Awesome question! To answer it, we need to
understand what light is. First, let's start with
electricity and magnetism: it turns out that if
you have a magnetic field and wiggle it (that is,
you make it change in time), you can produce an
electric field. For example, if you take a magnet
and move it through a metal ring, the changing
magnetic field (from moving the magnet) will
create a current in the ring (you can try
something similar to this at home if you have a
magnet and a narrow metal tube: if you drop the
magnet through the tube, it will fall very slowly
due to currents being created in the metal).
Similarly, it turns out that if you have an
electric field and wiggle that, you can create a
So what does this mean? Well, say you
start with a varying electric field; then that'll
produce a magnetic field. But if that magnetic
field is varying, then it'll produce an electric
field, which will in turn produce a magnetic
field, and so on. So in this way, you can create
a self-sustaining wave of varying electric and
magnetic fields: an electromagnetic wave.
So, where does light come into this?
Well, we just described what light is: it's an
electromagnetic wave! And because the
electric and magnetic fields need to vary to
generate one another, the wave has to move; it
can't just sit still.
I hope these help!
Light travels in tiny packets called photons.
These packets aren't actually particles: they
don't have a mass. The exhibit may properties of
waves (diffraction for example, like why a shadow
is dark but not pitch black) but aren't really
waves either, since they can be "quantized."
Quantized means they can be counted, essentially,
whereas waves cannot necessarily be counted. This
is one of the ideas of quantum mechanics
(quantizing things). So, light moves because
the photon has wave-particle duality, in that it
acts like both a particle and a wave.
Electromagnetic waves move... because they are
waves. That sounds like a strange answer, but
think of ocean waves. You can't truly lock an
ocean wave in place and have it still be a wave,
traveling is inherent to what waves are. In short,
light travels because it behaves partly like a