Billions of years ago the average day on Earth lasted less than 13 hours, and today it continues to grow. The reason lies in the interaction between the Moon and our oceans.
Throughout human history, the Moon has been an inseparable presence on Earth. Its gentle gravitational pull sets the rhythm of the tides, while its dim light illuminates the night sky.
More importantly, the Moon may have helped create the conditions that make life possible on our planet, according to some theories.
But the Moon is moving away from the Earth.
As it performs its balanced astro-ballet around Earth, it is gradually moving away from our planet in a process known as "lunar recession". By firing lasers from reflectors placed on the lunar surface, scientists have recently been able to measure with pinpoint accuracy how fast the moon is receding.
They have confirmed that the Moon is moving away at a rate of 1.5 inches (3.8 cm) each year. And as it does, our days are getting shorter and shorter.
"It has to do with the tides," says David Waltham, professor of geophysics at Royal Holloway, University of London, who studies the interaction between the Moon and the Earth. "Tidal drag on Earth slows its rotation".
The length of an average Earth day has increased by about 1.09 milliseconds per century since the late 1600s, according to recent analyses.
