Heat is a form of energy. The study of heat is really the study of the molecules and atoms of matter: the faster they move, the higher the temperature. The molecules of a substance are always more or less in motion, and the total heat of a substance is proportional to the total kinetic energy of its molecules. When heat is applied, the molecules move faster and their kinetic energy rises. Heat is thus a form of energy linked to molecular motion, which creates the sensation of cold or heat in our bodies.

The Chinese (and we foreigners too) are already feeling the heat. I hear it is extremely hot in Bangladesh too, with temperatures forecast to rise further. Beijing has a similar forecast. On 6 July Beijing's maximum temperature was 32 degrees Celsius, and on 21 July it could reach 38 degrees. Yet this period, from 6 July to 21 July, is known in China as "Minor Heat", or Xiaoshu, China's 11th solar term. In Chinese, "xiao" means "small" and "shu" means "heat".

Under China's lunar calendar the year is divided into 24 solar terms. They originated in the Yellow River basin in ancient China and are recognised internationally as the "Fifth Great Invention of China". UNESCO has also recognised them as intangible cultural heritage of humanity.

Each solar term has its own characteristics. The system arose in China thousands of years ago, and since ancient times the Chinese have organised their daily activities, especially farming, according to the solar terms.

The names show what the weather will be like in each term: Lichun (start of spring), Yushui (rain water), Jingzhe (awakening of insects), Chunfen (spring equinox), Qingming (fresh green), Guyu (grain rain), Lixia (start of summer), Xiaoman (lesser fullness), Mangzhong (sowing time), Xiazhi (summer solstice), Xiaoshu (minor heat), Dashu (major heat), Liqiu (start of autumn), Chushu (end of heat), Bailu (white dew), Qiufen (autumn equinox), Hanlu (cold dew), Shuangjiang (first frosty wind), Lidong (start of winter), Xiaoxue (minor snow), Daxue (major snow), Dongzhi (winter solstice), Xiaohan (minor cold) and Dahan (major cold).

The Chinese also change their food and clothing according to the solar terms of the lunar calendar. As I said, China is now in its 11th solar term, Minor Heat, which brings the heat that should grow day by day. In reality, though, Minor Heat is feeling like Major Heat, even though Major Heat, the 12th solar term, only arrives on 22 July.

Xiaoshu brings not only heat but also storms, lightning and hail. Where I live in Beijing I have not heard of or seen hail, nor heard thunder yet, but there has been rain with strong winds more than once, and it rains more or less every night, which lowers the temperature a little at night. On 6 July the night temperature fell to 22 degrees Celsius, and the forecast says it will be 25 degrees on the night of 21 July.

With frequent storms and rain, parts of China can flood during this solar term. Elsewhere the opposite happens, and drought strikes. The hard-working Chinese prepare for both. Farmers in particular watch the weather closely and act as the situation demands. In fact, the main task for farmers during Xiaoshu is dealing with the effects of flood or drought.

China is the land of tea, and of flowers too; many kinds bloom across this diverse country. During Xiaoshu the lotus blooms in particular, as the hot weather suits it. In this solar term the lotus opens fully and delights visitors, and tourists crowd places in China famous for lotus just to enjoy its beauty.

There are more than 2,000 species of firefly in the world, and fireflies become more active at this time along with the lotus. In China, Xiaoshu is also known as the "firefly season". Since ancient times the Chinese, especially children, have enjoyed fireflies at night during this solar term. The woman poet Zhu Shuzhen of the Southern Song dynasty (1127-1279) captured such a scene in her poem "Summer Fireflies", whose subject is children playing with fireflies in the woods and thickets on Xiaoshu nights. Such scenes can still be seen in rural China.

The Chinese also adjust what they eat by solar term. Xiaoshu is the best time to eat watermelon and similar fruit, and farmers bring in the watermelon harvest now. Thousands of varieties of watermelon are grown worldwide, and more than 60 million tonnes are produced each year, 60 per cent of it in China. After China come Turkey, India, Iran, Algeria and Brazil.

In fact, watermelon is available in China almost all year round, but its real season is now. In Nanjing, Jiangsu province, there is a custom of eating a "small watermelon" on the first day of Xiaoshu and a "big watermelon" on the first day of Dashu (Major Heat). The "small watermelon" mainly means the phuti or muskmelon, and the "big watermelon" means the ordinary watermelon.

Besides watermelon, the Chinese make a point of eating dumplings during Xiaoshu. Dumplings are called "jiaozi" or "shuijiao" in Chinese. The dish originated in northern China but is popular across the country. It was created by an ancient Chinese physician named Zhang Zhongjing, who, as you may have guessed, first used it as medicine, to save people from severe cold and loss of appetite.

He mixed mutton, chilli and a kind of medicine into half-moon-shaped dumplings, boiled them and gave them to patients, and it worked. Later dumplings became everyday food for the Chinese, though they still eat them ceremonially on special days of the year. Dumplings are an essential part of the Spring Festival, and during Xiaoshu too the Chinese make a point of eating them.

China is a vast and diverse country of 1.4 billion people and the world's second-largest economy. Extreme poverty was swept away in 2020, and more than 90 per cent of Chinese people now enjoy urban amenities. So many ancient customs are no longer as widely observed as before, such as airing clothes in the sun.

In ancient times the Chinese made a ceremony of putting clothes out in the sun during Xiaoshu. I have seen winter clothes being aired in sunlight in Bangladesh, especially in villages. In China this used to be a common sight, especially in Xiaoshu. In rural areas people still air their clothes with some ceremony in this solar term, and it is sometimes seen in towns too. Older people have kept this ancient custom alive, if only on a very small scale.

The writer is news editor at China Media Group (CMG).

Source: Jagonews24. First published in Bengali on The Agro News.