[ELI5] Why does the earth spin? How did it start spinning to begin with, why is it always the same speed and why does it spin at the speed it does?

Question

[ELI5] Why does the earth spin? How did it start spinning to begin with, why is it always the same speed and why does it spin at the speed it does?

In: 2

Answer 1

Earth spins because it was formed by small pieces of material that were also spinning. Those pieces were all spinning because the chaotic nature of the early solar system made it impossible not to spin. When it first formed, Earth spun significantly faster than it does today, completing a full revolution in 18-20 hours. Over billions of years gravitational interaction with the Moon has gradually slowed Earth’s rotation to the 24 hours we see today.