A day on Earth is described as 24 hours, but the planet has been slowing down for billions of years — and growth rings in ancient coral fossils show that 380 million years ago, hundreds of millions of years before any dinosaur existed, an Earth day was only about 22 hours long

The length of a day on Earth is not constant. The planet’s rotation has been slowing for billions of years, primarily because tidal friction transfers rotational energy from Earth to the Moon, which slowly moves outward to a higher orbit. The current rate of slowdown is small but measurable. According to the Wikipedia summary of […]