I am not sure whether this question is right or not so bear with me.

I understand 'Sun rise' and 'Sun set' is caused by the Earth's rotation.

I read that 'Sun light' takes around 8 minutes to reach Earth.

Every city in the world has its own 'Sun rise and Sun set' timings.

Lets assume the 'Sun rises' at 6 AM in 'City A'.

Does this mean that 'City A' sees/feels the light of the Sun which was in the sky @ 5:52 AM ?

In other words, does 'Sun rise' and 'Sun set' timings change according to 'light years'?

  • $\begingroup$ what do you mean by 'light years' ? $\endgroup$ – Knu8 Jun 5 '16 at 20:05

Sunrise and sunset times are based on when an observer at the location in question would see the first or last limb of the sun appear or disappear; they do not take into consideration the light-speed delay between the Earth and the sun. They do, however, take into consideration the average refraction of the atmosphere, so sunrise occurs a bit earlier than plain line-of-sight would predict as would sunset occur a bit later.


I understand 'Sun rise' and 'Sun set' is caused by 'earth rotation'. I read 'Sun light' takes around 8 minutes to reach earth Every city in this world has its own 'Sun rise and sun set' timings.

This is all correct. The apparent motion of the sun in the sky is mostly due to the rotation of the Earth.

Lets assume 'sun arises' at 6 AM in 'City A'. Does it mean that 'City A' sees / feels the light of Sun which was in the sky @ 5:52 AM ?

It means that at 6AM, light from the sun shines on city A. That light had left the sun at about 5:52. At 5:52, city A was in the shadow of the Earth. The time that the light left the sun is fairly irrelevant to the timing of sunrise. A 5:52 the light left the sun, in the 8 minutes that followed the Earth rotated by about 2 degrees and by 6 AM city A was just in the right position to catch a little of the light. We don't change the timings. We would not say that the sun rose at 5:52, because at 5:52 the sun appears to be below the horizon.


I love Einstein's explanation of "events". Not the exact words but he stipulated that an event has not happened until the light of that event has reached you.

So, the Sunrise time is when you actually see the disc of the Sun, not when it has actually been in your line of sight for a person who might be standing on the surface of Mercury observing you and Sun both.


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