【推荐1】Why do cats purr(发出咕噜声)?

We’ve all heard cats meow, but why do most of them purr?     1     Some believe that they are simply happy. Some suggest that they may be in need of something.

    2     Cats do purr when they show their appreciation for attention. They also make the noise when not in our company. The purring noise is a continuous sound that occurs while they both breathe in and out.

When it comes to how cats purr, most people believe that the cat’s brain signals the muscles to vibrate(震动), which produces the noise.     3     Some argue that the cat intends to purr, while others say it may be due to chemicals released by the brain as a reaction to pleasure or pain.

According to Leslie A. Lyons, an assistant professor at the School of Veterinary Medicine at the University of California, cats often purr while stressed, for example, when they head to the vets or are recovering from an injury.

    4     Some scientists believe it may actually promote muscle development, heal bones and injuries, ease breathing and reduce pain.     5    

In a word, the purring of a cat may have more uses than just telling you they’re enjoying attention.

【推荐2】A tragic case of Kitty Genovese, who was killed, happened in New York in 1964. However, subsequent investigations concluded that several people saw or heard what was happening, but did nothing to intervene. This has been termed the “bystander effect” — a well-known psychological phenomenon where individuals are less likely to offer help to someone when other people are present. The more people there are, the less likely they are to help.

None of us like to think we’d walk on by when someone needed our help. But sometimes we behave in ways we wouldn’t expect when faced with a situation we are unsure about. While we might like to think we would rush to someone’s assistance, we know from studies that often people hang back. Research from the British Heart Foundation has suggested that a third of people would not give first aid if they saw someone collapse on the street, with some even admitting they wouldn’t call an ambulance.

There are various factors contributing to this effect — people think that others will get involved. Afterwards people often say they did not feel qualified or important enough to be the one to intervene. It is also partly down to “pluralistic ignorance” — since everyone is not reacting to the emergency, they don’t need to either; it’s not serious because no one else is doing anything.

Other studies have shown that once people are aware of the bystander effect, they are less likely to be affected by it. Self-awareness is the best solution to it. When facing an emergency, think to yourself how you would behave if you were on your own. Ignore everyone else and go with your gut (直觉) — If you’d run for help, do it. If that’s how you would have behaved when you were on your own, then that’s probably the right course of action. The worst that can happen is that you’ll look a little foolish at having overreacted. You might also save someone’s life.

【推荐3】For most of human history, the stars shone brightly in a dark night sky. But today, cities and towns, increasingly lit by artificial light at night, dramatically reduce the visibility of stars.

Satellite data suggests that light pollution has been increasing in many parts of the world over the last decade. However, satellites miss the blue light of LEDs (发光的二极管), which are commonly used for outdoor lighting, resulting in an underestimate of light pollution.

An international citizen science project called Globe at Night (环球夜景) aims to measure how everyday people’s view of the sky is changing. The data shows that the night sky got, on average, 9.6% brighter every year. For many people, the night sky today is twice as bright as it was eight years ago. The brighter the sky, the fewer stars you can see. If this trend continues, a child born today in a place where 250 stars are visible now would only be able to see 100 stars on his/her 18th birthday.

The main factors leading to increasing brightness of the night sky are industrialization and the growing use of LEDs for outdoor lighting. The loss of dark skies threatens our ability as astronomers to do good science. But everyday people feel this loss too. Starry night skies have inspired artists, writers, musicians and philosophers for thousands of years. Light pollution also has a bad effect on the daily cycle of light and dark that plants and animals use to adjust their lifestyle. Two-thirds of the world’s key biodiversity (生物多样性) areas are affected by light pollution.

Individuals and their communities can make simple changes to reduce light pollution. The secret is using the right amount of light, in the right place and at the right time. Making outdoor lights shine downward, using lights that give out more yellow-colored light instead of white light and putting on light timers can all help reduce light pollution. A view of about 2,500 stars in a truly dark sky might convince you that dark skies are a resource worth saving.

【推荐1】As many as five billion people, particularly in Africa and South Asia, are likely to face shortages of food and clean water in the coming decades. Hundreds of millions more could face increased risks of severe coastal storms, according to the first-ever model examining how nature and humans can survive together. “I hope no one is shocked that billions of people could be affected by 2050,” says Rebecca Chaplin-Kramer, lead author of the paper Global Modeling Of Nature’s Contributions To People published in Science, who is an ecologist at Stanford University.

Nature sees a frightening sight. Human activity has resulted in the severe change of more than 75 percent of Earth’s land areas and 66 percent of the oceans, putting a million species (物种) at risk of being wiped out, according to the first-ever Global Assessment Report on Biodiversity and Ecosystem Services.

Human well-being is dependent upon nature’s contributions, also known as ecosystem services. The new model looked at three of nature’s contributions or services: providing clean water, coastal protection, or crop pollination (授粉). The model shows that the future declines in those services will hit people in Africa and South Asia hardest because they are more directly dependent on nature, says Chaplin-Kramer in an interview. Wealthier countries can buffer the effects on them through imports of food and other basic things that help their people and economy.

We have got a “deeply worrying picture of the social burdens of losing nature,” writes Patricia Balvanera, an ecologist at the Universidad Nacional Autónoma de México in an accompanying article in Science. “What’s really scary is that the model only looked at three of the 18 contributions to human well-being we’ve identified,” says Balvanera in an interview.