The giraffe is the tallest modern land animal. It can be over 5. 5 meters tall. Its neck alone may be 1. 9 meters long. Yet the giraffe has only seven bones in its neck, the same number as in the humans'. Even a small bird has many more bones in its neck than a tall giraffe. Each bone in a giraffe's neck is very long, while the bones in a human's neck are short. That makes the difference. A female giraffe gives birth to one baby at a time. The baby, called a calf, is about 1. 9 meters tall at birth. By the age of eight it is full-grown. The giraffe eats mostly leaves. Because it has a long neck, it can reach the high leaves on the trees.

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    According to a new study, cats may be just as smart as dogs. Both cats and dogs may have episodic memory（情景记忆）, similar to that of human beings.

    The discovery shows that cats can recall memories of positive experiences like eating a delicious snack. The study was a test of episodic memory. Episodic memory means memory of past experiences that happened at a special time and place.

    In the test, cats were led to four open bowls of food. They were allowed to eat from two of them. After fifteen minutes, empty bowls took the place of the old ones. Then the same cats returned to look for food again. They spent more time searching for the old bowls.

    It seemed that the cats were able to remember the information of “what” and “where” about the bowls. This discovery suggests that they may have episodic memory. However, it's still not clear whether cats can truly experience past memories in the same way as human beings do. “It's difficult to know whether the cats can subjectively（主观地）remember the experience,” Nick Diamond, a researcher at the University of Toronto, explained.

    Still, the test plays an important role in the development of memory research in animals. “It opens the door to new studies. How long can cats' memories last? We may do some research on this in the future,” Professor Laurie Santos from Yale University told BBC News.

    The road to new discoveries is long and difficult. Though there are lots of problems to be solved and discussed along the way, such studies do lead us a step closer to the final success.

    27 world records were broken during the 2016 Summer Olympics. They fell in swimming running weightlifting and a number of other sports. But how do athletes continue to get better, jump longer, run or swim faster? Although scientists say that athletes have reached their limits (极限), records continue to fall. In almost every sport, athletes have become better since the Olympic Games begin.

    One reason is that and more people than ever before have access to sports and exercise. They start at an earlier age and can compete longer in their sport. In schools more and more natural talents can be discovered.

    Besides, athletes can train full-time instead of training after works. As medicine improves, athletes can stay in competition for a longer time and overcome injuries (损伤) faster. Many top athletes achieve their best results later on in their careers. Technology has also helped improve scores.

    One of the most important reasons, however, is the human mind. We always want to be better and faster that someone else. It can release (释放) great power in our body.

    So, where are limits? One of the most difficult questions to answer is how fast a human being can run. Many years ago, nobody thought a person could ever run within 10 seconds in the 100-metre race. But the record was broken at the 1968 Mexico City Olympics. A t the moment Sustain Bolt is the fastest man on Earth at 9.58 seconds. Scientists say that 9.48 may be the limit, but, who knows, maybe some runners will one day run within 9 seconds.

    Today people can use the phone to talk with others almost anywhere on the earth. But when you use the phone, you don't see the person you are talking with. That may change in the near future.

    Today some people are using a kind of telephone called the picture phone or vision phone. With it, two people who are talking can see each other.

    Picture phones can be useful when you have something to show the person you're calling.

    They may have other uses in the future. One day you may be able to ring up a library and ask to see a book. Then you'll be able to read the book right over your picture phone. Or you may be able to go shopping through your picture phone. If you see something in the newspaper that you think you want to buy, you'll go to your phone and call the shop. People at the shop will show you the thing you're interested in right over the phone. You'll be able to shop all over the town and never leave your room!

    Now, it seems that artficial intelligence （人工智能）is becoming more and more popular in our life, and it has greatly influenced the ways we live, work and play. Can you imagine that you can play table tennis with a robot one day?

    Recently, a scientist has invented a special robot that can be a table tennis coach. That means people can practice table tennis not only with humans but also with a robot.

    Named Forpheus, the smart table tennis robot is quite special. It can study the movements of human players and the speeds of the ball. In this way, it can exactly judge (判断) the player' skill levels (水平). Then it uses the information to change the ways to play. If the player are just beginners, Forpheus will play in a slow and easy way, but if the players are better ones, the robot will play in a faster and more difficult way. What's more, while playing, it encourages players to try their beat with words like "Good job!", "Come on!" and so on. At the same time, it gives some good advice to improve their skills. So it is both a good partner and a clever coach.

    Science and technology is developing quickly these days and it's hard to imagine what will happen in the future. "In the next 20 years, it will be possible that one robot teaches another to play table tennis or even invents another one!" Takuoya, the inventor of the robot, said.

    The name of our galaxy(星系), the Milky Way, comes from its appearance. It's a milky white band of glowing light that spreads across the night sky. If you look up at the evening sky, there's a good chance you will not be able to see what your grandmother saw when she was a little girl. A new study says that nearly 80 percent of people in North America can't see the Milky Way because of light pollution.

    The most light-polluted country in the world is Singapore where researchers found that people living in the country never have the chance to experience true darkness. Other countries with large percentages of people living under such skies include Qatar, Kuwait and the United Arab Emirates.

    Too much light has a direct influence on human physiology and behavior. It can also destroy our sleep cycle. What's more, it also influences wildlife. For example, baby turtles may not swim into the ocean because of street lights near shorelines.

    In the U.S., some communities have been taking action on light pollution but in developing countries, people still want to make bigger, brighter light, like LED lights. They can save energy, but on the other hand, they will increase light pollution rapidly in fact.

    There are still people that can remember when they used to be able to see the Milky Way, when they would walk outside at night, but those are becoming fewer and fewer.

    Nighttime natural scenery needs protection just like daytime scenery. Don't let the light pollution steal the chance to experience the wonder of a natural night sky from us.