The hanging basket of the hot air balloon is very large, and it adopts a two-story structure, the upper floor is used to operate the hot air balloon, and the lower floor is the living area, as if hanging a two-story building.

Can this thing fly? Today is going to see the difference, a lot of people who watch the excitement gathered together, there are craftsmen and craftsmen's families, there are also idle royal relatives, and even Li Shimin has rushed over, after all, if he succeeds in taking off this time, mortals will be able to conquer the sky, which is of great significance.

This thing can also be used in the military, maybe in the future, Datang can directly use the method of airdropping when sending troops.

Of course, Li Shimin did not allow Yun Yao to take risks, so the first users of the hot air balloons were selected craftsmen. Yun Yao told them that if they succeeded, they could go down in history, and if they failed, they would have a pension for their families, so the five craftsmen also began to operate the hot air balloon without hesitation.

When everyone saw the hot air balloon getting bigger and bigger, and more and more bulging, they all stared at it in surprise, and when they saw the balloon floating with the two-story building, their jaws dropped even more.

Huang Bixia also nervously grabbed Yun Yao's hand, although she knew about the princess's plan from three years ago, but she always thought that there was no possibility of taking off, she never expected that it was right in front of her, just today, it turned out that the hot air balloon can really take off with heavy objects.

It's just that the cable hasn't been released yet, so the hot air balloon doesn't fly directly into the air, just tightens the cable and floats at a low altitude. But this is already shocking, how can this also have a height of three zhang, and it is almost catching up with the city wall of Chang'an City. Fly a little higher to overlook Chang'an, Li Shimin can only sigh that his daughter has surprised him too much, he doesn't understand the principle, he only listened to the students of Guozijian explained, what kind of heat goes up and cold goes down.

Li Shimin also asked at the time: "Why is it colder on the top of the mountain than at the foot of the mountain?" If the heat goes up and the cold goes down, then the top of the mountain should be hotter than the bottom of the mountain, right? ”

But science is counterintuitive, and while it is true that the air is colder and the ground is warmer, the heat and cold move in the opposite direction of human cognition. Guozijian's students explained that the bottom of the mountain is warm because they are close to the ground, and the temperature of the ground is warmer. The summit of the mountain is farther away from the ground so it is colder, which simply means that the temperature obtained by the earth is actually mainly from the storage of the ground, rather than the direct exposure of the sun.

At that time, Li Shimin also seemed to understand whether he understood or not, but now it does prove that the hot air is going up, so as long as the hot air is enveloped, this hot air can lift heavy objects to the sky. At this time, a little bit of scientific spirit suddenly appeared in Li Shimin's mind, and he couldn't help but say to himself: "When Guanyin Bodhisattva rode away on the clouds, is the cloud also hot?" ”

If it's hot, it's not the soles of the Bodhisattva's feet, but the bottom of the skirts.

The students of Guozijian were also very excited, this is science, amazing. They are also responsible for explaining to Li Shimin how the hot air balloon works, how to fly up, and how to fall down.

To fall is to let go of the hot air, and there is an outlet at the top of the hot air balloon, and as long as the hot air is released, the height can be reduced.

In short, today the people of Chang'an have seen that there is a behemoth outside the city beyond the city wall, just like a huge round head, which is really novel and fun.

Several generals also said that with a hot air balloon and a telescope, they could see thousands of miles away.

Li Shimin couldn't hold it anymore and decided to go up in person. Although there was danger, the ministers knew that Li Shimin was not afraid of danger, so they also rushed to be the first, and they all said that they would also follow the emperor into the sky.

Yun Yao thought to herself that this was not a toy, and she was going to take a hot air balloon to travel west, but such a fresh thing was too attractive to mortals. Yun Yao used to be able to fly, so he didn't have any curiosity about the sky, but it was the first time for a mortal to set foot on such a high altitude, how could he not be excited, how not to be curious?

Still didn't let go of the cable, but Li Shimin was already very happy, and stood in the fence on the second floor with a few ministers and looked into the distance.

"Hot air balloons." Li Shimin waved his hand on the hot air balloon and wrote three words, which was regarded as a formal recognition of the greatness of the hot air balloon, and then Shixing Dafa wrote a poem: "Chang'an is at the end of the mountain, Qujiang City is in the middle, and you want to be poor for thousands of miles, and board the hot air balloon." ”

Everyone said yes, but don't you just want to get on the hot air balloon? It's really proper. The emperor is really both civil and military, and his pen is full of flowers.

Li Shimin was also very happy, rewarding the craftsman who controlled the hot air balloon for him with 100 gold, and then he really wanted to put the hot air balloon in the palace, so that he could climb high in the palace and overlook Chang'an when he had time in the future, which was also a kind of fun. So he came down and said to Yun Yao: "Good daughter, my father is very fond of hot air balloons, and this hot air balloon will be sent to the palace, so that I can overlook Chang'an in my spare time, and it will also help me care about the people and the community." ”

Obviously it's for himself to play, and he has a half-dime relationship with the society?

Yun Yao could only say: "Father, this is the first hot air balloon and there are still many deficiencies, if my father needs a hot air balloon, then I must develop the second generation of safer and more comfortable hot air balloons for my father to use." ”

Li Shimin felt that it made sense when he heard it, the first generation definitely needed to be improved, and the second generation was definitely better than the first generation. So he accepted this argument and said, "Then I'll wait for you to develop the second generation of hot air balloons, but don't make me wait for a long time." ”

Yun Yao immediately said: "In order to develop the second generation of hot air balloons as soon as possible, I think the first generation of hot air balloons will need to use more and accumulate experience." So I decided to take my horse and take a hot air balloon back to Kennan Road to visit relatives, and I also asked my father for permission. ”

Li Shimin knew that Yun Yao liked the horse very much, if there was no hot air balloon, it would be difficult to return to Jiannan Road to climb to the sky, but now that the sky has been climbed, he should indeed go back to the horse's hometown to see. So he thought about it for a while and nodded in agreement: "Okay, but pay attention to safety, and don't run around, you will come back after visiting relatives in Jiannan Road, you can't stay with the horses, you know?" ”

"My daughter knows." Yun Yao said that Chang'an City was not subject to the foreign monarch's order, and she not only had to run, but also ran to Tianzhu.

"When are you going to go?" Li Shimin asked.

"Five days later, the use of hot air balloons is very important to the weather, I have invited the famous hexagram master Yuan Shoucheng in Chang'an to walk with me, and the weather divination along the way can ensure safety." Yun Yao didn't lie, Yuan Shoucheng's divination weather was exactly the same as the arrangement of the heavenly court, and it was more accurate than the weather forecast.

Seeing that his daughter was thoughtful, Li Shimin was relieved to let his daughter go on the road, the child has his own plans when he is older, and parents cannot tie their children to their side forever.

Soon everyone knew that the princess of Dancheng, Li Zhuyun, was going on her first hot air balloon journey, and the newspapers reported the news of flying to Jiannan Province this time. Since ancient times, there is a record of Shu road difficulty, from ancient times to the present to enter Shu is not an easy thing, and now with a hot air balloon everything is simple, if it can go well, it is to open up a new route into Shu, maybe in and out of Shu in the future will be all hot air balloons.

If it succeeds, the princess is really meritorious, and many Chang'an residents feel that the princess is willing to take risks, which is really remarkable. When other members of the royal family saw Yun Yao in the limelight, they were envious of their real names, and they couldn't wait to get a piece of the pie.

Anyway, the hot air balloon workshop is just outside Chang'an City, and when the time comes, they will produce new hot air balloons and fly everywhere to become famous.