It is easier to float in the ocean than in a swimming pool. Do you know why?

    Ocean water is full of salt - and salt water can hold up more weight than fresh water. See for yourself! (Ask an adult to help you.)  You will need: 3 cups warm water; A wide-mouth jar（罐）; Salt; A spoon; A potato. You will do: 1. Pour 1.5 cups of warm water into the jar. 2. Add 1/3 cup of salt.  3. Stir(搅拌) until the salt is completely dissolved(完全溶解) 4. Add another l.5 cups of water. Pour it slowly over the back of the spoon into the jar so that the two kinds of water will not mix together. 5. Softly place the potato into the jar. Don't drop it. What will happen: The potato will sink - but only halfway! Why: Salt water is heavier than fresh water, so it will stay on the bottom. The fresh water will remain on the top. The potato is heavier than the fresh water, but it is lighter than the salt water. That is why the potato will sink only halfway down.

    Have you ever heard of e-waste, which can be produced every day? How do you deal with your computers, MP4 players and mobile phones when they're broken or you want a new one?

    Most people just throw them away. With the development of electric industry, e-waste pollution has become a serious problem. According to the United Nations, in 2014, people around the world produced 41.8 million tons of e-waste and only recycled 6.5 million tons. The US was the biggest waster, producing 7.1 million tons. China came second, with 6 million tons.

    It's important to pay attention to e-waste. It can either be valuable or harmful, depending on how we deal with it. E-waste is a valuable urban mine. The value of the metals, like gold and silver in the waste around the world, is amazing. And the metals can be reused. But if people throw them away, the toxic chemicals can get into the earth or air, effecting the environment and people's health.

    Apple, for example, now recycle people's used products in China when they are buying new ones. The company will test and repair the used ones and sell them at lower prices. To help reduce e-waste, we can also take computers and phones to see if companies offer recycling programs.

    Scientists found that moderate (适度的) noise can make people more creative, The New York Times reported.

    Scientists did tests on students. They divided them into four groups. They then asked the students to do certain tasks involving creative thinking. But each group did the task with different volumes (音量) of background noise. They found that students did best when working under moderate noise—70 decibels (分贝). This is about the same volume of background noise in a cafe. Students did worse in low noise (50 dB). This is the volume of a quiet room. They did the poorest when in a high-noise (85 dB) environment. This is the noise level in a factory.

    Moderate noise can distract (分心) people just enough so that they think more creatively. "It helps you think outside the box," Raci Mehta, a lead researcher in the study, said to the Business Standard. On the one hand, working in a very quiet place can strengthen our focus. But it also stops

    us from thinking abstractly (抽象).

    "This is why if you are too focused on a problem and you can't solve it," said Mehta, "you leave it for some time and then come back to it and you'll get the solution."

    However, the scientists said that when you need to do detailed things, like proofreading (校对) a paper, a quiet place is better than a noisy one.

    Sometimes it seems that time is flying. Perhaps it doesn't need to feel this way. Our experience of time can be possibly changed. By understanding the psychological (心理学的) processes behind our different experiences of time, we might be able to slow down time a little.

    One basic law of psychological time is that time seems to slow down when we're exposed (接触) to new environments and experiences. The law is caused by the relationship between our experience of time and the amount of information our minds process. The more information our minds take in, the slower time seems to pass.

    It follows, then, that we have different experiences of time in different situations. In some situations, our life is full of new experiences. Our minds process a lot of information and time seems to slow down. In other situations, we have fewer new experiences and the world around us becomes more and more familiar (熟悉的). We become insensitive to our experience, which means we process less information, and time seems to speed up.

    How can we slow down time? Here are two suggestions.

    Firstly, since we know that familiarity makes time pass faster, we can expose ourselves to as many new experiences as possible. We can give ourselves new challenges, meet new people, and expose our minds to new information, hobbies and skills. This will increase the amount of information our minds process and expand (增加) our experience of time.

    Secondly, and perhaps most effectively, we can give our whole attention to an experience-to what we are seeing, feeling, tasting, smelling or hearing. This means living through our senses rather than through our thoughts. For example, on the way home, focus your attention outside of yourself, instead of thinking about the problems you have to deal with. Look at the sky, or at the buildings you pass, traveling among them. This open attitude to your experiences helps take in more information and also has a time-expanding effect.

    To a certain degree, we can understand and control our experience of time passing. It's possible for us to slow down time by expanding our experience of time.

    Welcome to the 26^th century! Cyborg technology is a way of life. People with human brains and artificial (人造的) bodies are everywhere.

    This is the future world shown in the film Alita: Battle Angel.US director James Cameron made the film. The movie came out in the Chinese mainland theaters on Feb 22.

    The story is based on Japanese manga artist Yukito Kishiro's popular manga series of the same name. The main character, a cyborg, is a girl named Alita.

    One day, she wakes up in wreckage and finds that she has lost her memory. Luckily, a doctor saves her. As she starts her new life, Alita finds she has superhuman abilities. She decides to find the truth behind her origin. She started a journey that leads her through a dark world.

    In Cameron's own words, the movie is "not like any of the films that I've done before". Its visual effects are especially impressive. The film's actors used the latest motion-capture (动作捕捉) technology. They wore special suits that record their movements. Later, motion-capture editors use these movements to make special effects. Rosa Salaza plays Alita. She wore a suit with more than 7, 000 pieces and layers. It can capture human movement. The model that was used for her face was changed nearly 5, 000 times to make it more lifelike.

    Hiccup is a young Viking. Toothless is a dragon and he can give off fire with his mouth. They go through many ups and downs together in the How to Train Your Dragon(《驯龙高手》) movie series. Now they are back with a new film!

    In the last movie, they had to protect their home. Humans and dragons lived together happily there. But now, there are too many dragons. A man tries to kill them. He burns down parts of their home. Hiccup and Toothless have to look for a new world for dragons to live in. Will they find it? Find out by watching How to Train Your Dragon: the Hidden World.

    Dragon acts

    The How to Train Your Dragon movies are from the book series of the same name British writer Cressida Cowell wrote the 12—book series. They came out from 2003 to 2015.

    How to Train Your Dragon the Hidden World is the last movie in the series. It opened in Chinese mainland theaters on March 1. Toothless get his name because he has retractable(伸缩自如的)teeth.