Do you know how it is when you see someone yawn and you start yawning too? Or how hard it is to be among people laughing and not laugh yourself? Well, apparently it's because we have mirror neurons (神经元）in our brains.

    Put simply, the existence of mirror neurons suggests that every time we see someone else do something, our brains imitate (模仿)it，whether or not we actually perform the same action. This explains a great deal about how we learn to smile, talk, walk, dance or play sports. But the idea goes further： mirror neurons not only appear to explain physical actions _y they also tell us that there is a biological basis for the way we understand other people.

    Mirror neurons can undoubtedly be found all over our brains, but especially in the areas which relate to our ability to use languages, and to understand how other people feel. Researchers have found that mirror neurons relate strongly to language. A group of researchers discovered that if they gave people sentences to listen to ( for example ："The hand took hold of the ball" ) , the same mirror neurons were triggered as when the action was actually performed (in this example, actually taking hold of a ball).

    Any problems with mirror neurons may well result in problems with behavior. Much researeh suggests that people with social and behavioral problems have mirror neurons which are not fully functioning. However, it is not yet known exactly how these discoveries might help find treatments for social disorders.

    Research into mirror neurons seems to provide us with ever more information concerning how humans behave and interact(互动）.Indeed, it may turn out to be the equivalent (相等物）for ncurosciencc of what Einstein's theory of relativity was for physics. And the next time you feel the urge to cough in the cinema when someone else does--well，perhaps you'll understand why.

    Think of a seed buried in a pot. It's dark down there in the potting soil. There's no light, no sunshine. So how does it know which way is up and which way is down? It does know. Seeds send shoots up toward the sky, and roots the other way. Darkness doesn't confuse them. Somehow, they get it right.

    More surprisingly, if you turn a seedling (秧苗) or a whole bunch of seedlings upside down, as Thomas Andrew Knight of the Royal Society did around 200 years ago, the tips and roots of the plant will sense, “Hey, I'm upside down. Look! I. will turn my way to the right direction and do a U-turn.”

    How do they know? According to botanist Daniel Chamovitz, Thomas Knight about 200 years ago guessed that plants must sense gravity. Knight proved it with a crazy experiment involving a spinning plate.

    He attached a bunch of plant seedlings onto a disc. The plate was then turned by a water wheel powered by a local stream at a speed of 150 revolutions (旋转) per minute for several days.

    If you have been at an amusement park in a spinning teacup, you know that because of centrifugal force (离心力) you get pushed away from the center of the spinning object toward the outside.

    Knight wondered, would the plants respond to the centrifugal pull of gravity and point their roots to the outside of the spinning plate? When he looked, that's what they'd done. Every plant on the disc had responded to the pull of gravity, and pointed its roots to the outside. The roots pointed out, and the shoots pointed in. So Thomas Knight proved that plants can and do sense the pull.

    Imagine, one day, getting out of bed in Beijing and being at your office in Shanghai in only a couple of hours, and then, after a full day of work, going back home to Beijing and having dinner there.

    Sounds unusual, doesn't it? But it's not that unrealistic, with the development of China's high-speed railway system. And that's not all. China has an even greater high-speed railway plan to connect the country with Southeast Asia, and eventually Eastern Europe. China is negotiating to extend its own high-speed railway network to up to 17 countries in 10 to 15 years, eventually reaching London and Singapore.

    China has proposed three such projects. The first would possibly connect Kunming with Singapore via Vietnam and Malaysia. Another could start in Urumqi and go through Kazakhstan and Uzbekistan, and possibly to Germany. The third would start in the northeast and go north through Russia and then into Western Europe. The new system would still follow China's high-speed railway standard. And the trains would be able to go 346 kilometers an hour, almost as fast as some airplanes. Of course, there are some technical challenges to overcome. There are so many issues that need to be settled, such as safety, rail gauge(轨距), maintenance of railway tracks. But the key issue is really money. China is already spending hundreds of billions of yuan on domestic railway expansion.

    China prefers that the other countries pay in natural resources rather than with capital investment. Resources from those countries could stream into China to sustain development. It'll be a win-win project. For other countries, the railway network will definitely create more opportunities for business, tourism and so on, not to mention the better communication among those countries.

    For China, such a project would not only connect it with the rest of Asia and bring some much-needed resources, but would also help develop China's far west. We foresee that in the coming decades, millions of people will migrate to the western regions, where the land is empty and resources unused. With high-speed trains, people will set up factories and business centers in the west once and for all. And they'll trade with Central Asian and Eastern European countries.

    The year is 2094. It has been announced that a comet (彗星) is heading towards the Earth. Most of it will miss our planet, but two pieces will probably hit the southern half of the Earth.

    On 17 July, a piece four kilometers wide enters the Earth's atmosphere with a massive explosion. About half of the piece is destroyed, but the remaining part hits the South Atlantic at 200 times the speed of sound. The sea boils and a huge hole is made in the sea bed.  Huge waves are created and spread outwards from the hole. The wall of water, a kilometer high, rushes towards southern Africa at 800 kilometers an hour. Cities on the African coast are totally destroyed and millions of people are drowned.

    Before the waves reach South America, the second piece of the comet lands in Argentina. Earthquakes and volcanoes are set off in the Andes Mountains. The shock waves move north into California and all around the Pacific Ocean. The cities of Los Angeles, San Francisco and Tokyo are completely destroyed by earthquakes. Millions of people in the southern half of the earth are already dead, but the north won't escape for long. Because of the explosions, the sun is hidden by clouds of dust, temperatures around the world fall to almost zero. Crops are ruined. The sun won't be seen again for many years. Wars break out as countries fight for food. A year later, no more than 10 million people remain alive.

    Could it really happen? In fact, it has already happened more than once in the history of the Earth. The dinosaurs were on the Earth for over 160 million years. Then 65 million years ago they suddenly disappeared. Many scientists believe that the Earth was hit by a piece of object in space. The dinosaurs couldn't live through the cold climate that followed and they died out. Will we meet the same end?

    When asked about her childhood in the documentary Alive Inside, a 90-year-old woman with dementia(痴呆) replies, "I've forgotten so much." Filmmaker Michael Rossato-Bennett then plays music from her past for her. “That's Louis Armstrong,” she says. “He's singing When the Saints Go Marching In and it takes me back to my school days.” She then recalls exact details from her life.

Why does it happen? Music tends to accompany events that arouse emotions or otherwise make strong impressions on us — such as weddings and graduations. These kinds of experiences form strong memories, and the music and memories likely become intertwined(紧密相连) in our neural(神经的) networks, according to Julene Johnson, a professor at the University of California. Movements, such as dancing, also often pair with our experience of music, which can help form memories. Even many years later, hearing the music can bring back memories of these long-past events.

    As Alive Inside shows, music has this power even for many people with dementia. Researchers note that the brain areas that process and remember music are typically less damaged by dementia than other areas, and they think it may explain the phenomenon.

    They also pay attention to elderly people with dementia, especially those in nursing homes. "It's possible those long-term memories are still there," Johnson says, “but people just have a harder time accessing them because they're in a strange place and there are not a lot of circumstances in which someone could pull out those memories.”

    Johnson also notes that music is not universally useful for all people with dementia since there are some people with dementia whose brain area that recognizes music is damaged.

    Despite music's apparent benefits, few studies have explored its influence on memory recall in people with dementia. “It's really an untapped area,” Johnson says. Petr Janata is one researcher investigating the topic of music and memory. He says that scientists still do not have the answers for why and how music reawakens memories in people with dementia, but this phenomenon is real and it's just a matter of time before it's fully borne out by scientific research.

A study of 500,000 songs released in the UK between 1985 and 2015 showed that pop music had decreased in happiness and increased in sadness.

In a report published in the journal Royal Society Open Science, researchers at the University of California examined hundreds of thousands of songs and classified them by their mood. "‘Happiness' is going down, 'sadness' is going up, and at the same time, the songs are becoming more 'danceable' and more 'party-like'," co-author Natalia L. Komarova told The Associated Press.

The study found songs in 2014 like Stay With Me by Sam Smith, Whispers by Passenger and Unmissable by Gorgon City have a "low happiness" trend. However, tracks from 1984 like Glory Days by Bruce Springsteen, "Would I Lie To You?" by Eurythmics and "Freedom" by Wham had a "high happiness" trend. "The public seems to prefer happier songs, even though more and more unhappy songs are being released each year," the researchers wrote.

Apart from the emotional trends, researchers discovered that dances and pop were the most successful styles of music and that there was a "clear downward" trend, with the popularity of rock beginning in the early 2000s. "So it looks like, while the overall mood is becoming less happy, people seem to want to forget it all and dance," Komarova wrote in an email.

It was also found that the "maleness" of songs—the frequency of male singers in popular music-had decreased during the last 30 years. "Successful songs are characterised by a larger percentage of female artists compared to all songs," they wrote.

This discovery appears at a time when the conversation around sex equality in the music industry is at its height, with more male artists and songwriters.