Did you know that we actually see the sunrise about 2 minutes before the sun is actually at that perceived position? Did you know that the sunset that we see is actually of a sun that has, in reality, already set? So why these different perceptions? It is because of a phenomenon termed as refraction of light.
What is refraction of light? Simply put, a ray of light ‘bends’ when it travels from one medium to another. This ‘bending of light’ is called refraction of light. If the light ray travels from a rare medium to a denser medium, it bends towards the imaginary normal and if it travels from a dense medium to a rarer medium, it bends away from the imaginary normal. Depending on the density of the different medium, the speed of the travelling light ray keeps varying, and this causes it to slow down or speed up, therefore bending in the process.
Effect of refraction of light on sunrise and sunset
So how this refraction of light is connected to our advanced sunrise and delayed sunset? Imagine the journey of light rays from the sun. Their initial journey is through vacuum and then through the atmosphere of the earth and then it is finally seen by us. In this case, vacuum will be a rare medium and the earth’s atmosphere with all its temperature changes, winds, different gases, will be a denser medium in comparison.
During sunrise, when the sun is just below the horizon, our atmosphere causes the light rays to bend and we see the sun early. Similarly, at sunset, the apparent position of the sun is visible to us and not the actual position due to the same bending of light rays effect.
To sum up, due to refraction we see the sun rise about two minutes before it’s actually there and during sunset we see it for around two minutes more, even though it has already moved from that position.
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