8
votes
1answer
72 views

Do we have 2 minutes of extra morning?

my physics teacher told me about the refraction and its applications one of them was 2 minutes of early sunrise and after she explained this effect she concluded that days are 2 minutes longer than ...
4
votes
2answers
241 views

Why do clouds appear black?

I have noticed clouds appearing black during rain. But I don't know what makes clouds to acquire that colour. This phenomenon doesn't appear every rainfall. There has to be distinction to white ...
6
votes
1answer
45 views

Refraction and scattered light for NLCs

For helping with judging NLC candidates (are they NLC or not) I have a set of formulas to calculate the minimum altitude (in km) of the candidate given an observed altitude (in degrees) of the ...
22
votes
3answers
2k views

Why does the sky change color?

Why the sky is blue during the day, red during sunrise/set and black during the night?