collected via gravity. Because it came from so far away, it tends to spin faster as it condenses (like a skater pulling in her arms on a spin). This spinning causes the planets to orbit the Sun and makes teh planets spin. Since there is no way to dissipate the energy, things just keep on spininng.

It turns out that the action of the Moon and the tides does slow the Earth down, but it takes a long time. Billions of years from now, the Earth will spin very slowly with one day being over a month long.

Answer 3

Formation of solar system:
1) Interstellar cloud of gas, dust, etc., imploding from self-gravitation
2) Any such random dispersion will statistically have a net angular momentum other than 0.
3) As this cloud shrinks down, presence of this net angular momentum will give rise to a form like a spinning disk.
4) In the center where most of the mass is concentrated, sufficient mass and pressure will form the sun, upon nucleosynthensis initation. This sun spins in the same direction as the spinning disk.
5) Meanwhile, in the remaining matter in spinning disk, planetary bodies form from coalescing matter, their orbits also in the same direction as the spinning disk.
6) Finally, planets form from the orbiting coalescing matter. Residual angular momentum will impart spin to the planets, also spinning in the same direction as the original spinning disk.

This is the reason why all the planetary orbits, all the moon orbits, all the planet spins (well, almost), and the sun all spin in the same direction. It's all statistics of net random angular momentum in a blob of interstellar gas.

Answer 4

because it rotates that way..