```6. Measure shadows across the country```
When you observe the sun on the horizon it appears a red/orange color.
When you observe the sun directly above you, it appears a yellow/white color.
It is reasonable to assume the most amount of refraction occurs when you observe the sun closest through the horizon.
The sunlight must go through the thickest amount of air closest to the horizon.
Take a look at Lapse Rate. There is a net change of air temperature of about 6-8 degrees celcius lower per kilometer of altitude gained.
Cold air has a higher refractive index than warm air.
Light will naturally curve upwards in air and the closer the apparent sun is to the horizon the more it curves upwards.
Attempting to apply linear trigonometry to an extremely curved beam of light when the sun is close to the horizon is pointless, it won't work.
"In fact, it can be shown that the refraction near the horizon depends mostly on the local temperature gradient, which is much more important than the local temperature itself. For this reason, all the refraction phenomena near the horizon — mirages, dip, terrestrial refraction, etc., as well as the astronomical refraction — are very sensitive to the temperature gradient; and they all vary a great deal more than does the astronomical refraction well up in the sky."
To: "It is obvious that the effect of temperature variation is decisive over the
other atmospheric factors on refraction, to the following proportions: Temperature to humidity to carbon dioxide content to air pressure = 100 : 6 : 2 : 1 "
INVESTIGATION OF REFRACTION
IN THE LOW ATMOSPHERE
By
K. HORV_,.TH
Department of Survey. Technical university. Budapest
(Received Alay 29, 1969)
Presented by Ass. Prof. Dr. F. SAHKOZY
