Liu An, grandson of Emperor Gaozu Liu Bang. He likes reading and playing the piano, but what makes him famous in history is not his powerful policy of governing the country, but that he is an outstanding inventor in ancient times. He was the first person in history to try to go to heaven in a hot air balloon, which was more than 1000 years earlier than ten thousand households in the Yuan Dynasty who carried rockets to heaven. He used wormwood as fuel and eggshells as soaring devices. After the wormwood is lit, the eggshell with special characteristics slowly rises to the sky under the impact of the hot air of wormwood.
He believed in Taoist alchemy for health, and unconsciously invented a delicious food-tofu when refining Dan medicine. Said he was the founder of tofu. Really, he deserved it. It is said that once he was drinking soybean milk, because he was thinking about an alchemist and was absent-minded. He sprinkled soybean milk on a piece of gypsum, and it didn't take long for the gypsum to disappear. Soymilk sprinkled on gypsum becomes an elastic white cube. Liu An let the servant at home taste it, and it tastes very good. And eating it without any discomfort, Liu An gave this technology to the people of Huainan. The world is widely circulated.
The earliest prototype of hot air balloon in Liu An is a hollowed-out eggshell, that is, find an egg, punch a hole in the egg, take out the egg liquid, and then put the burning wormwood in the eggshell. When the eggshell is heated, the gas expands downward, thus pushing the eggshell upward. According to this little experiment, did Liu An make a special eggshell that can hold people's eggshells, or did he order a lot of wormwood according to the previous method? Using hot air to push back, let the characteristic eggshell carry people slowly to heaven.