George Green was a baker and grain miller who became an important mathematician largely through self-study. He was born in England in 1793 and spent most of his life working in his family business while studying mathematics in his spare time. He had very little formal education, so it is not fully known how he learned advanced mathematics. Despite this, he developed ideas that later became important in mathematical physics. In 1828, he published an essay that introduced what we now know as Green’s theorem. In simple terms, Green’s theorem connects what happens along the boundary of a closed region with what happens throughout the area inside it. Instead of calculating certain quantities only along the boundary, we can calculate them by considering the corresponding quantities over the entire region. Green’s theorem is closely related to the divergence theorem and Stokes’ theorem. Green’s life also shows that important mathematical work can come from people working outside traditional academic settings.

This is a liquid rocket engine invented by me and my friends in 2018,using fuming nitric acid and Tonka-250 as propellant,the thrust can reach 500N. We were still high school students at the time, so we had to complete this project through self-study. #Rocket# #DIY#

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What Would Happen If Elon Musk Had Been Born in China? This is China’s version of Elon Musk @elonmusk. How strong do you think the resemblance is? This is Mr. Ma, a barbecue chef at a restaurant in Tongchuan, Shaanxi Province. Because he looks strikingly like Elon Musk, a customer took his photo and uploaded it online, unexpectedly making him famous. He said that over the past two days, more than a dozen people have asked to take photos with him, while several others have approached him about possible collaborations. In fact, there have long been many discussions on the Chinese internet about what would have happened if Elon Musk had been born in China. One fairly representative article argued: "Let us suppose that, in 1971, twenty people with the same potential as Elon Musk were also born into ordinary Chinese families. "If they were fascinated by science and technology, the most they could probably do would be to join an extracurricular hobby group at a children’s activity center and build model airplanes. "In 1981, a computer cost tens of thousands of yuan. There was absolutely no way an ordinary Chinese family could afford one. "It would not be until the 1990s that they might finally get access to computers in a school computer lab, where one hour of use could cost about as much as an entire meal. "But students had to attend morning reading sessions every day and evening self-study classes at night. Where would they find the time to learn programming? "Besides, what if they spent all their time messing around with these 'useless' things and then failed to get into a good university? 'A mild-tempered father might patiently lecture them: 'Focus on your studies. Stop wasting your time on improper pursuits,' until they finally gave up on their own. "A bad-tempered father would simply confiscate everything. If they dared to argue, he would grab something and beat them. "From the first grade onward, they would have to devote all their energy to exam scores. Otherwise, they might not even make it into university. "By the time they finally entered college, all their sharp edges would have been worn away. They would have been molded into conformity and would have had almost no chance of becoming another Elon Musk. "If Musk had been placed in China, his life would probably have followed a path like this: "No one would have paid for software like Zip2, an online city-guide and business-directory platform. Lenovo would not have acquired it. It would have ended up like Zhang Xiaolong’s Foxmail: users would simply use pirated copies. "Have you ever seen Lenovo pay a huge amount of money to acquire independently developed personal-computer software? "So Musk would probably have starved to death at the age of 28 and gone to meet Karl Marx. "Suppose he somehow survived until the age of 31 and developed a payment platform like PayPal. The major Chinese internet giants—Baidu, Alibaba, and Tencent—could simply copy it. Why would anyone pay to acquire his company? "Have you ever seen BAT pay an enormous price to acquire an internet application developed by an individual entrepreneur? Investors would know that his product would be copied, so they would refuse to fund him from the very beginning. This time, he would definitely be finished. "Even if BAT did not copy him, could Musk manage the necessary connections? Could he obtain the required licenses? "Those are not things an ordinary person can easily secure, as everyone understands. "Operating such a business without a license would be illegal. In the best-case scenario, the authorities would order him to shut down. In a more serious case, they might accuse him of illegal fundraising, and Musk could end up spending the rest of his life in prison. "Even if he successfully built PayPal and had more than a billion yuan in his hands, could he establish a company like SpaceX? "That is the domain of the state-owned aerospace corporations. "Even if he somehow obtained permission to enter the industry, no one would provide him with the necessary components or support. "If one private individual were allowed to accomplish all that, where would it leave the millions of people working within China’s state aerospace system? "I guess that, had Musk been born in China, the best possible outcome for him would have resembled Zhang Xiaolong’s career path: working for someone who had the connections and qualifications needed to obtain the necessary licenses."