Light and Mass
Name: Sonya L.
okay, I've been telling my students that light doesn't
have mass. That it is the only thing that doesn't because this is what I
learned. However, a friend told me that they are deflecting light in a
wind tunnel at NASA could this be correct? Does electromagnetic
radiation have mass?
It is true that light does not have mass. However, it does have energy and
momentum. This is at the level of quantum mechanics. It is possible for
light to interact with charged particles, such as electrons. Momentum can
be transferred to the light and deflect it slightly.
Dr. Ken Mellendorf
Illinois Central College
Nope, you are right, light does not have mass. As far as I understand,
general relativity will not hold up if it does. I am not familiar with the
experiments you mentioned, so I do not know their implications. But if they
showed that light has mass, I am sure it would have caused enough of a stir
that I would have heard of it by now.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
Light does not have mass. It is not unreasonable that light would be
deflected in a wind tunnel by variations in air pressure, which would
result in variations in refractive index.
Hi, Sonya !!
I also learned that an electromagnetic wave (=EMW) does not
carry mass, but carries energy. But some other aspects
should also be considerated, like momentum, for instance.
An EMW exert pressure, what means, it has inertia.
Well, have you heard that Einstein has been in Brazil
some decades ago ? He was there because by that
time a star should be eclipsed by a very massive
body. In this case, the light should - according to his
theory - make a curve and deviate from its original direction,
so that you still will see the star although it was not
to be seen. And that is what happened by that time.
The light was deviated because of the gravity of the
very massive body in space.
So, this seems to prove that light has mass and was
deflected by the gravitational field of the body.The general
conception is - however - that EMW have no mass.
The famous Einsteins equation E=m.c^2 shows us
that mass is a very concentrated form of energy, as you
know. And EMW is energy.
Light is refracted in wind tunnels due to differences in the density of the
air as it flows around objects. As the density changes, so does the index of
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Update: June 2012