Effect of the absence of atmospheric refraction to sun rise and sunset times What is the effect of absence of atmospheric refraction on sin rise and sunset time?
Is it will be delayed or earlier for sunrise and sunset, and why?
Thank you:)
The simple answer is that atmospheric refraction makes the disk of the sun visible at sunrise or sunset, when it's actually half a degree or so below the horizon:



In reality, both the extent of refraction of the sun's disk and the refraction of the apparent horizon come into play. Both depend on the atmosphere's density and temperature profile; which changes irregularly. That makes it impossible to predict exact sunrise or sunset times when there is an atmosphere.