Researchers have discovered the first Earth-sized planet. It was first marked by NASA's Kepler telescope(望远镜) so it's called Kepler-186f. It lies about 500 light years from Earth and goes around its star. The planet is the right distance from its star for water: not too close or not too far. Water is one important condition that scientists guess is necessary for life. So it could have water and possible life. It's called a true Earth cousin.

"This planet is an Earth cousin, not an Earth twin," said Barclay, who is among a team of scientists reporting on the discovery in the magazine Science this week.

"It's very exciting to find a planet similar to the Earth," Barclay said, "It's not easy work because things change as we get more measurements."

Scientists don't know anything about the air of Kepler-186f, but it will be a task for future telescopes which can study for chemicals that have something to do with life.

    "It's possible for life to live in this planet, but that doesn't mean there is life in it," Barclay said.

So far, scientists have found nearly 1,800 planets in the universe.

"The past year has seen a lot of progress in the search for Earth-like planets. Kepler-186f is very important because it is the first planet that is the same temperature and is almost the same size as Earth," scientist David Charbonneau wrote in an email.

    You know how much your telephone has changed over the past 10 years? Your car will change even more than that in the next 10 years. One of the biggest changes is that cars will drive themselves.

    "We certainly have the technology for it now." says Andrew Poliak of automotive(机动车辆的)technology supplier QNX." We expect self-driving cars to be a mainstream thing between 2020 and 2025."

    The American company Google has been working on self-driving cars for years. These cars are already on the roads in the United States and are truly self-driving. They have to steering wheels(方向盘）or pedals(踏板). Last week, the police ordered one of Google's cars to stop for driving too slowly on a public road. The car was not breaking any law, so no one was punished.

    Another American company, Tesla, added an "Autopilot" feature to its cars last month. With the Autopilot turned on, the vehicle drives itself. The car will speed up, slow down, brake and drive by itself. You can take over driving any time by turning the steering wheel or touching a pedal. The car uses sensors to know when driveway changing is safe and whether it should speed up or slow down.

    Tesla Autopilot is made for cross-country driving. It keeps you in the driveway and helps you avoid hitting other cars. It does not work well on local roads, for it will not stop at a red light or stop sign.

    Reporter Carolyn Nicander Mohr tried the Autopilot feature of a Tesla earlier this month. She had a hard time trusting the car to do what it should do. She thought about disabling the Autopilot feature many times during her trip. She wanted to take control at every bend in the road and hit the brake when the car in front of her slowed down. Yet the car drove perfectly.

    Other companies are working on self-driving cars, too. Marcedes-Benz, Audi, BMW. Volvo and Toyota all have plans for such vehicles.

    Scientists found that moderate (适度的) noise can make people more creative, The New York Times reported.

    Scientists did tests on students. They divided them into four groups. They then asked the students to do certain tasks involving creative thinking. But each group did the task with different volumes (音量) of background noise. They found that students did best when working under moderate noise—70 decibels (分贝). This is about the same volume of background noise in a cafe. Students did worse in low noise (50 dB). This is the volume of a quiet room. They did the poorest when in a high-noise (85 dB) environment. This is the noise level in a factory.

    Moderate noise can distract (分心) people just enough so that they think more creatively. "It helps you think outside the box," Raci Mehta, a lead researcher in the study, said to the Business Standard. On the one hand, working in a very quiet place can strengthen our focus. But it also stops

    us from thinking abstractly (抽象).

    "This is why if you are too focused on a problem and you can't solve it," said Mehta, "you leave it for some time and then come back to it and you'll get the solution."

    However, the scientists said that when you need to do detailed things, like proofreading (校对) a paper, a quiet place is better than a noisy one.

    Many scientists think that the Earth is getting warmer and warmer. If the change continues, the natural world and human society will face danger. Scientists believe human activity is responsible for the climate change. We produce too many greenhouse gases. They keep heat in the air and make the Earth warm.

    Many of the world's governments agree. And they want to solve the problem. So from 7 to 18 December, 2009，they held a conference in Copenhagen, Denmark to talk about global warming and climate change.

    Representatives(代表) from 192 countries and regions went to the meeting. Although they have not reached an agreement, the Copenhagen Accord(《哥本哈根协议》) was an important beginning to save the Earth. It was made by a small group of countries including China，the USA，India, Brazil and South Africa. Some other countries at the conference also showed support.

    What are the key points of the Copenhagen Accord? The accord limits global temperature increases to 2C by 2050. Scientists think it could help the world to avoid serious climate change.

    The accord also says that developed countries must promise to cut greenhouse gas emissions(排放) to the UN by 31 January, 2010. The accord asks developed countries to give money to help developing countries.

    Many countries and organizations are disappointed that the conference didn't reach a legal document(法律文书). And they think the accord is not clear enough about its goals.

African leaders are worried that the goal of a 2℃ global temperature increase isn't good enough, because it will mean a much higher increase in temperature across Africa. This could cause big problems like food and water shortages across the continent.

    Still, UN Secretary General believes the conference was an "improvement".

    "Finally we reached a deal," Ban said," the accord may not be everything everyone had hoped for, but this is an important beginning."

    Different weather makes people feel different. It influences health, intelligence(智力) and feelings.

    In August, is very hot and wet in the southern part of the United States, People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot at some times and very cold at other times. People in these states have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence. For example, in a scientific report, IQ (智商) of a group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10% below. The wind can help people have more intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools of the United States often get worse on exams in the hot months of the year (July and August).

    Weather also has a strong influence on people's feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather. But fat people may have a hard time in hot summer. At about 18℃, people become stronger.

    Low air pressure may make people forgetful. People leave more bags on buses and in shops on low-pressure days. There is a "good weather" for health. People feel best at a temperature of about 18℃.

    Are you feeling sad, tired, forgetful, or unhappy may be the weather's problem today?

    Which is the tallest mountain on the earth? The answer must come fast—MT Everest, at a height of 29,000 feet.

    But that is only on land. For, if you were to measure (测量) from the bottom (底部) of the ocean. The tallest mountain in the world will probably be Mauna Kea in Hawaii. It is more than 15,748 feet under the sea and another 13.779 feet above it.

    As US scientist Cindy Lee Dover points out that the seafloor is the largest and least known place on the earth. We know more about Mars (火星) and Venus (金星) and the back side of the moon than we know about the seafloor.

    Some people have travelled to the deep water of the ocean to try to find all kinds of unknown animals and plants living in the deep water. Even scientists know very little about them. Many of them perhaps do not even have names. Some of the names given by scientists to newly discovered (被发现) animals are really funny. Among them are the spaghetti worms (意大利面蠕虫), named as such it is found in a tangle (缠结), it is often difficult to make out where one ends and another begins! Just like spaghetti.