When are the vernal equinox, summer solstice, autumn equinox and winter solstice? Where does the sun shine?
The sun shines directly on the equator at the vernal equinox, the Tropic of Cancer at the summer solstice, the equator at the autumnal equinox and the Tropic of Cancer at the winter solstice.
The vernal equinox and autumnal equinox are due to the sun's direct exposure to the equator, so the northern and southern hemispheres return to the Tropic of Cancer day and night, while the summer solstice is direct exposure to the Tropic of Cancer. The northern hemisphere is long and the night is short, while the southern hemisphere is short, and the winter solstice is direct exposure to the Tropic of Cancer.
"Twenty-four solar terms" is the product of ancient farming civilization, and farming production is closely related to the rhythm of nature. It is a knowledge system formed by ancient ancestors following the farming season, observing the movement of celestial bodies and understanding the changing laws of seasons, climate and phenology throughout the year. It expresses the unique concept of time between man and the natural universe, and contains the long-standing cultural connotation and historical accumulation of the Chinese nation.
Extended data:
Vernal equinox:
At the vernal equinox, the direct point of the sun is on the equator, and then the direct point of the sun continues to move northward, so the vernal equinox is also called the "ascending equinox". The vernal equinox is an important solar term, which is of great significance in astronomy: the northern and southern hemispheres divide the day and night equally. Since then, the direct position of the sun has continued to move from the equator to the northern hemisphere. The days in the northern hemisphere are getting longer and shorter, and the nights in the southern hemisphere are getting shorter and shorter.
The significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Second, the vernal equinox is just in the middle of three months in spring, and spring is equally divided.
Summer solstice:
On the day of summer solstice, the position where the sun shines directly on the ground reaches the northernmost part of the year, almost directly on the tropic of cancer. At this time, the daylight hours in all parts of the northern hemisphere reach the longest in the whole year. For the Tropic of Cancer and its northern area, the summer solstice is also the highest day of the year at noon. On this day, the northern hemisphere received the most solar radiation, almost twice as much as the southern hemisphere.
After the summer solstice, the Tropic of Cancer and its northern region, the midday sun altitude angle also began to decrease. At the same time, after the arrival of the summer solstice, the stars in the night sky gradually became summer stars.
Beginning of autumn:
Beginning of autumn is the first solar term and the starting point of autumn. Entering autumn means rain, storm, humidity, etc. At the turning point of the year, there is a downward or decreasing trend; In nature, everything begins to grow from lush to mature.
According to the calculation method of "three volts", the day of "beginning of autumn" is often still in the midsummer period, that is to say, the heat is not over, and the real coolness usually comes after the Millennium solar terms. The watershed of summer heat is not in the solar terms in beginning of autumn.
Beginning of winter:
Beginning of winter is a seasonal solar term, which means that it has entered winter since then, which means that wind and rain, light and temperature are at a turning point, and the climate begins to transition from autumn to winter. It reflects the changing laws of phenology and climate, such as spring germination, summer growth, autumn harvest, winter storage, sunshine, rainfall and temperature.
It is generally not very cold in early winter (Meng Dong) in some parts of the south, but with the passage of time, cold air frequently goes south and the temperature gradually drops. The northern region is very cold from winter to spring, and the climate change of several solar terms in winter is not obvious. Snow is the main feature of northern winter.