Unless we spend money to spot and prevent asteroids(小行星)now，one might crash into Earth and destroy life as we know it，say some scientists.
Asteroids are bigger versions of the meteoroids(流星)that race across the night sky. Most orbit the sun far from Earth and don't threaten us. But there are also thousands whose orbits put them on a collision course with Earth.
Buy $ 50 million worth of new telescopes right now. Then spend $ 10 million a year for the next 25 years to locate most of the space rocks. By the time we spot a fatal one，the scientists say，we'll have a way to change its course.
Some scientists favor pushing asteroids off course with nuclear weapons. But the cost wouldn't be cheap.
Is it worth it? Two things experts consider when judging any risk are: 1) How likely the event is; and 2) How bad the consequences if the event occurs. Experts think an asteroid big enough to destroy lots of life might strike Earth once every 500，000 years. Sounds pretty rare-but if one did fall，it would be the end of the world. “If we don't take care of these big asteroids，they'll take care of us，”says one scientist. “It's that simple.”
The cure，though，might be worse than the disease. Do we really want fleets of nuclear weapons sitting around on Earth? “The world has less to fear from doomsday(毁灭性的) rocks than from a great nuclear fleet set against them，” said a New York Times article.
Believe it or not，optical illusion (错觉) can cut highway crashes.
Japan is a case in point. It has reduced automobile crashes on some roads by nearly 75 percent using a simple optical illusion. Bent stripes，called chevrons (人字形)painted on the roads make drivers think that they are d riving faster than they really are，and thus drivers slow down.
Now the American Association Foundation for Traffic Safety in Washington D.C. is planning to rep eat Japan's success. Starting next year, the foundation will paint chevrons and other patterns of stripes on selected roads around the country to test how well the patterns reduce highway crashes.
Excessive speed plays a major role in as much as one fifth of all fatal traffic accidents, according to the foundation .To help reduce those accidents，the foundation will conduct its tests in areas where speed - related hazards are the greatest - curves，exit slopes，traffic circles，and bridges.
Some studies suggest that straight，horizontal bars painted across roads can initially cut the average speed of drivers in half. However，traffic often returns to full speed within months as drivers become used to seeing the painted bar.
Chevrons，scientists say，not only give drivers the impress ion that they are driving faster than they really are but also make a lane appear to be narrower. The result is a longer lasting reduction in highway speed and the number of traffic accidents.
Amtrak(美国铁路客运公司)was experiencing a downswing in riders hip (客运量)along the lines comprising its rail system. Of major concern t o Amtrak and its advertising agency DDB Needham，were the long - distance western routes where ridership had been declining significantly.
At one time，trains w ere the only practical way to cross the vast areas of the west. Trains were fast，very luxurious，and quite convenient compared to other forms of transportation existing at the time. However，times change and the automobile became America's standard of convenience. Also，air travel had easily established itself as the fastest method of traveling great distances .Therefore，the task for DDB Needham was to encourage consumers to consider other aspects of train travel in order t o change their attitudes and increase the likelihood that trains would be considered for travel in the west.
Two portions of the total market were targeted: 1) anxious fliers - those concerned with safety，relaxation，and cleanliness and 2) travel - lovers - those viewing themselves as relaxed，casual，and interested in the travel experience as part of their vacation. The agency then developed a campaign that focused on travel experiences such as freedom，escape，relaxation，and enjoyment of the great western outdoors. It stressed experiences gained by u sing the trains and portrayed western train trips as wonderful adventures.
Advertisements showed pictures of the beautiful scenery that could be enjoyed along some of the more famous western routes and emphasized the romantic names of some of these trains(Empire Builder，etc.).These ads were strategically placed among family - oriented TV shows and programs involving nature and America in order t o most effectively reach target audiences. Results were impressive. The Empire Builder. Which was focused on in one ad. enjoyed a 15 percent increase in profits on its Chicago to Seattle route.
Why does cream go bad faster than butter? Some researchers think they the answer，and it comes down to the structure of the food，not its chemical composition - a finding that could help rid some processed foods of chemical preservatives.
Cream and butter contain pretty much the same substances，so why cream should sour much faster has been a mystery. Both are emulsions - tiny globules(小球)of one liquid evenly distributed throughout another. The difference lies in what's in the globules and what's in the surrounding liquid，says Brocklehurst，who led the investigation.
In cream，fatty globules and what's in the surrounding liquid，says Brocklehurst，who led the investigation. In cream，fatty globules drift about in a sea of water. In butter，globules of a watery solution are locked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the mixture.” This means that in cream，the bacteria are free to grow throughout the mixture，”he says.
When the situation is reversed，the bacteria are locked away in compartments (密封仓) buried deep in the sea of fat. Trapped in this way，individual colonies cannot spread and rapidly run out of nutrients. They also slowly poison themselves with their waste products.” In butter，you get a self - limiting system which stops the bacteria growing，”says Brocklehurst.
The researchers are already working with food companies keen to see if their products can be made resistant to bacterial attack through alterations to the food's structure. Brocklehurst believes it will be possible to make the emulsions used in salad cream，for instance，more like that in butter. The key will be to do this while keeping the salad cream liquid and not turning it into a solid lump.