A very long time ago, scientists had already accepted that the Earth was a ball and was orbiting the sun. Even so, scientists did not really understand how light worked. On very popular thought around 100 years ago revolved around the discovery that light behaved as a wave. There understanding of a wave was that it involved transmission of energy through a medium (think a sound wave traveling through air). Unfortunately, it was found that there was a vacuum between the Earth and sun. In order to explain how light got to Earth scientists invented the ether (sometimes aether); which was a mysterious, unmeasurable medium that light was conducted through.
Scientists then set out to try and find out what this ether was like. A very important question was: is the ether moving or stationary relative to Earth. Some thought that the ether would be “dragged” by massive objects; others thought that the ether was completely stationary to massive objects.
With this in mind, George Biddell Airy set about trying to measure ether drag (actual publication if you are interested circa 1871). Now with this background, our next proof of flat Earth can be viewed appropriately:
“16) The experiment known as “Airy’s Failure” proved that the stars move relative to a stationary Earth and not the other way around. By first filling a telescope with water to slow down the speed of light inside, then calculating the tilt necessary to get the starlight directly down the tube, Airy failed to prove the heliocentric theory since the starlight was already coming in the correct angle with no change necessary, and instead proved the geocentric model correct.”
Aberration of light refers to the apparent motion of stars in the night sky. Essentially, if you point a telescope at a star and wait a couple of seconds or minutes, the star will move out of the field of view. It is related to the movement of Earth traveling around the sun and rotating on its axis. James Bradley used this phenomenon of aberration and the speed of the Earth’s orbit around the sun to very accurately prove the finite speed of light within great accuracy to modern measurements in 1728.
At a time when people thought there was ether for light to move through, the movement of the ether could have serious implications for where something like the aberration of light for stars If there was ether moving through space, it could be effect the aberration of light.
It can be understood that Airy was not measuring the movement of stars relative to Earth’s movement. His experiment would not be able to distinguish between if the stars were moving relative to Earth or Earth relative to stars. His experiment involved placing a refracting medium (what causes light to “bend” so an observer may be able to see a greater distance around the curvature of the Earth) inside a telescope and looking at stars to see if this caused the aberration of light from stars to change because of the translational movement of Earth.
Direct quote: “A discussion has taken place…on the change of direction which a ray of light will receive when it traverses a refracting medium which has a motion of translation. The subject to which attention is particularly called is the effect that will be produced on the apparent amount of that angular displacement of a star or planet which is caused by the Earth’s motion of translation, and is known as the Aberration of Light.”
So, Mr. Airy clearly believes the Earth is moving.
If the star and scope are at rest relative to the ether, light moves in a straight line:
If, however, the ether were moving in some way it would cause light to move with the ether (like how sound waves move with the wind). In this case it would look like (where the dashed star is the perceived position of the star by the observer):
Airy put water in the scope to increase the effect of the ether drag so that it might be measurably different than in air. There was no change. Airy demonstrated that ether drag does not exist and the prior measurements of aberration are valid in demonstrating the movement of Earth around the sun and the speed of light.