Life may have evolved on at least three planets within a newly discovered solar system 39 light years from Earth. Astronomers at the NASA have discovered no less than seven roughly Earth-sized worlds orbiting a dwarf star in the system. Scientists had previously identified a tiny number of "exoplanets", which are believed to have the qualities needed to support life. However, the new system contains an unprecedented(前所未有) number of Earth-sized, probably rocky planets, and is being acknowledged as an "accelerated leap forward" in the search for extraterrestrial (外星球的)life.

    Three of the new planets are said to be particularly promising because there might exist oceans. Thomas Zurbuchen, associate administrator of NASA, told a press conference in Washington: "This gives us a hint that finding a second Earth is not a matter of 'if', but 'when'."

    The planets were discovered using NASA's Spitzer Space Telescope, which was able to track how fast each of the planets crossed the star Trappist-l and completed an orbit. From this the research team calculated how far the planets were from their star, and therefore how likely they are to be habitable.

    NASA's Hubble Space Telescope is already being used to search for atmospheres around the planets. Future telescopes, including the proposed European Extremely Large Telescope and the James Webb Space Telescope, may be powerful enough to discover markers of life, such as oxygen in the atmospheres of exoplanets.

    Astronomers believe there could be as many as 40 billion potentially habitable worlds in our galaxy, the Milky Way. Prof Zurbuchen said that now was a "gold-rush phase" in the search for these exoplanets.

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    For anyone still doubting the belief that our emotions influence our physical health, a new study from New Zealand should be able to settle the matter. It reports that the physical wounds of healthy seniors healed more quickly if they wrote about their most upsetting experiences.

    This confirms the results of a 2010 study, and extends those findings to cover older adults—a group that is likely to suffer wounds (as from surgery), and one with less access to other ways of lowering tension (such as exercise).

    Reported in the journal Psychosomatic Medicine, a research team led by the University of Auckland's Elizabeth Broadbent made a study featuring 50 healthy adults ranging in age from 64 to 97. They were asked to write for 20 minutes per day for three consecutive (连续的) days.

    Half were asked to write about the most upsetting experience in their life, describing their deepest thoughts, feelings, and emotions about the events, ideally not previously shared with others. The others were asked to write about their daily activities without mentioning emotions, opinions or beliefs.

    Two weeks after the third day of writing, all participants received a standard 4mm skin biopsy (皮下活体组织检查) on their inner arm. The very tiny wounds caused by the biopsy were photographed regularly over the following days to determine the rate at which they healed.

    On the 11th day after the biopsy, the wounds completely healed on 76.2 percent of those who had done the expressive writing. That was true of only 42.1 percent of those who had written about everyday activities.

    “The biological and psychological mechanisms (机体) behind this effect remain unclear,” the researchers wrote, noting that those who had done the expressive writing did not report lower stress levels or fewer depressive symptoms than the others in the control group. Even if they weren't consciously aware of feeling more relaxed or positive, the expressive writing appeared to have caused some sort of bodily reaction—probably involving their immune systems—that hastened their recovery.

The Domestication （驯化）of Cats

    For centuries, the common view of how domestication had occurred was that prehistoric people, realizing how useful it would be to have animals kept for food, began catching wild animals and breeding （繁殖）them. Over time, by allowing only animals with "tame"（驯养）characteristics to produce their babies, human beings created animals that were less wild and more dependent upon people. Eventually this process led to the domestic farm animals and pets that we know today, having lost their ancient survival skills and natural abilities.

    Recent research suggests that this view of domestication is incomplete. Prehistoric human beings did catch and breed useful wild animals, but specialists in animal behavior now think that domestication was not simply something people did to animals—the animals played an active part in the process. Wolves and wild horses, for example, may have taken the first steps in their own domestication by hanging around human settlements, feeding on people's crops and getting used to human activity. The animals which were not too nervous or fearful to live near people produced their babies that also tolerated humans, making it easier for people to catch and breed them.

    In this version, people succeededin domesticating only animals that had already adapted easily to life around humans. Domestication required an animal that was willing to become domestic. The process was more like a dance with partners than a victory of humans over animals.

    At first glance, the laming of cats seems to fit nicely into this new story of domestication. A traditional theory says that after prehistoric people in Egypt invented agriculture and started farming, rats and mice gathered to feast on their stored grain. Wildcats, in tum, gathered at the same places to hunt and eat the rats and mice. Over time, cats got used to people and people got used to cats. Some studies of wildcats, however, seem to call this theory into question. Wildcats don't share hunting and feeding areas, and they don't live close to people. Experts do not know whether wildcats were partners in their own domestication. They do know that long after people had acquired domestic dogs, sheep and horses, they somehow acquired domestic cats. Gradually they produced animals with increasingly tame qualities.

    Dodder is an unusual and unwanted plant that attacked other plants. Except for its flower, the plant looks like spaghetti, a kind of noodles in the shape of long thin pieces that look like string when they are cooked. It's almost leafless, thread-like stems hang down on top of other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals food from other plants. It feeds by sucking juices from the plant which is wrapped around, often making its host very weak or even killing it.

    Dodder can find other plants by their smell. When a young dodder plant starts growing, it follows the smell of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato smell-if a tomato happens to be growing nearby.

    However, a young dodder plant must find a host plant quickly. It no longer needs its root once it is attached to the host and wrapped around it. If it cannot catch a smell of potential host within a few days, it will dry up and vanish even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point the dodder plant will drop its root.

    Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer's harvest or even destroy crops completely. Before sowing their produce, especially farmers in warm parts of the world often check to make sure no unwanted dodder seeds have mixed with their crop seeds. This is a good way to stop dodder plants from making their way to a crop field secretly.

    Bad news sells. If it bleeds, it leads. No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning papers. But now that information is being spread and monitored in different ways, researchers are discovering new rules. By tracking people's e-mails and online posts, scientists have found that good news can spread faster and farther than disasters and sob stories.

    "The 'if it bleeds' rule works for mass media," says Jonah Berger, a scholar at the University of Pennsylvania. They want your eyeballs and don't care how you're feeling. But when you share a story with your friends, you care a lot more how they react. You don't want them to think of you as a Debbie Downer."

    Researchers analyzing word-of-mouth communication—e-mails, Web posts and reviews, face-to-face conversations—found that it tended to be more positive than negative, but that didn't necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things? To test for that possibility, Dr. Berger looked at how people spread a particular set of news stories: thousands of articles on The New York Times' website. He and a Penn colleague analyzed the "most e-mailed" list for six months. One of his first findings was that articles in the science section were much more likely to make the list than non-science articles. He found that science amazed tines' readers and made them want to share this positive feeling with others.

    Readers also tended to share articles that were exciting or funny, or that inspired negative feelings like anger or anxiety, but not articles that left them merely sad. They needed to be aroused one way or the other, and they preferred good news to bad. The more positive an article, the more likely it was to be shared, as Dr. Berger explains in his new book, "Contagious: Why Things Catch on."