英语听力：探索发现 科学新发现：我们的大气层-17（在线收听）

 You could use the balloons not just to go to the edge of the space as we do now,but go all the way over the line, and actually to use balloons or airships to go all the way into  space,space travel without rocket.Officially,  the atmosphere ends and space begins 62 miles up.This sounds high, bu t on a table top globe, that would only be as thick as a coat of varnish. And in reallity, the air extends out much farther.The atmosphere's lowest layer,the troposphere we live in,ends 40000 feet up, the cruising altitude of the airliners. Above are another 4 distinctive layers.They are seperated by the temperature,it's jus colder and colder and colder, that warms to nights host zero.And you start to get colder ,en,so whenever the temperature changes directions,you know you have made into anoter layer.First comes the stratosphere layer,a stable layer without strong winds.Then temperature in the messosphere plunges into minus 150 degrees Fahrenheit. Above that is the thermosphere, where the sollar readiation can push the thermometer back up to 4500 degrees.And finally,there is exosphere,an endless zone where the air molecues slowly thin out into the pure vicuum of space.The exosphere is really high, they actually detected the particles of the earth atmosphere on the far side of  the moon. As pile of balloons rise towards the space,they leave world we know far behind.