When asked about happiness, we usually think of something extraordinary, an absolute delight, which seems to get rarer the older we get.

For kids, happiness has a magical quality. Their delight at winning a race or getting a new bike is unreserved (毫无掩饰的).

    In the teenage years the concept of happiness changes. Suddenly it's conditional on such things as excitement, love and popularity. I can still recall the excitement of being invited to dance with the most attractive boy at the school party.

    In adulthood the things that bring deep joy—love, marriage, birth—also bring responsibility and the risk of loss. For adults, happiness is complicated (复杂的).

    My definition of happiness is “the capacity for enjoyment”. The more we can enjoy what we have, the happier we are. It's easy to overlook the pleasure we get from the company of friends, the freedom to live where we please, and even good health.

    I experienced my little moments of pleasure yesterday. First I was overjoyed when I shut the last lunch-box and had the house to myself. Then I spent an uninterrupted morning writing, which I love. When the kids and my husband come home, I enjoyed their noise after the quiet of the day.

    Psychologists tell us that to be happy we need a mix of enjoyable leisure time and satisfying work. I don't think that my grandmother, who raised 14 children, had much of either. She did have a network of close friends and family, and maybe this what satisfied her.

    We, however, with so many choices and such pressure to succeed in every area, have turned happiness into one more thing we've got to have. We're so self-conscious about our “right” to it that it's making us miserable. So we chase it and equal it with wealth and success, without noticing that the people who have those things aren't necessarily happier.

    Happiness isn't about what happens to—it's about how we see what happens to us. It's the skillful way of finding a positive for every negative. It's not wishing for what we don't have , but enjoying what we do possess.

    In the rush to get to school, you drop a piece of toast on the floor. Do you throw it away or decide it's still OK to eat? If you're like most people, you eat it. Maybe you follow the “5-second rule”, which says foods are safe to eat if you pick them up within 5 seconds after dropping them. But you might want to think again. Scientists now say that 5 seconds is all it takes for foods to become polluted with enough bacteria to make you sick.

    Bacteria can cause many kinds of illnesses. Some kinds of bacteria can grow on food. If you eat foods on which these bacteria are growing, you can become sick.

    One of these food-borne bacteria is Salmonella. It makes 1.4 million people sick every year. Salmonella is often found in raw eggs and chicken. Cooking kills these bacteria, which is why it is so important to cook eggs, chicken, and other foods thoroughly.

    But how long does it take these bacteria to pollute food? A team of scientists in South Carolina did an experiment. First, they placed an amount of Salmonella on three surfaces: wood, tile, and carpet. They placed a piece of bread and a piece of sausage on each surface for 5, 30, or 60 seconds. After just 5 seconds, both the bread and the sausage picked up enough bacteria to make you sick.

    So, forget the 5-second rule. If your toast drops on the floor, throw it away and get another piece of clean toast. And next time, be careful not to drop it!

    In his research work, Philosophical Investigations（哲学调查）, Ludwig Wittgenstein tries to clarify（澄清）some of the problems in people's thinking about how the mind works.

    Imagine, he says, that everyone has a small box in which they keep a beetle（甲壳虫）. No one is allowed to look in anyone else's box, only in their own. Over time, people talk about what is in their boxes and the word “beetle” comes to stand for what is in everyone's box. Through this example, Wittgenstein point out that the beetle is very much like an individual's（个体的）mind; no one can know exactly what it is like to be another person or experience things from another's point of view—look in someone else's “box”—but it is general considered that the mental working of another person's mind is very similar to that of our own. However, it does not really matter—he argues—what is in the box or whether everyone indeed has a beetle, since there is no way of checking or comparing. In a sense, the word “beetle” simply means “what is in the box”. From this point of view, the mind is simply “what is in the box”, or rather “what is in your head”.

    Wittgenstein considers language to have meaning because of public usage. In other words, when we talk of having a mind—or a beetle—we are using a term that we have learned through conversation. The concept might be perceived（感知）differently in each of our minds, so the word “mind” cannot be used to refer specifically to some entity（本质）outside of our own conception（概念）, since we cannot see into other people's boxes.

    After the examination, the doctor told my parents my sight would get worse and that I would lose my sight finally. On the way home from hospital, no one said a word. One day, would I only imagine the scenery beyond the glass rather than see it?

    That September, I entered middle school. Most nights I had homework that included an armful of books to read. To keep up with other children, I took great trouble to finish the task. With my nose a couple of inches from the page, I was tired easily. What's worse, after I had read several pages on my own, the words slipped off the page into inky pools.

    However, then I did not have audio books and electric devices like kids do now. Instead, Mum volunteered to read out loud. Mum worked part-time, cleaned the house, cooked and spent time with Grandma. In spite of being so busy, she showed up in my room like clockwork. She put on her reading glasses. Mum always thought those glasses made her look old. To me, she looked like a teacher.

    In my room, Mum's voice raced with the ticking of the clock. Being forced to focus on listening, I found a way to keep my marks up and compete with the other kids. When the teacher asked a question, I raised my hand with confidence. Teachers praised me for having a good memory. Reading removed my fear for my failing sight, reading also made me curious about other people's challenges and how they managed. Though I could not use my eyes to fix on each passage, my mind lit up with every new book.

    True to what the doctor said, the worst came, but thanks to Mum, my sense of hearing now allows me to “see”. This was the most precious gift from a mother to her child.

    The clearing of my parents' home has made me think about the importance, even centrality of books to the house's life and soul. The house, and our lives in it, would not have been the same without books. The force of the statement comes home to me as I see what happens when shelves are emptied. The rooms suddenly look uncomfortably bare.

    I always rather took it for granted that books furnished a room. The only rooms in our house without books were the dining-room and the bathrooms. Otherwise there were books everywhere: in all the bedrooms, in the drawing-room and in the piano room which became my parents' comfortable winter study.

    I couldn't help feeling that books were rather like people: some more formal and boring, others more entertaining; some simply for show, others with unpromising outsides but rich interiors. They did more, in fact, than furnish a room; they were companions who could offer insights, good advice.

    Now the books are being contributed (not all, to be sure, but very many), and I fear for their future, almost as if they were refugees (难民). “Habent sua fata libelli”, goes as the old Latin saying, originally written by Terentianus; it meant that the fate and future of books were determined by the capability of the reader. But the meaning of the phrase has been misunderstood by time and is now associated with the physical fate of particular books, how they have passed from owner to owner. This is how Walter Benjamin read the saying when he wrote his essay “Unpacking My Library”, which analyses the extraordinarily close relationship between a collector and his or her books.

    When I deal with the books that many are going to charity shops, I hope they will find good homes, I can't help wondering if my generation is the last that will oversee such a process. Books are disappearing, as more and more are bought in electronic form and exist only as bytes of information on e-books or other devices. Does this matter? Could books become more spiritual, as they lose their physicality?

    By the end of the century, if not sooner, the world's oceans will be bluer and greener thanks to a warming climate, according to a new study.

    At the heart of the phenomenon lie tiny marine microorganisms (海洋微生物) called phytoplankton. Because of the way light reflects off the organisms, these phytoplankton create colourful patterns at the ocean surface. Ocean colour varies from green to blue, depending on the type and concentration of phytoplankton. Climate change will fuel the growth of phytoplankton in some areas, while reducing it in other spots, leading to changes in the ocean's appearance.

    Phytoplankton live at the ocean surface, where they pull carbon dioxide (二氧化碳) into the ocean while giving off oxygen. When these organisms die, they bury carbon in the deep ocean, an important process that helps to regulate the global climate. But phytoplankton are vulnerable to the ocean's warming trend. Warming changes key characteristics of the ocean and can affect phytoplankton growth, since they need not only sunlight and carbon dioxide to grow, but also nutrients.

    Stephanie Dutkiewicz, a scientist in MIT's Center for Global Change Science, built a climate model that projects changes to the oceans throughout the century. In a world that warms up by 3℃, it found that multiple changes to the colour of the oceans would occur. The model projects that currently blue areas with little phytoplankton could become even bluer. But in some waters, such as those of the Arctic, a warming will make conditions riper for phytoplankton, and these areas will turn greener. "Not only are the quantities of phytoplankton in the ocean changing." she said, "but the type of phytoplankton is changing."