Earth’s Day is Getting Longer: What’s the Mystery?

Earth's rotation has been slowing down due to friction effects associated with the tides driven by the Moon. That process adds about 2.3 milliseconds to the length of each day every century. A few billion years ago an Earth day was only about 19 hours.

Over millions of years, Earth’s rotation has been slowing down due to friction effects associated with the tides driven by the Moon. That process adds about 2.3 milliseconds to the length of each day every century. A few billion years ago an Earth day was only about 19 hours.