Why does the Earth rotate about its own axis?
In: Earth Science
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.
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