PTE考生目前最大的问题之一就是练习题缺乏。除了有限的基本官方书（PLUS，Testbuilder, OG）之外，就没有题了。很多英语基础不是很扎实的同学很难找到练习材料。墨尔本文波雅思PTE培训学校专门为墨尔本，悉尼PTE考生准备了适合PTE听力阅读练习的科学60秒。各位PTE同学可以练习PTE听力中的summarise spoken text和PTE口语中的retell lecture，练习记笔记技巧和复述。废话少说，下面开始：
Air Pollution Could Reveal ET’s Home
60秒科学节目（SSS）是科学美国人网站的一套广播栏目，英文名称：Scientific American – 60 Second Science,节目内容以科学报道为主，节目仅一分钟的时间，主要对当今的科学技术新发展作以简明、通俗的介绍，对于科学的发展如何影响人们的生活环境、健康状况及科学技术，提供了大量简明易懂的阐释。
Searches for extraterrestrial intelligence have focused on various signs of life. And one signature of alien intelligence may be, cough, cough, air pollution.
NASA’s James Webb Space Telescope, due to launch in 2018, should be powerful enough to detect chlorofluorocarbons, CFCs. These ozone-destroying chemicals are used in aerosol sprays on Earth. Maybe another planet’s denizens also employ them.
A new analysis of this idea notes that aliens would have to be heavy users. The Webb scope could only detect the chemicals if they were 10 times more prevalent than here on Earth. And even then, the planet would have to orbit a special kind of star, a white dwarf, for the CFCs to show up. White dwarfs—the ultimate destiny of stars like the sun—maximize the pollution signal.
The study is in the Astrophysical Journal. [Henry W. Lin, Gonzalo Gonzalez Abad and Abraham Loeb, Detecting industrial pollution in the atmospheres of Earth-like exoplanets]
CFCs could hang around in a planet’s atmosphere for a long time. So if an extraterrestrial civilization wised up and stopped polluting, we might still see the effects. Even a society that managed to destroy itself long ago could leave a chemical trace. Let’s hope that’s not how they discover us.