Professional athletes in most sports start to slow down after the age of 35. Some retire (退役). Jamaican Olympic runner Usain Bolt has talked about retiring, for example. He is only 30 years old. But on Thursday, Serena Williams earned a spot in the Australian Open finals. She will face her older sister, Venus, who won her semifinal (半决赛) match a day earlier. It is the first time that the Williams sisters will play in a Grand Slam final since 2009. Venus is 36. Serena is 35. One of them will win the championship (冠军) at last.

    One older champion will play in the men's final, too. Roger Federer qualified for the final by defeating Stan Wawrinka. Federer, like Serena Williams, is 35 years old It will be one of the sport's oldest finals in a long time.

    Ken Rosewall of Australia is the oldest winner of a Grand Slam. He was 37 when he won the Australian Open in 1972.

    Serena Williams is already the oldest winner of a women's Grand Slam match. She won Wimbledon last year at the age of 34.

    Many people are impressed that three of the finalists are 35 or older. All of the players have recently had injuries (受伤). Federer missed six months due to back and knee injuries.

    He told the crowd that he did not think he would be able to make it back to a Grand Slam final.

    The Williams sisters have had difficulties, too. Earlier this month, Venus won a match in New Zealand but withdrew (退出) from the final after hurting her arm. She also learned in 2011 she had the immune system disorder. The disorder kept her from practicing and staying in good physical condition for a number of years.

    Serena took time off to recover from knee and shoulder injuries after losing in the semifinals of the U. S. Open last September. It is the ninth time that the sisters will face each other in a major final. Serena has defeated her sister six of those times. If she wins, Serena will beat Steffi Graff's record for the most Grand Slam titles ever in women's tennis.

    You have never seen him,but they're with you every time you fly.They record where you are going,how fast you're traveling and whether everything on your airplane is functioning normally.Their ability to withstand（经受得住）almost any disaster makes them seem like something out of a magic book.They're known as the black box.

    When planes fall from the sky,as a Yemeni airliner did on its way to Comoros Islands in the India ocean June 30,2009,the black box is the best bet for identifying what went wrong.So when a French submarine（潜水艇）detected the device's homing signal five days later,the discovery marked a huge step toward determining the cause of a tragedy in which 152 passengers were killed.

    In 1958,Australian scientist David Warren developed a flight-memory recorder that would track basic information like altitude and direction.That was the first mode for a black box,which became a requirement on all U.S.commercial flights by 1960.Early models often failed to withstand crashes,however,so in 1965 the device（装置）was completely redesigned and moved to the back of the plane-the area least affected bu impact-from its original position in the landing wells（起落架舱). The same year, the Federal Aviation Authority required that the boxes,which were never actually black,be painted orange or yellow to aid visibility.

    Modern airplanes have two black boxes: a voice recorder,which tracks pilots' conversations,and a flight-data recorder,which monitors fuel levels,engine noises and other operating functions that help investigators reconstruct the aircraft's final moments.Placed in an insulated ( 隔绝的) case and surrounded by a quarter-inch-thick panels of stainless steel,the boxes can withstand massive force and temperatures up to 2,000℉.When in deep water,they're also able to emit signals from depths of 20,000 ft.Experts believe the boxes from Air France Flight 447,which crashed near Brazil on June 1,2009,are in water nearly that deep,but statistics say they're still likely to turn up.In the approximately 20 deep-sea crashes over the past 30 years,only one plane's black boxes were never recovered.

    Brian Greene, a professor of physics and mathematics at Columbia University, has created an online science education platform. He tries to "build a bridge" with things you know about, and then "bring you across that bridge to the strange place of modern physics."

    Recently I had a chance to ask Greene about wormholes (a hole which some scientists think might exist, connecting parts of space and time that are not usually connected), time travel and other mysteries of the universe. I asked him a million-dollar question: What if I went through a wormhole and prevented my parents from meeting? "Most of us believe that the universe makes sense," Greene said. Although there are several interesting theories about time travel, he added, the laws of physics would probably prevent something so illogical from taking place. The good news is that the time paradox（悖论） is open for future physicists to solve.

    When asked how physics could become more exciting for kids, Greene said that books by Stephen Weinberg, Leonard Susskind, and other physicists, "make it a great time for people who want to learn about big ideas but aren't yet ready, perhaps, to learn math."

    When I pointed out that some students still might find physics boring, Greene said that the key is to teach them about things that are strange. "The basic stuff is important," Greene said. "But I think it's really important to also describe the more modern ideas, things like black holes and the Big Bang. If kids have those ideas in mind, then at least some of them will be excited to learn all the details．"

    Greene has followed Albert Einstein's lead in trying to solve the mysteries of the universe. Now he wants kids to do the same. As Greene said, physics is "not just a matter of solving problems in an exam." It's about experimenting, showing an interest in strange phenomena（现象）-- and having fun!

    Kerala, India, has placed a tax on hamburgers, pizza and other fast food. The 14.5 percent tax will be added to foods at restaurants such as McDonald's, Pizza Hut and Burger King.

    The tax is being called a "fat tax" because it adds cost to foods considered high in fat and calories. It is the first fast food tax enacted in India, where obesity levels are rising in the growing middle class.

    Kerala's Finance Minister Thomas Isaac suggested the tax after learning of similar measures in other countries. He hopes it will get people to choose to eat healthy food, which he said is "going out of fashion."

    Dr. Anoop Misra at New Delhi's Fortis Hospital strongly supports the" fat tax" as a way to reduce the number of diabetes cases in young people.

    A government finance official in central Gujarat says that the state is considering a similar 14.5 percent tax." This idea can also be adopted in the state, as we also have high consumption of junk and unhealthy food," the official said.

    Critics of the tax say it probably will not stop people from buying fast food. IT engineer Gaurav Singh wants the government to focus on education and awareness instead of taxing fast food.

    "The one food that is eaten widely in Kerala is the 'paratha', which is basically high in fat, high in refined(精制的)flour, and it is cheap. It can't be taxed because it is highly unorganized."

    Some doctors and health experts say the tax should also include other snack foods and sugary drinks sold across the country.

    One fast food customer In New Dehli, Vijay Deoli believes the government should deal with more important issues. "First you have to clear up the air, the water, etc. This is a small thing."

    Others say the government should do more to bring attention to fast food and obesity rather than changing people's choices.

    Many health experts agree that bringing attention to the issue is important. But Dr. Misra thinks education alone does not work.

    He compared the tax to a law passed several years ago that got people to wear seat belts to avoid paying a fine. "Laws can change people's habits."

    With a focus now on the environmental influence over the fashion industry, some bloggers who cut their teeth sharing details of endless clothes and products are changing their direction-enter the "no-buy" movement. The idea is simple: instead of buying new clothes or beauty products, you make a promise to use the things you already own. Some people sign up to a "no-buy year". Others decide not to buy for a few weeks or months or choose "low-buy" with a strict spending cap.

    This life style has caught the attention of many people who struggle to keep up with the latest fashion. Modern people's desire for material things is often not caused by poverty (贫穷) , but by anxiety, which is further enlarged by the rise of social media.

     "Social media puts pressure on people to spend money," says Katherine Ormerod, author of Why Social Media is Ruining Your Life. Many online influencers are given the items they use and wear for free, but Ormerod is determined not to wear any new products she is given. "Really I just want to convince people they don't have to spend a lot of money on fashion to look stylish and there's no such thing as 'last season' anymore," she says. "True style has never been about that anyway."

    However, self-satisfied expressions of minimalist (极简主义的) living have earned plenty of doubts. "Minimalism is a good quality only when it's a choice, and it's telling that its fan base is from the well-off middle class. To people who don't have enough in the first place, celebrations of 'less is more' can sound more like a luxury (奢侈) than a considerable loss." Stephanie Land wrote in The New York Times.

Three grade 11 students from Harbour View High School, Canada, wanted to convey their message of fighting climate change to a younger audience. So, they wrote a children's book named Keeping It Cool as part of a project.

Upon receiving their first order of 12 copies, Claire Malco, the illustrator of the book, vividly recalls the moment when the realization struck. "I just sat there with my mouth open and was like, wow, this is actually happening," Malco told CBC News.

Coauthored by Joanna Jackson and Olivia Jordan, the book employs age-appropriate analogies (类比), coupled with vibrant illustrations, to promote actions kids can take against climate change. To explain the concept of the atmosphere, for example, the young authors drew a bubble(气泡) around Earth throughout the story. They also call for actions, such as planting trees and vegetable gardens – explaining how plants absorb CO2 from the "bubble" atmosphere just like a vacuum cleaner (真空吸尘器). The book also tells kids how they can avoid polluting the bubble by trying to walk, bike or scoot instead of taking a car or bus.

"The entire second half of the book is just things kids can do without needing their parents' support … We wanted it to be something that every kid could finish," Jordan explained to CBC News.

On Earth Day, the students visited a local elementary school where they read their stories and facilitated discussions about the text with every grade 5 class. They spread awareness that, regardless of age, anybody can help make a positive impact on Earth's climate."Educating students was the intention when writing this book. Having the opportunity to present to 10 different classes helped us gain insight on how to better our presentation and content, as well as see the impact this book will have on students," the students told Our Canada Project.