Page:Illustrated Astronomy.pdf/59



Now, apart from the theory about the Moon’s formation, every one of them agrees on something: in the past, it was closer to Earth, and it is a phenomenon we can observe today. At the moment it was formed, the Moon was very close to us, around 25,000 kilometers away, which means, less than a tenth portion of the current distance, this situation caused massive tides, and distortions on Earth’s surface, producing at the same time the slower rotation of Earth. The energy that our planet lost by rotating so slow transferred to the Moon’s orbit and caused the Moon to move away, and consequently, to move slightly slower.

Today, our satellite moves away about four centimeters from us every year. Such is the case that in 100 years more, the day would last two thousandths of a second less, which means that in the not-too-distant future, the Moon is going to look smaller than we see it today, tides won’t change so much as they do currently, and the day is going to have more than 24 hours.

If the Moon produces a tidal force on Earth, does the Earth also cause a tidal force on the Moon?

The answer is yes, it does. The difference is that the Moon’s surface is solid, so the deformation is much lower, whereas the liquid water is easily deformable. • • • 59