What is atmospheric refraction?
In: Planetary Science
atmospheric refraction is when light bends as it passes through the earth’s atmosphere. it happens because air density changes at different heights, making light travel slightly different paths. this effect makes the sun appear higher in the sky than it actually is, especially near the horizon. it’s why we can see the sun for a few minutes after it’s technically set below the horizon.
Light tends to bend as it hits a denser medium. That’s why glass lenses work, or why if you stick a pole into water it seems to be at a different angle in the water.
The atmosphere around a planet gets denser the further down you get, so it acts as a gradual lens that curves the light as it goes deeper into the atmosphere. As a result the sun seems higher up in the sky than it really is (the light has been curved downwards), but this has an effect on all electromagnetic radiation (Light, infrared, UV, radio, microwaves, x-rays etc).
This effect is the most extreme when something is very low on the horizon, so unless you’re viewing something straight up it will be slightly out of position (and once you get close to the horizon this distortion is so big that any astronomical observation is useless).
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