Here's why:

* Electromagnetic radiation consists of oscillating electric and magnetic fields that propagate as waves. These waves do not require a medium (like air or water) to travel and can move through the vacuum of space.

* Mechanical waves like sound waves, water waves, or seismic waves require a medium to travel. They are caused by the vibration of particles within a medium, and without a medium, they cannot propagate.

Examples of electromagnetic radiation:

* Light (visible light)

* Radio waves

* Microwaves

* X-rays

* Gamma rays