What causes the Earth’s rotation to slow down over time?

The Earth’s rotation slows down over time due to tidal friction caused by gravitational interactions with the Moon. As the Moon’s gravity pulls on Earth’s oceans, it creates tidal bulges that resist Earth’s rotation, gradually transferring rotational energy to the Moon. This process causes Earth to lose a tiny fraction of its rotational speed and adds to the Moon’s orbital distance. Over billions of years, this effect has led to a gradual slowing of the Earth’s rotation.