China is a country on the move—especially around its Lunar New Year holiday. This year, the holiday crush（客流量） promises to be even heavier than before.

    Government officials estimate that Chinese people will take to the air, roads and railways 3.62 billion times over a 40-day period around the nation's most important holiday this year as people push their way home for family gatherings or to satisfy their new-found passion for travel.

    Getting tickets to all those would-be travelers is a discounting challenge that annually tries patience. And it is the railway system that routinely is most unable to cope. Railways are the transport of choice for low-cost long-distance travel, and that's where the ticketing system routinely falls down.

    Much of the criticism has, focused on the railway's online purchasing system, which has been unable to keep pace with the huge demand and also failed to stop scalpers（票贩子） from ending up with many of the hard-to-find tickets.

    While insisting that online sales were the fairest way to get tickets for travelers, railway officials told reporters that the public need to be patient. Efforts were being made to provide online identity checks that would reduce the ticket scalping problems. While officials had little good news for rail passengers, they did manage to bring a few smiles to those traveling by car as the country's extremely expensive highway tolls （通行费） will be free of charge for the period of the official holiday.

    Well, parents, surprise! Lots of us are using Twitter and Facebook to thumb rides, and not just to school. It's awkward to be refused when you call a friend and ask for a ride. But with Twitter, you just look for other people heading the same way.

    It may sound risky, so many teens stay within their own social circles to find rides, and don't branch out beyond friends when asking on Twitter just like me, but to some young people, especially those taking longer trips, stranger danger is less of a concern.

    “I think the digital connection of young people is really important, because younger generations grew up sharing things on line, sharing files, photos, music, etc, so they've been very used to sharing,” said Juliet Schor, a sociology professor at Boston College.

    The sharing economy got big during the recession (经济衰退), allowing people to access more goods, services using technology and even to share costs. And that technology, for me, is what the car was for my mom, a gateway to more freedom, like what my friend Earl says, “The symbol of freedom isn't the car any more because there's technology out there connecting you to a car.”

    According to the researchers at the University of Michigan, 30 years ago, eight in ten American 18-year-olds had a driver's license compared to six in ten today. So it's not that surprising that on my 16th birthday I wasn't rushing to get a license but an iPhone.

“Driving, for young people, does mean they have to disconnect from their technology, and that's a negative. So if they could sit in the passage side and still be connected, that's going to be a plus.” Schor continued.

    To me, another plus is that ridesharing represents something, something much bigger than trying to save money. I see it as evidence that people still depend on each other. My generation shares their cars and apartments the way neighbors used to share cups of sugar. For the system to work, some of us still need our own cars. But until I get my own version of the silver Super Beetle, you can find me on Twitter.

    Google's new artificial intelligence can defeat both humans and other AIs. Fortunately, the only war zone where it fights and wins is the ancient board game Go（围棋）.

    AlphaGo Zero, developed by Google-owned DeepMind, is the latest AI program. The original AlphaGo defeated Go master Lee Sedol last year, and AlphaGo Master, an updated version, went on to win 60 games against top human players. What's different about AlphaGo Zero is that it became potentially the world's best Go player without any help from humans.

    The program AlphaGo Zero started off knowing only the basic rules and then played millions of games against itself in just a few days. After almost five million games played against itself, AlphaGo Zero could outplay humans and the original AlphaGo. After 40 days, it was capable of beating AlphaGo Master.

The program learned the strategies humans accumulated over thousands of years in a matter weeks and also developed nontraditional strategies and moves that beat the techniques of the human masters, leaving them astonished. "At each stage of the game, it seems to gain a bit here and lose a bit there, but somehow it ends up slightly ahead, as if by magic," said Andrew Jackson of the American Go Association

    DeepMind says it has plans for the technology behind AlphaGo Zero beyond just defeating all over an ancient game board. "In the end, we want to apply these breakthroughs to helping solve all sorts of pressing real world problems like designing new materials," said Demis Hassabis, co-founder and CEO of DeepMind, in a statement.

    That sounds great, but just as a precaution, let's take the advice of Elon Musk and Stephen Hawking and keep any super-fast learning AI away from the nuclear launch codes for now.

    Miss Parker taught physics in a New York school. Last month she explained to one of her classes about sound ,and she decided to test them to see how successful she had been in her explanation. She said to them, “Now I have a brother in Los Angeles. If I was calling him on the phone and at the same time you were 75 feet away, listening to me from across the street, which of you would hear what I said earlier, my brother or you and for what reason?”

    Tom at once answered, “Your brother. Because electricity travels faster than sound waves.”“That's every good,” Miss Parker answered; but then one of the girls raised her hand, and Miss Parker said.“Yes, Kate.”

    “I disagree,” Kate said.“Your brother would hear you earlier because when it's 11 o'clock here it's only 8 o'clock in Los Angeles.”

    Even by the standards of poor countries, India is alarmingly — and unnecessarily — dirty. It needs to clean up. Most time of year, its capital, Delhi，smells as if something is burning. That is because of many things: the carcinogenic diesel（柴油）that supplies three quarters of the city's motor fuel, the dirty coal that supplies most of its power, the rice stalks that nearby farmers want to clear after the harvest and so on. All these make Delhi's air the most poisonous of any big city.

    This does not just make life unpleasant for a lot of Indians. It kills them. Recent estimates put the annual death toll from breathing PM 2.5 alone at 1.2—2.2 million a year. The lifespan of Delhi residents is shortened by more than ten years, says the University of Chicago-Consumption of dirty water directly causes 200,000 deaths a year, a government think-tank estimates, without measuring its contribution to slower killers such as kidney disease. Some 600 million Indians, nearly half the country, live in areas where clean water is in short supply. As pollutants taint groundwater, and global warming makes the vital monsoon（季风）rains more abnormal, the country is poisoning its own future.

    Indian pollution is a danger to the rest of the world, too. Widespread dumping of antibiotics（抗生素）in rivers has made the country a hotspot for anti-microbial（抗微生物）resistance. Emissions of carbon dioxide, the most common greenhouse gas, grew by 6% a year between 2000 and 2016, compared with 1.3% a year for the world as a whole.

    In the past India has explained its failure to clean up its act by pleading poverty, noting that richer countries were once just as dirty and that its output of waste per person still lags far behind theirs. But India is notably grubby（肮脏的）not just in absolute terms, but also relative to its level of development And it is becoming grubbier.

    It is true that some ways of cutting pollution are expensive. But there are also cheap solutions，such as undoing mistakes that Indian bureaucrats（官僚）have themselves made. By funding rice farmers, for instance, the government has in effect cheered on the overusing of groundwater and the burning of stalks. Rules that encourage the use of coal have not made India more self-reliant, as intended, but instead have led to big imports of foreign coal while blackening India's skies. Much cleaner gas-fired power plants, meanwhile, sit idle.

    Reliant on big business for funding and on the poor for votes, politicians have long ignored middle-class complaints about pollution, failing to give officials the backing to enforce rules. That is a pity, because when India does apply itself to ambitious goals, it often achieves them

    Next year it will send its second rocket to the Moon.

    Narendra Modi, the prime minister, promised with admirable frankness when he took over to rid the country of open defecation（缺陷）. Four and a half years and some $9 billion later, his Clean India campaign claims to have sponsored the building of an astonishing 90 million toilets. This is impressive, but India is still not clean. Its skies, its streets, its rivers and coasts will remain dangerously dirty until they receive similar attention.

    Bus Tours in Washington DC

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    Duration: 3 hours $56.99

    BEST WAY to Experience the Cherry Blossoms! Each year from mid March to mid April, see the beautiful Cherry Blossoms in Washington DC and get great photos because you'll be led to all the best spots by the best guides. The annual spring bloom in DC is a magical time and this tour promises to provide the very best tour opportunity for you!

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    Duration: 3 hours $56.33

    Highest-rated Night Tour in DC! The ONLY DC Night Tour where the Tour Guides HOP OFF with you at each stop and tell you about each monument and attraction. HOP aboard the The Lights Night Tour! The best time to take a tour of Washington DC is at night.

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    Duration: 3 hours $ 46.92

    See all the key attractions DC has to offer in a 3-hour format. You will learn all about the history and trivia (琐事) that surrounds Washington and visit the major monuments and attractions DC has to offer.

    Please Note: Rates for this tour vary by day of the week. When you choose your specific date on the availability calendar, the rates for that date will be displayed.

Best Mount Vernon & Arlington Cemetery Tour from Washington DC

    Duration: 6 hours $ 78.96

    See Arlington Cemetery, Old Town Alexandria and George Washington's Mount Vernon Estate on this small group bus tour from Washington DC. Your tour guide will accompany you through Mount Vernon, telling you about all of the attractions there and the history of George Washington's home on the Potomac River.