|Is light matter? |
If it is, what form/state of
matter is it?
If it is not, why not?
|Question Date: 2004-01-20|
I'm not sure if other scientists would answer this
question the same why I do, but I think this is a
very philosophical question that depends on what
you mean by matter.
If you are asking if light
carries energy and momentum, the answer is
definitely yes. But perhaps you mean: is light a
Quantum mechanics makes this
question a little murky: everything, including
light, in quantum mechanics is both a particle and
a wave (really, it is a definite something that
has both wave-like and particle-like properties).
So if you think matter is something that is made
of particles, either everything is or isn't matter
depending on how you look at it.
In fact, I
think that is the wrong way to think about it.
What you really want to know is: does light have
properties that other kinds of particles don't?
The answer is yes. Most of the particles that make
up everything we traditionally call matter are
Things like photons are
called "bosons". There are many properties not
shared by fermions and bosons - one is that two
fermions cannot exist in exactly the same state.
Two bosons, on the other hand, can exist in the
same state. Though there are composite particles
made up of smaller fermions that behave as bosons,
the fundamental particles that are bosons - we
think they're fundamental, anyway - do behave
differently than the fundamental particles that
To make a long story short, these
differences in properties are responsible for the
way these particles manifest themselves at large
scales in the everyday world, where quantum
mechanics is not important. A boson appears as
some kind of field or wave, and can be directly
linked to one of the four forces
(electromagnetism, gravity, the strong force, and
the weak force) whereas fermions form individual
particles such as atoms.
So, there is
definitely a sense in which light is very, very
different than electrons or protons.
sure if I would call light matter or not, however.
Certainly it can do some of the things you would
think only traditional matter can do - like carry
momentum and transfer it in a collision. But it
certainly has some properties that are
fundamentally different than the stuff that makes
up traditional matter (things that are made of atoms).
Light is not matter. Light is just light --- it
has its own qualities. Light is made up of
"things" called photons, and these photons can
possess some of the properties of matter.
example, they are always moving, and when they
move, they can exert a (usually very small) force
on an object (just like moving matter can). But
most of the time, light is just light.
not matter as much as it is energy.
Light is a form of energy, not matter. Matter is
made up of atoms. Light is actually
electromagnetic radiation. Moving electric charge
or moving electrons (electric current) cause a
magnetic field, and a changing magnetic field
creates an electric current or electric field. So,
changing magnetic and electric fields interact
with each other and produce an electromagnetic
wave composed of two parts: a magnetic field and
an electric field.
has many forms: the visible light spectrum, UV
rays, radio waves, and x-rays to name a few. I
found all this information on a great website:
This is a fun question. There are two main
theories of thought about light. The first is
that light is a photon and the second is that
light is a wave. Neither theory has been proven
wrong. It would seem that photons would be matter
whereas the waves wouldn't. It turns out that for
both theories light isn't matter. A photon is not
matter because it has no mass. This is different
from matter such as electrons and neutrons which
have masses. I hope this helps.
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