You know that balloons must be kept away from sharp objects. They also needed to be kept away from flames. A fire can weaken the rubber and cause it to break. However, in this experiment you will find out how you can hold a balloon directly in a flame without breaking the balloon.

    Materials needed:

● two round balloons not inflated(充气的)

● several matches

● water

    Inflate one of the balloons and tie it. Place 1/4 cup of water in the other balloon, and then inflate it and tie it. Light a match and hold it under the first balloon. Allow the flame to touch the balloon. What happens? The balloon breaks, perhaps even before the flame touches it. Light another match. Hold it directly under the water in the second balloon. Allow the flame to touch the balloon. What happens to this balloon? It doesn't break.

    Why does the balloon with no water break in the flame? The flame heats the rubber of both balloons. The rubber of the balloon without water becomes so hot that it becomes too weak to resist the pressure of the air inside the balloon. However, when the balloon with water in it is placed in the flame, the water takes in most of the heat from the flame. Then, the rubber of the balloon doesn't become very hot, it doesn't weaken, and the balloon doesn't break.

    Water is a particularly good absorber(吸收者) of heat. It takes a lot of heat to change the temperature of water. On the other hand, when water cools, it gives off a great deal of heat. That's why areas near oceans or other large bodies of water don't get as cold in winter as areas at the same latitude(纬度) further inland.

    Whether in the home or the workplace, social robots are going to become a lot more common in the next few years. Social robots are about to bring technology to the everyday world in a more humanized way, said Cynthia Breazeal, chief scientist at the robot company Jibo.

    While household robots today do the normal housework, social robots will be much more like companions than mere tools. For example, these robots will be able to distinguish when someone is happy or sad. This allows them to respond more appropriately to the user.

    The Jibo robot, arranged to ship later this year, is designed to be a personalized assistant. You can talk to the robot, ask it questions, and make requests for it to perform different tasks. The robot doesn't just deliver general answers to questions; it responds based on what it learns about each individual in the household. It can do things such as reminding an elderly family member to take medicine or taking family photos.

    Social robots are not just finding their way into the home. They have potential applications in everything from education to health care and are already finding their way into some of these spaces.

Fellow Robots is one company bringing social robots to the market. The company's “Oshbot” robot is built to assist customers in a store, which can help the customers find items and help guide them to the product's location in the store. It can also speak different languages and make recommendations for different items based on what the customer is shopping for.

    The more interaction the robot has with humans, the more it learns. But Oshbot, like other social robots, is not intended to replace workers, but to work alongside other employees.“We have technologies to train social robots to do things not for us, but with us,” said Breazeal.

    One of the most exciting and interesting international cities to visit is London, England. Here is a look at four free things to do during a vacation to London.

    Visit the Trafalgar Square

    Built more than 200 years ago, Trafalgar Square is a popular gathering place for locals and travelers, too. The area is close to good shopping and dining opportunities, and there are usually some sorts of public events or celebrations going on there during most weekends.

    Wander Along the Thames

    Visitors wanting to sec some great architecture, attractions and views should spend an afternoon walking along the River Thames. The best place to start is at the world-famous London Bridge crossing over the river and you can walk all the way to Westminster Bridge a short distance away. Travelers doing this will find themselves passing by a great many historic buildings.

    Explore the Local Markets

    While purchasing items at any of the open markets in London is not necessarily free, walking through them to view the merchants（商人）, their products and the other shoppers is of great fun. Some of the popular open markets in London worth visiting include Spitafields Market, Portobello Road Market and Leadenhall Market.

     Visit the British Museum

    One of the top museums in the entire United Kingdom can be found in London, and it charges no admission（人场费）for entry. This museum is so highly regarded that it is not only popular with locals and tourists, it is also seen as a major and valuable scholarly resource.

Fishy Weather Conditions

    Laj amanu, Australia, is a dry little town, sitting right on the edge of the Tanami desert. Can you imagines how surprised were people when live fish rained down on them from a dark gray cloudy. It happens that there are similar cases in England and Honduras.

    How do clouds make fishy. The simple answer is that they don't. There is a particular weather phenomenon(现象)called a waterspout. A waterspout is just like a tornado, only it forms above oceans, lakes, or rivers. Like a tornado, a waterspout moves in a circle at high speeds. When it moves above the water, it tends to carry the fish with it, as well as frogs or other small plants or animals.

    Scientists couldn't work it out at first. To make matters stranger still, the fish in Honduras were very much alive when they rained down to the ground, but they were all blind. In England and Australia, it rained fish and snakes, and none were blind. It was difficult to puzzle out, but the blind fish gave them a place to start.

    Scientists knew that some fish that lived in deep, underground caves with no light sources often lost their eyesight. So when blind fish rained down on Honduras, scientists began to connect some dots. Clearly, these particular fish were pulled from an underground water source by force.

    It has rained fish on every continent, and each time, people have tried in various ways to explain this strange phenomenon. Historically, villagers thought the “fishes from the heavens” might be answers to prayers for food.  Others suggested that floods overran river banks and oceans, leaving the fish on the city streets. No scientist had actually seen the rain as it occurred, only the fish left on the ground. But in 1990, a National Geographic team happened to be in Honduras when the Rain of Fishes began. They recorded what was happening and made history by finally proving that the fish really did fall from the sky.

    This huge breakthrough wasn't just a spot of good luck. It changed thousands of years of myths and legends into true stories and provided scientific explanations for how fish came to live in deep caves. It explained ancient cave paintings and shed new light on how species have spread over time. It turned out to be a lot more than just a little fishy weather.

    It's hard to talk to Dad sometimes. His silence about his feelings and thoughts made him mysterious and hard to see through. You could never break his hard shell and get to know him. And he seemed to want to stay that way too.

    But a year ago when my relationship with my wife and career took a hit, I needed my dad to pull back the curtain so I could see him as real and accessible. I was facing serious problems, and I wanted to know whether he had faced them before and how he had found his way, because I felt like I had lost mine. In desperation, it occurred to me that sending an email might be the key, so I wrote him one, telling him about my regrets and fears, and I asked him to answer, if he felt like it.

    Two weeks later, it showed up in my inbox: a much thought, three page letter. Dad, a 68­year­old retired technologist and grandfather of four, had carefully considered my message, and crafted a response. He mentioned his lost love, the foolish mistake he made in career and the stupid pride he had between him and his parents. He comforted me that “life will still find its right track despite many of its twists and turns”.

    I closed the email and started to cry, because I wished I had opened it up earlier but was grateful it wasn't too late. I cried because at first, in the midst of my own struggles, his letter instantly put me at ease. And I cried because in the end, it was so simple: I just had to hit “Send”.

    We've since had many email exchanges. This increasing communication opened a door into his world. My problems haven't been magically solved, but getting to know my dad better has made the tough stuff more manageable and life sweeter. It's hard to talk to Dad sometimes, but I'm glad I found a way to talk to mine.

    From American Express, wedding guests will, on average, spend $673 on each wedding they attend this year. It includes airfare （$225）, hotel （$170）, dining out （$116）and dressing up （$95）and the gift. If you have weddings to attend this year, here are some tips for you to avoid breaking the bank.

    ⒈Book flights in advance

    The moment you decide to attend a wedding is the time to check flight prices at the best time. Plane fares are higher in the summer, especially in July and August. Booking in advance will save you money, as will watch for sales on lower﹣cost carriers like JetBlue and Frontier. You can check Google Flights for a calendar of prices showing the cheapest days to fly from apps like Hopper to get real﹣time alerts when a fare is at its lowest price point.

    ⒉Don't blow your budget on the gift

    If you've got the money, an expensive gift is lovely. But there's no need to take out loans to prove your love for the happy couple. Skip an expensive necklace by giving （an appropriate amount of） cash instead. To save on the gift, consider making one： A photo album or scrapbook of memories with the bride and groom shows how much you care. You could also share the gift with other guest(s) or even make gifts with DIY ideas by yourself to save money.

    ⒊Use old dresses and suits

    You don't always have to be on a new dress for a wedding. While men have the option of repeating their suits, women are more likely to spend money on new clothes for the special occasion. But before you take out your wallet, consider reinventing something already in your closet. Belts, colorful scarves, shoes can bring life to any outfit.