Reading can be a social activity. Think of the people who belong to book groups. They choose books to read and then meet to discuss them. Now, the website BookCrossing.com turns the page on the traditional idea of a book group.

    Members go on the site and register the books they own and would like to share. BookCrossing provides an identification number to stick inside the book. Then the person leaves it in a public place, hoping that the book will have an adventure, traveling far and wide with each new reader who findsit.

    Bruce Pederson, the managing director of BookCrossing, says, “The two things that change your life are the people you meet and books you read. BookCrossing combines both.”

    Members leave books on park benches and buses, in train stations and coffee shops. Whoever finds their book will go to the site and record where they found it.

    People who find a book can also leave a journal entry describing what they thought of it. E-mails are then sent to the BookCrossing to keep them updated about where their books have been found. Bruce Peterson says the idea is for people not to be selfish by keeping a book to gather dust on a shelf at home.

    BookCrossing is part of a trend among people who want to get back to the “real” and not the virtual(虚拟). The site now has more than one million members in more than one hundred thirty-five countries.

    Getting older is a natural part of life. Changes as you get older are usually gradual. Certain physical changes are common. How fast your body can burn calories slows over time, which means that your body needs less food energy than before.

    How much and how well you sleep will likely change. Most people start needing reading glasses around forty, and many have some hearing loss later in life. Starting in your fifties, bone aging increase. How you feel as you get older depends on many things, including what health problems run in your family and the choices you make.

    If your family members have diseases or chronic (慢性的) health problems like high blood pressure, then you may have a greater chance of having those problems yourself. But it doesn't mean you will definitely have the same problems. Actually, the lifestyle choices you make can help reduce your chances of getting illness that run in your family. And even if you do get a family illness, choosing to be physically active, to eat healthy foods, and to learn how to deal with stress can keep the illness from destroying your ability to enjoy your golden years.

    What do you need to do to feel your best as you age? One of the most important things you can do for your health at any age is to be physically active. Physical activity keeps your body strong, and it helps with how you feel. People who stay active are less likely to get depressed.

    Your mental and emotional health is also important. Protect or improve your emotional health by staying in touch with friends, family, and the community. People who feel connected to others are more likely to feel happy than those who do not.

    Astronomy (天文学) is the oldest science known to man. Thousands of years ago man looked at the stars and wondered about heavens(天堂). But the six planets that he could see with his eyes alone limited man.

    The Greeks studied astronomy over 2,000 years ago. They could see the size, color, and brightness of a star. They could see its place in the sky. They watched the stars move as the seasons changed. But the Greeks had no tools to help themselves study the heavens.

    Each new tool added to the field of astronomy helped man reach out into space. Until there were telescopes(望远镜), man did not know much about the moon. He did not know that the planet called Saturn(土星) had rings around it. His sight was so limited that he could not see all the planets. In the early 1700s, people thought there were only six planets. Pluto (冥王星), the last of the nine planets to be discovered was seen until 1930.

    Before the spectroscopes (分光镜), man didn't know what kind of gas was in the sun or other stars, without radio telescopes(射电望远镜), we did not know that radio noise came from far in space.

    Today, astronomy is a growing science. We have learned more in the past fifty years than in the whole history of astronomy.

    Kay and Charles Giddens sold their home to start a bed and breakfast. Four years later, the couple now dishes out banana pancake breakfasts, cleans toilets, serves homemade cookies to guests in a bed and breakfast surrounded by trees on a mountain known for colorful sunsets.

    “Do I miss the freeways? Do I miss the traffic? Do I miss the trees? No,” says Ms. Giddens. “This is a phenomenon that's fairly widespread. A lot of people are rethinking their lives and figuring out what they want to do.”

    Simple living ranges from cutting down on weeknight activities to sharing housing, living closer to work and commuting(通勤) less, avoiding shopping malls, borrowing books from the library instead of buying them, and taking a cut in pay to work at a more pleasurable job.

    Vicki Robin, a writer, tells us how she deals with the changes in her budget, now far less than what she used to make.

    “You become conscious of where your money is going and how valuable it is,”Ms. Robin says. “You tend not to use thing up. You cook at home rather than eat out. You find your life is not a mess anymore, and you discover your living costs have gone way down.”

    Janet Luhrs, a lawyer, quit her job after giving birth and leaving her daughter with a babysitter for two weeks.“It was not the way I wanted to raise my kids,”she says.“Simplicity is not just about saving money ; it's about me sitting down every night with my kids to a candlelit dinner with classical music.”

    Ms. Luhrs now edits a magazines called Simple Living, which publishes tips on how to buy recycled furniture and shoes, and organize potluck（家常便饭）dinners instead of fancy receptions.

    “Simplicity is about conscious living and creating the life you want. The less stuff you buy, the less money goes out the door, and the less money you have to earn,” Ms. Luhrs explains.

    Chocolate could soon be a thing of the past, after scientists warned that the cacao plant, from which chocolate is made, could be extinct within 32 years.

    Over half of the world's chocolate comes from just two countries in West Africa­Cote d'Ivoire and Ghana­where the temperature, rain, and humidity provide the perfect conditions for cacao to grow. But the threat of rising temperatures over the next three decades caused by climate change, is expected to result in a loss of water from the ground, which scientists say could upset this balance.

    According to the related data, a temperature rise of just 2.1℃ could spell an end for the chocolate industry worldwide by 2050. Farmers in the region are already considering moving cacao production areas thousands of feet uphill into mountainous area­much of which is currently preserved for wildlife. But a move of this scale could destroy ecosystems that are already under threat from illegal farming and deforestation.

    Part of the problem, according to Doug Hawkins, is that cacao farming methods have not changed for hundreds of years. "Unlike other tree crops that have benefited from the development of modern, high yielding strains and crop management techniques to realize their genetic potential, more than 90% of the global cocoa crop is produced by small farms with unimproved planting material," he said. "It means that we could be facing a chocolate decrease of 100,000 tons a year in the next few years."

    Now scientists at the University of California at Berkeley have teamed up with American candy company Mars to keep chocolate on the menu. Using the controversial(有争议的) gene-editing technology known as CRISPR they are trying to develop a type of the cacao plant capable of surviving in dryer, warmer climates. If the team's work on the cacao plant is successful, it could remove the need for farmers in West Africa to relocate to higher ground, and perhaps even allow cacao to be grown elsewhere in the world.