In astronomical calendars and yearbooks, when there are two full moons in a month, the second full moon is given a mysterious and romantic name-Blue Moon. The blue moon is a rare astronomical phenomenon, but it is not very rare. Generally speaking, there is only one full moon in a month. According to the calendar, the interval between two full moons is about 29.5 days, but in the current Gregorian calendar, the time of each month is 365,438+0 days, and the time of the small moon is 30 days, which leads to a time difference, which may lead to two full moons in a month of the lunar calendar. According to calculations, the blue moon appears once every 32 months on average.

In fact, there is no essential difference between the blue moon and peacetime, and it is impossible for the moon to appear truly blue. Usually, the moon is pearly white, sometimes it is pale yellow. From the viewpoint of astronomical science, the color of the moon is related to the principle of reflecting sunlight, but has nothing to do with the specific date.

People once said that the blue moon is a sign of disaster. According to records, the blue moon did appear in history, and it was often accompanied by disasters. The blue moon in the night sky is actually indirectly caused by the refraction of light by smoke particles gathered in the earth's atmosphere due to disasters such as forest fires and volcanic eruptions.

1883, Krakato volcano erupted in Indonesia, and volcanic ash floated to the high places in the earth's atmosphere, and the moon people saw at night turned blue. However, the blue moon phenomenon is caused by the natural laws of celestial bodies, and there is no scientific basis for linking natural disasters with the blue moon.

Dark red "red moon"

We all know that sunlight is a mixture of seven colors: red, orange, yellow, green, blue, indigo and purple. When sunlight passes through the earth's atmosphere and refracts into the shadow behind the earth, they are scattered and absorbed by tiny atmospheric molecules in the atmosphere. The light waves of yellow, green, blue, indigo and purple are relatively short, which are greatly influenced by scattering in the atmosphere, and most of them scatter in all directions; Red light has a long wavelength and is not affected by scattering. It can penetrate the atmosphere and refract to the moon hidden behind the earth's shadow. Therefore, during the total lunar eclipse, the moon seen by the public is dark red, the so-called "red moon". And the sun we see in the morning and evening is always red, which is why.

lunar eclipse