Airy’s Failure, FECORE’s Success
George Biddle Airy was born in 1801. At age 35, he was appointed Astronomer Royal at the national observatory in Greenwich, UK. He had many prestigious positions and created several noteworthy theories during his illustrious life. FECORE’s newest project is a repeat of an observation Airy published in 1871, which was counted as a failure. It has come to be known as “Airy’s Failure.” But it was called at the time The Water Telescope of the Royal Observatory.
That this observation should be called a “failure” is significant. Airy made an accurate observation of a fact of nature. Yet it was dubbed a failure.
FECORE has decided to perform the same test Airy did using modern equipment that can produce more exact measurements. The angle of our instrument will be set by high-precision stepper motors with digitally controlled inputs which are expected to result in more accuracy than the instruments used in 1871.
In 1871 it was known that when we view a star through a telescope the telescope is not actually pointed directly at the star. Unless a person is taking very accurate measurements of the angle of the star and the angle of the telescope it would never be noticed since we are trying to view the star and once it is centered we will think that the telescope and the star are aligned. But it was noticed when the star is at zenith the telescope is slightly tilted toward the apparent motion of the stars. The amount of tilt is at maximum 20 arc seconds. That is 55/10000 of a degree. This effect of needing a slight tilt was called stellar aberration or the aberration of light. Airy was trying to determine its cause.
The goal of the FECORE experiment will be to determine the cause of stellar aberration and the cause of the relative movement between the stars and the earth.
So how can we determine why we must tilt the scope? What could be the cause? If the earth is moving and the stars are motionless then the light from a star at zenith is coming directly perpendicular to a level surface on the earth. Therefore if the earth and telescope are moving then the tilt is required to compensate for the slight angle caused by that the earth’s movement. But earth to star relative motion could be caused by the stars moving in which case the light would not be coming down perpendicular but would be at a slight angle on a motionless earth. The tilt of the telescope alone doesn’t tell us which it is.
George Airy knew that as the light propagates down to the telescope eye piece, it is moving through the lenses and air. That combination produces an overall refraction of the light. He began this experiment based upon information from an 1867 account by Professor Klinkerfues who said it was possible to change the amount of tilt needed by altering the refraction in the telescope. Since Airy believed the light from the stars was coming in exactly vertical when the star is at zenith then he thought by changing the refraction then the telescope would require a different angle of tilting. That was the success he was seeking.

You may be surprised to know that you have experience with this effect. What happens when we put a pencil halfway into water at an angle to the surface? The pencil appears to bend. The light from the part of the pencil out of the water is only passing through air. But light from the part of the pencil under water is passing through water and air. The light path is different in each case and makes the pencil appear to bend. But if the pencil enters the water perpendicular to the surface of the water then the pencil does not appear to bend. This is the same principle which Airy used to determine if light from the stars was coming to us at an angle or straight down.
Airy called his test The Water Telescope of the Royal Observatory. If we fill a telescope with water, we have altered the refraction properties. The light from the star will be slowed down; it will not propagate as fast in water as it does in air. Because of this change, the light will take longer to reach the bottom of the telescope tube. And since the light from stars is in motion relative to the earth’s surface the image of the star might shift depending on if there was water or not water in the tube.
If it is the telescope and earth which are moving, then the light from the star is coming straight down and the telescope must be tilted forward so that the light will be in the center of the eyepiece. Therefore, with an increased refraction by adding water the light will reach the eyepiece after a longer period of time, and the telescope must be tilted even further forward for the light to still be in the center of the eyepiece.
However, if the angle of the light is caused by the movement of the stars, then as it propagates into the telescope tube, it is already at the same angle as the tube and a slowing caused by the water will not change its direction and the star will still be in the center of the eyepiece.
To recap– if the earth is moving and the stars stay still, then star light falls straight down for any star at zenith. That means a telescope with only air in the tube must be tilted at one angle for the star to be seen. But when filled with water, the telescope must be at a different angle for the star to be seen.
But, if the earth is motionless and it is the stars that are moving, then the star light is already moving at an angle towards the surface of earth and is not perpendicular. That means a telescope with air and a telescoped filled with water must remain at the same angle to see the star in the same location in the eyepiece.
We believe it’s possible to build two telescopes with equal refraction properties, and then mount them side by side with the line between them being perpendicular to the direction of the movement between earth and the stars. Verification that both scopes have the exact same refraction properties would be simple. When both have only air and are tilted at the exact same angle, then the star will be visible in the same location in both eyepieces at the same instant. Real-time video captured from both scopes is an observation that was not possible in 1871. As we do this test real time video from both telescopes will give visual proof that both scopes were equal.
This dual-scope feature would allow the actual observation data to be not just numbers, but real time video capture to prove the fact. We plan to complete this test within 12 months.