It is generally believed that humans can't live without sleep. As any person suffering from lack of sleep knows, dark circles under the eyes usually stand out after a bad night's sleep.

    But why do people get these dark eye bags? The answer is both genetic (that is, relating to your DNA) and environmental (a result of your everyday living, such as rubbing your eyes or getting too little sleep), said Dr. Carol Clinton, a skin-care researcher in Dublin, Ohio.

    But “the biggest reason is genes,” Clinton told Live Science. Eye bags are generally more noticeable in people who, because of genes, have thin or pale skin. When people are tired or very nervous, blood circulation in the eye area becomes slow, allowing blood to pool there, Clinton said. Capillaries（毛细血管）stand out, leading to dark eye circles, she said.

    Besides, eye bags result from eyes' fat moving forward. An age-connected increase in fat beneath the eyeballs leads to eye bags. “Anyway, when your eyes' fat is moving forward, you may think about having an operation in that area,” Clinton said, “A person can get 9 hours of sleep a night, but still have eye bags because of a genetic development.”

    In other cases, environmental problems cause eye bags. For example, allergies（过敏）—especially seasonal allergies—can cause capillaries to stand out. Getting too much sun can also damage and thin the skin, making dark circles under the eyes easy to see. Besides, eating salty foods can cause the body to hold more water, which makes eye bags worse, according to the Mayo Clinic.

    The world has lost one of its brightest stars. British physicist Stephen dies on March 14, at the age of 76.

    Hawking is probably the world's most famous scientists after Albert Einstein. He is an expert on black holes. He has devoted his whole life to digging into the beginning (and the end) of the universe. “My goal is simple,” Hawking once said. “It is to completely understand the universe, why it is as it is and why it is there at all.”

    Hawking's achievements are even greater if you think about his disability. When he was 21, Hawking caught a bad illness that slowly stopped him form moving or talking. For a period of time, he had no way to communicate except by blinking（眨眼）. Later he sat on a wheelchair with a computer by his side. To communicate, he moved two fingers to control the computer's mouse. He selected his words from the screen, which were then spoken by a voice synthesizer（音响合成器）.

    “I have had the disease for most of my life,” Hawking once said. “Yet it has not stopped me from being successful at my work.”

    Though Hawking was a disabled man, he made great achievements. He received many awards and prizes for his work during his lifetime. This included winning the Albert Einstein Award, which stands for the highest achievement in theoretical physics.

    Despite the fact that he's no longer with us, his legacy will surely live on. As Sajid Javid, a UK government minister, put it, “A brief history on Earth; an eternity in the stars.”

    In the fight to conserve tropical rainforests, here's a tool you don't often hear about orange peels. Specifically, 12,000 tons of them, dumped (倾倒) on the land. “You don't usually associate waste treatment with biodiversity benefits, something that's good for the environment.

    Tim Treuer is an ecologist at Princeton University, and he's talking about a unique conservation story. It started in the early 1990s, when an orange juice producer called Del Oro set up a company near the Guanacaste Conservation Area in Costa Rica, a region that contains several national parks and a wildlife protection zone.

    Del Oro needed somewhere to dump the orange peels, and the company also owned forested land next to the parkland that it had no intention of growing crops on. So a deal was struck: if Del Oro donated its forested land, it could dump orange peel waste on degraded(退化的) land within the conservation area. Then a thousand dump trucks' worth of orange peels were lying on the land in 1998. “And within about six months the orange peels had been turned from orange peels into this thick black rich soil.”

    “I couldn't even find the site the first time I saw it.” He couldn't find it because, over 16 years, the orange peel waste had sent the land on a journey to become a vine-choked jungle, with three times the diversity of tree species of the neighboring control plot, richer soil and a much thicker covering. In other words, the experiment was a success. The results appear in the journal Restoration Ecology.

    Treuer says perhaps this lesson could be applied elsewhere. “It's a shame that we live in a world with nutrient-limited degraded ecosystems and also nutrient-rich waste streams. We'd like to see those things come together a little bit. That's not license for any agricultural company to just start dumping their waste products on protected areas, but it does mean that land managers, people involved with industrial-scale agricultural operations should start thinking about ways to do thoughtful experimentation to see if in their particular system they can have similar win-win-win results.”

    We can video chat with astronauts aboard the International Space Station and watch live footage from the frozen heights of Everest. But communicating with a submarine (潜艇）or a diver is not so easy. The lack of practical methods for sharing data between underwater and airborne devices has long been a frustration for scientists. The difficulty stems from the fact that radio signals work perfectly in air travel but poorly in water. Sonar (声呐）signals used by underwater sensors reflect off the surface of the water rather than reaching the air.

    Now, researchers at MIT have developed a method with the potential to revolutionize underwater communication. "What we've shown is that it's actually feasible to communicate from underwater to the air," says Fadel Adib, a professor at MJT's Media Lab, who led the research.

    The MIT researchers designed a system that uses an underwater machine to send sonar signals to the surface, making vibrations (震动)corresponding to the ls and Os of the data. A surface receiver then reads and decodes these tiny vibrations. The researchers call the system TARF. It has any number of potential real-world uses, Adib says. It could be used to find downed planes underwater by reading signals from sonar devices in a plane's black box and it could allow submarines to communicate with the surface.

    Right now the technology is low-resolution. The initial study was conducted in the MIT swimming pool at maximum depths of around 11 or 12 feet. The next steps for the researchers are to see if TARF is workable at much greater depths and under varying conditions—high waves, storms, schools of fish. They also want to see if they can make the technology work in the other direction— air to water.

    If the technology proves successful in real-world conditions, expect "texting while diving" to be the latest underwater fashion.

    In the US and Britain, the slogan around colleges was "Save water. Shower with a friend." Now, Wuhan University has come up with another system for the campus bathhouse. It charges students for the amount of time in a shower. Before entering the bathhouse, students pay for the amount of time they want in the shower with cash or their student ID card. The clock starts ticking the minute the tape is turned on. It pauses when a button is pressed for soap. An integrated circuit (IC) card reader at each tap shows the time. No money, no water. The benefits of the new system can be seen with the old system, which charged 1 yuan for each person regardless of time in the shower. The university used about 320 tones of water daily under the old system, but only 160 tons now.

    Many students use the new system but opinions on it are divided. Some students say it is bad because bathing had become a sort of race. Many people using it for the first time are not sure how long they need to shower. Some might be embarrassed if their time is up and they're still covered in soap. They have to ask the bathhouse worker to help them buy extra time.

    "It's a flaw in the system that you can not buy extra time on the ID card," said Ren, a freshman in Wuhan University. The university is also considering some students' suggestions that they be allowed to pay after they've finished the shower. Not surprisingly, some are complaining about losing the hour shower. But many students say the move helps them develop a water-saving sense.

    Without the time limits, most students tended to shower for 30 to an hour in the bathhouse.

    Some even used the hot water to wash their clothes. "In my experience, 10-20 minutes is enough," said Dai Zhihua, a third-year student who usually takes 8 minutes.

    A similar system has been installed in other universities. Shanghai Normal University introduced it at its Fengxiang Campus in September. The bathing fee there is 0.2 yuan per minute. One male student responded by setting a record with a two-minute shower.

Growing up on a tobacco farm, Emma Avery was used to hard times. When she was seven, her family's farmhouse burned to the ground. Her father made a temporary shelter, where eight people had to sleep in two beds. As soon as Emma and her four brothers and two sisters were big enough, they were out in the fields.

Emma would find her comfort in school, even as a C student, thanks to one teacher. When she moved on to middle school, Emma was alarmingly far behind her classmates. She kept her head down, trying not to be noticed, struggling to catch up, and feeling like an outsider.

Then one day, when Emma was 16, a teacher named Mr. Potts changed everything. Looking his students in the eye, Mr. Potts said, "Being a C student does not mean you do not have a valuable contribution to make. Some of you have to work in the fields in the evening and do not have time to study. But if you do your best, you have a gift to give."

The teacher's words made Emma believe she could do well, and she worked harder. In the end she won a scholarship to St. Paul's College, graduated with a degree in elementary education in 1967, and got a job in the public-school system. Then, at George Washington University, she received a master's in education in 1970, and afterwards in the same year she married Ron Smothers.

Over the next six years, Emma taught in public schools in Miami. In 1976, after saving $10,000, she opened her first restaurant in Los Angeles. Eventually Emma stopped teaching, and her business expanded to six restaurants.

In gratitude for what she has been able to achieve, Emma donates a lot. She has no idea how much money she's given away. She says, "Those I want to help are the C students who just need help, direction and confidence."