Have you seen Avatar《阿凡达》? It's a popular 3D movie, and you may have to wear 3D glasses to see it. The 3D glasses make the images(图像)from the movie look as if they were coming straight towards you. 

 More and more 3D movies are coming to theaters. Some say that 3D TV sets will come into our homes in the near future. 3D technology can make TV and movies are more exciting. However, people with eye problems may get headaches if they spend too much time watching 3D movies. Why?

When we look at an object(物体), each eye sees it at a different angle(角度). Our eyes send the two images to our brain(大脑), and the brain puts them together. 3D technology uses two film projectors(投影机). One projects a left-eye-image and the other projects a right-eye-image. 3D glasses allow us to see a different image in each eye. So, when we are watching a 3D movie, our brain can't put together the images sent to our eyes. The brain needs to work harder at “reading” the images. That makes it easier for people with eye problems to get dizzy(头晕的) or have headaches. A famous eye doctor said if your eyes can't focus(聚焦) on the same object at once, you will have trouble watching 3D movies.

    Why don't birds get lost on their long flights (飞行) from one place to another? Scientists have studied this puzzle for a long time. Now they're starting to fill in the blanks(空白).

    Not long ago, experiments showed that birds use the sun to guide them during daylight hours. How do birds fly at night? Tests with artificial stars, which are made by people, have proved that certain night-flying birds are able to follow the stars in their long-distance flights.

    They found a bird that spent its lifetime in a cage and never flew under a natural sky. But it was born with the ability to use the stars to look for the direction. This bird's cage was placed under the sky filled with artificial stars. Any change in the position of the artificial stars caused a change in the direction of the bird's flight. From the experiment, they found that the bird tried to fly in the same direction as those artificial stars moving under the natural sky.

    But the stars are of course birds' main ways of navigation (航行), when the stars are hidden by clouds, they can still find their way by such landmarks (路标) as river courses, mountain ranges (山脉), coast lines and so on. Because of this ability, people use the dove (鸽子) to send messages in some fields. For example, the doves were used to send messages in both World War I and World War II. During that time, thousands of doves were used to carry important messages in order to save the lives of many thousands of people. So it is also the symbol of peace.

    But when it's too dark to see these things, the doves are not able to find their way. They only circle helplessly and get lost.

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    Life in the future will be different from life today. Between then and now many changes will take place. But what will the changes be?

    The population is growing fast. There will be many people in the world and most of them will live longer than people live now.

    Computers will be much smaller and more useful, and there will be at least one in every home. And computer studies will be one of the most important subjects in schools then. People will work for fewer hours than they do now and they will have more free time for sports, watching TV and travelling. Travelling will be much cheaper and easier. And many more people will go to other countries for holidays.

    There will be changes in our food, too. More land will be used for building new towns and houses for all the people. Then there will be less room for cows and sheep, so meat will be more expensive. Maybe no one will eat it every day. Instead, they will eat more fruit and vegetables. Maybe people will be healthier. Work in the future will be different, too. Robots will do dangerous and hard work. Because of this, many people will not have enough work to do. This will be a problem.

    SoFi is a special "fish". It is 47 centimeters long. It is all white. It has a small round head. What kind of fish is it? Actually, SoFi is a soft robotic fish. Scientists from MIT made it look like a real fish. They want to use it to study sea animals when the ocean environment changes.

    SoFi's skin is made of a kind of rubber. It's soft. The robotic fish's head is 3D printed. There is a camera in its nose and it can take photos and videos underwater. SoFi can swim among real fish. It is quiet. It doesn't scare other fish. It can also turn left and right, and even change its speed.

    Although SoFi is not the first lifelike robotic fish, it is the most advanced of its kind, according to MIT scientists. Many other countries have also made robotic fish, including the UK and China. Scientists said these robotic fish can easily get close to other fish. And other fish can even interact (互动) with them.

    It's hard to turn down a tasty banana. They taste good and you don't have to wash them before eating them. However, British scientists say that the fruit may disappear by 2050.

    One reason for this is climate(气候) change. Scientists at the University of Exeter collected data(数据) from 27 countries and regions that produce 86 percent of the world's bananas. They found that climate change has improved growing conditions in 21 of these countries. In the past 60 years, the average yield(平均产量) has reached 1.37 tons of bananas per hectare(公顷).

    However, if temperatures keep rising, this advantage will disappear. Ten of the countries, including India, the world's biggest producer of bananas, will produce fewer bananas. By 2050, the fruit may die out.

    Shouldn't bananas grow more easily if it's hotter outside? In fact, the perfect temperature range for growing bananas is between 24 and 32 C. If temperatures get too high, they will stop growing.

    Diseases are another danger to bananas. Unlike other crops, the bananas we grow come from shoot cuttings(茎段) rather than seeds. This means that all banana plants have the same genotype(基因型). In other words, if a disease is able to kill one plant, it could kill them all.

    One serious disease is called Panama. Caused by fungus(真菌) in the soil, it spreads easily. It has spread across South Asia, Africa, the Middle East, and Australia. If one banana plantation(种植园) suffers from the disease, it will take 30 years until it is able to grow bananas again. Scientists have yet to find a cure for this disease.