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The daytime darkness in 2009 refers to the spectacular total solar eclipse that occurred in the Yangtze River valley of Chinese mainland on July 22nd, 2009. At 8: 00 am on July 22nd (the first day of the sixth lunar month), the most important and longest-lasting total solar eclipse of this century appeared in the middle and lower reaches of the Yangtze River in China, including Chengdu, Chongqing, Wuhan, Hefei, Hangzhou and Shanghai, with a duration of 398.8 seconds (6 minutes and 38.8 seconds).

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Total solar eclipse principle

Today, with the prosperity of science, many people are familiar with the principle of total solar eclipse. Its basic condition is that the three celestial bodies, the sun, the moon and the earth, run very close to a straight line at a specific moment. Because the orbital plane of the earth and the orbital plane of the moon have an intersection angle, it is difficult to have such an opportunity.

Because the total eclipse zone caused by the shadow of the moon on the earth is very narrow, only about 200 kilometers, for a specific place on the earth, the probability of total eclipse will only appear once every 370 years. The longest total eclipse time will not exceed 7 minutes and 40 seconds, with an average of 3 minutes and 30 seconds.

This time is also different for different positions on the total solar eclipse belt. The longest duration of this eclipse is 6 minutes and 39 seconds. In Shanghai and Hangzhou, people can "enjoy" the total lunar eclipse for about 5-6 minutes.

References:

Baidu encyclopedia-Yangtze daquan gourmet