If the tour group sees that the transit of the moon is 16, what is the first day of the lunar calendar?

2004 college entrance examination questions

A tour group enjoys "Lei Feng Zhao Xi" and "Moon to Midheaven" (the mirror of the highest height of the moon) in Hangzhou West Lake. (Note: The period of revolution of the moon is 30 days, and the apparent position of the moon in the sky is closest to the sun on the first day of the first lunar month).

If the group sees "the moon arrives at noon" around 16, then this day is the lunar calendar (b).

A Grade 2 B Grade 5 C 8th grade D 11

First of all, you should understand the law of the moon's phase change. On the first day of every month (lunar calendar, the same below), the apparent positions of the sun and the moon coincide, so we can't see the moon. After that, the apparent angle between the moon and the sun gradually increased, and the crescent moon could be seen on the third day. On the eighth day of each month, the viewing angle of the Moon River reaches 90 degrees. We can see that when the sun is due west, the moon is in the sky and on the Xuan Yue (and semicircle). On the 15th of each month, 16, the sun is definitely not due west, and the moon is in the middle of the sky, which means that the apparent angle between the moon and the sun is less than 90 degrees, which should be before the eighth day of the eighth month, and it is difficult for the naked eye to observe the moon the next day. So the answer is B, the fifth day.