地震波与地球内部
Seismic Waves & Earth's Interior
区分纵波和横波：纵波是压缩波，能在固体和液体中传播；横波是剪切波，无法穿过液体。解释为什么与震中相对的地球另一侧会存在地震阴影带；说明地震学家如何利用地震波的折射和反射，推断出地球具有固态内核、液态外核、地幔和地壳。
Distinguish between P-waves (compression, travel through solids and liquids) and S-waves (shear, cannot pass through liquids); explain why a seismic shadow zone exists on the far side of an earthquake; describe how seismologists use wave refraction and reflection to infer that Earth has a solid inner core, liquid outer core, mantle, and crust
评估问题 / Assessment
{{name}}能解释一下，既然从来没有人钻探到那么深，科学家是怎么知道地球有一个液态外核的？地震波为我们了解地球内部隐藏的结构提供了哪些线索？
Can {{name}} explain how scientists know Earth has a liquid outer core if nobody has ever drilled that deep — what clues do earthquake waves give us about Earth's hidden interior?