Big luck: Why the sun and moon are the same
A total solar eclipse is an event that needs to be seen at least once in a lifetime. Fortunately, even if you don’t leave home anywhere (as the editors of Popular Mechanics did, who wrote a report for you on their business trip: “Night in broad daylight”), you will almost certainly have such a chance ... if only the weather did not fail and just not to forget the smoked glass. And then you will see how the two most famous celestial bodies converge, and how almost exactly they coincide: the solar disk covered by the Moon is not visible at all, and only the very edges of the rays are pulled out due to its uneven edges.
All this is the result of a striking coincidence. Indeed, the size of the Sun (average radius of 696 thousand km) exceeds the Moon (radius of 1737 km) by about 400 times - and about the same distance from us. As a result, the apparent dimensions of both of them are almost exactly the same. This situation is unique to 8 planets of the solar system and 166 of their famous satellites.
Many moons of large planets - Jupiter, Saturn, Uranus and Neptune - are believed to have arisen as a result of one of two processes. The first is collecting them from an accretion disk of gas and dust, which was attracted by the planet’s gravitational field. This is the same process that led to the appearance of the entire solar system, only in miniature. The second option - "capture" by the attraction of a large planet flying past the body. Most likely, it was in this way that a pair of satellites - Deimos and Phobos - appeared at Mars. However, this question is not so unambiguous, as we talked about in the article “The nature of“ fear ”.”
With our Moon, the situation is different. Neither one nor the other way explains some characteristics of the satellite (first of all, its impressive size) and, most likely, it appeared as a result of a powerful cataclysm that happened in the first 100 million years of the existence of the solar system. Then a lot of debris and all kinds of “garbage” left after the formation of young planets were rushing in space. And a rather large - approximately from Mars - body collided with the Earth, largely changing its appearance and throwing a lot of fragments into space, some of which gradually attracted to form the Moon. You can read more about this (and see an impressive video) in the article “Priceless satellite”.
The moon not only changed the face of the Earth, it made the appearance of life on it much more likely. For example, each planet, rotating, fluctuates, deviating its axis quite significantly, which causes serious changes in climate and makes it less stable, which means it is much more difficult for a young, not yet strong life to develop here. The moon, being not so small in comparison with the Earth’s body, gently “slows down” these vibrations, stabilizing the planet’s motion and the climate on it. For more information on what benefits the moon brings to life, read: "Without the moon."
However, let us return to the strange coincidence of the apparent sizes of the Moon and the Sun. The fact is that this coincidence is not just “cosmic, ” but also temporary. From the moment of its appearance as a result of the collision, the Moon slowly but constantly moves away from us, at a speed of about 3.8 cm per year. This looks like a frivolous speed, however, over long periods of time noticeably changes the "balance of power." If we observed an eclipse during the time of dinosaurs, somewhere 200 million years ago, we would see that the Moon is large enough to close the Sun completely, leaving no crown. Well, our descendants, who (if everything goes well) will live on Earth another 200 million years later, will not be able to see a total solar eclipse: the moon will be too small.
So the main coincidence is how strikingly the position of the slowly receding Moon and the development of intelligent beings on Earth combined. So, we can say that we were at the right time when the moon came to the right place.
According to the publication of New Scientist Space