I recently watched a documentary which said that the sun is 8 light minutes away from the earth. I know that at the rise of the sun we actually see it a few minutes ago, say 2 minutes before it is actually there due to refraction by the atmosphere. Now as these two minutes pass by, the sun actually appears but for its light to come to earth it should take another 8 minutes. That means after these 2 minutes there should be no sunlight for another 8 minutes. But it is not actually there. What's the reason?

I tried but I could not imagine how this process works.

  • $\begingroup$ 'I know that at the rise of the sun we actually see it two minutes ago before it is actually there due to refraction by the atmosphere.' Do you have a reference for that? $\endgroup$ – Gert Jan 14 '17 at 14:12
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    $\begingroup$ @Gert en.wikipedia.org/wiki/Atmospheric_refraction . "the observed time of sunrise or sunset can vary by several minutes from day to day" $\endgroup$ – anna v Jan 14 '17 at 16:16

To start, let's be clear - the Sun is continuously producing light. It doesn't turn off at night. When it's night time where you are it's daytime on the other side of the Earth.

You see the Sun rise as the Earth rotates so that your location switches from facing away from the Sun to facing towards the Sun. Say you see the Sun rise at 7:00 AM, the light you are seeing was produced by the Sun at 6:52 AM (approximately).

The effect of atmospheric refraction is to bend sunlight around the Earth a bit so that we see light that would otherwise miss the Earth. Without the Earth's atmosphere you would see your 7:00 AM sunrise at 7:02 (more or less, I'm not sure how accurate your 2 minute figure is), but either way you are always seeing sunlight that was produced about 8 minutes earlier.

  • $\begingroup$ That also means that if we are seeing light 2 minutes earlier at the sun rise, we are actually looking 8-2= 6 minutes into past at the sun rise instead of 8 minutes during the day. Am I right? $\endgroup$ – Anubhav Singh Jan 15 '17 at 5:53
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    $\begingroup$ No. Whenever you see sunlight, first thing at sunrise, middle of the day, sunset, the light has always taken almost exactly the same amount of time to reach you. You are always seeing light that was produced about 8 minutes earlier. The same would be true if you were on the Moon where there is no atmospheric refraction. $\endgroup$ – M. Enns Jan 15 '17 at 20:46

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