The information will travel like the compressional wave ahead of an earthquake, detectable only by special equipment.

这些信息将像地一样传播，只有特殊设备才能检测到。

These are longitudinal waves that have to travel through a medium.

这些是必须通过介质传播。

In the case of a longitudinal wave, the back-and-forth motion is more of a compression-and-expansion.

在情况下，来回运动更像是压缩和膨胀。

Sound, you'll recall, is a wave: a 'longitudinal' wave.

如所述，声音是一种： 。

But there are also longitudinal waves, where the oscillations happen in the same direction as the wave is moving.

但是也有，其中振荡发生在与移动方向相同方向上。

So the p wave and the s wave, and the different phases that move out from the site of rupture in the earth, are used by seismologists to locate the event.

地学家用、以及地球破裂部位移出不同阶段来定位地发生地点。

But sound is the other kind of wave: it’s a longitudinal wave, meaning that the wave’s back-and-forth motion happens in the same direction in which the wave travels.

但声音是另一种：它是一种，这意味着来回运动发生在与传播相同方向上。

Eventually, new experiments and ideas about light kept popping up — like that it's a transverse wave instead of a longitudinal wave like sound, and that it's a form of electromagnetic radiation.

最终，关于光新实验和想法不断涌现——比如它是而不是像声音一样，它是电磁辐射一种形式。