Here's why:

* Mechanical waves are disturbances that travel through a medium. They are created by the vibration or oscillation of particles within that medium.

* The particles themselves do not travel long distances, but the energy is transferred from particle to particle. Think of a slinky: when you shake one end, the disturbance travels down the slinky, but the individual coils of the slinky don't move far.

* Without a medium to vibrate, there's nothing to carry the energy. This is why you can't hear sound in a vacuum – there are no particles for the sound waves to travel through.

Examples of mechanical waves:

* Sound waves: Travel through air, water, solids, etc.

* Water waves: Travel through water.

* Seismic waves: Travel through the Earth's crust.

Electromagnetic waves, on the other hand, do not require a medium. They can travel through the vacuum of space, as they are disturbances in electric and magnetic fields. Examples include light, radio waves, and X-rays.