How to deal with waste has been a problem since humans started producing it. As more and more people choose to live close together in cities, the waste-disposal (处理) problem becomes increasingly difficult.

    During the eighteenth century, it was usual for several neighboring towns to get together to select a faraway spot as a dump site. Residents or trash haulers (垃圾拖运者) would transport household rubbish, rotted wood, and old possessions to the site. Periodically (定期的) some of the trash was burned and the rest was buried. The unpleasant sights and smells caused no problem because nobody lived close by.

    Factories, mills, and other industrial sites also had waste to be disposed of (处理). Those located on rivers often just dumped (倾倒) the unwanted remains into the water. Others built huge burners with chimneys (烟囱) to deal with the problem.

    Several facts make these choices unacceptable to modem society. The first problem is space. Dumps, which are now called landfills, are most needed in heavily populated areas. Such areas rarely have empty land suitable for this purpose. Property is either too expensive or too close to residential (住宅区的) neighborhoods. Long-distance trash hauling has been a common practice, but once farm areas are refusing to accept rubbish from elsewhere, cheap land within trucking distance of major city areas is almost nonexistent (不存在).

    Awareness (意识) of pollution dangers has led to more strict rules of waste disposal. Pollution of rivers, ground water, land and air is a price people can no longer pay to get rid of waste. The amount of waste, however, continues to grow.

    Recycling efforts have become commonplace, and many towns require their people to take part. Even the most efficient recycling programs, however, can hope to deal with only about 50 per cent of a city's reusable waste.

    There's a trend that more city people decide that they want to grow crops and raise some live-stock (家禽). After all, there are few things more satisfying than biting into a bunch of tender, red carrots you grow yourself, or a fresh egg from the backyard.

    Most gardeners understand that the soil in big cities is often polluted with lead and know to get their soil tested. But most are pretty clueless about how to prevent other types of pollutants, like heavy metals and asbestos(石棉)from getting into their vegetables.

    Part of the problem is that “there might be pollutants that gardeners can't test for,” says Brent Kim, a program officer. Most soil tests look for lead, cadrniunt(镉)and arsenic(砷). But they don't test things like chemicals left behind by cars, which might have escaped into the soil.

    So if you're thinking of staring an urban garden, Kim says, once you've found a plot of land, you should learn what's now an empty plot or a backyard might once have been a parking lot, a gas station or a chemical ground. “Knowing its past will give you some idea about what might be in that soil,” he says.

    “People tend to think raised beds are going to solve their pollution problem,” Kim says. But polluted soil could easily kicked onto your plants, especially if the beds are low to the ground.

    “Another consideration is that you have to be careful about the materials that you're using to build a raised bed,” Kim says. Recycling wood from an old construction site might seem like a good, eco-friendly idea. But that wood could be treated with chemicals you don't want touching your fruits and veggies, Kim says. And it's always a good idea to use gloves while gardening, and wash all your produce thoroughly.

    “I see these urban growing spaces as these oases(绿洲)in the middle of these urban environments,” Kim says. “They bring communities together, and they help people save money on fresh produce. Urban growing spaces are amazing. Let's keep doing this, but let's do it safely.”

A

    In the summer of 1848, in Guatemala, a man called Ambrosio Tut went out into the jungle, as he did almost every day. Tut was a gum collector, looking for gum in the jungle. To do this, he had to climb the trees. One day, he got to the top of one tree and something caught his eye. He looked out across the trees and saw the tops of some old buildings.

    Tut didn't really know what he had seen but he knew it was something special. He ran to tell the local governor excitedly, and together they walked into the jungle. There they found Tikal, the city that the Mayans had built, many hundreds of years before. The two men saw pyramids, squares and houses.

    For a long time before that day, local people had known that somewhere in the jungle there was an old Mayan city. But no one had seen it for centuries. Between 200 and 900 AD, the city of Tikal had ben the centre of Mayan civilisation in the area, but then the Mayas let it—nobody knows why! After 1000 AD, the jungle began to cover it. And then people forgot that it was there.

    Seven years before Tut found Tikal, two British explorers had gone to Guatemala and had written a report about Mayan treasures in the jungle—but they hadn't mentioned Tikal. Even earlier than this, local Indians had told people about a great city hidden in the trees, but no one had listened to them. So they lost the chance to find the treasure. Now the lost city had been found again, and people went there immediately to see it.

    Sue Hendrickson is a self-taught fossil（化石）hunter. As a kid, Sue Hendrickson often walked with her head down. “People said, 'Look up. Smile!” she says. “Now, I realize I was born to look for things and just didn't know it.”

    Sue Hendrickson does more than look—she finds valuable things: Shipwrecks（沉船）with treasure, ancient sunken cities, and in 1990, she found Sue, the world's largest, most complete Tyrannosaurus rex（霸王龙）. Is Hendrickson lucky? Well, maybe. But she also knows how to look.

    “I limit the area where I'm going to look,” she says. No one knew the location of the sunken ship San Diego in the Philippines. For a year, Hendrickson and other researchers searched papers and sailors' diaries. “The descriptions of the ship's sailors led us to the wreck,” she says. The team also used a tool that can respond to metal. This tool found the San Diego. All the work paid off. The 400-year-old ship was complete, with valuable gold and silver coins.

    To find the dinosaur she calls “the biggest animal that ever walked on earth,” Hendrickson started with maps made to search for oil. What Hendrickson found was the largest and most complete T-rex found to date. The T-rex is 42 feet long with 200 bones! Because it is so complete, scientists were able to infer that Sue walked at about 6 miles per hour and did not run faster than 15 miles an hour. Before Sue was discovered, they thought T-rex was much faster. To learn more about T-rex Sue, go to the Field Museum in Chicago.

    There's plenty left to be found, Hendrickson says, including answers to mysterious such as how T-rex lived. “I tell kids that they need to grow up and work them out because all of us old persons haven't yet!”

    People say that text messages and e-mails lack emotion compared to phone or face-to-face conversations. But one thing seems to improve it – the emoticon(表情符).

    These little symbols – whether it's a wink(眨眼); -), a smiley : -) or a sad face : -) - always add a little something to whatever you are sending out, making it more expressive than cold words on a screen.

    To be sure, emoticons have changed the way that we communicate with each other. But there is more: a new study found that they are even changing how our brains work – we now react to emoticons in the same way as we would to real human faces, reported Live Science.

    It's actually amazing when you start to think about it: what an emoticon consists of is simply three punctuation marks(标点符号) – on their own, they carry no meaning as a pair of eyes, a nose or a mouth, but after they were first put together as symbols for faces in 1982, they began to appear more and more in our written materials.

    Owen Churches, a scientist at Flinders University in Australia, wanted to find out what people see in emoticons that make them so popular. So he showed 20 participants images of real faces, a smiley emoticon and a series of meaningless characters while their brain activities were monitored.

    Previous studies have already shown that our brains process human faces differently than they do other objects – they analyze the position of the mouth relative to the nose and the eyes to “read” for emotions. As a result, certain parts of our brain, such as the occipital-temporal cortex, are activated(激活).

    When Churches compared participants' brain activities, he was surprised to find that the brain areas that were activated when people looked at smiley emoticons were the same as when they were shown pictures of real faces.

    According to Churches, this is a good example of how culture is shaping our brains. “Emoticons are a new form of language that we're producing,” Churches told ABC Science. “Before 1982 there would be no reason that ':-)' would activate face-sensitive areas of the cortex, but now it does because we've learnt that this represents a face.”

    Next time you chat with your friends online, try to use emoticons where they are needed. It'll be almost like you're smiling or winking at them yourself.

Mark and his brother Jason both were looking at the shining new computer enviously. Jason was determined not to go against their father's wishes but Mark was more adventurous than his brother. He loved experimenting and his aim was to become a scientist like his father.

"Dad will be really mad if he finds out you've been playing with his new computer." said, "He told us not to touch it."

"He won't find out," Mark said, "I'll just have a quick look and shut it down."

Mark had been scolded before for touching his father's equipment. But his curiosity was difficult to control and this new computer really puzzled him.

It was a strange-looking machine — one his dad had brought home from the laboratory where he worked. "It's an experimental model." his father had explained, "so don't touch it under any circumstances." But his father's warning only served to make Mark more curious. Without any further thought, Mark turned on the power switch. The computer burst into life and seconds later the screen turned into colours, shifting and changing, and then two big white words appeared in the centre of the screen: "SPACE TRANSPORTER."

"Yes!" Mark cried excitedly. "It's a computer game. I knew it! Dad's only been pretending to work. He's really been playing games instead!" A new message appeared on the screen:

"ENTER NAMES

VOYAGER 1:…

VOYAGER 2:…

Mark's fingers flew across the keyboard as he typed in both of their names.

"INPUT ACCEPTED. START TRANSPORT PROGRAM. AUTO-RETRIEVE INITIATED. "

The screen turned even brighter and a noise suddenly rose in volume.

"I think we'd better shut it off, Mark," Jason yelled, reaching for the power switch. He was really frightened.

But his hand never reached the switch. A single beam of dazzling white light burst out of the computer screen, wrapping the boys in its glow, until they themselves seemed to be glowing. Then it died down just as suddenly as it had burst into life. And the boys were no longer there. On the screen, the letters changed:

"TRANSPORT SUCCESSFUL. DESTINATION: MARS. RETRIEVE DATE: 2025."