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!
So there are two different types of isotopes. There’s stable isotopes like the one I just told you about which have no time information. There’s radiogenic isotopes which decay at a certain rate and so that’s how we know how old the earth is, right, that’s how we know how old mediates are by measuring the radioactive decay so there are ways people have used to be using dating techniques for using these radio genic isotopes in order to map out you know when the solar system first formed when the first solids in the solar system formed. So those are called calcium aluminum inclusions and they’re thought to be the first solid that forms in our solar system so we know how old those are and then we know how old the parent bodies of the contracts are and we know how old the earth is so using those sorts of dating techniques you can kind of getting a timeline for when we had tiny little specs, when we had more planetary sized to when the moon formed, that sort of timeline can absolutely be obtained.