How did the Moon end up with an orbit the perfect distance to cause total eclipses?
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It’s a complete coincidence that the moon is the right size and distance to appear almost exactly the same size as the sun from our vantage point. The iconic total eclipse with the slight ring of light around its edge is unique among the terrestrial planets in our solar system.
If we ever were to become part of a larger, interstellar community, the Earth solar eclipse might be a tourist destination for aliens who would not have a chance to see something quite like it elsewhere.
It’s not a perfect distance. If it were closer the [eclipse paths](https://solarsystem.nasa.gov/internal_resources/6216/Solar_Eclipses_2023_and_2024_Map.png) would be far larger than they are. Further away, they’d be smaller to non-existent.
The moon is very gradually drifting away from the earth. In the distant future it will be too far to completely cover the sun. In the distant past, meanwhile, it was closer, and the moon was always larger than the sun in our sky.
In other words, it’s the perfect distance *now,* and we only care because our civilization arose during that window. If this weren’t the case, then we wouldn’t have even realized that we were missing out; no one would be sitting around going “boy I wish the moon and the sun were the same size so one could *just* cover the other when they line up.”
It’s also *not* perfect; the moon’s orbit is elliptical, as is the earth’s orbit around the sun, and the moon’s orbit also doesn’t line up with the ecliptic. New moon only aligns with the ecliptic a couple of times each year (from our perspective), and for a total eclipse you still need the orbits to be at the right distance. If they’re not, you only get an annular eclipse (which is what we got last weekend), or a total eclipse that just grazes one side of the earth and no one really gets to see it. Total eclipses affect a relatively tiny part of the earth’s surface and if you live your entire life in one spot then chances are you will never see one. My idea of a “perfect” system would be one where the entire surface of the earth gets to see a total solar eclipse at regular intervals, perhaps once a decade or so, common enough that no one misses out but rare enough that they’re still appreciated.
The moon’s orbit isn’t perfectly circular, sometimes it’s too far away to cause a total eclipse, which is what happened for the most recent eclipse.
Now, because of tidal forces, some of the rotational energy of the Earth is getting transferred to the moon, slowly pushing it to a higher orbit. So eventually it won’t have total eclipses anymore.
It’s pure coincidence and chance. Some religious fruitcakes cite this as evidence of god’s intelligent design of the universe.
It isn’t permanently at that distance it is slowly moving away from the Earth, it is just a fluke that causes the eclipse.
It hasnt always. Its gets further out every year. It wont totally eclipse in x# of years. We happen to be here at the right time.
It’s a complete coincidence. The moon’s original orbit was much closer to the Earth, and it has been moving ever so slowly further away ever since. Eventually, the moon will be too far away for total eclipses to happen at all. So, it’s not so much that the moon’s orbit just happened to work for eclipses, but rather that we happened to be alive at the right part of the moon’s life to be here to see them (although earlier in time, they all woulda been total).
Pure luck
Fun fact, if you go back in time or forward in time say a Billion years, the moon wouldn’t be the same apparent size as the sun, as it is drifting away. So in the past, the moon was bigger than the sun, in the future it’ll look smaller
This is because the moon tugs on the earth unevenly, because it’s orbit is slower than the earths rotation, it steals energy from the earths rotation, causing the day to lengthen and the moons orbit to rise.
It’s worth pointing out that total eclipses occur any time the moon is angularly the same size or larger than the sun.
People seem to think it’s only when they’re exactly the same size, but that isn’t true.
For example, many of jupiter’s moons are so large that they would appear many times larger than the sun, these cause total eclipses sll the time.
So, Earth. Well, Earth’s moon actually isn’t at a ‘perfect’ distance.
Just last week there was an Annular eclipse, which occurs when the moon is further away in its orbit, and therefore not large enough to fully block the disk of the sun, leaving a ring of sunlight shining around the moon.
This is most certainly not ‘perfect’.
At some points in its orbit, the moon is a little too far away.
At other points it is close enough to fully cover the disk of the sun. This is merely a coincidence.
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