在PTE中,无论是Summarise Spoken Text 还是 Re-tell Lecture的考题大都是从真实的讲座或者演讲中截取的,中间经常经常夹杂很多不同的环境音.很多同学都反映有时未必是听不懂,而是听不到. 鉴于此,墨尔本文波雅思PTE专门为大家总结了真实讲座的PTE练习音频,相比新闻音频来说,整体更加接近PTE考试的真题,内容方面,我们也会为大家提供考试中存在的近似题,最近我们会持续更新,敬请期待!
What do you do if you want a better ticker, what do you do especially if you want a really good ticker that is the same for every clock you might make with ticker. Here, every ticker is a little bit different and the answer is atoms. Atoms tick, they have characteristic frequencies and we can use that those characteristic frequencies or vibrations to run at an atomic clock. The great thing about atoms is that every atom of the same kind is absolutely identical to every other atom of that same kind. The atoms that we use in atomic clocks are cesium 137 if you remember from your chemistry classes. It’s on the left hand side of the Periodical Chart, down toward the bottom. It’s a metal that burns in the air, but we put it in a vacuum so we don’t have to worry about that. But every cesium atom in the world in the entire universe, as far as we know is absolutely identical to every other cesium atom and therefore anybody makes clock using cesium atoms, is going to be getting the same ticking frequency. Every quartz crystal is a little bit different from every other quartz crystal. Now for less than 100 dollars, you can get a quartz watch. It’s good to 30 seconds in a year. But for 100,000 dollars, you can get a clock is good to 30 seconds in a million years. Now you laugh, you’re thinking 10,000 dollars for a clock. But think about this, you pay 100 dollars for a 30 second-year clock, you pay 100,000 dollars for a 30 second in a million-year clock. Thousand times more money, million times better performance. That’s a bargain in my book.