What is a 'blue moon' and how often can you see one?
Lunar events of this nature happen only once every two or three years.
Transcript
00:00 [Music]
00:04 So the moonlight we see is reflected white light from the sun
00:08 and if there's something in the way that blocks the red light,
00:12 the moon can appear blue.
00:14 That can sometimes happen after volcanic eruptions,
00:17 for example Krakatoa in 1883,
00:20 the moon was blue for over a year.
00:22 The ash from the volcano was just the right size to block the red light
00:26 and the moon appeared blue.
00:28 [Music]
00:57 (gentle music)