Moon and Earth

Photo by NASA: Image of the Earth and Moon

By Scott Hamilton

Last week I wrote about two interesting facts regarding the Moon, but did not have a scientific reason for the observation of shallow crater depths on the moon. If you believe some of the claims that the Moon is actually an artificial satellite due to some of its strange features, I have some bad news this week.

One of these observations was in regards to the apparent shallow craters on the moon. The claims are that all the craters on the Moon are less than 300 feet deep, and if you were to take photos on the surface of the moon, it would seem that this is true. In reality, the deepest crater on the moon is nearly eight miles deep. This raises a big question. If the biggest crater is that deep, why does it appear only a few hundred feet deep from the surface?

To explain this appearance, I need to share a couple of interesting facts about Earth, and then compare them to the moon. The first was asked while I was on my last cruise.

“How far away is the edge of the horizon, where the sky and ocean meet?”

Most people would say 20 or 30 miles. In reality, you see the “edge” of the Earth’s curvature at only three miles away on the lower decks of a cruise ship. The higher up in the ship you are, the farther you can see. It comes out at about a half a mile per foot above sea level. What this means is that on earth, you can see something as tall as Mount Everest barely sticking above the horizon 230 miles away. This means that the 5.4-mile-high mountain looks like a rock a few feet tall at 230 miles.

If we take the same math and look at the curvature of the Moon, we see something quite different. The moon is about one fourth the size of Earth, making the horizon much closer, at 1.5 miles. On the moon you can see about a quarter of a mile further per foot above the surface. Taking this into account, if you had a crater eight miles deep and 1600 miles around, you could not see the edge of the crater from the center of the crater. In fact you would only begin to notice the top of the eight mile ridge when you are 1,363 miles away, and it will just begin to rise above the horizon. To compare it directly to Mount Everest, you would just see the tip appear above the horizon on the moon at a distance of 920 miles.

As you can see, you cannot rely on how tall or deep something looks from the surface in order to know its true size. This proves true whether you are on Earth, the Moon or any other spherical surface. The issue is how our minds perceive the world around us. We expect the horizon to be a straight line, and honestly, within our short line of sight (3 miles on Earth, and 1.5 miles on the Moon), it is true. The curve of the horizon is not perceivable on Earth until we reach an altitude of 6.6 miles. On the Moon, this altitude is much lower at a mere 1.6 miles. What this means is that from the highest point on Earth, you still cannot see the curve of the horizon, but if you put Mount Everest on the Moon, you would see the curve of the Moon clearly from only halfway up the mountain.

I guess this brings me to the conclusion that the surface of the Moon is not covered with shallow craters, but just appears that way from the surface, because the edge of the craters drop below the horizon, making them seem nearly non-existent from the surface. If the Earth were smaller, even the massive Mount Everest would appear small from a distance on the surface. This fact defeats the premise that the Moon has an impenetrable material a few hundred feet below its dusty surface, because it does, in fact, have very deep craters.

If you are interested in some of the math behind the numbers, the distance to the horizon is quite simple to calculate. The formula for the distance is the square root of two times the height of your eyes (6 feet, 0.0011 miles) times the radius of the Earth (3,959 miles) or the Moon (1,080). A fun thing to try would be to figure out these numbers for other planets.

Until next week stay safe and learn something new.

Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to shamilton@techshepherd.org or through his website at https://www.techshepherd.org.

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