Why does it get colder after the winter solstice? | Expo Daily

Why does it get colder after the winter solstice?

Logically, the daylight hours will increase after the winter solstice, so why does it feel colder when the daylight hours are longer?

From the winter solstice to the summer solstice of the following year, although the sun's direct point gradually moves toward the northern hemisphere, the recovery of energy is a slow process. For a period of time after the winter solstice, although the northern hemisphere absorbs more solar energy, this energy can only reduce the energy deficit.

During this period, the energy in the northern hemisphere is in a state of "not enough to cover expenditure" every day, so the temperature drops a little bit every day, so we will feel colder and colder. If the cold air from the north moves south, the temperature will drop further during this period.

The summer solstice and winter solstice are not the hottest or coldest time of the year. Due to the slow loss of heat, the third nine days after the winter solstice is the coldest period of the nine-day long winter, which is what the elders call "walking on ice for the third and fourth nine-day long winter".

Although the temperature rises occasionally in winter, friends should not change their cotton pants easily. They still need to guard against cold waves and temperature drops before the "three-nine-nine" days. Only after the 81st day of the nine-nine days (the ninth "nine-nine days" after the winter solstice) can they wear light clothes and embrace the spring.

Image source: veer gallery

How do Chinese scientists overcome the problem of saline-alkali land?

Although my country has a huge grain output, in the process of economic development and industrial transformation, my country has gradually become a country that imports a large amount of grain crops.

In order to maintain and increase grain production, in addition to increasing yields through breeding and agricultural technology, another method is to increase the area of ​​arable land. At present, my country's arable land area is about 1.9 billion mu, but there is limited room for further increase in arable land. Scientists have focused on a special type of reserve arable land - saline-alkali land.

The team led by Academician Cao Xiaofeng from the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, in cooperation with the Grassland Research Institute of the Heilongjiang Academy of Agricultural Sciences, successfully selected the extremely salt- and alkali-tolerant legume green manure/forage "Sesbania sesbania" from more than 800 plant resources, and bred the Zhongkejing Sesbania sesbania variety, which successfully achieved high yields on severely saline-alkali land.

The reason for choosing Sesbania is that planting Sesbania and turning it over can improve soil quality and increase nutrients. On the other hand, Sesbania's nitrogen fixation can add nitrogen fertilizer to the soil. In addition to nourishing the soil, Sesbania is soft and has a high protein content. The crude protein content in the early flowering period is as high as 20%, which can provide very high nutritional value for livestock.

Cao Xiaofeng's team is developing suitable varieties and cultivation methods for different regions based on the changing topography, landforms, and soil conditions of my country's saline-alkali land. It is believed that with the development of my country's agricultural science and technology, the saline-alkali land that has been uncultivated since ancient times will one day become fertile fields.

This is not snow from the sky, but white salt from the ground (Source: flickr)

Hangnails on hands, isn’t it a sign of vitamin deficiency?

In autumn and winter, many people start to get hangnails on their hands. There has been a saying that "hangnails are caused by vitamin deficiency", but in fact, no research has shown that it is related to vitamin deficiency, but mainly related to the damage of the skin barrier function.

The small area on the fingertips where barbs grow is called the periungual fold, and its main function is to wrap and protect the nail matrix to ensure the healthy growth of the nail plate. In the skin tissue there, there are very few hair follicles and sebaceous glands, so the sebum membrane is already very thin. In the autumn and winter when the temperature drops sharply, the secretion of sebum will further decrease, the sebum membrane may even be missing, and the exposed stratum corneum becomes easily damaged.

The formation mechanism of hangnails is also very simple. When we move our fingers in daily life, the nail folds will be stretched repeatedly, coupled with countless local friction and collisions, the stratum corneum may not be able to hold and crack, eventually forming hangnails.

There is no medical research evidence to prove that hangnails have a direct causal relationship with nutritional deficiencies or certain serious physical diseases. The relationship between hangnails and "vitamin deficiency" is completely fictitious. It is really unnecessary to test vitamin levels just because you have a few peeling spots on your fingers.

The content is compiled from China Science Expo Weibo, Science Academy, and Science Popularization China

This article was first published in China Science Expo (kepubolan)