The nature of electromagnetic waves

• Perhaps in chemistry you have seen the bell jar demonstration.
• 
• A ringing bell is placed inside a bell jar, and can be heard to ring.
• As air is removed from the sealed jar with a vacuum pump, the sound of the ringing bell diminishes until it cannot be heard. The medium through which the sound wave travels has been removed. Thus sound waves cannot propagate through vacuum.
• But the demonstration also shows that light can propagate through a vacuum. How so?
• Here is an animation of a moving electric charge producing a changing electromagnetic field that propagates through space at c.
• 
• The crests and troughs of each wave move to the right at the speed of light c.
• Each region in space executes SHM in the form of oscillating E- and B-fields.
• The red arrows represent the electric field.
• The blue arrows represent the magnetic field.

A more smooth animation is shown here.

FYI
Each dot is in simple harmonic motion.