Solar System: How the moon got its bump

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Solar System: How the moon got its bump
Solar System: How the moon got its bump

How the moon got its bump

If there's one object in astronomy that we know a lot about, it's the moon. Nevertheless, he is still full of mysteries. Or did you know that he has a big bump and has been secretly running away since birth? Theoretically, it can't be like that at all. If you take the masses of the earth and moon, their orbits, their rotations and whatever other data and values are available and plug them into the equations of celestial mechanics, it turns out - the moon cannot orbit the earth in which it orbits the earth. A realization that is "uncomfortable" to say the least and has therefore deservedly been causing headaches in the calculating profession for many years. And that's a good thing.

It's good because science, in its stubborn quest to understand everything, always makes the greatest strides when it has just discovered that it understands nothing. Freely based on Socrates' motto "I know that I know nothing - and because I don't want to remain a fool, I set heaven and brain in motion to learn." In the case of the stubborn lunar orbit, this meant: observe, record, theorize, calculate, discard, start over.

And this is how astronomers found out amazing facts about the moon. For example, there are more than 300 perturbing influences bending its orbit. These include the decelerated rotation of the earth and ongoing friction losses due to the tides. And the secret flight of the satellite, which moves 3.8 centimeters away from the earth every year. If we trace this trend back in time, there must have been a time when the moon was only about a third of its current distance and whizzed around an earth in 18 hours where a day was just 12 hours. No wonder the physics seem a little more bizarre with a story like this in the background.

This express edition of the Earth-Moon system appears almost moderate if we consider the currently favored theory of the formation of the moon. After that, our satellite was born with a big bang when, in the early solar system, a near-planet the size of Mars collided with young Earth, ripping a sizable chunk out of it. About 10,000 miles away, this pile of debris formed the body that would later become our moon (today, the average distance between the moon and the earth is 240,000 miles).

However, in its infancy, this progenitor was not only closer and faster, but also hotter and more fluid. Only gradually did it cool down and freeze, while centrifugal and gravitational forces tugged at it powerfully. At the age of 100 million to 200 million years, it also went through the above-described phase of a coupling of self-rotation to orbital period of 3:2 - rotating three times around itself takes as long as two orbits of the earth.

If one can speak of "orbits" in this context, because the lunar orbit was an unusually elongated oval at that time. The astronomers around Ian Garrick-Bethell from the Massachusetts Institute of Technology came to these results when they calculated the conditions under which the moon could take the orbit it actually takes.

And something else must have happened in that resonance period to give us the current moon: It must have largely frozen. However, at a time when powerful forces were working in different directions, this could not remain without consequences. Instead of forming a well-formed sphere, the moon got a bulge on what is now its farthest part-a fairly large bulge that plays a correspondingly important role in the satellite's mass distribution, thereby in turn enabling its impossible orbit.

So the MIT team has largely restored the honor of science with their calculations. Assuming the moon has reached its resonance phase in the calculated period and has solidified into a teardrop shape, astronomers can now understand why it can still be seen in the sky instead of moving through space on its own. However, if one of the conditions is not met, it means: continue researching as soon as possible.

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