As the rural proverb says, "Eating noodles on the solstice in winter can grow a thread a day". What is a "thread"? How many minutes exactly?

There are many proverbs circulating in rural areas. One of them is "eating noodles on the solstice in winter, and the queue is getting longer every day". In fact, there is another way to say this sentence, that is, "eat a meal on the winter solstice, and it will take a long day", in which both noodles and rice mean a meal.

It's August in the lunar calendar, and it's only half a year before the winter solstice. This sentence means that after the winter solstice, there will be more "lines" every day. In fact, this is about some changes in winter solar terms.

So how long does the "first line" here mean? In ancient China, there were no clocks and mobile phones. The ancients relied on their own invention-sundials to tell the time every day.

The sundial is different from the timing tool we use today. The time it provides is not very accurate, but a slender stone needle is inserted in the middle of a slate marked with time, and then the time is judged according to the shadow of the stone needle reflected by different sunlight.

There is a record about sundial in Chinese ancient books: "The sundial is long in winter and short in summer." In other words, in winter, the shadow of the sundial will become longer.

So having said that, how long does the "first line" mean? According to the statement that the sundial is three feet and five inches in winter and six inches in summer recorded in the book Weekly Arithmetic, we can calculate that the sun rises at 7: 40 in the morning and 5: 47 in the evening every day, and then it rises at 7: 60 in the morning and ends at 5: 50 in the afternoon. The so-called "first line" is almost a minute.

In fact, this time may not be accurate, but with the support of such conditions in ancient China, people at that time already had such opinions, which were excellent.