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.

    All over the world the need for more laptops and computers increases each year. Networks have been part of our life. Probably everyone with a portable device （移动设备）has once logged on to a public WiFi network without paying for it, while they are having a coffee, on a train, in a shopping mall or at a hotel. However, is this kind of public WiFi network safe?

    Some networks are better protected than others because encryption （加密）methods are used. Therefore, they are safer than others. But a survey in 2015 showed that more than 950 million records were not protected, including addresses, emails, birth dates, phone numbers, passwords and so on. These open WiFi networks are really not safe, because it is very easy for hackers （黑客） to break into the operating system and get people's private information.

    Most smartphones and laptops, by themselves, search and connect to WiFi networks. They usually prefer a network with a connection that has been used before. Hackers' devices are able to record these searches and look like the trusted WiFi networks. When these smartphones and laptops log on to the networks which are not real, hackers can easily steal their private information.

    So next time, when we want to use our laptops or our smartphones in public places which offer free WiFi networks, please think it twice or take safe measures before using them.

    Noise pollution is doing much harm to our health now. Noise, in fact, is unwanted sound and is a kind of invisible (无形的) killer. More and more students enjoy listening to music very much. When they listen to MP3 players, they like to turn up the volume (音量). Some people love listening to loud music. Furthermore, while watching TV, they keep the volume up. But they haven't realized that the noise is weakening their hearing. In fact, the noise not only influences each member in the family, but also makes a difference to the comfort of neighbors.

Noise pollution is a source of increasing misery (痛苦) to people in our society. If people are often disturbed by it, they may feel uncomfortable or upset. What's worse, the noise can make people mad sometimes. If a worker works in a printing factory for too long, his/her hearing loss is much faster than a common person working in a quieter environment. So everybody must pay more attention to noise pollution. Generally speaking, the following four types of noise should be watched out for:

    ◆Noise in the street

    ◆Construction site (建筑工地) noise

    ◆Noise at work

    ◆Transportation noise

    I think the local department (部门) should take measures to control the noise levels, but it's everybody's duty to keep a quiet environment.

    On May 17, 2009, according to the plan, Mike Good and I would take a space walk to the Hubble Space Telescope to repair an instrument. The power supply on this instrument had failed, so it could no longer be used. I would be the person doing the repair and Mike my assistant.

    Working in space is more difficult than you can imagine. As there is no gravity, you can't stand and any slight push can result in tragedy -you can be pushed into space, never be back.

    We got to the telescope. Before we could replace the power supply, we would have to remove from the telescope a handrail fixed with four screws. Having taken out the first three, I found the fourth stripped. I realized that the handrail would not come off, which meant we could no longer be able to replace the power supply and repair that instrument, which meant scientists could no longer look at the universe and find life on other planets.

    I tried all kinds of things, and nothing worked. Then Houston, the control centre on the earth, called up and told me to use the tape to tape the bottom of the handrail and pull it off the telescope. They said it was going to take about 27 kilograms of force for me to do that.

    I knew what it meant: The handrail could be completely pulled off and the safety tether might break, and I might therefore be pushed into space.

    Mike was next to me in his space suit but he could not take over my role. I turned and looked into the cabin where my five crewmates were, and nobody in there had a space suit on. However, I knew they were all looking at me. "Come on Mass, we are all behind you." The telescope must be repaired.

    "Bam!" The handrail came right off. The rest of the walk went well. We finally got the new power supply in. They tried it; turned it on from the ground. The instrument came back to life.

    At the edge of darkness, after about eight hours, I turned around and saw the Earth from our altitude at Hubble, 568 kilometers up. I saw the huge round pure blue globe home planet. It's the most beautiful, magnificent thing I've ever seen. It's like looking into heaven. It's paradise.

    Welcome to our museum(博物馆). It is free and you can come only with your ID card. We don't ask you for any money, but we have some rules for you.

    First, don't bring any food to the museum. You can't eat in the museum. But you can bring some water to the museum. Second, you can take photos here, but you can't touch (触摸) the things. Third, keep quiet in the museum. Don't talk loudly. Fourth, don't run in the museum. Finally (最后), our museum closes at half past five in the afternoon. Please leave before five and we need thirty minutes to do some cleaning. Have a good time here! Thank you.