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Moonquakes are causing the Moon to shrink over time
Image source, Getty Images
The Moon is shrinking but don't worry too much - it isn't going anywhere fast.
According to scientists, the Moon has shrunk by about 50 metres over the last several hundred million years.
This is because its core is cooling, which causes the surface to crack, creating step-like cliffs called 'scarps'.
Each is roughly nine metres tall, making it look like there is a giant stairway on the lunar surface. They were first discovered more than 50 years ago by the Apollo astronauts.
"Just as a grape wrinkles as it shrinks down to a raisin, the Moon gets wrinkles as it shrinks", say the team of Nasa scientists.
"Unlike the flexible skin on a grape, the Moon's surface crust is brittle, so it breaks as it shrinks".
These cracks in the Moon's surface can cause moonquakes, sometimes as strong as level five on the Richter scale.
What is the Richter scale?
Scientists measure earthquakes - or in this case moonquakes - using the Richter scale. It is a way of measuring the how big and forceful the earthquake is, and the result is a number from 0 to 10.
It is measured on a machine called a seismograph.
Image source, NASA