Why does the Earth rotate about its own axis?



Why does the Earth rotate about its own axis?

In: Earth Science


Anything in a weightless environment is going to have some momentum about its different axis. Its hard to get something to sit perfectly still and not rotate. The Earth got its rotational momentum from the energy of the collisions of the debris that formed Earth during its creation.

About 4.6 billion years ago the solar system was a cloud of gas and dust. Gravity collapsed the material in on itself and it began to spin and forming the sun in the center of the material. The remaining material began to clump together to form the planets. The earth rotates because of the initial formation. This is also why the majority of planets spin in the same direction and same plane. Venus and Uranus may have had large collision in it’s past to cause their weird rotations

Ultimately, the Earth got its rotational momentum from the movement of the giant gas cloud as it collapsed to form the solar nebula. Debris which formed in the nebula may well have imparted momentum to the Earth, but such rocks and planetesimals all had their respective momentums from the collapse of the gas cloud too.

Usually collapse from a ginormous, diffusive gas cloud is centred around two points (binary systems are more common, probably some complicated maths reason why), in our case it seems to have been just one point which eventually became our Sun. As things collapse and start to rotate around the clump(s) of mass, rotation inevitably occurs due to conservation of angular momentum. Any tiny bit of relative movement is amplified exponentially when matter is being concentrated from a diffuse cloud that’s light years across into a solar system — like the way an ice skater’s spin speeds up as they pull their limbs closer into them.