题目内容
Jupiter and Saturn are com worlds of the solar system.
查看答案
搜索结果不匹配？点我反馈
更多问题
听力原文： A country's latitude, or distance from the equator, has an important effect on its climate. In places located at low latitudes, or near the equator, like Ecuador and northern Brazil, the amount of sun shine changes the least during the year. At mid-latitudes, in places like Japan or Argentina, there is more sunshine in the summer than in the winter. The greatest change occurs at the highest latitudes, in places like northern Canada or Alaska. In these places, the nights are very long for half the year, and the days are long during the other half. At the North or South Pole, sunlight lasts the longest during the summer. But light and heat are the most intense at the equator.
Altitude and distance from the sea also affect climate. The thin air in high mountain areas absorbs less of the sun's heat than the thicker air at sea level. The daily changes in temperature also increase with distance from the sea.
Snow and rain are- very important to climate. Snow reflects as much as eighty or ninety percent of the heat from the sun, and makes the weather even colder, but a large forest area can reflect as little as five percent of the sun's heat. This makes the weather warmer.
Of course, the general effects of climate do not explain every thing about the weather. For example, both the driest places in the world and the place with the most rainy days are located in Chile. Calama, in the Atacama Desert, had no rain for over 400 years. But during the year 1916, it rained in Bahia Felix, Chile for 348 days.
(30)
"Feel out of sorts", as it is used in the second paragraph, could best be replaced by ______.
Electric Backpack
Backpacks are convenient. They can hold your books, your lunch, and a change of clothes, leaving your hands free to do other things. Someday, if you don't mind carrying a heavy load, your backpacks might also power your MF3 player, keep your cell phone running, and maybe even light your way home.
Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole, Mass., have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions, search-and-rescue operations, and scientific field studies, people rely increasingly on cell phones, global positioning system (GPS) receivers, night-vision goggles, and other battery-powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries, report Rome and his colleagues in the Sept. 9 Science.
The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal frame. The frame. sits against the wearer's back, and the whole pack moves up and down as the person walks. A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator, producing up to 7.4 watts.
Unexpectedly, tests showed that wearers of the new backpack alter their gaits in response to the pack's oscillations, so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage, Rome plans to commercialize both electric and non-electric versions of the backpack.
The backpack could be especially useful for soldiers, scientists, mountaineers, and emergency workers who typically carry heavy backpacks. For the rest of us, power-generating backpacks could make it possible to walk, play video games, watch TV, and listen to music, all at the same lime. Electricity-generating packs aren't on the market yet, but if you do get one eventually, just make sure to look both ways before crossing the street!
Backpacks are convenient because
Light Night, Dark Stars
Thousands of people around the globe step outside to gaze at their night sky. On a clear night, with no clouds, moonlight, or artificial lights to block the view. people can see more than 14,000 stars in the sky, says Dennis Ward. an astronomer with the University Corporation for Atmospheric Research (UCAR) in Boulder. Colo. But when people are surrounded by city lights, he says, they're lucky to see ISO stars.
If you've ever driven toward a big city at night and seen its glow from a great distance, you've witnessed fight pollution. It occurs when light from streetlights, office buildings, signs, and other sources streams into space and illuminates the night sky. This haze of light makes many stars invisible to people on Earth. Even at night, big cities like New York glow from light pollution, making stargazing difficult.
Dust and particles of pollution from factories and industries worsen the effects of light pollution. "If one city has a lot more light pollution than another." Ward says, "that city will suffer the effects of light pollution on a much greater scale."
Hazy skies also make it far more difficult for astronomers to do their jobs.
Cities are getting larger. Suburbs are growing in once dark. rural areas. Light from all this new development is increasingly obscuring the faint light given off by distant stars. And if scientists can't locate these objects, they can't learn more about them.
Light pollution doesn't only affect star visibility. It can harm wildlife too. It's clear that artificial light can attract animals, making them go off course. There's increasing evidence, for example, that migrating birds use sunsets and sunrises to help find their way, says Sydney Gauthreaux Jr., a scientist at Clemson University in South Carolina. "When light occurs at night," he says, "it has a very disruptive influence." Sometimes birds fly into lighted towers, high-rises, and cables from radio and television towers. Experts estimate that millions of birds die this way every year.
When can people see 14,000 stars？
微信支付 
支付宝支付