Mid -Autumn Festival this year, why is the fifteenth moon fifteen circle? "

In a few days, it is the annual Mid -Autumn Festival. As the saying goes, "Fifteen Moon Sixteen Circles", this year, Mid -Autumn Festival is "Fifteen Moon Fifteen Circles." This means that when the Mid -Autumn Festival is enjoying the moon this night, as long as the weather is fine, we may see the big and round moon.

Why is the Mid -Autumn Festival "Fifteen Moon Fifteen Circles" this year? August the moon in August of the lunar calendar is round? What is the reason behind? Recently, the reporter visited the Yunnan Observatory of the Chinese Academy of Sciences with these issues.

Mid -Autumn Festival this year, the fifteenth moon of the fifteenth day

A full moon shot by the staff of Yunnan Observatory in 2021.

The Mid -Autumn Festival, the full moon is reunited.

Tang Rufeng, assistant researcher at the Yunnan Academy of Sciences Yunnan Observatory, introduced that on the day of the Mid -Autumn Festival, you can enjoy the most round moon in August in the lunar calendar, that is, "the fifteenth moon of the fifteen fifteen", the specific time of the most round moon is September 10th at 17:59 on September 10th about.

"On the Mid -Autumn Festival, the moon will not rise until 19:35 Beijing time, so when we see the moon, it is no longer the most round. But people can't see this slight difference." Tang Rufeng said.

In fact, the phenomenon of "fifteen moon fifteen circles" is not uncommon. Experts introduced that from 2021 to 2023, this Mid -Autumn Festival was the case for three consecutive years.

Tang Rufeng explained that in general, the full moon appeared in the fourteenth, fifteenth, sixteen, and seventeen seventeen of the lunar calendar. Among them, the fifteen and sixteen of the lunar calendar. Taking 2022 as an example, 12 times in the full month, 5 times in the lunar calendar, 5 times in lunar calendar, and 2 times in the seventeen of the lunar calendar. Taking 2023 as an example, 13 times in the full month, 4 times appeared in the fifteenth lunar calendar, 7 times appeared in the sixteenth lunar calendar, and the seventeen times appeared in the lunar calendar.

"A total of 25 times appeared in two years, of which the lunar calendar was 9 times, the 16th month of the lunar calendar, and the lunar calendar was 4 times." Tang Rufeng said, this is why everyone often says "the fifteen moon and sixteen circle". Essence

What is the reason behind?

According to Li Zhifei, a staff member of the Yunnan Observatory of the Chinese Academy of Sciences, from the astronomical point of view, when the earth is in the middle of the moon and the sun, the moon we see on the ground is the most round when the moon is in front of the earth; , The ground can't see the moon. Generally speaking, we call a cycle of the lack of the moon circle as a "Shuangwang Moon", which is called "Shuo Ri" that cannot be seen at all. ", Usually the fifteenth or sixteen of the lunar calendar.

The cycle of Shuangwangyue is about 29.5 days. That is, about 14.75 days, the moon will just turn to the rear of the earth. Li Zhifei said that the rotary track of the moon is not round but oval, and the moon's rotation track itself is also rotating. The gravity of the moon is different, making the moon's rotation speed uneven. Therefore, there is also a difference between the time when the moon appears behind the earth. Sometimes it may be a little faster. It may be the fifteen moon of the fifteen moon, and sometimes a little slower, that is, fifteen, sixteen circles, and even seventeen circles.

How to accurately measure the distance between the moon?

Li Zhifei said that the most round of the moon depends mainly on the relative position relationship of the earth, the moon and the sun. So how far is the moon from us? Many people know that it is about 380,000 kilometers. In fact, the moon is more than 405,000 kilometers away from us, and it is only more than 360,000 kilometers near us.

It is understood that at present, the most accurate way to measure the moon distance is the laser ranging of the moon. The so -called lunar laser ranging is the round -trip time from the ground observation station to the moon reflex by accurately determining the laser pulse to calculate the moon distance.

Speaking of simple, but behind this is a major technical breakthrough in my country in this field.

Laser laser ranging real picture of the Chinese Academy of Sciences Yunnan Observatory. Interviewee confidence

After a long -term lunar laser ranging technology research, on January 22, 2018, researchers of the Yunnan Observatory of the Chinese Academy of Sciences used the 1.2M telescope laser ranging system to successfully detect the laser pulse signal returned by the moon -faced reflector Apollo15 to successfully realize the moon laser laser Situing.

Li Yuqiang, a researcher at the Yunnan Observatory of the Chinese Academy of Sciences, introduced that the Yunnan Observatory successfully realized the laser ranging of the moon, filling the gap in the field of laser ranging in the moon, and also provided ranging technical support for the implementation of the Tianqin gravitational wave detection project in my country.

Source: Xinhua News Agency

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