We know the mosquito very well. Mosquitoes fly everywhere. They can be found almost all over the world, and there are more, than 2, 500 kinds of them.

No one likes the mosquito. But the mosquito may decide that she loves you. She? Yes, she. It's true that male mosquito doesn't bite and only the female mosquito bites because she needs blood to lay eggs. She is always looking for things or people she wants to bite. If she likes what she finds, she bites. But if she doesn't like your blood, she will turn to someone else for more delicious blood. Next time a mosquito bites you, just remember you are chosen. You're different from the others!

    If the mosquito likes you, she lands on your body without letting you know. She bites you so quickly and quietly that you may not feel anything different. After she bites, you will have an itch(痒) on your body because she puts something from her mouth together with your blood. By the time the itching begins, and she has flown away.

And then what happens? Well, after her delicious dinner, the mosquito feels tired. She just wants to find a place to have a good rest. There, on a leaf or a wall, she begins to lay eggs, hundreds of eggs.

    Some people claim they" never forget a face". But what does that saying mean? Is there really no limit to the number of faces a person can remember? A new study at the University of York in England has found that, on average, people can remember as many as 5,000 faces.

    The study is the first time that scientists have been able to put a number to the abilities of humans to recognize faces. The research team tested people on how many faces they could remember from their personal lives and in the media. They also tested them to see how many famous faces they recognized. Rob Jenkins works in the psychology department at the University of York. He said the researchers' study centered on the number of faces people actually know. He said the researchers were not able to discover whether there is a limit on how many faces the brain can handle.

    In the study, people spent one hour writing down as many faces from their personal lives as possible. At first, they found it easy to come up with many faces. But by the end of the hour, they found it harder to think of new ones. Their change in speed let the researchers estimate when they would have run out of faces completely.

    The results showed that these people knew between 1,000 and 10,000 faces. Jenkins explained that some people may have a natural ability for remembering faces." There are differences in how much attention people pay to faces and how well they process the information," he said. Jenkins also said it could be because of different social environments. Some people may have grown up in more populated places. Therefore, they may have had more social contact throughout their lives.

    The people in the study included 25 men and women between 18 and 61 years old. Researchers think age may be an interesting area for further research. "It would be interesting to see whether there is a peak age for the number of faces we know", Jenkins said. He said it is possible that we gather more faces throughout our lifetime. But, he added, there also may be an age at which we start to find it harder to remember all of those faces.

    The study suggests our facial recognition abilities enable us to deal with the many different faces we see on the screens, as well as those we know, like family and friends. Today, facial recognition technology is used in many ways, including by law enforcement agencies to prevent crime and violence. Governments use it to keep secret areas secure and, in extreme cases, control populations. .Even Facebook uses facial recognition. For example, when you "tag" or name a friend, Facebook technology may recognize the person's face from a different picture you had shared before.

    Art, as we know, is subjective. What one person considers a priceless masterpiece others might see as nothing more than a giant black square. But there's one very specific kind of painting that almost everyone sees the same way-the kind with the" "strange" eyes that seem to follow you around the room. So what causes this optical illusion (视觉错觉) and how do artists achieve this effect?

    It turns out, for even a moderately skilled artist, this effect isn't a difficult thing to achieve, In fact, the artists need to use a little illusion of depth, making the person depicted on the canvas appears somewhat 3D on a 2D canvas, and to adjust .the gaze (凝视) of the eyes so that they would be looking at someone standing right in front of the picture.

    So what exactly is going on here in our brains that then makes it seem like the eyes follow you even if you move away from being front and center? As demonstrated by a team of researchers from Ohio State University, as you move to the side, the "near? and "far" points of the 2D image don't really change. These near and far points are defined as visible points that, if the image was 3D, would appear nearest and furthest away from the viewer at a given angle.

    The idea is simple. No matter what angle you look at a paining from, the painting itself doesn't change. You're looking at a flat surface. The key is that the near points and far points of the picture remained the same no matter the angle the picture was viewed from. When observing real surfaces in the natural environment the near and far points vary when we change viewing direction. When we observe a picture on the wall, the visual information that defines near and far points is unaffected by viewing direction. Still, we willingly accept and interpret the thing in the painting as if it were a real object.

    Thus, because the perspective, shadows, and light on the painting don't change as you move around, if the eyes in the painting would be staring directly at the observer who is standing in front of the painting, it creates something of an optical illusion in your brain so that the eyes will continue to seem to stare at you as you move to the side.

    In contrast to the eyes following you trick, if the artist tweaks the painting a bit, for example the artist adjusts the gaze of the eyes so that the eyes are looking off somewhere else instead of directly looking at a potential observer, no matter where you stand, the eyes will never seem to be looking at you.

    The technique first began popularly showing up in art around the 14th century when the artist and architect Fillipo Brunelleshi introduced the art world to the idea of "linear perspective", being painting with the idea of everything in the picture converging (聚集) on a specific point on the horizon, creating the illusion of depth. Linear perspective, combined with skilled use of light and shadow, allows artists to create masterfully realistic paintings, including sometimes of people that stare at you creepily no matter where you stand.

    How do people find their ways? At first, people did it by looking at the sun, the moon and stars, Later, we started to use the compass(指南针).Today, there are navigation satellite systems.

    A navigation satellite system uses groups of satellites, they send information to a receiver, such as your smart phone. Then they can find where you are.

    The earliest navigation system is the Global (全球的) Positioning System(GPS) of the United States, The US has put 24 satellites into space to make sure GPS can locate a person correctly and globally. Russia's GLONASS and European Union's Galileo can also work globally.

    The BeiDou Navigation Satellite System (BDS) is China's homegrown navigation system. It was set up in 2000. With it, China became the third country to build a navigation system after the US and Russia.

    BeiDou can find you wherever you are. It helps you go faster by finding shortcuts and using correct directions. When you are in trouble and call the police, they will know exactly where you are if you have a smart phone that uses BeiDou.

    Today, there are more than 20 BeiDou satellites above our heads. And the system is able to offer open services to the Asia— Pacific area.

    China plans to send more BeiDou 3 satellites into space. BeiDou—3's position accuracy(精确度) is less than five meters, By 2020, the BeiDou system will have 35 satellites and  begin serving Globally.

    Different weather makes people feel different. It influences health, intelligence(智力) and feelings.

    In August, is very hot and wet in the southern part of the United States, People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot at some times and very cold at other times. People in these states have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence. For example, in a scientific report, IQ (智商) of a group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10% below. The wind can help people have more intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools of the United States often get worse on exams in the hot months of the year (July and August).

    Weather also has a strong influence on people's feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather. But fat people may have a hard time in hot summer. At about 18℃, people become stronger.

    Low air pressure may make people forgetful. People leave more bags on buses and in shops on low-pressure days. There is a "good weather" for health. People feel best at a temperature of about 18℃.

    Are you feeling sad, tired, forgetful, or unhappy may be the weather's problem today?