Jiang Wei waited for a moment before he spoke,

"First of all, on a rainy day, do we see dark clouds?"

Many people in the audience nodded, and Brother Gongzi also began to listen carefully.

"So what are the clouds? Where did it come from? Eventually, the immortals discovered a problem, and that was that the lake would dry up when it was hot. When we cook vegetables and make tea, there will be white gas drifting into the sky. And after boiling the water for a long time, the water will disappear, and later the immortals got the answer. That is the clouds in the sky, which are formed by the heat of the sun, or boiling water, that fly up to the sky. ”

When Shahr heard this, he also suddenly realized, and he admired Jiang Wei more and more.

"Then, when enough water mist has accumulated, the water mist will collide and form water droplets. The immortals discovered that there is an air flow in the sky above the sky, what is an air flow? Let's define it as wind for the time being. This air flow is upward, so it holds the water droplets. When the water droplets collide and get bigger and bigger, so big that the air flow can't support the water droplets, then it will rain. ”

Everyone in the audience suddenly realized again. Under Jiang Wei's explanation, they knew why it was raining. But at the same time, a thought popped up in my head, that is, why is there an air flow in the sky?

"So, if you want water droplets to fall and form rain, you just need to quickly form large water droplets. How to quickly form large water droplets? It is recorded in the book of heaven given to me by the immortal master that there are at least three things that can make water droplets grow in size quickly and produce rain. ”

At this time, Fang Xuanling couldn't help it, although he still had a lot of questions, but the immortals Jiang Wei said were not like the kind of ethereal immortals, but like the hundreds of schools, he remembered. Among the hundreds of schools of thought, Taoism and Yin-Yang are those who study the nature of heaven and earth, and the universe, so will Jiang Wei be the successor of the Yin-Yang family?

However, he didn't care much about Fang Xuanling, he was concerned about the rain. You must know that natural disasters and droughts are very harmful to people's crops. If there's a way to get the rain down, it's worth it anyway. He listened carefully, for fear of missing a word, but at this time, Jiang Wei just didn't speak, which made Fang Xuanling anxious.

"Old man Fang Xuanling, please tell the little brother, how can I urge the rain?"

Jiang Wei looked at this thin old man seriously, this is the famous Fang Xuanling. Nodding to the old man, he spoke,

"Although there are more than three things that can promote rain, I only get one at the moment."

"Say it quickly."

Fang Xuanling saw him talking indifferently, and was a little anxious.

"Carbon dioxide."

Jiang Wei said a word, which made Fang Xuanling stunned.

Fang Xuanling wanted to ask, are you fooling me? Diogen, whatever.

He held his breath and almost didn't mention it, his face flushed.

Jiang Wei saw it and hurriedly said,

"Carbon dioxide is a kind of gas, what is gas?" Jiang Wei looked at the sky, a little unsure of what to say, sorted out his language, and then said,

"Qi, it exists in the air, beside you, it is everywhere. But you need to breathe, and what you breathe is the oxygen in the gas. ”

Now many people understand.

Originally, the word "air" was derived from Taoist writings. Also written as "empty Qi". During the Tang Dynasty, the existence of air had already been demonstrated.

Qi is a philosophical concept full of wisdom in ancient China, which is different from the materialization of wind, fire, earth and water in ancient Greece, and it is also a highly abstract concept product, believing that all things come from one qi.

There are very few books that specifically and systematically talk about qi, because it was a bit late when "qi" was put forward as a clear idea, roughly between the Wei, Jin, Sui and Tang dynasties.

Jiang Wei stood on the podium and continued to preach calmly,

"Carbon dioxide, on the other hand, is a gas in the air. Carbon dioxide is a special gas, and under certain conditions, carbon dioxide will form water. And when the temperature is below minus 78 degrees, it will freeze, and I just brought it today, carbon dioxide ice at minus 78 degrees, I call it, dry ice, you can feel it first. ”

Jiang Wei nodded to Li De, and Li De saw it, so he went backstage to take out an iron basin and walked to the crowd in the audience. People saw a pile of white ice slag in the iron basin, and white smoke was emitting.

Jiang Wei made dry ice, but it took a lot of effort. After all, in this day and age, it is difficult to have the conditions to reach minus 78 degrees.

By taking advantage of the properties of carbon dioxide, it is possible to reduce the temperature and make dry ice.

But the difficulty lies in liquefiing carbon dioxide. Because it requires a lot of air pressure, it can't be made out of dry ice without liquefiing.

For this reason, Jiang Weituo's uncle Xu Xiaode asked the Ministry of Industry to help build a steel gas cylinder, which liquefies carbon dioxide, and then opens the valve valve of the gas cylinder to make dry ice.

At first, Jiang Wei didn't have much hope, but after he really made it, Jiang Wei had to admit the power of ancient handicrafts. Especially the top craftsmen of the Ministry of Industry.

When I touched the dry ice and felt the stinging pain, I realized that the temperature was too low, and it would make people feel pain.

One by one, they were amazed, and Fang Xuanling had a question.

"So how do you use this...... What kind of carbon dioxide is used to promote rain? ”

Jiang Wei smiled, and the dry ice basin handed over by Li De.

"There are many ways, of course, these are about immortal arts, and immortal arts, which are too complicated, come from the various truths in the world. I'm afraid it's unconvincing if I'm just saying, but if it does come to the day when it needs to rain, I'll let the carbon dioxide go to the clouds and push the rain down. ”

"Next, let's move on to the temperature, iron is familiar to everyone, but you may not know how many degrees it melts. The Book of Heaven given to me by the immortal master records that when the iron reaches more than 1,500 degrees, it will melt. So, what would happen if this dry ice, which had a temperature of minus 78 degrees Celsius, encountered molten iron at more than 1,500 degrees? ”

Everyone in the audience froze.

The first thought is, will this ice turn into water in an instant? Or will it become carbon dioxide and disappear?

Jiang Wei smiled, and the villagers of Yunling Village, who were in the background, carried a small stove to the stage, and Xiao Shi of a Ministry of Industry held an iron hook and hooked out a red cylinder.

This little official of the Ministry of Works was borrowed from his uncle.

"There's 1,500 degrees of molten iron in it. What happens if I pour this molten iron on this dry ice? ”

Jiang Wei smiled and nodded to Xiao Shi of the Ministry of Industry.

The officials in the Ministry of Works were a little dumbfounded, but no one told him that they were here to do this.

He glanced at the ice in the iron basin. If this falls, this thin iron basin will not be able to withstand it, and when the time comes, it will leak out, and this wooden platform may catch fire in an instant. And there is no water around, what to put out the fire? This garden is burned, whose is it? Will I be to blame?

The little official looked crying,

"Childe, isn't this too dangerous, how can the ice withstand it? What if it causes a fire? ”

The audience in the audience also tensed their nerves one by one, Gao Yang was also dumbfounded, and Princess Changle frowned even more.