After years of debate, gray wolves were reintroduced (重新引进) to Yellowstone National Park. Fourteen wolves were caught in Canada and moved to the park. By 2016, the Yellowstone wolf population had grown to more than 170.

    Gray wolves once were seen here and there in the Yellowstone area and other pans of United States, but they were gradually displaced by human development. By the 1920s, wolves had disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around. The disappearance of the wolves had many unexpected results. Deer and elk populations—major food sources(来源) for the wolf—grew rapidly. These animals ate large amounts of plants, which reduced plant diversity(多样性) in the park. With the disappearance of gray wolves, coyote (草原狼) populations also grew quickly. The coyotes killed a great number of red foxes in the park, and completely drove away the park's beavers (河狸).

    As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many framers were against the plan because they feared that wolves would kill their farm animals or pets.

    The government spent nearly 30 years thinking lip a plan to reintroduce the wolves. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

    If you thought pilots dimmed（调暗）the lights before takeoff to give you some shuteye, think again. Believe it or not, the dim lighting could actually help save your life in case of a plane emergency.

    The dimmed lights before taking off the runway and landing are a flight precaution used to help passengers' eyes adjust quicker during an emergency escape. “Going from a brightly lit environment to one that's completely dark would require some time for our eyes to focus and see the escape slide,” Alice Theriault, service director for Air Canada wrote in a press statement. “Since we need to have all the seconds on our side in the event of an emergency, dimming the lights is one of many steps we take to ensure the safety of our customers.”

    The phenomenon that your eyes see those strange speckles (小斑点) as your sight adjusts to a dark place after being in a light place is called dark adaptation. It normally takes our eyes about 20 to 30 seconds to see best in a dark room. The brighter the lights, the longer it takes for our eyes to adjust, which is why dimming the plane lights could shorten your “dark adaptation” time since you haven't been sitting under fluorescent bulbs (荧光灯) all flight.

    Not only does dimming lights add valuable time to the escape process, but it reduces the tension on your eyes if you need to look outside, or see the emergency lighting along the passage. “It helps keep you in the right direction.” Patrick Smith, an airline pilot and author of Cockpit Confidential told The Telegraph. “It also makes it easier for flight attendants to assess any outside risks, such as fire or debris, that might affect an escape.” So next time a pilot dims the lights, just know it's for your safety, even though it creates a gentle atmosphere for your takeoff into the sky.

    No one knows how much money Dr. Lyle Tullis gave away to students. I was his colleague for nearly a decade and I never stopped being amazed at his generosity. Our college has a program of providing cross-cultural experiences for students. Lots of students take advantage of summer experiences oversea. I discovered that no group left for overseas without some of its members receiving financial help from Dr. Tullis.

    It wasn't that he made a lot of money. For one thing, he taught in a church-run school. There, his salary (薪水) was half of what those people earned in a tax-supported school.

    Other colleagues occasionally complained about the low pay. Not Lyle Tullis. Occasionally some professors would leave our campus for a better-paid position. They told me they did so because, with better pay, they could provide for their families.

    The size of Lyle Tullis' paycheck never seemed to be the most important thing to him. I realized that one day when I was thanking him for helping a student, his eyes shone as he said to me, "I've got so much money that I don't know what to do with it. So, I just give it away."

    Most people wouldn't have thought that way. Dr. Tullis drove one of the oldest cars on campus. It was even older than almost any of the students' cars. His home, while comfortable, was not fancy at all. But Lyle Tullis lived with the feeling that he had so much money that he needed to give it away.

    He was one of the favorite on campus. Cynics (愤世嫉俗) might say he bought fame. But they would misunderstand. Lyle wanted to devote his life, all of it, to helping others.

The Coolest Inventions

    An Oceans Vacuum(吸尘器)

    There's a collection of plastic trash in the middle of the Pacific Ocean. It's bigger than Texas and growing. The way to clean it up now is to catch it with nets. That is both costly and slow. Instead, the Ocean Cleanup Project proposes a 62-mile-long floating barrier that would use natural currents to trap trash. If next year's trials succeed, a full cleanup operation would aim to start in 2020. It could reduce the trash by 42 % over 10 years.

    Easy-On Shoes

    In 2012, Matthew Walzer, a high school student with a disability, sent a note to Nike. "My dream is to go to college," he wrote, "without having to worry about someone coming to tie my shoes every day." Nike assigned a design team to the challenge. This year, they came out with their solution: the FlyEase. The basketball shoe can be fastened with one hand. A pair of Nike FlyEase shoes sells for $ 130.

    An Airport for Drones (无人机)

    As Amazon, Google, and others get ready for drone delivery service, there is one big question: What kinds of home bases will their drones have? Rwanda, in Africa, may have the answer. There, workers will soon start work on three "drone ports". The goal is to make it easier to transport food, medical supplies, electronics, and other goods through the hilly countryside. Construction is set to be completed in 2020.

China's Tianwen 1 Mars probe (探测器) conducted its fourth orbital correction on Friday evening, as the spacecraft makes ready for its arrival in orbit around Feb. 10, according to the China National Space Administration.

The name comes from the long poem Tianwen, meaning Heavenly Questions or Questions to Heaven, written by Qu Yuan, one of the greatest poets of ancient China. In Tianwen, this name conveys the Chinese nation's steady effort in pursuing truth and culture of exploring nature and the universe. CNSA also unveiled (发布) the logo of China's planetary exploration missions, featuring the letter C, signifying China, international cooperation and capacity of entering space.

Tianwen I has flown for 197 days and more than 465 million kilometers on its journey to the planet. It is now around 184 million km from Earth and I. I million km from Mars. Depending on the two planets' orbits, Mars is between 55 and 400 million km from Earth. Mars probe Tianwen I is seen in its first selfies in space on Oct. 1, 2020. The administration also published a black-and-white picture of Mars taken by Tianwen I, the first snapshot (抓拍的照片) from the Chinese craft.

Tianwen I, the country's first independent Mars mission, was launched by a Long March 5 heavy-lift carrier rocket on July 23 from the Wenchang Space Launch Center in Hainan province, kicking off the nation's planetary exploration program.

A successful landing would make China only the second nation to place a spacecraft on the Martian planet. China would also be the first to successfully orbit, land and deploy (部署) a vehicle in the same mission. According to experts, searching for signs of life on Mars will be the first and foremost scientific goal. China is open and inclusive in the development of its space technology not least because it believes that the exploration of outer space should help build a community with a shared future for mankind.

The famous Peking opera artist Yuan Huiqin hosted two culture talks {#blank#}1{#/blank#}were called "Charm (魅力) of Peking Opera" in Stockholm and St. Petersburg last year.

The two sessions, as programs of Chinese Culture Talk,{#blank#}2{#/blank#}(organize) by the Bureau for External Cultural Relations of the Ministry of Culture of China, Chinese embassies and local cultural organizations.{#blank#}3{#/blank#}(member) of Chinese embassies, famous sinologists (汉学家) and those {#blank#}4{#/blank#}(show) an interest in Peking opera, attended the two culture talks.

The host, Yuan Huiqin, is a national class A artist of China National Peking Opera Company and a winner of the Plum Blossom Prize. During the talks, she {#blank#}5{#/blank#}(patient) shared the charm of Peking opera in more than one way.

With the help of the local sinologists,{#blank#}6{#/blank#}(she) talks were translated into Swedish and Russian. These words explored the concepts and artistic characteristics of {#blank#}7{#/blank#}(tradition) Chinese operas, which got audience {#blank#}8{#/blank#}(experience) the distinct charm of Peking opera.

{#blank#}9{#/blank#}addition, young artists from the China National Peking Opera Company performed classic opera selections. During the interaction of the talks, some opera lovers performed with young artists and on{#blank#}10{#/blank#}spot the audience tried costumes (戏装) of Peking opera with great curiosity.