We are all very familiar with the cycle of day and night due to the Earth spinning around once on its axis every 24 hours. We get dark skies on a cloudless night when the Moon is not visible. Against the pitch-black sky, we can see distant shining stars and a band of light which is from our Milky Way galaxy. Distant stars are still present during the day, but their light is too faint to be seen against the scattered light produced by our atmosphere. Some of the darkest astronomical observing sites are found at high altitudes in Hawaii, Chile and the Canary Islands.
