The baby is just one day old and has not yet left hospital. She is quiet but alert (警觉的). Twenty centimeters from her face researchers have placed a white card with two black spots on it. She stares at it carefully. A researcher removes the card and replaces it by another, this time with the spots differently spaced. As the cards change from one to the other, her gaze(凝视) starts to lose its focus—until a third, with three black spots, is presented. Her gaze returns: she looks at it for twice as long as she did at the previous card. Can she tell that the number two is different from three, just 24 hours after coming into the world?

    Or do newborns simply prefer more to fewer? The same experiment, but with three spots shown before two, shows the same return of interest when the number of spots changes. Perhaps it is just the newness? When slightly older babies were shown cards with pictures of objects (a comb, a key, an orange and so on), changing the number of objects had an effect separate from changing the objects themselves. Could it be the pattern that two things make, as opposed to three? No again. Babies paid more attention to squares moving randomly(随意地)on a screen when their number changed from two to three, or three to two. The effect even crosses between senses. Babies who were repeatedly shown two spots became more excited when they then heard three drumbeats than when they heard just two; likewise(同样地) when the researchers started with drumbeats and moved to spots.

    It is important to protect yourself from harmful rays. But if you think a high-factor sunscreen keeps you safe from harmful rays, you may be wrong. Research in this week's Nature shows that while factor 50 reduces the number of melanomas（黑瘤）and delays their occurrence, it can't prevent them. Melanomas are the most aggressive skin cancers. You have a higher risk if you have red or blond hair, fair skin, blue or green eyes, or sunburn easily, or if a close relative has had one. Melanomas are more common if you have periodic intense exposure to the sun. Other skin cancers are increasingly likely with long-term exposure.

    There is continuing debate as to how effective sunscreen is in reducing melanomas – the evidence is weaker than it is for preventing other types of skin cancer. A 2011 Australian study of 1,621 people found that people randomly selected to apply sunscreen daily had half the rate of melanomas of people who used cream as needed. A second study, comparing 1,167 people with melanomas to 1.101 who didn't have the cancer, found that using sunscreen routinely, alongside other protection such as hats, long sleeves or staying in the shade, did give some protection. This study said other forms of sun protection – no sunscreen – seemed most beneficial. The study relied on people remembering what they had done over each decade of their lives, so it's not entirely reliable. But it seems reasonable to think sunscreen gives people a false sense of security in the sun.

    Many people also don't use sunscreen properly applying insufficient amounts, failing to reapply after a couple of hours and staying in the sun too long. It is sunburn that is most worrying – recent research shows five episodes of sunburn in the teenage years increases the risk of all skin cancers.

    The good news is that a combination of sunscreen and covering up can reduce melanoma rates, as shown by Australian figures from their slip-slop-slap campaign. So if there is a heat wave this summer, it would be best for us, too, to slip on a shirt, use sunscreen and slap on a hat.

    While it's books that make a library, being in lovely surroundings may provide inspiration and help you work a little bit harder. Here are some of the coolest libraries of the world.

    Library of Birmingham – Birmingham, U.K.

    The new Library of Birmingham is said to be not only Britain's biggest public library, but also the largest in Europe. Designed by Dutch architects, this replacement for the Birmingham Central Library was opened in 2013 and has a wealth of resources within its walls, including adults and kids' libraries, music collections, a Shakespeare Memorial Room, and even a gym room. Gardens crown the roof, while the changing seasons bring variations in the shadows and reflections inside.

    National Library of France – Paris, France

    The National Library of France, which now contains an astonishing collection of 30 million, dates back to the 14th century and this royal library was set up at the Louvre by King Charles V. The Library was moved to Rue de Richelieu site in 1868, with major design work carried out by French architects Henri Labrouste and, following his death, Jean-Louis Pascal. Here, the reading rooms are elegance itself. There are more than just books to be found.

    State Library of New South Wales – Sydney, Australia

    The public State Library of New South Wales holds the honor of being the oldest institution of its kind in Australia. It was originally set up as the Australian Subscription Library in 1826, but it wasn't until 1942 that its permanent home was ready. Designed by Sydney architect Walter Liberty Vernon and completed in 1910, the magnificent sandstone Mitchell Wing is one of the architectural highlights.

Seattle Central Library – Seattle, Washington, USA

    Seattle Central Library's distinctive design ensures it stands out. Architect Rem Koolhaas is one of the names attached to its design. Architects sought to envelop the 11-story building with “a layer of transparency”, using a skin of glass and metal. The finished article houses about 1.45 million books and other things, as well as more than 400 computers available for public use. The building, which opened in 2004, was included on the American Institute of Architects' list of America's 150 favorite buildings in 2007.

    Have you ever pressed the pedestrian button at a crosswalk and wondered if it really worked? They're called "placebo(安慰剂）buttons"一buttons that mechanically sound and can be pushed, but provide no functionality.

    In New York City, only about 100 of the 1, 000 crosswalk buttons actually function. Crosswalk signals were generally installed before traffic jam had reached today's levels.

    But while their function was taken over by more advanced systems—such as automated lights or traffic sensors — the physical buttons were often kept, rather than being replaced at further expense. Other cities, such as Boston, Dallas and Seattle, have gone through a similar process, leaving them with their own placebo pedestrian buttons. In London, which has 6, 000 traffic signals, pressing the pedestrian button results in a reliable "Wait" light. But that doesn't necessarily mean that the "green man"— or "pedestrian stage" in traffic signal design profession — will appear any sooner.

    "We do have some crossings where the green light comes on automatically, but we still ask people to press the button because that enables accessible features,'' said Glynn Barton, director of network management at Transport for London.

    These features, such as blind tracks and hearable traffic signals, help people with visual disorder cross the road and only function when the button is pressed. As for the lights, a growing number of them are now combined and become a part of an electronic system that detects traffic and adjusts time frequency accordingly (giving priority to buses if they're running late, for example), which means that pressing the button has no effect.

    According to Langer, a Harvard psychologist, placebo buttons give us the illusion (错觉)of control — and something to do in situations where the alternative would be doing nothing. In the case of pedestrian crossings, they may even make us safer by forcing us to pay attention to our surroundings. "They serve a psychological purpose at the very least," she added.

    When you're on the go, your best friend and resource can be your phone. In the age of smart phones, apps are like guiding stars: They can point you in the right direction for a hotel, list expenses, send postcards, and much more. When used together, these apps can be the basic travel tool, placing a wealth of information at your fingertips no matter where you are on the planet. U.S. News Travel has picked the essential travel apps, known for their utility and reliability. Best of all, they cost absolutely nothing.

    Trip It

    Your Personal Travel Agent

    Be your own travel agent and plan every detail of your trip-- from car rental to accommodating restaurants-- with Trip It. You can make travel schedule by hand, or simply forward the email confirmations of your flight, rental car, train tickets, and hotels to plans.

Weather Free

    Your Go-To Meteorologist(气象学者)

    Stop trying to explain the weather forecast on the evening news (particularly when it's in a foreign language.) The Weather Free app informs you (in English) of the climate in various locations. It features the local weather, and other key factors that will inform your decision about what to wear before stepping outside.

    Goby

    Your Event Guru

    When you're in a foreign city, you sometimes look around and ask: Where are all the people? Goby has the answer. This app pinpoints the neighborhood hot spots (including museums, hotels, eateries, and more) in your neighborhood. But its true value comes in finding nearby events. You'll discover concerts, plays, and more right around the corner.

    A home science experiment recently took the world by storm. Two teens from Toronto, in Canada, sent a Lego man rising above the Earth and captured their tiny astronaut's trip on film.

    Mathew Ho and Asad Muhammad, both 17, used a weather balloon to launch their plastic lego model 16 miles above the Earth. This is inside a part of Earth's atmosphere.

    The two teens were inspired by a similar project performed by students at the Massachusetts Institute of Technology(MIT). The MIT students had launched a weather balloon with a camera into near space and taken many unusual images of the Earth. Mathew and Asad then spend four months figuring out how to launch their own spacecraft into the space.

    Travelling to space is expensive for NASA, but Mathew and Asad worked hard to keep their costs down. They bought much of their equipment used and even sewed the Lego man's parachute by hand. In total, the project cost only$400.

    "We had a lot of anxiety on launch day because there were high winds when we were going up," Mathew told reporters. They had to pump extra helium(氦)into the balloon so that it would rise quickly and avoid being blown too far off course by the strong winds.

    The toy astronaut's journey lasted 97 minutes before the balloon broke and he fell back to Earth. Mathew and Asad then spent two weekends looking for their spacecraft. It had landed 76miles away from the launch site.

    The student scientists are currently finishing up their final year of high school and applying for colleges. They are also looking into more do-it-yourself space projects.

    "I guess the sky is not really the limit anymore," Mathew told reporters. "We never knew we'd get this far. It's been a lesson for us that hard work pays off."