Almost every machine with moving parts has wheels, yet no one knows exactly when the first wheel was invented or what it was used for. We do know, however, that they existed over 5,500 years ago in ancient Asia.

    The oldest known transport wheel was discovered in 2002 in Slovenia. It is over 5,100 years old. Evidence suggests that wheels for transport didn't become popular for a while, though. This could be because animals did a perfectly good job of carrying farming tools and humans around.

    But it could also be because of a difficult situation. While wheels need to roll on smooth surfaces, roads with smooth surfaces weren't going to be constructed until there was plenty of demand for them. Eventually, road surfaces did become smoother, but this difficult situation appeared again a few centuries later. There had been no important changes in wheel and vehicle design before the arrival of modem road design.

    In the mid-1700s, a Frenchman came up with a new design of road—a base layer (层) of large stones covered with a thin layer of smaller stones. A Scotsman improved on this design in the 1820s and a strong, lasting road surface became a reality. At around the same lime, metal hubs (the central part of a wheel) came into being, followed by the pneumatic tyre(充气轮胎) in 1846. Alloy wheels were invented in 1967, sixty years after the appearance of tarmacked roads (柏油路). As wheel design took off, vehicles got faster and faster.

    Elizabeth Freeman was born about 1742 to African American parents who were slaves. At the age of six months she was acquired, along with her sister, by John Ashley, a wealthy Massachusetts slaveholders. She became known as “Mumbet” or “Mum Bett.”

    For nearly 30 years Mumbet served the Ashley family. One day, Ashley's wife tried to strike Mumbet's sister with a spade. Mumbet protected her sister and took the blow instead. Furious, she left the house and refused to come back. When the Ashleys tried to make her return, Mumbet consulted a lawyer, Theodore Sedgewick. With his help, Mumbet sued(起诉) for her freedom.

While serving the Ashleys, Mumbet had listened to many discussions of the new Massachusetts constitution. If the constitution said that all people were free and equal, then she thought it should apply to her. Eventually, Mumbet won her freedom—- the first slave in Massachusetts to do so under the new constitution.

    Strangely enough, after the trial, the Ashleys asked Mumbet to come back and work for them as a paid employee. She declined and instead went to work for Segdewick. Mumbet died in 1829, but her legacy lived on in her many descendants(后裔). One of her great-grandchildren was W.E.B. Du Bois, one of the founder of the NAACP, and an important writer and spokesperson for African American civil rights.

    Mumbet's tombstone still stands in the Massachusetts cemetery where she was buried. It reads, in part: “She was born a slave and remained a slave and remained a slave for nearly thirty years. She could neither read nor write, yet in her own sphere she had no superior or equal.”

    One day an out-of-work mime(哑剧演员)is visiting a zoo and attempts to earn some money as a performer. As soon as he starts to draw the crowd, a zoo keeper grabs him and drags him into his office. The zoo keeper explains to the mime that the zoo's most popular attraction, a gorilla, died suddenly and the keeper fears that the attendance at the zoo will fall off. He offers the mime a job to dress up as the gorilla until they can get another one. The mime accepts.

    So the next morning the mime puts on the gorilla suit and enters the cage before the crowd comes. He discovers that it's a great job. He can sleep when he wants to, play and make fun of people and he draws bigger crowds than he ever did as a mime. However, eventually the crowds get tired of him and he doesn't like just swinging on wires any longer. He begins to notice that the people are paying more attention to the lion in the cage next to his.

    Not wanting to lose the attention of his audience, he climbs to the top of his cage, crawls across a partition(隔开物), and dangles(悬荡) from the top of the lion's cage. Of course, this makes the lion furious, but the crowd loves it. At the end of the day the zoo keeper comes and gives the mime a raise for being such a good attraction. Well, this goes on for some time, the mime keeps laughing at the lion, the crowds grow larger, and his salary keeps going up.

    Then one terrible day when he is dangling over the furious lion he slips and falls. The mime is terrified. The lion gathers its strength and prepares to pounce(猛扑). The mime is so scared that he begins to run round and round in the cage with the lion close behind. Finally, the mime starts screaming and yelling, "Help me! Help me!", but the lion is quick and pounces. The mime soon finds himself lying on his back looking up at the angry lion and the lion says, "Shut up, you idiot! Do you want to get us both fired?"

    With the development of our society, cell phones have become a common part in our lives. Have you ever run into a careless cell phone user on the street? Maybe they were busy talking, texting or checking updates on WeChat without looking at what was going on around them. As the number of this new "species" of human has kept rising, they have been given a new name—phubbers (低头族).

    Recently a cartoon created by students from China Central Academy of Fine Arts put this group of people under the spotlight. In the short film, phubbers with various social identities bury themselves in their phones. A doctor plays with his cell phone while letting his patient die, a pretty woman takes a selfie (自拍) in front of a car accident site, and a father loses his child without knowing about it while using his mobile phone. A chain of similar events finally leads to the destruction(毁灭) of the world.

    Although the ending of the film sounds unrealistic, the damage phubbing can bring is real. Your health is the first to bear the effect and result of it. "Always bending your head to check your cell phone could damage your neck," Guangming Daily quoted doctors' words. "The neck is like a rope that breaks after long-term stretching." Also, staring at cell phones for a long time will damage your eyesight gradually, according to the report.

    But that's not all. Being a phubber could also damage your social skills and drive you away from your friends and family. When getting together with family or friends, many people prefer to play their cell phones while others are chatting happily with each other and this creates a strange atmosphere, Qilu Evening News reported.

    It can also cost your life. There have been lots of reports on phubbers who fell to their death, suffered accidents, and were robbed of their cell phones in broad daylight.

    We are lucky to live in a world that is full of incredible technology. Our living rooms are packed with computers, LCD TVs, video game systems, and Blue-ray players that help us enjoy the latest entertainment. Although these items bring us joy and convenience, they also create a lot of junk. Each device needs its own plug and adaptor to keep its batteries recharged, and over time these wires get tangled (缠绕在一起的). Thankfully, something has come along to help rid our homes of this mess while still supplying these devices with the power they need. It's called wireless charging and this trend is just starting.

    Wireless charging has a lot of potential for smartphones and other electronic devices. Electronic devices can absorb the electricity once they're placed on a special charging mat. There are several advantages that wireless charging offers over traditional methods. For starters, cords (电线) have a tendency to wear out with use. Wireless charging users never have to worry about buying replacement cords. Wireless charging is also far more convenient for medical implants, as patients won't need to recharge their devices through the skin using cords. In turn, this cuts down on the risks of infection. Wireless charging can also bring safety benefits, as wired charging devices that come in contact with water can increase the chances of getting an electric shock. Wireless charging gets rid of that danger completely.

    Still, there are a few drawbacks to wireless charging. The first is speed. It takes a bit longer to charge devices wirelessly than it does if the device is plugged in. The process also requires more heat, so devices tend to get a bit hotter, which could create other safety issues. Also, since devices must be left on a special pad while charging, it is harder to operate them while they are powering up. This limitation may be gotten rid of in the future, as researchers are developing transmitters (发射器) that can charge several different devices in a room without the need to connect to a charging pad. Although wireless-charging technology may be far from perfect, it seems like a step in the right direction as we move towards a less-tangled future.

    Madame Marie Curie famously won two Nobel Prizes, but many other women have also been awarded the prize, too. Here are their stories.

    Selma Lagerlof

    Selma Lagerlof was a Swedish author and teacher. She published her first novel, Gosta Berling's Saga, at the age of 33. She was the first female writer to win the Nobel Prize in Literature which she was awarded in 1909. Additionally, she was the first female to be granted membership in the Swedish Academy.

    Gerty Theresa Cori

    Gerty and her husband, Carl Cori, met in Prague and lived in Austria before immigrating to the United States in 1922, where the two medical doctors worked together at Roswell Park Comprehensive Cancer Center in New York. In 1947, Gerty and Carl were awarded the Nobel Prize in Physiology or Medicine, making Gerty Cori the first woman to hold the honor.

    Maria Goeppert-Mayer

    In 1942, Maria Goeppert-Mayer joined the Manhattan Project. From there, she moved on to Los Alamos National Laboratory, then to Argonne National Laboratory, where Goeppert-Mayer developed the nuclear shell model. For this, she shared the 1963 Nobel Prize in Physics with J. Hans D. Jensen and Eugene Paul Wigner.

    Dorothy Crowfoot Hodgkin

    Dorothy Hodgkin's mother encouraged her love of science as a child, and at age 18, she began studying chemistry at a women-only Oxford college. Her work on mapping vitamin B12 earned her the Nobel Prize in Chemistry in 1964.