No one is sure how the ancient Egyptians built the pyramids near Cairo. But a new study suggests they used a little rock‘n'roll. Long-ago builders could have attached wooden pole s to the stones and rolled then across the sand, the scientists say.
“Technically, I think what they're proposing is possible,” physicist Daniel Bonn said.
People have long puzzled over how the Egyptians moved such huge rocks. And there's no obvious answer. On average, each of the two million big stones weighed about as much as a large pickup truck. The Egyptians somehow moved the stone blocks to the pyramid site from about one kilometer away.
The most popular view is that Egyptian workers slid the blocks along smooth paths. Many scientists suspect workers first would have put the blocks on sleds(滑板). Then they would have dragged them along paths. To make the work easier, workers may have lubricated the paths either with wet clay or with the fat from cattle. Bonn has now tested this idea by building small sleds and dragging heavy objects over sand.
Evidence from the sand supports this idea. Researchers found small amounts of fat, as well as a large amount of stone and the remains of paths.

However, physicist Joseph West thinks there might have been a simpler way , who led the new study . West said , “I was inspired while watching a television program showing how sleds might have helped with pyramid construction . I thought , ‘Why don't they just try rolling the things?'“A square could be turned into a rough sort of wheel by attaching wooden poles to its sides , he realized . That , he notes , should make a block of stone” a lot easier to roll than a square”.
So he tried it.
He and his students tied some poles to each of four sides of a 30-kilogram stone block. That action turned the block into somewhat a wheel. Then they placed the block on the ground.
They wrapped one end of a rope around the block and pulled. The researchers found they could easily roll the block along different kinds of paths. They calculated that rolling the block required about as much force as moving it along a slippery(滑的)path.
West hasn't tested his idea on larger blocks, but he thinks rolling has clear advantages over sliding. At least, workers wouldn't have needed to carry cattle fat or water to smooth the paths.

    I had arrived at the airport to catch an early flight home.It had been a very busy three days for me on an interstate trip with lots of meetings，business to do and new customers to meet.Then came the announcement that the flight had been delayed due to a technical problem.I could see a group of technicians and ground staff rushing about，obviously trying hard to fix the problem.I watched and listened as many of the passengers sitting near me shared their frustration about the inconvenience.

    As I sat waiting，I reflected on my last meeting for the day.It was not a business meeting but rather a very enjoyable and brief lunch with an old business associate and friend I had not seen for over 12 years，and who I had worked with for nearly 15 years before we lost in touch.I had been given his phone number by a customer I had visited on the first day of my trip，so I called him out of the blue and made a time for us to meet.

    Our lunch was spent recollecting(回忆) times gone by and as well filling each other in on what had happened in our lives over the last 12 years.Our conversation was frequently interrupted with statements such as 'remember when we did...'，'whatever happened to...' and of course the one we all liked to hear...'you know you haven't changed one bit，except for a few more grey hairs.'

    We both laughed and smiled as we recalled the good times and the great experiences we had shared over the 15 years we had worked together. Each event we discussed caused another recollection and everything we talked about centered on the good times.Almost at the same time，right at the end of our time together，we both said how much we both enjoyed it and that we must do it again.We agreed to catch up when I was next in town，then said our goodbyes and I was off to the airport.

    So with this extra time on my hands as I waited for my flight，it was great to revisit and replay in my mind all that we had talked about over lunch.I realized at that moment just how important it is to have regular reminders of the good times in your life and to be able to take the time to recall the past，for so much of what we have done in our past，shapes us and makes us who and what we are today and beyond.

    At the end of my busy trip with the focus on getting all the business done，I was indeed fortunate enough to have had the chance to take a short break and reflect on the good things that had happened in my life over 12 years ago.It was somewhat like looking at an old photo album that you have found stored away in a cupboard in your house.There before your eyes are lots of wonderful memories in print that take you back to that time and place，and most importantly to those people who are in the photos.It also made me realize that when you get caught up doing what has to be done in the moment，it is easy to forget the people you have met in your life who have made a positive effect on and enriched you，often in only the smallest of ways.

    My flight home was finally called nearly three hours later and yes as you would have expected many of the passengers cheered when the announcement was made.I smiled as I boarded the plane and realized that I was not at all upset about the delay，as I had been able to spend much of my time reflecting on the good times from days gone by and now eagerly look forward to many more opportunities to recall the past.

    Feifei, an 11-year-old boy from Xuzhou, Jiangsu Province, suffered from a sudden acute eye disease which has almost led to blindness. The disease was caused when he overused his eyes during the winter vacation, during which he played computer games for continuous 10 days and nights.

    Many youngsters in China nowadays are increasingly addicted to computer games and other electronic products. This is followed by a series of health problems, with the most typical case being myopia, or nearsightedness.

    According to the latest research report released by the World Health Organization (WHO),the myopia rate among Chinese teenagers ranks first in the world—70 percent of high school and college students. The rate is nearly 40 percent in primary school students, while it is only 10 percent for their peers in the United States.

    There are at least 10 million people in China with severe myopia, and they are likely to get pathological myopia（病理性的近视） in middle age. Pathological myopia can't be treated with glasses or surgery, and it is one of the biggest factors that lead to blindness, Xu Xun, an expert at Shanghai General Hospital, pointed out.

    Experts explain that two major factors lead to the high rate of myopia among Chinese people. One is high academic pressure, and the other one is excessive use of electronic devices over a long period of time. Genetics, on the other hand, are not the main reason, as only 20 percent of Chinese people had myopia in the 1960s.

    "Teenagers are now faced with severe academic pressure, which means they often study without natural light. This increases their risk of becoming nearsighted," Xu said. Experts suggest that youngsters maintain a proper balance between study and rest so as to protect their eyesight, and parents should play an active role in the process.

    Have you ever lost your car on a parking lot? You don't have a clue where your car is after shopping. Then you start walking around clicking on your car keys so the alarm goes off. It can be annoying, especially on a hot sunny day.

    No, you needn't install (安装) an expensive GPS system to keep track of your car. That's too expensive. You would need to pay a monthly fee to use it.

    But is there a way to track your vehicle without spending a fortune? Yes, now there is! A California-based company has created a tiny device that works with your smartphone, which could be exactly what you're looking for!

    What is it?

    It's called TrackR. It is a state-of-the-art tracking device the size of a coin. It's changing the way we keep track of the important things in our lives.

    How does it work?

    It's easy! Install the free TrackR app on your smartphone, connect the app to your device and you're ready to go! Simply attach TrackR to whatever you want to keep an eye on. The entire process of setting it up only takes 5 minutes or less.

    You can attach it to your keys, briefcase, wallet, your latest tech gadgets and anything else you don't want to lose. Then use the TrackR app to locate your missing item in seconds.

    If you forget where you have parked your car, pull out your smartphone and open the TrackR app. Tap on the “find device” button on the screen and the app will tell you the exact spot of the last known location of the TrackR.

    What else can I do with TrackR?

    The device is small and unnoticeable enough that you can attach it to your pet. Put it on their collar, and the issue of searching for them when they run away to nearby places will be over! You'll never waste a minute searching the whole house for it.

    TrackR even comes with a double-sided glue (胶水) so you can stick it to your laptop or under your bike seat. Track down and punish the thieves who steal your expensive things!

    How much does it cost?

    You're probably thinking that this device is very expensive. False! TrackR only costs $29! That's a small price to pay for peace of mind, isn't it?

    Where can I buy one?

    You can buy it directly from the company's website by clicking here https: //buy. thetrackr. co/gu/special- offers/15/.

    March 21 has been declared World Sleep Day, a time to recognize and celebrate the value of sleep. Many sleep experts hope it will be a wake-up call.

    According to a 2016 poll（民意调查）by the National Sleep Foundation, nearly 4 in 5 Americans don't get as much sleep as they should during the workweek. On average, adults are thought to need at least eight hours of sleep a night, although some can manage with less and some won't do well without more. But the survey found that, on workdays, only 21% of Americans actually get a full eight hours of sleep, and another 21% get less than six.

    To many of us, the thought of spending more time sleeping is, well, a big yawn. On the other hand, the thought of being smarter, thinner, healthier and more cheerful has a certain appeal. And those are just a few of the advantages that can be ours if we consistently get enough sleep,  researchers say. Also on the plus side： We're likely to have better skin, better memories, better judgment, and, oh, yes, longer lives.

    "When you lose even one hour of sleep for any reason, it influences your performance the next day, " says Dr. Alon Avidan, director of the UCLA Sleep Disorders Center.

    A study published last year found the same to be true even of children.  When kids aged 8 to 12 slept for just one hour less for four nights, they didn't function as well during the day.

    But sleeping has an image problem. "We see napping or sleeping as lazy, " says Jennifer Vriend, a clinical psychologist in Ottawa, Canada, and the leading author of the study with children. "We put so much emphasis on diet, nutrition and exercise. Sleep is in the back seat. " In fact, she adds, no matter how much we work out, no matter how well we eat, we can't be in top physical shape unless we also get plenty of sleep.

    A new restaurant in Indonesia is on a mission (使命) to support locals trapped in poverty, many of whom are earning less than $25 a month, by providing them with an alternative way to pay for their food.

    The Methane Gas Canteen, run by husband and wife team Sarimin and Suyatmi, is located in an unexpected place for an eatery — Jatibarang Landfill. The landfill is a mountain of purifying waste, where poor locals spend their days collecting plastic and glass to sell. Meanwhile, the couple, who spent 40 years collecting waste before opening the restaurant, is busy cooking.

    What makes the restaurant unusual, aside from its location, is that no cash is required to pay for meals. Poor people have the option to pay for their food with recyclable waste instead of cash. Sarimin weighs the plastic customers bring in, calculates its worth, and then deduct that value from the cost of the meal, giving any extra value back to the customer. The scheme is part of the community's solution to reduce waste in the landfill and recycle non-degradable plastics.

    “I think we recycle 1 tonne of plastic waste a day, which is a lot. This way, the plastic waste doesn't pile up, drift down the river and cause flooding,” said Saimin. “It benefits everyone.”

    The restaurant seats about 30 people and serves meals that cost between $0.40 and $0.80 each. Since opening the canteen Sarimin and Suyatmi have seen their daily income more than double to $15 a day.

    “I'm happy to see our customers enjoying their meals,” Sarimin told NHK World. “The poor must also have the right to enjoy healthy eating. I want to give them that chance as much as possible.”