A rare blue moon is appearing!
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One of the most remarkable astronomical phenomena of 2018 was the total lunar eclipse that occurred on the evening of January 31st, Beijing time. That night, if the weather was clear, people in most parts of the country, with the exception of a small area in the far west, could observe the entire process of the total lunar eclipse.
A total lunar eclipse will occur tonight, and the spectacular sight of a \"super blue blood moon\" can be seen across the country. The last time such a moon was seen was in 1866, 152 years ago, during the Qing dynasty. Everyone is very enthusiastic about this rare moon; various impressive and cool names such as “total lunar eclipse,” “blue moon,” “red moon,” “supermoon,” and “super blue blood moon” are everywhere. A total lunar eclipse occurs when the Sun, Earth, and Moon are in a straight line with Earth in between, blocking the direct light from the Sun that reaches the Moon; in other words, the entire Moon ends up in Earth’s shadow. During a total lunar eclipse, the moon does not disappear; rather, its brightness decreases and its color turns red. Therefore, the moon at that time is called a \"red moon\" or \"blood moon\".
Why is the moon so red? To answer this question, two important factors need to be taken into account: 1) The visible light in sunlight is nearly white light, comprising visible light of different wavelengths; the shorter the wavelength, the bluer the color ； 2) The Earth's atmosphere. During a total lunar eclipse, the Earth comes between the Sun and the Moon, preventing sunlight from reaching the Moon directly. Only a portion of sunlight can reach the moon after being refracted by Earth’s atmosphere. Since light is scattered by particles in Earth’s atmosphere that are smaller than its wavelength (such as gas molecules), light with a bluer color is scattered to a greater extent. As a result, the light that reaches the Moon after passing through Earth’s atmosphere is mainly red in color; hence, the Moon appears as a \"red moon\".
How many critical moments are there in a total lunar eclipse? The entire process of a total lunar eclipse can be represented by 7 key moments. 1. The Moon orbits the Earth from west to east; the moment when the edge of the Moon first touches the Earth’s penumbra is the start of a penumbral eclipse ； 2. The Moon continues to move, and the moment its edge just touches the umbral shadow is the time of first occultation ； 3. When the Moon has just completely entered Earth’s umbra, it marks the beginning of the eclipse ； 4. When the center of the Moon is closest to the center of the Earth’s umbra, it indicates the maximum phase of this total lunar eclipse ； 5. As the moon’s position continues to change, when it just touches the other end of the umbra and is still within that umbra, it means that the moon is about to enter the penumbra area; it will then become brighter. Therefore, this moment is referred to as “the onset of brightness” ； 6. As the Moon just emerges fully from Earth’s umbra, the moment of “re-circle” arrives ； 7. When the Moon just emerges completely from Earth’s penumbra, the penumbral eclipse comes to an end.
Initially, there was only one definition for a blue moon that was not blue: it referred to the third full moon in an astronomical season, when four full moons occurred, which was then called a \"blue moon\". As for why it is called a “blue moon,” there is a historical reason for that. The ancients liked to use the changes in the moon phases to track the passage of seasons, as can be seen clearly from the lunar calendar. Depending on different cultural backgrounds, each full moon of the month is given a special name; for example, the full moon in January is called the Wolf Moon, the Old Moon, the Ice Moon, the Blood Moon, or the Moon after Christmas. An astronomical season lasts three months, and under normal circumstances there are three full moons. If there are four full moons, the first, second, and fourth ones are still named using the names of the original three full moons, but the third full moon does not have a name. So, people gave it a romantic name—blue moon.
It’s a sight that occurs once in over a hundred years, so it’s best to take it in properly.
I’ve been a bit busy lately; things will get better gradually
It is expected that during the total lunar eclipse tonight, there will be little to no rain or snow across our country. Most areas in the central and eastern regions as well as the northwest will have clear skies with few clouds to obstruct the view, allowing people to easily enjoy the spectacle of the \"super blue moon\" combined with the total lunar eclipse. However, nighttime temperatures will be low, with temperatures generally below freezing in these areas, making it feel cold. For those living in these regions, the advice is to eat well, dress warmly, and look up at the sky. The viewing conditions in southwestern Hubei, central South China, Gansu, as well as the northeastern part of Inner Mongolia and the western regions of Heilongjiang and Jilin provinces are slightly less favorable, with cloud cover present; fortunately, it is mainly high clouds, so there is still a chance to see a total lunar eclipse. It is recommended that people in these areas hold out hope – after all, one should always have dreams, in case they get to witness the beautiful sight of the moon surrounded by clouds In southern Sichuan, central and western Guizhou, central and eastern Yunnan, central and western Fujian, southern Guangdong, and most of Hainan, the cloud cover is heavy, with low clouds being predominant; the sky is overcast, making it difficult to see the moon clearly. For those in these areas who want to see the moon, the situation of \"dark clouds covering the moon and preventing it from shining\" only serves to make them feel \"deeply disappointed.\" The \"supermoon\" is something others get to see, and total lunar eclipses as well.