A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces(熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.

    The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.

    After the explosion, gravity pulls in what's left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so solid that a teaspoon of matter from it weighs billion of pounds.

    The more the star shrinks(收缩), the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!

    That's what we know about black holes. What we don't know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.

    But if the black hole doesn't keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world. They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a "white hole" in a different universe. As the black hole swallows(吞噬) light, the white hole shines brightly--somewhere else. But where? A different place, perhaps, or a different time--many years in the past or future.

    Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed(挤压). So far the time being, black hole must remain a mystery.

    Black holes are a mystery--but that hasn't stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth's energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste--a sort of huge waste disposal(处理) in the sky!

A hybrid electric vehicle (混合动力车) or HEV is a vehicle driven by the combination of petrol engine and electric motor. Terrence has been driving a HEV for five years. He really doesn't understand why more people aren't accepting them. "I probably spend about $ 7 a day on petrol," the taxi driver told news. com. au. In his previous conventional vehicle Terrence said he was spending up to $ 30 a day on petrol, meaning he saves almost $ 6000 every year.

The Toyota spokesman said this was quite a high saving and official tests estimate (估计) an average driver would only save about 33 percent off their current bill. This means a driver paying $ 30 a day on petrol would see their bill drop to about $ 20 using the hybrid. "A taxi driver that drives in built-up areas and spends little time on highways will notice a higher fuel saving," he said. "Low speeds allow the electric motors to be used more and the petrol engine used less."

While some people are skeptical about how reliable hybrids are, Terrence said he had never run out of power. His Camry cost about $ 34,000 and so after five years, it's nearly paid for itself. "For cab drivers, it's a real advantage because of the cost-effectiveness," he said. Terrence has no complaints about the car. "I love it, the calm and quietness of it, the simplicity of it—you just jump in and go. The maintenance（保养）is really low. But the only difficulty is finding someone to service the car as there are not many experienced mechanics（机修工）."

Terrence said it's "extraordinary" that more drivers aren't buying more hybrid electric vehicles and that governments are not encouraging this more. "I think people have a view that you have to plug it in, which is not true. A lack of information about the cars may be stopping people from taking the plunge. It's not promoted at all for the public to understand—it's simplifying the actual owning of a car—you don't have to do so many things to own it and run it, it's just so much simpler. Why wouldn't the government promote such a thing?"

    There are about 5,000 different kinds of ladybugs(瓢虫)in the world. They are also known as lady beetles or ladybird beetles. They come in many different colors and patterns, but the best-known in North America is the seven-spotted ladybug, with its shiny, red-and-black body.

    In many cultures, ladybugs are thought to be good luck. Most people like them because they are pretty, lovely and do no harm to human beings. But farmers love them because they eat aphids and other plant-eating pests. One ladybug can eat up 5,000 insects in its lifetime!

    Most ladybugs have dome-shaped bodies with six short legs. Depending on the kind, they can have spots, stripes, or nothing at all. Seven-spotted ladybugs are red or orange with three spots on each side and one in the middle. They have a black head. Ladybugs are colorful for a reason. They tell the enemy: "Eat something else! I taste terrible." When threatened, they may play dead. Birds are ladybugs' main predators(天敌), but they are also eaten by frogs, spiders, and dragonflies.

    Ladybugs are happy in many different places, including grasslands, forests, cities, suburbs, and along rivers. Seven-spotted ladybugs are native to Europe but were brought to North America in the mid-1900s.

    Ladybugs are most active from spring until fall. When the weather turns cold, they look for a warm place to hibernate, such as in rotting logs, under rocks, or even inside houses. These hibernating places can have thousands of ladybugs.

    The name "ladybug" was given by European farmers who prayed to the Virgin Mary when pests began eating their crops. After ladybugs came and wiped out the invading insects, the farmers named them "beetle of Our Lady". This later was shortened to "lady beetle" and "ladybug".

    Find a quiet location. Keep a routine. Focus on one subject at a time. It all seems like sound advice for students who need to hit the books, {#blank#}1{#/blank#} . Here's a list of tips from Carey, a scientist, for getting the most out of your study time.

    {#blank#}2{#/blank#}.

    Doing practice quizzes can help you retrieve（检索）information on test day. “Tests have a very bad reputation as a measurement tool,” Carey says. But psychologists have found self-tests slow down the forgetting of material you've studied. “If you study something once, and then you test yourself on it,” Carey says, “you do better than if you study it twice over.”

    Move around

    {#blank#}3{#/blank#} . “If you move around and study the same material in several places,” he says, “you may be forming multiple associations for the same material. So it's better anchored in your brain, and you can pull it out easier.”

    Mix it up

    Think about a football who does strength training, speed training and drills. Carey says alternating between different facets facts of a subject in a single sitting can “leave a deeper impression on the brain”. For example, when studying French, do some verbs, some speaking and some reading. {#blank#}4{#/blank#} .

    Space it out

    Information learned in a hurry is lost just as fast. So if you really want to learn, space out shorter, hour-long study sessions. “There's no doubt that you can cram for（突击备考）an exam.” Carey says, “{#blank#}5{#/blank#} . And once it's gone, “it's gone. You're not getting it back.”

A. Test yourself

B. Study it and practice more

C. and it turns out that some of them are in great help

D. but recent studies indicate the conventional wisdom is wrong

E. The problem is that it's so easy to forget what you just crammed

F. Changing up where you study can help you keep more information

G. Spending your time in deep concentration on just verbs isn't effective

    Researchers at the University of York in England published their findings on facial recognition that, on average, people can remember as many as 5,000 faces.

    There have been many studies recently on facial recognition technology. But the authors of this study say theirs is the first time that scientists have been able to put a number to the abilities of humans to recognize faces. Rob Jenkins, leader of the research, said the researchers' study centered on "the number of faces people actually know." and were not able to discover whether there is a "limit on how many faces the brain can handle."

    Jenkins said the ability to tell individual people apart is "clearly important." In today's modern world of big cities, we meet and deal with thousands of people. The study suggests our facial recognition abilities help us to deal with the many different faces we see on the screens, as well as those we know. The results of the study give a baseline for comparing the "facial vocabulary" of humans with facial recognition software.

    Today, facial recognition technology is used in many ways, including by law enforcement agencies to prevent crime and violence. Governments use it to keep secret areas secure and, in extreme cases, control populations. Some governments use the software to watch people and find out where they go and what they do. Even Facebook uses facial recognition. For example, when you name a friend, Facebook technology may recognize the person's face from a different picture you had shared before.

    For the human study, people spent one hour writing down as many faces from their personal lives as possible. At first, they found it easy to come up with many faces. But by the end of the hour, they found it harder to think of new ones. Their change in speed let the researchers estimate when they would have run out of faces completely. 1,000 to 10,000 faces remembered. People who took part in the study were also shown thousands of photographs of famous people. Researchers asked them which ones they recognized. To make sure they knew these people, researchers required them to recognize two different photos of each famous person. The results showed that the participants knew between 1,000 and 10,000 faces.

    How do they explain such a wide range? Jenkins said one explanation may be that some people have a natural ability for remembering faces. "There are differences in how much attention people pay to faces and how well they process the information." Also it could be because of different social environments. Some people may have grown up in more populated places. So, they may have had more social contact throughout their lives.

    Researchers think age may be an interesting area for further research. “It would be interesting to see whether there is a peak age for the number of faces we know”, Jenkins said. He said it is possible that we gather more faces throughout our lifetime. But, he added, there also may be an age at which we start to find it harder to remember all of those faces.

A group of small, waggling (扭动) robots that communicate by flashing lights can make collective decisions. This is similar to the process bees use to reach an agreement on where to build their nest.

"We believe that in the near future there are going to be simple robots that will do jobs that we don't want to do, and it will be very important that they make decisions on their own," says Carmen Miguel at the University of Barcelona in Spain. She and her team tested how copying bees might help with that.

When bees go house-hunting, they communicate their preferred locations through a "waggle dance". The more a bee recommends one location, the longer and harder it waggles. Eventually other bees join them, and they reach an agreement when a majority are waggling together. Researchers previously translated this behavior into a mathematical model, and Miguel and her colleagues used it to program decision-making rules into small robots called kilobots.

Each kilobot with three thin legs had an infrared-light emitter (红外线发射器) and receiver, and a colored LED light. Within a group, kilobots could move around, turn clockwise or anticlockwise and use infrared signals to exchange information.

Ezequiel Ferrero at the University of Barcelona says that across all the experiments, kilobots reached an agreement within about half an hour, even when they didn't have many immediate neighbors to communicate with. He says that getting the right combination of how long they spend transmitting their message and how much they walk around allowed them to make a collective decision in the end.