It’s the reliable celestial companion that’s stuck around for 4.5 billion years.
But the moon is slowly drifting away from Earth, a physicist has revealed.
Dr Stephen DiKerby, a researcher in Physics and Astronomy at Michigan State University, said the moon is getting 1.5 inches (3.8cm) further away from our planet every year.
As a result, the Earth’s rotation is also slowing down, he revealed. And it means that – over time – days could get longer.
The revelation helps explain why around 70 million years ago, near the end of the time of the dinosaurs, Earth’s days were only 23.5 hours long.
As the moon continues to move further away, the number of seconds, minutes and eventually hours in a day will also gradually increase – but it’s likely none of us alive today will be around to notice it.
‘Don’t worry, these effects are so small,’ he wrote on The Conversation. ‘1.5 inches per year compared to a distance of 239,000 miles (384,000 km) is just 0.00000001 per cent per year.
‘We’ll keep having eclipses, tides and days that last 24 hours for millions of years.’
The moon is getting 1.5 inches further away from our planet every year, an expert revealed. Pictured: The moon over London in February 2023
Dr DiKerby explained that the moon is getting further away due to our tides.
The Earth’s tides are strongly influenced by the moon’s gravitational pull, which causes our oceans to slosh in two bulges.
One points towards the moon, because this is where the force of gravity is the strongest, while the other points away from the moon, where the force is weakest.
‘These liquid bulges do not quite line up with the moon,’ Dr DiKerby said. ‘They “lead” it a little bit because the Earth is rotating and dragging them forward.
‘This forward pull from the closer tidal bulge causes the moonto speed up, which causes the size of its orbit to increase.
‘This means that the moongets slightly farther away from the Earth.’
However, he reassured that the effect is very gradual and is only detectable on average over years.
‘If we fast–forward tens of billions of years into the future, eventually the Earth’s rotation could slow down until it is tidally locked with the moon,’ he said.
The Earth’s tides are strongly influenced by the moon’s gravitational pull, which causes our oceans to slosh in two bulges. Pictured: The moon over the Dolomites
‘At this point the moon would stop getting more distant, and you would see the moon only from one side of the Earth.’
Future generations will never get to witness this phenomenon, however.
First, in around a billion years, the Sun will get brighter and boil away the oceans, meaning there are no longer tides to influence the moon’s position in the sky, he explained.
And second, a few billion years later, the Sun will expand into a red giant, likely destroying the Earth – and the moon.
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