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From: Darwin123 on 13 Mar 2010 22:07
On Mar 11, 7:23 pm, "I. F." <exformat...(a)gmail.com> wrote:
> hello,
>
> are you really sure that the mass of the photon is zero and that its
> speed is c, since photons have a variable energy and frequency, and
> that the frequency of the electron depends on its speed?
The rest mass of a photon is zero, so far as can be currently
measured. A photon has an inertial mass which is equal to its
gravitational mass. The inertial mass of a photon is not zero.
The inertial mass of a photon can not be zero since the photon
has a linear momentum and a kinetic energy.
The rest mass of a particle is the mass which would be measured in
the rest frame of the particle. Since the photon is never at rest in
any frame, it doesn't have a rest mass. The inertial mass is not
measured in the rest frame of the photon, since the rest frame of a
photon doesn't exist.
>
> its mass might be extremely low and its speed extremely close to c
That is correct. However, an upper bound to the rest mass of a
photon can be measured. If the rest mass of the photon is not zero,
the speed of a photon would be slightly less than "c". For this
reason, "c" should not be understood as the actual velocity of light.
It is an upper bound to speed in any inertial frame.
So far as can be measured with the current technology, the rest
mass is effectively zero.
From: BURT on 13 Mar 2010 22:25
On Mar 13, 7:07 pm, Darwin123 <drosen0...(a)yahoo.com> wrote:
> On Mar 11, 7:23 pm, "I. F." <exformat...(a)gmail.com> wrote:> hello,
>
> > are you really sure that the mass of the photon is zero and that its
> > speed is c, since photons have a variable energy and frequency, and
> > that the frequency of the electron depends on its speed?
>
>      The rest mass of a photon is zero, so far as can be currently
> measured. A photon has an inertial mass which is equal to its
> gravitational mass. The inertial mass of a photon is not zero.
>         The inertial mass of a photon can not be zero since the photon
> has a linear momentum and a kinetic energy.
>     The rest mass of a particle is the mass which would be measured in
> the rest frame of the particle. Since the photon is never at rest in
> any frame, it doesn't have a rest mass. The inertial mass is not
> measured in the rest frame of the photon, since the rest frame of a
> photon doesn't exist.
>
> > its mass might be extremely low and its speed extremely close to c
>
>       That is correct. However, an upper bound to the rest mass of a
> photon can be measured. If the rest mass of the photon is not zero,
> the speed of a photon would be slightly less than "c". For this
> reason, "c" should not be understood as the actual velocity of light.
> It is an upper bound to speed in any inertial frame.
>      So far as can be measured with the current technology, the rest
> mass is effectively zero.

Light can never be at rest. And all its energy of motion would come
from its constant motion of C. We know that light's energy is not a
constant but C is.
Light therefore has no kinetic energy or rest energy.

Light energy comes from its waving frequency.

Mitch Raemsch
From: Darwin123 on 14 Mar 2010 16:09
On Mar 13, 11:25 pm, BURT <macromi...(a)yahoo.com> wrote:
> On Mar 13, 7:07 pm, Darwin123 <drosen0...(a)yahoo.com> wrote:
>
>
>
> > On Mar 11, 7:23 pm, "I. F." <exformat...(a)gmail.com> wrote:> hello,

> Light therefore has no kinetic energy or rest energy.
>
Photons do not have a rest energy since they can not be at rest.
However, photons have kinetic energy. The energy of photons is
completely kinetic.
An electron energy is partly rest energy and partly kinetic
energy. However, a photon does not have rest energy. So the energy is
completely kinetic.
What happened to you? For a while, you were almost coherent. You
are back in the white noise.

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