Here's why:

* Mechanical waves are disturbances that travel through a medium. This medium can be a solid, liquid, or gas.

* The particles of the medium vibrate or oscillate as the wave passes through. This vibration transfers energy from one particle to the next.

* Without a medium, there is nothing to vibrate and transmit the energy.

Examples of mechanical waves:

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

* Water waves: Travel on the surface of water.

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

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