A small white robot on a food delivery mission at George Mason University in Virginia was blocked by a group of students when it stopped. It could let the students go first, try to walk around them, or walk through the middle of the crowd. After a few seconds, the robot decided to walk straight through the students, splitting the crowd in half. ‘These robots sometimes come right at your legs,’ said Alice Christensen, an anthropology major at the university. She lifted the top of another robot car and pulled out a Subway sandwich. Christensen, 22, often uses an app similar to Grubhub or Uber Eats, where food delivery tasks…

In everyday life, when we put two pieces of metal of the same material close together, nothing strange will happen. But in the space environment, two pieces of metal might fuse into one piece and never separate. The Galileo probe’s high-gain antenna was unable to fully open due to the cold welding effect The antenna won’t open, disrupting the Jupiter mission On October 9, 1989, NASA launched Galileo, a probe to Jupiter. To ensure Galileo can receive command signals from Earth, which is so far away from Jupiter, NASA has specially equipped the spacecraft with a “high-gain antenna” capable of transmitting 80 kilobytes per second. In order to reduce the…

As anyone who has flown a kite knows, it is easy to use the high winds to keep it flying steadily, as long as you can get it high in the air. Now scientists are trying to harness this property to generate electricity by placing large “kites” more than 200 metres above the ground. The higher you go, the more energetic you are Winds close to the ground tend to slow down or even change direction because of friction with trees, hills, buildings, etc. As height increases, the average wind speed increases. High-altitude wind energy is more abundant and stable than current near-surface wind energy. Over the past few decades,…

　　In the hot summer, five minutes outside the home can make people sweat profusely. In order to drink a can of iced Coke, you can buy a mini refrigerator for tens of yuan. It can not only cool down, but also become a heating box in winter. But is this cheap and cold refrigerator really reliable? Is the mini fridge a “proper” fridge? 　　This kind of mini refrigerator and the large refrigerator at home, except that there is a refrigerator in the name, the refrigeration principle can be said to have nothing to do with it. The core element of the mini refrigerator is a semiconductor refrigeration chip. 　　The structure…

　　Since its birth in France in 2009, visible light wireless communication technology has developed rapidly, successfully passed tests in office buildings, museums and supermarkets, and is expected to enter thousands of households in the near future. 　　At home, French quantum physics professor and researcher Souart Taupsou can download movies, attend teleconferences at work or surf the Internet simply by turning on the lights without connecting to a Wi-Fi network! To be precise, what he turned on was a new type of light—light-emitting diodes. This kind of technology that can connect to the Internet as long as people are under the light is called visible light wireless communication technology, which came…

　　Have you ever noticed that after a thunderstorm, plants grow faster and look fresher, brighter, and more verdant! What is the reason? 　　Some people think that the plants have received more abundant rain, some people think that the temperature after the rain has become more suitable for growth, and some people say that this is due to the increase in air humidity. 　　While all of these factors contribute to rapid plant growth, there is a lesser-known reason for this, and that is the action of lightning. Lightning ‘fertilizes’ plants 　　We know that plants “produce their own food” through photosynthesis. But in fact, this production process will be directly or indirectly…