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.

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    Almost all cultures celebrate the end of one year and the beginning of another in some way. Different cultures celebrate the beginning of a new year in different ways, and at different times on the calendar(日历).

    In Western countries, people usually celebrate New Year at midnight on December 31st—January 1st. People may go to parties, sometimes dressed in formal(正式的) clothes, and they may drink champagne(香槟酒)at midnight. During the first minutes of the new year, people cheer and wish each other happiness for the year ahead. But some cultures prefer to celebrate the new year by waking up early to watch the sunrise. They welcome the new year with the first light of the sunrise.

    Many cultures also do special things to get rid of(摆脱) bad luck at the beginning of a new year. For example, in Ecuador(厄瓜多尔), families make a big doll from old clothes. The doll is filled with old newspapers and firecrackers. At midnight, these dolls are burned(燃烧) to show the bad things from the past year are gone and the new year can start afresh(重新). Other common traditions to keep away bad luck in a new year include throwing things into rivers or the ocean, or saying special things on the first day of the new year.

    Other New Year traditions are followed to bring good luck in the new year. One widespread(普遍的) Spanish tradition for good luck is to eat grapes on New Year's Day. The more grapes a person eats, the more good luck the person will have in the year. In France, people eat pancakes for good luck at New Year. In the United States, some people eat black­ eyed peas(豌豆) for good luck—but to get good luck for a whole year you have to eat 365 of them!

    Some days, don't you think, "Wouldn't it be nice if the laundry would just do itself?” Self-cleaning clothes may sound crazy. But Australian researchers have found a way to make something like this possible!

    A team at RMIT University in Melbourne, Australia, found a way to put special nanostructures (纳米结构) into clothing, which can then clean the clothes. When sunlight hits the nanostructures, they break down the dirt and stains (污渍) that don't belong on your clothes.

    The nanostructures don't break down the actual clothing because cotton and the other clothing materials are too strong to be broken down. According to CNN, the researchers cover the clothing in a solution made of silver and copper (铜) nanostructures. All it takes is 40 minutes of sunlight and your clothes will look as good as new.

    So if you spill on yourself during lunch, you can step outside for a walk, and it will be clean by the time you go inside. It not only makes your life easier, but it can also be good for the environment.

    According to the US Department of Energy, the average load of laundry uses about 25 gallons (about 94 liters) of water. Water is a very important resource, so using less of it to wash clothes is better for the environment. But one of the scientists at RMIT University knows more needs to be done.

    “There's more work to do before we can start throwing out our washing machines,” said Dr Rajesh Ramanathan, “but this is a strong foundation (基础).”

    So what's the next step? Ramanathan wants to either start selling the solution by itself or convincing (说服) clothing makers to treat the clothing with the solution while clothes are being made.

    Honey(蜂蜜）from African(非洲）forest is very delicious.

    Most people and many animals like eating it. However, the only way for them to get that honey is to find a wild bees' nest(蜂巢）and take honey from it. Often, these nests are high up in trees, and it is difficult to find them. But in parts of Africa, people and animals have a strange helper — a little bird called a honey helper.

    In fact, the honey helper does not like honey, but it likes the wax(蜂蜡）in the nest. The little bird cannot reach the wax because it is inside the bees' nest. So, when it finds a nest, it looks for someone to help. The little bird sings loudly to get the attention(注意） of both passing animals and people. When it has their attention, it flies through the forest, waiting for the following animal or person that loves honey. Then it helps them find the nest. When they finally arrive at the nest, the follower tries to get the delicious honey and the bird waits and watches. Some of the honey and the wax always fall to the ground, and this is when the bird takes its share.

    Scientists do not know why the bird likes eating the wax, but they seem to be able to smell the wax far away.

    A new camera made by a company named Netatmo has facial recognition software(面部识别软件). It can tell parents at work that their children have returned from school, or that a package has been taken to their home. It can also tell them if a stranger has entered their home.

    Janina Mattausch is the product marketing manager for Netatmo.

    "The common security(安全)camera at present are not that smart. They can tell if something is moving but they don't necessarily know if it's a human being or, ah, if it's your kids. They don't know the difference, so they will warn you all the time."

    When family members enter a home, the new camera "recognizes(识别)" them and sends information to the owner's smartphone. The owner can choose to see the video then or later. But if an unknown person enters a home, the camera will send the warning that will cause an alarm to sound on the owner's smartphone.

    That is what happened recently to an owner of the smart camera named Damien, He lives in Paris.

    "On a Friday I was at work, attending(出席) a big monthly meeting when my phone warned. At first I told myself, 'Oh, it must be a mistake, maybe I have to set the system again.' But the notice on my phone was telling me that there was a movement in my flat and also a face that the software did not recognize."

    He watched the video and was very surprised by what he saw. "I was watching it live on video. So I felt totally unbelievable and frozen. I asked a workmate to take me back home as fast as possible and I called the police on the way."

    With the help of the video, the police found the intruder(闯A者) later that day.