Here's why:
* Seismic waves travel through Earth's interior. There are two main types of seismic waves: P-waves (primary) and S-waves (secondary).
* P-waves travel faster and through both solids and liquids.
* S-waves travel slower and only through solids.
* Earth's core is liquid. This means S-waves cannot travel through it.
* P-waves are refracted (bent) as they pass through the core. This creates a region on the opposite side of the Earth where neither P-waves nor S-waves are detected.
The shadow zone is a key piece of evidence that helped scientists understand the structure of Earth's interior.
