You may think that light pollution isn't something extraordinarily important. You may believe that every other type of pollution has a larger impact on the environment that light pollution does. But light pollution is serious.

    Light pollution, or “sky glow”, is the glow you can see at night above cities and towns. Light pollution is a problem that has been accompanying man ever since he started his first fire some 15,000 years ago. Light pollution is the light that comes from streetlights, buildings, parking lots and any other source of light that is reflected or directed into the atmosphere.

    Urban light pollution means that one-fifth of the world's population can no longer see the Milky Way(银河) with the naked eye(肉眼). Many city kids, even if they did look through the orange smog above their heads, would probably see only a handful of stars. We have lost our view of the stars, and we have mucked up our  night-time environment as well. Astronomers are calling for the dark places on Earth to be preserved as national parks.

    Lots of people find the ever-brightening night annoying, and animals that are programmed to prefer the dark may avoid a brightened habitat. Sea turtles can get lost searching for a beach to lay eggs, and their hatchlings(孵化的幼仔)may confuse over-lit beachfront resorts(度假胜地) for the ocean horizon, wasting precious energy needed to find the sea and escape predators(食肉动物). Because their necks aren't yet long enough to see things far away, baby turtles rely on the mirror image of the moon to guide them to the sea, to begin their new life. A car may even hit a particular turtle, which was thinking the light from a nearby city was moonlight reflecting off the ocean waves. Birds that live in and around cities can die because of sky glow, too. The bright lights can blind them, leading to countless collisions with buildings and other tall structures.

    On an individual level, people can help reduce much sky glow by using lighting only when necessary. The stars above us are priceless heritage— for not only for astronomers but for all humans. More of our children should be able to look up at night and see the Milk Way.

    Every day, a homeowner in Pennsylvania is reminded of a mistake he made 13 years ago. At around 8 in the evening, his peaceful house comes alive with the noise of an alarm clock he dropped into the wall over ten years ago. It's been stuck in the wall ever since.

    13 years ago, Jerry Lynn wanted to make a hole through his living room wall, so he could pass the television cable (电缆)through it. He didn't want to destroy any pipes in the wall, so he came up with a good idea to make sure that he was drilling(钻孔) in an empty place. He took his alarm clock, tied it to a string(线) and set it to go off in 10 minutes. Then he lowered it into the wall, and waited for it to ring. His goal was to drill a hole in a safe place near the place where the ringing was coming from, making sure that there was nothing to pass through there. It all went smoothly until the alarm clock fell into the wall.

The man didn't get back the alarm clock, but thought it would probably run out of battery(电池)in several months, so he wasn't too worried about it. But 13 years later, the alarm clock still rings every day.

    As you can imagine, Jerry and his wife have gotten used to the ringing living room wall, but it can still surprise  guests. So Jerry decides to pull down that wall, just to stop that boring thing, though after putting up with it for 13 years, he think it will be a pity. He says, “I've never herd of a clock battery lasting that long and my friends think it may be interesting to see how long it will keep ringing for.”

    In choosing a friend, one should be very careful. A good friend can help you study. You can have fun together and make each other happy. Sometimes you will meet fair weather friends. They will be with you as long as you have money or luck, but when you are down, they will run away. How do I know when I have found a good friend? I look for certain qualities of character, especially understanding, honesty and reliability(信任)．

    Above all else, I look for understanding in a friend. A good friend tries to understand how another person is feeling. He is not quick to judge. Instead, he tries to learn from others. He puts himself in the other person's place, and he tries to think of ways to be helpful. He is also a good listener.

    At the same time, however, a good friend is honest. He does not look for faults in others. He notices their good points. In short, a friend will try to understand me and accept me.

    Another quality of a friend is reliability. I can always depend on a good friend. If he tells me he will meet me somewhere at a certain time, I can be sure that he will be there. If I need a favor, he will do his best to help me. If I am in trouble, he will not run away from me.

    There is a fourth quality that makes a friend special. A special friend is someone with whom we can have fun. We should enjoy our lives, and we would enjoy our friendship. That is why I especially like friends who are fun to be with. A good friend likes the same things I like. We share experience and learn from each other. A good friend has a good sense of humor too. He likes to laugh with me. That is how we share in the joy of being friends. And I know that he is looking for the same quality in me.

    When I meet someone who is reliable, honest, and understanding, I know I've found a friend!

    Recently we made a survey and asked a large number of people to tell us about their teachers. Here is what they remembered about their teachers:

    "What teachers do I remember? Well, I remember my first teacher. She was so kind and pretty, and she told us many interesting stories."

    "I remember an English teacher —— he always had colored socks: red, green, even orange."

    "I remember a math teacher. She always dressed very well. I couldn't stop looking at her. I wanted to be like her."

    "Our chemistry teacher. He was so strict. We were afraid of him. I don't think he liked us."

    "The physics teacher was so boring. He could make us fall asleep very quickly!"

    "One year we had a really good Chinese language teacher. He was very patient and told very funny stories. He was popular with all the class. We always worked hard for him. We are his friends."

    "The PE teacher always said I was stupid. I thought teachers should give us encouragement. I am not interested in sports because of him."

    "I had one history teacher who always wore clothes of the same color. During the three years, I never saw him change."

    "I remember two teachers well. One was my music teacher who was very active, and usually had a loud voice. The other was my computer teacher who was very serious, but he really helped me when I had problems at any time."

    Have you ever taken a test that you thought you could have passed easily, only to make some silly mistakes that really hurt your grade? More than a few students have done that. And some seem to do it over and over again.

    There are several problem areas that can cause students to goof up or do poorly in a test that they could have passed.

    Some students can become overconfident in their knowledge of the subject matter. They think they know the material better than they actually do. It is easy for students to misjudge their own knowledge, and when they realize that they don't know the material, it is too late.

    What happens more often, though, is that some students feel they are smart enough to be able to guess their way through a test. So they don't bother studying the material. They are overconfident in their ability to figure things out.

    In either case, overconfidence can result in lower grades in tests. Does this apply to you?

    Another thing that can happen is that students underestimate (低估) the difficulty of the test. They expect an easy test, but the teacher throws in a real tough test that they haven't prepared for. Sometimes the teacher may cover material in the test that students weren't expecting. That can happen, especially if you weren't paying attention in class.

    Finally, there are students who don't feel that getting a good grade is important to them, so they don't bother to study or even try to do well. Such students may be trying to punish their parents, have a poor image of themselves, or are just plain foolish. Hopefully, you are not one of these students.

"Consumers complain that the modern tomato has little flavor. It's like a water bomb," said Sanwen Huang, who works at the Agricultural Genomics Institute at Shenzhen at the Chinese Academy of Agricultural Sciences. "Tomato farmers care about yield, and the genetic variants related to yield are not related to tasty tomato flavors."

How can farmers ditch this unpleasant thing and recover the rich, sweet flavor of the tomato? To find out, Huang and colleagues investigated which genes are related to tomatoes' taste. The scientists created a 100-person group that sampled 160 tomatoes based on sensory qualities. Based on the group's feedback, the researchers identified dozens of chemical compounds(化合物) that could be related to the tomato's taste. Using a statistical model that determined the concentration of various chemicals in the tomatoes, the scientists identified 33 most important flavor compounds. The researchers then measured the content of them in each of the tomatoes, and identified about 250 genetic loci(基因座) that controlled tomato flavor. This finding revealed the genetic basis of tomato flavor.

But the researchers also wanted to determine why store-bought tomatoes don't taste good. It turns out that modern tomato varieties are selected according to qualities such as big size because buyers prefer large fruit, and firmness because it makes tomatoes easier to ship. Meanwhile, the quality of flavor has been ignored, said the researchers.

Volatiles(挥发性物质), in particular, are essential for good flavor. The removal of specific volatiles from tomatoes results in significant reduction in people's liking. Moreover, refrigeration can change a tomato's volatile compounds.

"But there is hope for a future filled with tasty, new varieties of store-bought tomatoes, as our results provide a road map for improvement of flavor. By working together, geneticists, biochemists, farmers and customers can provide better-flavored tomatoes for our society." Huang said.