Ever wonder how much a cloud weighs? What about a hurricane? A meteorologist（气象学家） has done some estimates and the results might surprise you.

    Let's start with a very simple white puffy cloud—a cumulus cloud(积云). How much does the water in a cumulus cloud weigh? Peggy LeMone, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, did the numbers. “The water in the little cloud weighs about 550 tons,” she calculates. “Or if you want to convert it to something that might be a little more meaningful...think of elephants.” Assume（假设） an elephant weighs about six tons, she says, that would mean the water inside a typical cumulus cloud would weigh about one hundred elephants.

    The thought of a hundred elephants' worth of water floating in the sky begs another question—what keeps it up there?

    “First of all, the water isn't in elephant-sized particles(微粒); it's in tiny tiny tiny particles,” explains LeMone. And those particles float on the warmer air that's rising below. But still, the concept of so much water floating in the sky was surprising even to a meteorologist like LeMone. “I had no idea how much a cloud would weigh, actually, when I started the calculations（计算）,” she says.

    So how many elephant units of water are inside a big storm cloud—10 times bigger all the way around than the “puffy” cumulus cloud? Again, LeMone did the numbers: About 200,000 elephants.

    Now, come to the calculations for a hurricane about the size of Missouri and the figures get really massive. “What we're doing is weighing the water in one cubic meter theoretically pulled from a cloud and then multiplying by the number of meters in a whole hurricane,” she explains.

    The result? Forty million elephants. That means the water in one hurricane weighs more than all the elephants on the planet. Perhaps even more than all the elephants that have ever lived on the planet.

    A new book called “Battle Hymn of the Tiger Mother” by Amy Chua has caused a debate (争论) about cultural differences in parenting. Amy Chua is a teacher in an American university and both of her parents are Chinese. In the book, Ms. Chua writes about how she taught her daughters. She told NBC television that she had a clear list of what her daughters were not allowed to do, such as having a play date, watching TV or playing computer games and getting any grade less than an A.

    Many people are against Amy Chua's parenting style (风格), even her husband, who is American. They say it is rude and unfair to children. But she says her parents raised her and her three sisters in that way.

    Ms. Chua says after her younger daughter shouted “I hate my life! I hate you!” she decided to retreat because she was afraid of losing her daughter. But she also says American parents often have low expectations of their children's abilities.

    “The debate is about what it means to be a successful parent and what it means to be a successful child,” said Stacy DeBroff, who has written four books on parenting. She says Amy Chua's parenting style is not limited to Chinese families. It is a traditional way of parenting among immigrants (移民). They hope to get a better future for their children.

    She also sees a risk (风险). When children have no time to be social or to develop their own interests, they might not develop other skills that they need to succeed in life. DeBroff advises parents to develop their own style of parenting and not just repeat the way they were raised.

    Moments before I could lift my case to put it in the plane's overhead locker ahead of our recent holiday to Europe, my father gently urged me to stop. He held the thick handles of the case and lifted it with his thin arms, pushing it into place with a sigh. “You should relax and be the lady, and let me do the heavy tasks,” he said seriously. “In the future, someone special will come into your life and take over such tasks from me, but that will never happen if you do everything yourself.”

    I was stunned into silence. This was not the father I remembered from childhood, who trained me to study hard at school, asked me to earn my own pocket money as a teenager at a local coffee shop, and even taught me household chores so that my life alone in London wouldn't turn into a mess. But then, eight years after I left home and started a new life in the UK, I realized for the first time that my dad still has expectations for me to be like a princess and to stay dependent and delicate, which were considered necessary qualities of women in traditional China.

    Well, that came a little late. Little did Dad know that over the three years of my university life, I moved flats five times all by myself, dragging suitcases of books and clothes, and waiting for the taxi in the rain while holding tight onto cardboard boxes. Meanwhile, living in the UK – a country currently led by a female prime minister – I have never thought there is anything girls cannot do. Most of my female friends are professionals working in the City of London, and after work, we frequently go down to the pub for a drink, just like the guys do – something my mother never did.

    I wondered how I might make Dad understand the new world his little girl has entered. Perhaps one day, he will realize the “someone special” in my life will appreciate my confidence and independence above dependence, and admit that times have changed.

    While many countries love their tea, UK citizens are particularly proud of being “tea people”. The average UK citizen consumes nearly 2 kilograms of tea each year.

    Tea only made its way to England in large quantities in the first years of the 17^th century. Tea from China and a few other Asian countries was being sold more widely in England at that time. Then tea was getting more and more popular among different social classes.

    There are many varieties of tea. Black tea mixtures are still the most common type drunk in the UK. Black tea is dark in colour, because the leaves have been allowed to oxidize (氧化) before drying. This is why we usually serve it with milk, although it is not uncommon to drink it black or with lemon. You may still find tea made with loose tea leaves, served up in a pot, and poured into the best china cups with saucers (茶托) for visitors.

    Tea is still a large part of daily life in the UK today, but it seems to be on the decrease. The amount of tea sold in the UK fell by more than 10% in the five years leading up to 2002, and has been dropping ever since. Tea sales fell by 6% in 2014 alone, and most restaurants report selling more than twice as many cups of coffee as they do tea. More than ￡1 billion was spent on coffee in high street stores in 2013, more than twice what was spent on tea bags.

    Still, what goes around comes around; it's sure to become fashionable again.

    Being able to land safely is a critically important skill for all flying animals. Whereas terrestrial animals face no particular challenge when they need to stop running or crawling, flying animals move at much higher speeds, and they must be careful about how they land. Hitting the ground, or even water, at full flight speed would be quite dangerous. Before touching down, they must decrease their speed in order to land safely. Both bats and birds have mastered the skill of landing, but these two types of flyers go about it quite differently.

    In the past it was believed that, in terms of flying mechanics, there was little difference between bats and birds. This belief was based only on assumption, however, because for years nobody had actually studied in detail how bats move their wings. In recent years, though, researchers have discovered a number of interesting facts about bat flight. Bats are built differently from birds, and their wings incorporate(结合) both their front and hind limbs (后肢). This makes their limbs working together more difficult for bats and, as a result, they are not very good at flying over longer distances. However, a bat can quickly change its direction of flight or completely reverse it, something a bird cannot easily do.

    Another interesting characteristic of bat flight is the way in which bats land—upside down! Unlike birds, which touch down on the ground or on tree branches, bats can be observed flying around and then suddenly hanging upside down from an object overhead. How do they do it? A group of researchers recently used video cameras to film bats landing on nets suspended from the ceiling of their laboratory and studied the recordings in slow motion. They painted spots on the bats' wings to see in detail what happens to the wings in flight and during touchdown. It turns out that the bats flew in a straight line up to the net and then quickly flipped over and attached themselves to it upside down. One disadvantage to this landing routine is that the bats often slam into their landing spot with some force, which probably causes pain. However, not all bats hit their landing spots with the same speed and force; these will vary depending on the area where a bat species makes its home. For example, a cave bat, which regularly rests on a hard stone ceiling, is more careful about its landing preparation than a bat more accustomed to landing in leafy treetops.

    What is eBay? The simple answer is that it is a global trading platform(贸易平台) where nearly anyone can trade practically anything. People can sell and buy all kinds of products and goods, including cars, movies and DVDs, sporting goods, travel tickets, musical instruments, clothes and shoes—the list goes on and on.

    The idea came from Peter Omidyar, who was born in Paris and moved to Washington when he was still a child. At high school, he became very interested in computer programming and after graduating from Tufts University in 1988, he worked for the next few years as a computer engineer. In his free time he started eBay as a kind of hobby, at first offering the service free by word of mouth. By 1996 there was so much traffic on the website that he had to upgrade(升级) and he began charging a fee to members. Joined by a friend, Peter Skill, and in 1998 by his capable CEO, Meg Whitman, he has never looked back. EBay has gone from strength to strength. It is now one of the ten most visited online shopping websites on the Internet.

    eBay sells connections, not goods, putting buyer and seller into contact with each other. All you have to do is make an e-photo, write a description, fill out a sales form and you are in business: the world is your market place. Of course for each item sold eBay gets a percentage and that is great deal of money. Every day there are more than sixteen million items listed on eBay and eighty percent of the items are sold.