Sports can help you keep fit and get in touch with nature. However, whether you are on the mountains, in the waves, or on the grassland, you should be aware that your sport of choice might have great influence on the environment.

    Some sports are resource-hungry. Golf, as you may know, eats up not only large areas of countryside, but also tons of water. Besides, all sorts of chemicals and huge amounts of energy are used to keep its courses(球场) in good condition. This causes major environmental effects. For example, in the dry regions of Portugal and Spain, golf is often held responsible for serious water shortage in some local areas.

    There are many environment-friendly sports. Power walking is one of them that you could take up today. You don't need any special equipment except a good pair of shoes; and you don't have to worry about resources and your purse. Simple and free, power walking can also keep you fit. If you walk regularly, it will be good for your heart and bones. Experts say that 20 minutes of power walking daily can make you feel less anxious, sleep well and have better weight control.

    Whatever sport you take up, you can make it greener by using environment-friendly equipment and buying products made from recycled materials. But the final goal should be "green gyms". They are better replacements(代替物) for traditional health clubs and modern sports centers. Members of green gyms play sports outdoors, in the countryside or other open spaces. There is no special requirement for you to start your membership. And best of all, it's free.

    When introducing American universities, some of the first institutions（机构）to mention are the Ivy League schools. Originally, the Ivy League was an athletic conference made up of 8 private institutes of higher learning in northeastern United States. However, as time went on, these schools also became known for their excellence in academics besides athletics. Included in the Ivy League schools are Brown University, Columbia University, Cornell University, Dartmouth College, Princeton University, University of Pennsylvania, Yale University, and Harvard University. These 8 schools have been recognized as some of the best colleges and universities in the United States.

    Harvard University is a private institution located in Cambridge, Massachusetts. The university includes a number of graduate and professional schools, as well as a college for undergraduates. In 2012, Harvard ranked number one in US News' ranking of national universities again. Founded in 1636, Harvard is the oldest institute of higher education in the United States. It can be said that first there was Harvard, then the United States of America. Also, Harvard's library contains the oldest collection of books in the United States as well as the largest private collection in the world. Harvard has also been described by Forbes Magazine as one of the “billionaire universities” as of their recent list of 469 billionaires, 50 received a degree from Harvard.

    Harvard College (the institute for undergraduate students) is one of the most famous schools in the United States. It offers over 40 undergraduate fields of study, including astrophysics（天体物理学）, mathematics, neurobiology(神经生物学), etc. And the financial aid program there is amazing. Even though the tuition is about 37,576, and there are other expenses throughout the year, about 70% of undergraduate students received financial aid. Out of those students, over 90% of them had their full need met. And the policies for international students are the same for U.S. citizens.

    Harvard College is very selective, as it only admits about 6% of their applicants. For admission into Harvard College, it is required that students take the SAT or the ACT, as well as 2 SAT Subject Tests. Harvard will also look at other factors during admission such as your application essay, high school transcript, work experience, GPA (Grade Point Average), your interview, recommendations, and most importantly, your character and personal qualities.

    If you see a group of people dancing and singing on the street or in the railway station, you don't need to feel surprised. They are a flash mob(快闪族), which is a group of people who come together suddenly in a public place, do something unusual for a brief period of time, and then quickly break up. They are usually organized with the help of the Internet or other digital communication network. At a predetermined(预先决定的) time, they gather and perform some distractions(消遣) such as waving their hands and exchanging books. Then, they quickly break up before the police can arrive. Using mobile phones, the flash mob can change its location if the first one has been replaced for any reason.

    Bill Lasik, senior editor of Harper's Magazine, organized the first flash mob in Manhattan in May 2003 and the first successful flash mob came together on June 3, 2003 —after the first attempt failed at Macy's department store. Lasik claimed that the activity was designed to make fun of hipsters(赶时髦的人), and call attention to the cultural atmosphere.

    Flash mob gatherings can sometimes shock people. Such an activity might seem amusing and untrue, but it also might frighten people who are not aware of what is taking place. Undoubtedly, flash mobs can serve as good political tools in any direction. They also have great economic potential, such as using flash mobs to advertise a product.

    The flash mob is now becoming more and more popular. People use it to do many things. For example, in 2009, Michael Jackson's fans took part in a flash mob to remember him. Hundreds of his fans gathered singing and dancing Michael's famous song “Beat It” together. Flash mobs give people from all walks of life an opportunity to come together to create a memory.

    If humans pump enough carbon dioxide (CO₂) into the atmosphere, the stratocumulus clouds(层积云) could disappear, and the earth's temperature could climb sharply to heights not predicted in current climate models. It would burn the planet. That's the conclusion of a paper published in the journal Nature Geoscience and described in detail by Natalie Wolchover for Quanta Magazine.

    As Wolchover explained, clouds have long been one of the great uncertainties of climate models. Computer models that easily capture the complexity and detail of most climate systems just aren't powerful enough to predict worldwide changes in cloud behavior. But clouds are important. They reflect sunlight away from the earth's surface. And stratocumulus clouds are those white blankets you might have seen as you looked out the window of arm airplane, rolling out below you and hiding the ground Researchers suspect that certain sudden, past jumps in temperature may have been caused by changes to clouds like these.

    For the new research, scientists modeled just a small patch of sky using a supercomputer. They found that if carbon dioxide levels reach about 1, 200 parts per million(ppm) in the atmosphere, stratocumulus clouds break up. That's a very high carbon dioxide concentration.  Right now, levels have climbed past 410 ppm--a dangerous change from 280 ppm before the Industrial Revolution.

    But humans put more and more CO₂ into the atmosphere every year. If current trends continue, the earth could reach 1, 200 ppm within 100 to 150 years. This could happen if our society doesn't follow through on any of its commitments to reduce emissions(排放), Wolchover reported. And even if it does, the result would be another 8 degrees Celsius of heat added to the global average, on top of the dangerous changes already underway due to greenhouse gases.

    That's an enormous change, and it goes beyond predictions of worldwide ice melt and catastrophic sea level rise. And, once the stratocumulus clouds are gone, Wolchover reported, they likely wouldn't reappear until atmospheric carbon dioxide levels dropped below where they are currently.

    There's still some uncertainty in the data. The 1, 200 ppm figure could change as scientists look into the issue further.

    A food additive (添加剂) is any substance that is added to food. Many people are put off by the idea of "chemicals in food." The truth is that all food is made up of chemicals. Natural substances like milk, as well as man-made ones like drinks on sale in the market, can be described by chemical formulas. Some chemical substances are indeed harmful, but a person who refused to consume any chemicals would find nothing to eat.

    The things we eat can be divided into natural and man-made substances. Some people feel that only natural foods are healthy and that all man-made ingredients are to be avoided. But many natural chemicals, found in plants and animals, are harmful when eaten, and some laboratory-made substances increase the nutritional value of food. Other chemicals have natural and man-made forms that are exactly alike: vitamin C is vitamin C, whether it comes from a test tube or from an orange. Like "chemical", "man-made" doesn't necessarily mean "not fit to eat".

    Food additives are used for many reasons. We add sugar and salt and other things to foods we prepare at home to make them taste better. Food producers have developed a range of additives that stabilize, thicken, harden, keep wet, keep firm, or improve the appearance of their products. Additives can make food more convenient or nutritious, give it a longer shelf life, and make it more attractive to the consumer, thus increasing the sales and profits of the producers.

    Food additives are presently the centre of a storm of serious argument. Food producers have been known to use additives that have not been proved safe; some substances in common use have been proved unsafe and have been taken off the market. Many people feel there's a risk of eating food to which anything has been added. But food additives are now regulated by the FDA of the federal government, and new additives will go through strict testing before they can be placed on the market. For most people, the chances of developing serious side effects (副作用) from the long-term use of presently approved (批准) food additives are very small.

    You can relax if remembering everything isn't your strong suit. Recent research makes the case that being forgetful can be a strength—in fact, selective memory can even be a sign of stronger intelligence.

    Traditional research on memory has focused on the advantages of remembering everything. But looking through years of recent memory data, researchers found that the neurobiology of forgetting can be just as important to our decision-making as what our minds choose to remember.

    Making intelligent decisions doesn't mean you need to have all the information at hand. It just means you need to hold onto the most valuable information. And that means clearing up space in your memory palace for the most up-to-date information on clients and situations. Our brains do this by creating new neurons(神经元）in our  hippocampus, which have the power to overwrite(重写)existing memories that are influencing our decision-making.

    If you want to increase the number of new neurons in our brain's learning region, try exercising. Some aerobic exercise like jogging, power walking and swimming has been found to increase the number of neurons making important connections in our brains.

    When we forget the names of certain clients or details about old jobs，the brain is making a choice that these details don't matter. Although too much forgetfulness can be a cause for concern, the occasional lost detail can be a sign of a perfectly healthy memory system. The researchers found that our brains facilitate decision-making by stopping us from focusing too much on unimportant past details. Instead，the brain helps us remember the most important part of a conversation.

    We can get blamed for being absent-minded when we forget past events in perfect detail. These findings show us that total recall(记忆)can be overvalued. Our brains are working smarter when they aim to remember the right stories, not every story.