Last night's meteor (流星) shower left many people in the community dissatisfied and demanding answers. According to Gabe Rothschild, Emerald Valley's mayor, people gathered in the suburbs of the city, carrying heavy telescopes, expecting to watch the brightly burning meteors passing through the sky. What they found instead was a sky so brightened by the city's lights that it darkened the light of the meteors passing overhead.

     “My family was so frustrated,” admitted town resident Duane Cosby, “We wanted to make this an unforgettable family outing, but it turned out to be a huge disappointment.”

    Astronomers—scientists who study stars and planets—have been complaining about this problem for decades. They say that light pollution prevents them from seeing objects in the sky that they could see quite easily in the past. They call on people and the government to take measures to fight against it.

    There is yet a population besides professional and amateur star observers that suffers even more from light pollution. This population consists of birds, bats, frogs, snakes, etc. For example, outdoor lighting severely affects migrating (迁徙的) birds. According to the International Dark-Sky Association, “100 million birds a year throughout North America die in crashes with lighted buildings and towers.”

    Countless more animal casualties (伤亡) result from the use of artificial lighting. Clearly, people enjoy the benefits of lighting their evenings. But some scientists think it can be harmful for humans, too. They worry that exposure to light while sleeping can increase a person's chances of getting cancer.

    Emerald Valley is only one community that is becoming aware of the negative effects of light pollution. For years, Flagstaff, Arizona, has enforced lighting regulations in its city in order to assist astronomers at the Lowell Observatory. Similar efforts have been made worldwide, and a movement is underway to remind us to turn off lights when we are not using them, so that other creatures can share the night.

    Can exercise during childhood protect you against memory loss many decades later?Exercise early in life seems to have lifelong benefits for the brain,in rats at least.

     “This is an animal study,but it shows that physical activity at a young age is very important—not just for physical development,but for the whole lifelong track of cognitive（认知的）development during ageing,”says Martin Wojtowicz of the University of Toronto,Canada.“In humans,it may delay the appearance of Alzheimer's symptoms（阿茨海默氏症）,possibly to the point of preventing them.”

    Wojtowicz's team divided 80 young male rats into two equal groups,and placed running wheels in the cages of one group for a period of six weeks.Around four months later—when the rats had reached middle age—the team taught all the rats to connect an electric shock with being in a specific.When placed in the box,they froze with fear.

    Two weeks later,the team tested the rats in three situations: exactly the same box in the same room,the same box with the room arranged differently,and a completely different box in a different room.

    The rats without access to a running wheel when they were young now froze the same percentage of times in each of these situations,suggesting they couldn't remember which one was dangerous.But those that had been able to run in their youth froze 40 to 50 percent less in both changed box settings.

    "The results suggest the amount of physical activity when we're young,at least for rats,has influence on brain and cognitive health—in the form of better memories—when we're older,"says Arthur Kramer of Northeastern University in Boston,who has found that,in humans,exercise promotes the growth of new brain cells.

    “Heaven (天堂) is where the police are English, the cooks are French, the mechanics are German, the lovers are Italian and everything is organized by the Swiss. Hell (地狱) is where the police are German, the cooks are English, the mechanics are French, the lovers are Swiss, and everything is organized by the Italians.”

    Obviously the national stereotypes (模式化的思想) in this old joke are generalizations (普遍化), but such stereotypes are often said to “exist for a reason”. Is there actually a sliver (裂片) of truth in them? Not likely, an international research team now says.

    “National and cultural stereotypes do play an important role in how people see themselves and others, and being aware that these are not dependable is a useful thing,” said study author Robert McCrae of the National Institute on Aging. “These are in fact unfounded stereotypes. They don't come from looking around you,” McCrae said.

    If national stereotypes aren't rooted in real experiences, then where do they come from? One possibility is that they reflect national values, which may become known from historical events. For example, many historians have argued that the spirit of American individualism (个人主义) has its origins in the experiences of the pioneers on the Old West.

    Social scientists such as psychologist Richard Robins have given several other possible explanations for stereotypes and why they may be incorrect. Robins notes that some stereotypes may have been correct at one point in history and then remained unchanged while the culture changed.

    We may be “hard-wired”, to some degree, to keep incorrect stereotypes, since we are less likely to notice and remember information that is different from our stereotypes. Generally, according to Robins, when we meet people who are different from our stereotypes, we see them as unique individuals rather than typical national or cultural groups.

    Pizza is a pretty universal treat, but where did it start? Here are three things you probably didn't know about pizza.

    1: Pizza's Origins Are Half-Baked.

    The Neapolitans（那不勒斯人）in Italy are proud of saying they invented pizza, but it's probably more accurate to say, they perfected it. The idea of putting toppings on a flatbread and baking it started in the 6th century B. C. But the people of Naples were the first to put tomato on a flatbread in the 16th century. From its start, pizza was a food of the poor, as it was cheap, filling and easy to eat on the run. In Italian, the word “pizza” refers to anything that is made and then pressed flat.

    2: Pizza Margherita Is Not Exactly a Symbol of Italy.

It was said some day in 1889, a local baker named Raffaele Esposito created three pizzas for Queen Margherita when she was on a tour of Italy. The queen loved the version that had tomato, basil and mozzarella cheese— and just happened to match the colors of the Italian flag. So Esposito named the pizza after her.

    But Pizza historian Scott Wiener points out that Italy was unified in name only in 1889 so it was unlikely any Neapolitan baker would want to celebrate “the Northern conquerors.” Further, the letter of gratitude for the pizza from the royal household that Pizzeria Brandi displays appears to be a fake（赝品）and may just have been a marketing plan.

    3: Hawaliian Pizza Invented by a Canadian.

    Sam Panopoulos, from Greece originally moved to Canada at the age of 20. In 1962, he decided to put some ham and pineapple on a pizza at one of his restaurants in Ontario.

    “We just put it on for fun to see how it was going to taste,” he told the BBC in 2017. Panopoulos named it the Hawaiian pizza after the brand of canned pineapple he used. The mix of sweet and savory toppings caught on with a certain part of the pizza-loving public. The inventor died in 2017.

    Imagine a brand-new, magical pill which can measurably improve your memory, overall cognitive (认知的) performance, ability to learn new information, mood, ability to handle problems and more. Would you buy it?

    Yeah, yeah, you saw this coming: That pill exists, but not in pill form. You can have all of those benefits for free, and all it takes is going to bed a little bit earlier. So what are we to do to get a better night's sleep?

    First, learn how much sleep you need. Generally, if you're waking up tired, you're not getting enough. However, the gold standard of eight hours per night might not be right for you. A study from 2015 brought into question whether we need that magical number, so following your body is the best way to figure out the right rhythm. The only real guideline is to get as much sleep as you need to feel refreshed and energized the next day.

    Next, figure out your body's natural rhythm. Maybe after years of trying, you need to acknowledge that you're just not a morning person. And that's perfectly fine! Click the link and take the quiz to find out what kind of sleeper you are, and don't fight your body's natural sleep tendencies.

    Last, keep a consistent sleep schedule. This can be the most important part of your overall sleep quality We're all equipped with circadian clock (生物钟), which s that internal 24-hour timer that naturally tells us when to sleep, and the best way to getting rest and feeling rested is to keep this consistent. Fall asleep and wake up at the same time every day, and try to build as much regularity into your schedule as possible. And don't forget to keep your bedroom cool.

Any schoolchild knows that a whale breathes through its blowhole. Fewer know that a blowhole is a nostril （鼻孔） slightly changed by evolution into a form more useful for a mammal that spends its life at sea. And only a dedicated expert would know that while toothed whales, such as sperm whales, have one hole, baleen （鲸须） whales, such as humpback and Rice whales, have two. 

Even among the baleen whales, the placing of those nostrils differs. In some species they are close together. In others, they are much further apart. In a paper published in Biology Letters Conor Ryan, a marine biologist at the Scottish Association for Marine Science, suggests why that might be. Having two nostrils, he argues, helps whales smell in stereo （立体空间）. 

Many types of baleen whales eat tiny animals known as zooplankton （浮游动物）， which they catch by filtering （过滤） them from seawater using the sheets of fibrous baleen that have replaced teeth in their mouths. But to eat something you first have to find it. Toothed whales do not hunt by scent. In fact, the olfactory bulb-the part of the brain that processes smell-is absent in such creatures. But baleen whales still have olfactory bulbs, which suggests smell remains important. And scent can indeed give zooplankton away. Zooplankton like to eat other tiny creatures called phytoplankton （浮游植物）. When these are under attack, they release a special gas called dimethyl sulphide, which in turn attracts baleen whales. 

Most animals have stereoscopic senses. Having two eyes, for instance, allows an animal to compare the images from each in order to perceive depth. Having two ears lets them locate the direction from which a sound is coming. Dr Ryan theorized that paired blowholes might bring baleen whales the same sorts of benefits. 

The farther apart the sensory organs are, the more information can be extracted by the animal that bears them. The researchers used drones to photograph the nostrils of 143 whales belonging to 14 different species. Sure enough, baleen whales that often eat zooplankton, such as the North Atlantic right whale, have nostrils that are farther apart than do those, such as humpback whales, that eat zooplankton occasionally. Besides allowing them to breathe, it seems that some whales use their blowholes to determine in which direction dinner lies.