Some back-of-the-envelope numbers: Standing on the ground, the horizon is about 3 arc minutes below 'eye level'. How is that even possible? Well, by rotating the box, the image of an outer point of the horizon moves not only from boundary to middle of screen, but also closer to the pinhole! Now if you rotate the box around the vertical axis, the image does not really change, i.e., you still have the outer ends higher above the middle line than the centre. The horizon on the image plane on the back is very close to a straight line and is only approximately at eye level, i.e., with a properly aligned box, the horizon will be slightly above (inverted image!) the middle of the screen and the outer ends will be even further above. Unless you adjust your direction of sight: In order to look exactly at the horizon in front of you, you'd have to nod forward by a very, very tiny angle if you then rotate around the tilted, not quite vertical axis of your head, you'd look slightly above the horizon after half a round.Įyes are unreliable instruments anyway, so let's build a camera obscura from a used shoe box. More importantly, if you rotate your head left or right, you will not follow some further downfall of the curved horizon line, but instead its central point directly ahead of you will again be highest at (pretty close to) eye level.

That is almost as if you observed that circle from within its plane, in which case you would observe a straight line exactly. In fact, what you observe is a circle with several kilometers of radius that has its centre only about four or five meters below your eyes (namely the tangent circle of a cone and the earth sphere where the cone apex is in your eye). Flat Earth Debunked.The horizon is pretty much flat when observed from pretty low.

Flat Earth Water Level Test #2 – Jon McIntyre – YouTube.

Flat Earth Water Level Test – Jon McIntyre – YouTube.

It is not that much different from 0°, or ‘horizon is at the eye-level’. If the distance to the ‘edge of the world’ is 5000 km, then the dip of the horizon from the altitude of 2 km is 0.023°. So, we created this diagram to illustrate what would happen in the flat model. But some of them -presumably after reading this piece- claims that the dip of the horizon also happens in the flat-Earth model. “The horizon always rises to eye-level” is claimed by most flat-Earthers. The surface of the water is level, or equipotential, but not perfectly flat. Conversely, as we approach sea level, the dip approaches zero.įlat-Earthers often use water level as ‘proof’ that the surface of the water is flat. If we are at a sufficient altitude, we should be able to observe that the horizon -the line separating the sky and the ground- lies below the eye-level.Īs we climb higher, the larger is the dip. Looking at the surface of water formed in two vessels, we can aim at the horizon and determine the projected eye-level. Despite their insistence to use a water level to ‘prove’ water is flat, the same device can be used to demonstrate the dip of the horizon, proving the water surface has curvature, and consistent with the spherical Earth model.Ī water level exploits the fact that water always finds its level.

The angle becomes larger as we go higher.įlat-Earthers often claim that “the horizon always rises to eye-level”, and thus ‘proving’ the flat Earth claim. The angle between the eye-level and the horizon is the dip of the horizon. As the Earth is spherical, the horizon is below the eye-level (or the astronomical horizon).

Flat earther perfect horizon