The relativistic mass of light? - Science Forum

Moderator Joined: Jun 21, 2005 Posts: 271

The argument is that light has no rest mass but has
mass by virtue of its motion.

But its motion isn't relative. If its mass comes from
its kinetic energy or speed then all light particles would
have the same mass.

Not a valid argument you see.

Mentor Joined: Jun 21, 2005 Posts: 94

Moderator Joined: Jun 21, 2005 Posts: 271

The relativity of the energy of light is directional.
The Doppler shift on light can make the wavelength
grow(lower energy) if you are moving away from
the light source; or it can make the wavelength shrink
(higher energy) by moving toward it.

This is only energy. Its not necessarily mass in
my opinion.

It is interesting to note that for accelerated matter
relativistic mass goes up regardless of direction of
motion. Cool

Mentor Joined: Jun 21, 2005 Posts: 94

Moderator Joined: Jun 21, 2005 Posts: 271

If light's mass comes from its motion frankinstien
then all light would have the same amount of mass.
The motion of light isn't relativistic. So its "relativistic"
mass can't come frome any "constant" motion.

The mass would have to be in the wave. But if there is
motion toward the source it would have more mass/energy
than when there is motion away from the source.

So the relativistic energy/mass of light depends on whether
you are moving toward or away from the source of light.

You are misusing rest mass for light.
It is not that it is zero. It is that it doesn't even exist
at all(or null set). You can't bring light to rest. If you
did it would be energyless. And energyless light doesn't
even exist.

Thankyou frankinstien.

Mentor Joined: Jun 21, 2005 Posts: 94

Moderator Joined: Jun 21, 2005 Posts: 271

You are still misusing rest mass for light.
It doesn't even exist. Its not even zero!

About light becoming rest mass?
That would be light transforming into
matter. It is no longer light so it
doesn't apply frankinstien.

Mentor Joined: Jun 21, 2005 Posts: 94

Moderator Joined: Jun 21, 2005 Posts: 271

If light can never be brought to rest you can't say
anything about it. Rest mass here simply doesn't exist.

Its mass comes from its wave not its motion.
Since its waves are relative that is where
its relativistic mass comes from.

Rest mass doesn't apply to lights motion at all.
And you can't apply it to waves.
So I am sorry but you are the one who is confused here!

Mentor Joined: Jun 21, 2005 Posts: 94

Moderator Joined: Jun 21, 2005 Posts: 271

I know that its hard to find that a widely accepted argument
is wrong frankinstien. I see the rest mass argument is
wrong.

Light doesn't have mass simply because it moves.
It has mass because it waves.

Expert Joined: Nov 17, 2004 Posts: 158 Location: Egypt

Naturally, that semantic confusion has its roots in duality and wrong conception of the corpuscular nature of light quanta called photons. Photons do not exist prior to wave action on matter, such as in the photoelectric effect. Light propagates in the form of waves only.
The moving particle energy equation is defined as:

E = sqrt(m^2.c^4 + p^2.c^2)
Where:
m is the mass at rest with the system measuring the energy.
p is the momentum
c is a constant scalar of the speed of light in vacuum.
E is the total energy.

This means that for a stationary corpuscular body at rest, there is no momentum of motion, hence:

E = mc^2

For a massless wave quanta that may never be at rest we get:

E = pc
Since c is not a vector, then the direction of interaction is irrelevant.
There is no such thing as "the relativistic mass of light", because light propagates as a wave and does not stop.
This means that the corpuscular quantification is in the energy transfer, where:

p = h.nu/c = h/lambda
then:

E = pc = h.nu, which we may call the frequency of action quanta.

Amazingly, the variance of frequency is obtained equally if we follow the SR second postulate when saved by Lorentz transformations to vary the time and length scales, or by an anti-relativistic classical formalism postulating the variance of the relative speed of light while keeping the created wavelength invariable.
In other words, the wavelength is critical but irrelevant to the frequency of quanta as much as the velocity of light is critical but irrelevant. One quantity varies to compensate for the invariance of the other to yield are variant frequency of action quanta, to which variance in energy of waves is accounted for.
_________________
Hemetis

Moderator Joined: Jun 21, 2005 Posts: 271

I see you don't believe in relativistic mass coming
from the wave either Hemetis?

I find that no one can prove light doesn't have mass.
As science isn't about proof but disproof alone.

I believe that for the momentum of light you can
use either mass or energy.

If you use wavelength or frequency you would not
be precluding the use of mass simply because the
mass of light would be in its wave in the first place!

How do you like that?

Expert Joined: Nov 17, 2004 Posts: 158 Location: Egypt

Nick, you certainly know the simple classical Newtonean equation:

F = m * a
Mass never had any physical essence as being "The quantity of material in a body".
If you accepted that definition of mass, then light is not even a body to begin with, right?
Now let us redefine mass by its dynamic indicators rather than the static appearance.

M = F / a, which reads: Mass is the force per acceleration.

What! How about the inertial mass! Wink

Mass = Momentum / velocity
What I am saying is that why would you look for a derived phenomena if you had the fundamental one!
We know that we may not hold a lump of photons in our palm to feel the quantity of metrical in a body.
That is why as much as the energy of light is the product of its momentum and its velocity so is its mass a ratio between its momentum and its velocity.
The conclusion is that neither Energy nor Mass are as fundamental as Momentum and Velocity and even the later two are derived from Force, Length and Time dimensions.
_________________
Hemetis

Moderator Joined: Jun 21, 2005 Posts: 271

Hemetis.
The wave is the body of light.

Momentum and velocity aren't a wave.

The mass/energy is in the wave!

Mass is fundumantal. I see it is not a derived
phenomenon. What are you getting at? Question

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