Life in the Clear

    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet—as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, “These animals live through their life alone. They never touch anything unless they're eating it, or unless something is eating them.”

    And they are as clear as glass. How does an animal become see-through? It's trickier than you might think.

    The objects around you are visible because they interact with light. Light typically travels in a straight line. But some materials slow and scatter(散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks. Both scattering and absorption make an object look different from other objects around it, so you can see it easily.

But a transparent object doesn't absorb or scatter light, at least not very much, Light can pass through it without bending or stopping. That means a transparent object doesn't look very different from the surrounding air or water. You don't see it —-you see the things behind it.

    To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments(色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

Animals are built of many different materials—-skin, fat, and more—-and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat. Without much tissue to scatter light, it is easier to be see—through. Others build a large, clear mass of non-living jelly-lie(果冻状的)material and spread themselves over it .

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process. When they die, they turn a non-transparent milky white.

    One day, a poor man, who had only one piece of bread to eat, was walking past a restaurant. There was a large pot of soup on the table. The poor man held his bread over the soup, so the steam from the soup went into the bread, and gave it a good smell. Then he ate the bread.

    The restaurant owner was very angry at this, and he asked the man for money, in exchange for the steam from the soup. The poor man had no money, so the restaurant owner took him to Nasreddin, who was a judge at that time. Nasreddin thought about the case for a little while.

    Then he took some money from his pocket. He held the coins next to the restaurant owner's ear, and shook them, so that they made a dingling (叮当声) noise.

    “What was that?” asked the restaurant owner.

    “That was payment for you,” answered Nasreddin.

    “What do you mean? That was just the sound of coins!” said angrily the restaurant owner.

    “The sound of the coin is payment for the smell of the soup,” answered Nasreddin. “Now go back to your restaurant.”

    You are watching a film in which two men are having a fight. They hit one another hard. At the start they only fight with their fists. But soon they begin hitting one another over the heads with chairs. And so it goes on until one of the men crashes through a window and falls thirty feet to the ground below. He is dead!

    Of course he isn't really dead. With any luck he isn't even hurt. Why? Because the men who fall out of high windows or jump from fast-moving trains, who crash cars or even catch fire, are professionals. They do this for a living. These men are called stuntmen. That is to say, they perform tricks.

    There are two sides to their work. They actually do most of the things you see on the screen. For example, they fall from a high building. However, they do not fall on to hard ground but on to empty cardboard boxes covered with a mattress. Again, when they hit one another with chairs, the chairs are made of soft wood and when they crash through windows, the glass is made of sugar!

    But although their work depends on trick of this sort, it also requires a high degree of skill and training. Often a stuntman's success depends on careful timing. For example, when he is “blown up” in a battle scene, he has to jump out of the way of the explosion just at the right moment.

    Naturally stuntmen are well paid for their work, but they lead dangerous lives. They often get seriously injured, and sometimes killed. A Norwegian stuntman, for example, skied over the edge of a cliff a thousand feet high. His parachute(降落伞) failed to open, and he was killed.

    In spite of all the risks, this is no longer a profession for men only. Men no longer dress up as women when actresses have to perform some dangerous actions. For nowadays there are stuntwomen, too!

    If you're a fan of smart technology, you may have had some sleepless nights lately.

    That's because Alexa, the artificial intelligence (AI) behind US company Amazon's Echo smart speakers, has been "letting out an automatic, creepy (令人毛骨悚然的) cackle," for no apparent reason, according to BBC News.

    Many social media users shared their stories of Alexa scaring them with the seemingly unprompted laugh.

    "Every time Alexa laughs, an angel dies," Tesla and SpaceX founder Elon Musk joked on social media.

    On March 7, Amazon released an update that fixed the problem, saying that the laugh was triggered (引发) by Echo devices mistakenly thinking that users had said the command "Alexa, laugh".

    However, what should have been a funny story raised the ongoing topic of man versus machine.

    With the rise of artificial and robotic technology, "Digital machines have started to demonstrate (展示) broad abilities in pattern recognition, complex communication, and other fields that used to only belong to human," wrote Erik Brynjolfsson and Andrew McAfee in their book The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies. They believe that AI will "do more and more, and our lives will get better".

    However, ever since the earliest days of AI, there have been concerns that some day, software will take over the world, leaving the fate of humans unknown.

    "With artificial intelligence we are summoning (召唤) the demon ," Musk told students during a meeting at MIT in 2014. "If I had to guess at what our biggest existential threat is, it's probably that. So we need to be very careful."

    Many scientists have shared the same concern. The late British physicist Stephen Hawking said at a technology conference in Portugal in November that "computers can, in theory, imitate human intelligence, and exceed it… AI could be the worst event in the history of our civilization." If creators are to safely control AI, however, Hawking suggested that they "employ best practice and effective management".

    "I am an optimist and I believe that we can create AI for the good of the world," he said at the conference. "We simply need to be aware of the dangers, identify them, employ the best possible practice and management, and prepare for its consequences well in advance."

    Each year there is an increasing number of cars on roads and streets as millions of new cars and trucks are produced. One out of every six Americans works at putting together the parts of cars, driving trucks, building roads or filling cars and trucks with gas. Americans won't live without cars!

    Most Americans would find it hard to think what life would look like without cars. However, some have realized the serious problems of the air pollution that is caused by the car.

    The polluted air becomes poisonous and dangerous to health.

    One way to get rid of the polluted air is to build a car that does not pollute. That's what several of the large car factories have been trying to do. But to build a clean car is easier said than done. Progress in this field has been slow.

    Another way is to take the place of the car engine by something else. Inventors are now working on steam cars as well as electric cars. Many makers believe that it will take years to develop a practical model that pleases man.

    To prevent the world from being polluted by cars, we'll have to make some changes in the way many of us live. Americans, for example, have to cut down on the number of their total cars. They are encouraged to travel and go to work by bicycle. Bicycling is thought to help keep the air clean.

    But this change does not come easily. A large number of workers may find themselves without jobs if a car factory closes down. Thus the problem of air pollution would become less important than that of unemployment.

    Although cars have led us to a better life, they have also brought us new problems.