**A remarkable fact — people know that our planet has been in the shape of a ball for more than two thousand years. Nevertheless, there are still people who seriously believe that the Earth is flat and are convinced that all the stories about its sphericity are simply a conspiracy of insidious scientists, all photographs from space are fakes, etc. In this article, we’ll look at five simple ways to make sure the Earth isn’t flat.**

**Simple life experience tells everyone that the higher you stand, the further you see. But the field of view is still limited. This fact is especially noticeable at sea or on plains where there are no obstructions to the eyes.**

*Being on the surface of the Earth, the horizon is limited to a few kilometers, while if you go higher it immediately expands at times. That is why observation posts on ships are located on high masts.*

*It is also noteworthy that objects beyond the horizon cannot be discerned with the help of even the most powerful binoculars or a telescope, while if the observer rises only a few meters above the surface, he will again be able to see objects hidden behind the horizon even with the naked eye.*

**This is easily explained by the fact that objects, as they move away from us, hide behind the roundness of the earth’s surface and disappear from our field of vision, since the light reflected from them simply cannot reach our eyes.**

*Particularly clear confirmation is two mountains in Hawaii: Mauna Kea — on the main island of the Hawaiian archipelago, the highest point of Hawaii and Kawaykini on the island of Kauai. Between the two peaks — 509 kilometers.*

*The height of Kavaikini is 1598 meters above sea level, Mauna Kea is 4207 meters above sea level. A straight line to them runs mainly along the sea, crossing only the islands of Oauhu and Kahoolave, while on this line there are no significant elevations that could block observation.*

**If the Earth were flat, then from the top of Mauna Kea one could see the top of Kavaikini, because there would be no obstacles between them. However, this is not the case. In cloudless weather, the gaze of the observer rests on the horizon and no binoculars, telescopes and telescopes will help.**

*At the same time, our eye is quite capable of distinguishing Mount Kavaikini at such a distance. The angular resolution of the human eye is 0.02 degrees. Knowing the geometry at the level of the 8th grade of secondary school, it is easy to calculate the size of the minimum object that the eye with an angular resolution of δ = 0.02 degrees is able to distinguish at a distance of D = 509 km.*

**Substituting the numbers into the formula, we see that at a distance of 509 kilometers, the human eye is able to distinguish objects with a size of 177 meters and more.**

**The second simple way to refute the assumption that the Earth is flat is to observe the pole star and determine its angular height, i.e. the angle between the straight line connecting the observer’s eye with the polar star and the Earth’s surface.**

*Mariners and geographers are well aware that the angular height of the pole star is always equal to the geographical latitude. So at the equator, the angular height of the polar star is 0 (i.e., it actually lies on the horizon), in Jerusalem — 31 °, in Moscow — 56 °, and at the north pole — 90 ° (i.e., it is located strictly at the top).*

**Knowing the distance from Moscow to the North Pole and assuming that the Earth is flat, it is easy to calculate at what height the polar star is.**

*The distance from Moscow to the North Pole is 3089 kilometers. The angular height is 56 degrees. It is easy to calculate that for a right-angled triangle with one leg length of 3089 kilometers and an adjacent angle of 56 degrees, the length of the second leg will be 2083 kilometers.*

*But the trouble is — if we carry out the same calculations for an observer located in Jerusalem, it turns out that the polar star is 3891.8 kilometers, and for each new observer at a new geographic latitude, we will get a different height of the polar star that does not coincide with all the others.*

**The lines connecting the observers and the polar star do not converge at one point, as if each observer had his own polar star, which, of course, is impossible and testifies to the erroneousness of the initial premise that the surface of the Earth is a plane.**

While on a spherical Earth, no contradictions arise. The North Star is located at a huge distance of 447 light years, and all photons from it reaching the Earth are essentially moving along parallel trajectories. We get different angular heights corresponding to the geographic latitude precisely due to the sphericity of the Earth’s surface.

*If the Earth’s surface were a plane, then the angular heights of the polar star would have to be the same at different latitudes, which is obviously not the case.*

*In fact, there are many other visual ways to make sure the Earth is not flat. These are different lengths of shadows at different latitudes at the same time, and observations of sunrise and sunset, different pictures of the starry sky depending on the position of the observer and the sinking of receding ships under water and much more, but we have already written about most of them in other articles.*