Solstice is an important festival in ancient China. When is the solstice in winter?
The earliest ancients stood a stick on the flat ground and observed the change of the sun shadow of this stick. Through observation, the ancients found that the length of the sun shadow of this stick changed every day of the year. Among them, at noon in a summer, the shadow of the sun is the shortest, and the position of the sun is at the southernmost tip of this day, so this day is called "south solstice", also called summer solstice; In winter, at noon, the sun has the longest shadow and the northernmost position, so this day is called "northern solstice", also called winter solstice. This is how the ancients calculated the "winter solstice".
The vertical one is called "table", and the one marked horizontally on the ground is called "gauge", which together is called "gauge table". The information we have now proves that at the latest in the Spring and Autumn Period of our country, our ancients have already determined two solar terms: summer solstice and winter solstice.
How did the ancients calculate the time of winter solstice? I believe many people are curious. How did the ancients know that the winter solstice was around 65438+February 22nd? In fact, the ancients did not know that this day was the winter solstice. The ancients only knew that the solstice in winter was the longest shadow day, with only one day in a year. The calendar we are using now is a calendar imported from the west, so this statement is more accurate: the winter solstice generally corresponds to the Gregorian calendar around 65438+February 22.
In the twenty-four solar terms, why did the "winter solstice" evolve into an important festival? Everyone knows the proverb "The solstice in winter is as big as a year". Why did the ancients attach so much importance to the winter solstice in all solar terms? Scientists speculate that it may be because the shadow of the winter solstice is relatively long when measuring solar terms, so the relative error can be smaller when measuring, and the "Gui" of measuring and recording the winter solstice is also relatively long, which can include all the shadow lengths of other solar terms, so the date of the winter solstice has a special meaning and finally evolved into an important festival.
Because in ancient history, a world called the month of the winter solstice "the first month", which means the first month, which led to the saying that the winter solstice was as big as a year.
The ancients first measured the summer solstice and winter solstice with shadows, and on this basis, divided a year into multiple intervals. The ancients first added vernal equinox and autumnal equinox between winter solstice and summer solstice, so that a year became "four seasons", that is, a year was divided into four sections. Later, on the basis of the four seasons, it was divided into equal parts, so beginning of spring, Changxia, beginning of autumn and beginning of winter were added, and it became eight sections, which is what we often call "four seasons and eight sections".