Wikipedia:Reference desk/Archives/Science/2019 September 17

= September 17 =

Green moon
Did anyone ever see actual green-colored moon in history? What are the causes of literal green moon? Planet Star  00:09, 17 September 2019 (UTC)


 * It seems to be a gag or hoax: . But is it possible ? Maybe, if it was behind an aurora (which is often green) ? Of course, then it would only appear green from that perspective. (In the pics I've found of the combo, the Moon seems to overpower the aurora, but there might be cases where the Moon is dimmer or the aurora brighter.) SinisterLefty (talk) 00:33, 17 September 2019 (UTC)
 * And what about stand-alone green moon? I say the possible causes of green-colored moon are unusual amounts of suspended dust or aerosols in the atmosphere (caused by dust storm or volcanic eruption) that if in right combination of materials would allow to scatter light from the moon mostly in the green region of the spectrum. I believe the humanity had seen the green moon at least few times, perhaps just after a major volcanic eruption, a nearby dust storm, a fire covering a huge area (forest or city), or even a smog. Agree? Planet  Star  01:34, 17 September 2019 (UTC)


 * Could those make the whole Moon appear green ? Probably not. Those particulates might be able to create a prism effect, where the colors would be separated, and some of that might be green. I would expect water droplets or ice particles to have more of this rainbow effect: . See green flash for a similar event involving the Sun, which can also happen with the Moon: . It only appears right at dawn or dusk, where the maximum amount of atmosphere must be traversed. SinisterLefty (talk) 01:45, 17 September 2019 (UTC)
 * Well, it possibly could.... People reportedly saw literal blue moons, such as in 1950 and 51 after forest fires in Sweden and Canada, and in 1883 after the Krakatoa volcanic eruption. Other times when there's large amount of dust in the atmosphere, the moon looks red, even when high up in the sky and not eclipsed. Just like large amount of dust or aerosols in the atmosphere causing blue or red moons, why not green moon too? Perhaps when people saw blue moon high up in the sky in the early 1950s and in 1883, they may have saw green moon during the same period, when the moon was low in the sky, during which the moonlight has to pass through more of the atmosphere, scattering away blue light from the moon and shifting towards the red, making it green (in other words, green moon is a "reddened" blue moon). Planet  Star  02:11, 17 September 2019 (UTC)
 * Improved your link. --76.69.116.4 (talk) 07:08, 17 September 2019 (UTC)

During World War I, when chlorine was used as a weapon, to the soldiers being attacked it had the appearance of a gray-green cloud. No doubt if the Moon had been in the sky behind the gas cloud, it would have appeared green. Not an experiment I would want to imagine anyone repeating, though! --76.69.116.4 (talk) 07:14, 17 September 2019 (UTC)


 * I personally have seen a green-coloured Moon. It was around 1972 give or take a year, in Kent, England, and seemed to me at the time to be caused by a slight haze of fine smoke resulting from woodland fires in the general vicinity. At the time I was about 15 and had been actively interested in astronomy for several years (my school had a small observatory with an 8" reflector, and I went on to read Astronomy at university) so I was alert to celestial phenomena. {The poster formerly known as 87.81.230.195} 90.202.210.107 (talk) 12:49, 17 September 2019 (UTC)