Here's why:

* Mechanical waves are disturbances that transfer energy through a medium. They do this by causing particles in the medium to oscillate or vibrate.

* Without a medium, there's nothing to vibrate or transfer energy to. Imagine trying to create a wave on a rope that isn't attached to anything – it wouldn't work!

Examples of media that mechanical waves travel through include:

* Solids: Sound waves in a metal bar, seismic waves in the Earth's crust

* Liquids: Sound waves in water, ocean waves

* Gases: Sound waves in air

Important Note: Electromagnetic waves, like light and radio waves, do not need a medium to travel. They can travel through the vacuum of space.