We astronomers have a habit of throwing around terms that we consider to be obvious, only to watch the eyes of normal people glaze over. For example, albedo, analemma, aphelion, air mass … and that’s ...

After sunset, there is period of time where the sky gradually darkens, and before sunrise there is a period of time during which the sky gradually brightens. Twilight, the time between day and night, ...

As the sun rises in the morning, the sunlit portion of the aurora begins at high altitudes and gradually spreads downward over time. Auroras: Auroras are natural phenomena where electrons from space ...

There is something transformational about twilight. When the sun has just set in the west, the sky changes from the vibrant blue of afternoon to a more relaxed hue, as if it’s settling down for the ...