 The apparent location of the Moon from different cities at the same time provides evidence that the surface of the Earth is not flat. The Moon can appear high in the sky in one city, while simultaneously appearing low in the sky somewhere else. For example, there's a moment in time when the Moon is directly overhead Guatemala City and simultaneously appears 60 degrees above the horizon in New York and 30 degrees above the horizon from Montevideo, Uruguay and only 14 degrees in Dublin, Ireland, all at the same moment in time. Let's simplify by looking at just Guatemala City and Montevideo. How is it that the Moon appears at these two different angles? Here are two possible explanations. One, the surface of the Earth is flat and the Moon is close enough such that the angles between the level ground and the line of sight to the Moon are different. Or two, in those two cities the surface of the ground itself tilts different directions and is not parallel. Let's look at the first explanation. Drawing this on a flat surface, this makes a nice 30-60-90 right triangle with a hypotenuse twice as long as the shortest side. So, at that moment in time, the distance from Uruguay to the Moon would be twice the distance from Guatemala to the Moon. Therefore, we should expect the Moon to appear about half as wide from Uruguay as it does from Guatemala, but that doesn't happen. In fact, the Moon appears almost exactly the same size from everywhere on Earth at any moment in time. This suggests that it's about the same distance from both cities. Or that there's something else somehow causing it to appear the same size. The second possible explanation is that the Moon actually is about the same distance from both places and that the reason it appears at two different angles is not because of distance but because the ground itself is tilted differently in both of those cities, which would mean that the surface of the Earth is not flat. Both of these explanations bring up more questions. If the Earth is not flat, why is the ground tilted in different directions on different parts of the Earth? And if the Earth is flat, how does the Moon appear the same size when it's twice as far away? If the Earth is not flat, the standard answer is to say that the surface of the Earth is close to spherical and gravity causes the direction of down to always be pointing toward the center of the Earth. And if the Earth is flat, one answer would be to say that atmospheric lensing makes the Moon appear the same size even though the distances are different. But the problem with that is that you still see these same angles 40,000 feet above each of those cities, which is above 80% of the atmosphere. So it's not clear how atmospheric lensing could accomplish that. Well, and also we don't see much magnification or distortion of star constellations. So it's not too clear how atmospheric lensing could be so drastically changing the size of the Moon without affecting the stars behind it. Another answer would be to say that the Moon is not a physical object but instead some kind of projection or light energy source. So we shouldn't expect it to diminish size with distance. If this is true, then well, I guess we can't really tell anything about the Earth by looking at the Moon. But to me, the Moon seems to be an actual physical object. Just look at it through a telescope. Another answer would be to object to these observations, saying why are we looking at the sky to determine the shape of the ground? Well, these Moon observations don't make a positive claim about the shape of the ground, just whether the ground is tilted in different directions. Is the ground in Guatemala City parallel to the ground in Montevideo? If not, that's enough to say that the surface of the Earth isn't flat. To determine which of these explanations is correct, you'll need to look at the evidence and explanations on both sides and see which seems most reasonable and logical, or come up with a third option. I say that if you agree with me that the Moon is an actual physical object and that everyone who sees the Moon simultaneously is looking at the same thing, then the most rational explanation is that the surface of the Earth is not flat. Thanks for watching. Subscribe if you'd like to see more. Leave a comment below, and if you do, remember to be civil. I know this kind of topic can generate a lot of controversy. Also, it's a pretty broad topic, so it might be helpful if you keep your comments related to those specific observations about the Moon I mentioned. Okay, thanks, have a good day.