Also, the length of the ISS is several times the height of a typical tree, but it orbits about 250 miles above the Earth’s surface.) (For an earthbound observer, the apparent size of the sun is roughly equal to the apparent size of the full moon, as we know from observing solar eclipses. Without the aid of a telescope, each object would certainly have a smaller apparent size, but the ratio of their apparent sizes would be the same as when viewed through a telescope.

All that matters is the relative sizes of the two objects, and their corresponding distances from an observer. And interestingly, the presence of a telescope has no bearing on the extent of the illusion.

In the case of the ISS and the sun, the same logic holds, but neither of those objects is located on earth, so the horizon plays no role. When the moon is overhead, you can’t make these comparisons with terrestrial objects because you typically can’t look straight up and see a tree that’s located a mile away from you. However, although you are also one mile closer to the moon, your distance from it is practically the same as it was originally was because it’s about 240,000 miles away from you, making it’s apparent size seem unchanged. If you were to drive toward that tree, stopping a couple of yards away from it, the disk of the moon would appear small in comparison to it, because your distance from the tree is now one thousandth of what it originally was, causing the tree to occupy a much larger fraction of your visual field. Your brain automatically makes this comparison when the two objects are viewed in the same direction, making them seem “close together.”

The moon seems larger on the horizon because, when compared to a tree that’s located, say, one mile away from you, the apparent size of that tree comprises a very small fraction of the apparent size of the moon.

The extent of the illusion you mention depends on the relative sizes of two objects (like the rising moon and a tree, or the ISS and the sun), as well as their distances from an observer.

Flat earth society cruise