There was an event in 1178 that might have been a lunar impact bright enough to be seen with the naked eye. (On the other hand, an impact that big should have thrown up enough ejecta to create noticeable meteor showers on Earth, of which there are no accounts.)
The biggest crater the Earth has had in 50,000 years is less than one mile across.
Strikes that size were much more common in the very early solar system than they are today. (Except after major collisions in the asteroid belt, such as the one around 470 million years ago):
I, for one, understand you clearly.
By definition, the craters on the near side of the moon are the result of meteors that passed the earth and then hit the moon. Similarly, the craters on the far side of the moon are the result of meteors coming in the other direction: they hit the moon before reaching the earth.
If all the meteors in the universe are moving in random directions, then about half of them would be coming from a direction where the moon is closer, and about half would be coming from a direction where the earth is closer.
But here’s the big gotcha: Of all the meteors which start out on the earth side, a lot of them are not going to reach the moon. First of all, the earth is an obstacle (though not nearly as large as many people would imagine), which will simply block many of the meteors that are heading to the moon. But much more importantly, the earth’s gravity is so much stronger than the moon’s that it will be much more likely to knock the meteors off course. Some of those meteors will be captured by the earth’s gravity and crash on earth, and others will simply go off course. In contrast, of the meteors coming from the other direction, relatively few will go off course because of the earth’s gravity, and a great many will crash into the moon.
To me, the above explains why the far side of the moon is rather uniform and is totally covered with random craters, whereas the near side - which has been protected by the earth to some degree - still retains the gigantic “seas” of so long ago. There have simply been fewer meteors hitting the near side to ruin the scenery.
Surely someone smarter than me has either confirmed or debunked this idea. Anyone know?
Read the “differences” section on the “far side of the moon” Wikipedia page linked up-thread.
(Also, being pedantic):
Yes, I see what you mean (in the 3rd paragraph there). I’m a little disappointed that it uses the words “obscure” and “shield” (which connote a physical barrier) and doesn’t mention anything about gravitational effects. But I concede that they know more about it than I’ll ever hope to.
Ignorance fought. Thank you.
I’ve visited Meteor Crater, in early 2016, and it is a good place to go. The visitors center displays and film are good. They have a piece of the meteorite there, and you can touch it. What’s interesting is that when I knocked on it with my wedding ring, it rang metallically, almost like a bell.
Highly recommended, if you’re near Winslow AZ on I-40.
That is because asteroids/meteoroids are travelling so fast and Earth’s gravity is so relatively weak that gravitational effects aren’t that significant. Meteoroids that hit Earth aren’t drawn in by gravity–they hit because they are trying to pass through the same space at the same time.
The area of the moon as seen from Earth is 0.2 square degrees. The area of the whole sky is 41,253 square degrees. The ratio is about 1 to 200,000. So ignoring gravitational effects, which as mentioned are small, the chance of a meteoroid heading for Earth coming from a random direction being blocked by the moon is about 1 in 200,000. However this underestimates the probability since a meteor is more likely to approach near the ecliptic than randomly across the sky. On the other other hand, the Moon is always near the ecliptic too.
I took the family there when we were visiting my brother when he lived in Flagstaff. I preferred checking out the casinos along I40 in New Mexico.
It’s like that Victorian-era phrase, “darkest Africa.” They didn’t mean it was really shady under all those trees in the jungle nor that the locals had extra melanin but that it was unknown – from the European point of view.
Oh, and doing a quick google-search, 300-km across is about the smallest crater that can be distinguished by the naked eye. That’s a pretty big thump.
Cite.
The smallest features we can observe on the moon with the naked eye are generally greater than 300km across. A great example of a small but still visible object on the moon is the brilliant crater Tycho on the south of the moon.
Matter of fact, it’s all dark.
That’s fine. To each their own. I’d only stop at a casino to use their bathroom.
And even that I would avoid, because they force you to walk deep into the pits of the casino just to get to the bathroom. That, and also the cigarette smoke. No casinos for me, except on the rare occasions I want to play.
Meteor Crater’s visitors center is a nice diversion in that part of the country. I’d also like to visit The Eye of Quebec, Lake Manicouagan. It’s massive. At 750 sq miles it’s much larger than MCAZ. MCAZ is less than 1 sq mile.
It’s amazing how close the crater is to the visitor’s center. Talk about a near miss! 
But only the fifth largest known impact site remaining on Earth.
And also in the US is the Chesapeake Bay crater:
I know you’ve already learned this isn’t quite right, but here’s another factor. Ref this:
As Darren says, Earth’s gravity bends the path of income asteroids a smidgen. But it is just as likely to convert what would, absent Earth, be a near miss into a hit as it is to convert what would, absent Earth, be a hit into a near miss.
For an simpler example, imagine shooting a gun towards a target with no wind. But you’re a crappy shot with shaky hands and sometimes your aim is a little left, sometimes a little right, and sometimes on the money. So some shots hit and some go to either side.
Now let’s crank up a big wind from the left and do the same shooting. Some that would have gone by to the left now hit the target and some that would have hit the target now miss on the right side. No net difference.
Yes, truly. I’m very surprised that I didn’t think of that. Thanks!
Right, so even what gravitational effects there are still (mostly) cancel out (not completely, but it’s a good approximation). Roughly speaking, the amount of shielding the Moon provides for the Earth is the Moon’s size in the sky compared to the size of the whole sky (or vice-versa, for the shielding Earth provides to the Moon). And while the Earth takes up a larger portion of the lunar sky than the Moon does in our sky, it’s still not very much.
Gravity falls with the inverse square of distance, so an object just a million km out (practically nothing on the scale of the solar system) feels just a 0.0004 meter per second tug from Earth: