"Only once did I send a large stone weighing more than 40 kilograms into the sky." Huang Han said excitedly.

"How high did it fly?" Yu Ren asked simply and directly.

Huang Han's voice became much softer at this time. "It was about ten feet high and fell down."

"Rare, rare!" Yu Ren praised heartily.

"In this case, how dare you make that bet with Fatty Xu just now?" Yu Ren asked in confusion.

"I have recently improved the four fireworks used in the previous experiments and put more gunpowder in them. I believe that these four fireworks must be much more powerful than the last time. So I am confident that they will

You can send me to heaven." Huang Han said.

Yu Ren nodded. "I have a question I want to ask you. Does any of you know why the things we sent to the sky with such difficulty fell down so quickly?"

When Cao An heard this, he couldn't help laughing. "Sir, are you confused? If this thing doesn't fall to the ground, will it still fly into the sky?"

Yu Ren patted Cao An's shoulder lightly. "You are really smart. There are things that don't fall to the ground, but fly to the sky!"

"What?" everyone asked together.

"Kongming lantern!"

"But it will eventually fall down!" Huang Wu interjected. "All the Kongming lanterns I saw eventually fell down."

Yu Ren nodded. "You are right. So, have any of you ever thought about why the Kongming Lantern flies up to the sky on its own, and why it eventually falls down?"

This time, no one spoke. After a while, Cao An asked Yu Ren in confusion, "Sir, what do we want to do to understand this?"

Huang Han raised his head and answered Cao An's question for Yu Ren. "Because, if we understand this, can we come up with a way to prevent the Kongming Lantern from ever coming down? In addition, can we also make a

How about a big Kongming Lantern that never stops rising and takes us to the moon?"

Yu Ren had to admit that this Huang Han was indeed a very scientifically talented person. Although what he said was not entirely correct, at least he had grasped some key points after Yu Ren's reminder.

Yu Ren is like a physics teacher, teaching the ordinary children in front of him in a persuasive way.

"You are right. So, have you figured out why the Kongming Lantern can rise into the sky?"

The three of them were silent. Huang Han's brows were furrowed.

After a while, it seemed that there was still no result after seeing the three people. Yu Ren didn't want them to waste any more time, so he explained to them in detail what air is, what density is, and the density of air.

"The reason why the Kongming Lantern rises is because the air inside it expands when heated and is less dense than the surrounding air, so it rises. This is the function of buoyancy. When the contents of the lamp are burned out, the air inside the lamp gradually cools down.

They have the same density as the surrounding air. So, the sky lanterns fall from the sky like other things. This is the effect of gravity."

Seeing that the three of them still looked half-informed, Yu Ren had to give some further explanations.

"To put it simply, let me take water as an example! If you put something heavier than water, such as a stone, into the water, it will immediately sink to the bottom. If you put something lighter than water, such as cotton,

.Even if you put it at the bottom of the water, it will immediately float up from the water. This is the function of buoyancy. In the same way, air also has buoyancy."

When Huang Han heard this, he seemed to have some understanding. A knowing smile appeared on his face for the first time. But Huang Wu and Cao An knew from their expressions that they still found nothing.

But Yu Ren no longer wanted to explain to them any more on this issue. Because he knew that it would take too long to explain everything to them one by one. So he turned to Huang Han and said, "Now, do you think

Is there any better way to send people to heaven?"

"I think we can really make a big Kongming Lantern and let people sit in it, so that they can go to heaven," Huang Han said.

Yu Ren patted Huang Han's shoulder gently. "A boy can be taught!"

Just do it. Huang Han thought of a way and planned to take action immediately. However, Yu Ren suggested that he draw the drawings first and then make them according to the drawings. This can reduce the occurrence of mistakes. Huang Han followed Yu Ren's advice.

, and asked Huang Wu to go to the city to buy the four treasures of the study. But Yu Ren picked up a carpenter's ink fountain that was thrown on the ground and said that there was no need to buy it, but to use this one first. This one was easier to use. It happened that the ruler was also ready-made.

So, under the auspices of Yu Ren, this group of people started their new flying plan: making a big Kongming Lantern - a hot air balloon.

The production diagram of a hot air balloon is relatively easy to draw. The most important thing is what materials to use. This really made everyone think a lot. Finally, under Yu Ren's suggestion, they decided to use bamboo baskets and paper first.

, bamboo pieces, make a small hot air balloon.

Seeing that it was already past noon, everyone hurriedly went down the mountain to prepare materials.

Because the production this time was a relatively simple test product, the size was relatively small. As a result, before dark, they had basically completed it. This is an enlarged Kongming Lantern. Below is a bamboo basket with

There is a brazier with a large round ball made of simple thick paper on top.

When everything was completed, everyone was full of hope. Yu Ren lit the brazier under everyone's expectant eyes. Then, their eight pairs of eyes were fixed on the bamboo basket.

Time passed by, and everyone was extremely anxious. After about a quarter of an hour, they finally saw the bamboo basket start to beat. At first, it just jumped lightly a few times, and then slowly floated away.

He reached the ground and rose up step by step.

At this time, everyone held their breath, looking at the Kongming Lantern that had been magnified several times, filled with their hopes and dreams, and flying towards success step by step.

When the hot air balloon flew over his head, Cao An finally couldn't help shouting, "Ah! It's successful!". Huang Wu also shouted, and after the two shouted, they hugged each other tightly. But Huang Han on the side

Standing still without moving, he felt something wet flowing in his eyes. His dream for many years! At this moment, he could finally clearly feel that he was getting closer to his dream step by step. Dream, too.

It’s no longer that illusory castle in the air!

Only Yu Ren is calm, because he is thinking about what fuel to choose as fuel and what cloth to use to make the hot air balloon in order to continue to enlarge the hot air balloon. During production, the weight must be taken into consideration to make it as light as possible.

, but also consider firmness and airtightness.

Just when everyone was immersed in joy, a loud shout suddenly came from behind them, "Quick, quick. It's on, it's on!"

Several people heard the cry and hurriedly looked up. Sure enough, they saw that the hot air balloon that had just risen above the head was already on fire. At first, only the bamboo pieces connecting the upper and lower parts were on fire, but soon the fire spread.

The paper above. So, the hot air balloon, which had only been in the air for more than a minute, suddenly fell from the sky within a few seconds, fell into the nearby mountain stream, and disappeared.

Seeing this, Cao An rushed to the mountain stream and went down to look for it.

"Forget it." Yu Ren stopped him. "This is just one of our test items. As long as it can achieve this effect. I didn't expect it to fly very far. But this result clearly tells us

, the expanded Kongming Lantern that we plan to carry people will definitely be successful."

Initially, Cao An and Huang Wu looked depressed when they saw the hot air balloon on fire, but after hearing Yu Ren's words, they cheered up again.

Yu Ren walked up to Huang Han, who had been staring at the hot air balloon falling into the mountain stream without saying a word, and patted his shoulder gently. "Don't worry, we will make a better hot air balloon soon."

Huang Han looked up at Yu Ren and nodded firmly.

Yu Ren comforted the emotions of several people, and then walked towards the person who had been hiding in the dark until the hot air balloon caught fire, and finally couldn't help but scream.
Chapter completed!