Here's why:

* Mechanical waves require a medium: They need a substance (like air, water, or a solid) to travel through. The particles in the medium vibrate and transfer energy from one particle to the next.

* Examples: Sound waves, water waves, and seismic waves are all examples of mechanical waves.

In contrast, electromagnetic waves do not require a medium to travel. They can move through a vacuum (like space). Examples include light, radio waves, and X-rays.