Why on Earth is the planet’s day getting shorter?

Earth will complete a rotation 1.33 milliseconds earlier than usual on Tuesday, August 5. That makes it one of the shortest days of 2025 at 86,399.99867 seconds long. How that happens, and how we can even measure it with such precision, might make your head spin faster too.

On average, Earth physically rotates in 23 hours, 56 minutes, 4 seconds and 90.5 milliseconds – this is called a sidereal day. It is Earth’s “true” rotation relative to distant objects in deep space, like stars.

However, the kind of day most people go by is 24 hours long and that is called a solar day…

© La Conversation - mardi 5 août 2025