Re: Photon, Momentum, Mass

On Apr 20, 4:21 am, John Kennaugh
<J...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Y wrote:
Ok first I'd like to say thank-you to those who responded to my last
post. I kind of get whats going on now with the different frames of
reference.

But what still has me confused is this idea that a photon can be
regarded at times to have a 'relativistic mass', while also having no-
mass at other times. What I mean is this, does a photon change its
behavior from a particle of mass to a particle of no-mass ?

How was it determined that light exerts pressure on objects ?

and,

If light has this 'relativistic mass' is it a constant value, or does
it change ?

I have read that if light is contained within a box with perfect
mirrors then it is considered that light adds mass to the box, and
that there is energy but no momentum within the box's frame of
reference. This is in contrast to freely moving moving particles.

So, what happens when light is moving freely, then it gets trapped
into the box then escapes the box.

Does this mean the photons of that light go from having no-mass to
having mass within the box, to having no-mass again when its outside
the box ?

I mean to me, that sounds ridiculous.

You are studying the wrong subject and are posting to the wrong
newsgroup if you want anything to appear sane. Relativity is based upon
the assumption that the speed of light is constant w.r.t the observer
observing it no matter how far away the source is nor how long ago the
light set out. This is clearly absurd.

No.

Special relativity is based upon the principle of relativity and the
demand that Maxwell's equations be invariant. Constancy of light speed
is not a required postulate - it is derivable from the previous two.

You may think it is absurd, but nobody cares. Relativity is supported
by experiment.


According to relativity anything with mass increases its mass as its
speed increases until it becomes infinite when it reaches the speed of
light c. Therefore if you accept relativity a photon cannot have any
mass because if it had it would have to be infinite. OTOH a photon has
energy and energy and mass are equivalent. The result is that they
invent a different sort of mass which isn't really mass but behaves like
mass when they need it to .........

E = mc^2 means there is an equivalence between mass and energy, not
that they are the same thing.


--
John Kennaugh


.

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