Re: Photon bend another photon


Randy M. Dumse wrote:
<rambus2005@xxxxxxxxx> wrote in message
news:1156001002.217451.177670@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Nice post. A small correction, though, the "box full of photons" is a
bad example. What you are measuring is the effect of the increased
"pressure radiation" which manifests itself as a measurable force,
not the increased mass of the system.


Thanks. I hear, and appreciate, your objection. I even worried a bit
about putting it as I did. Notice I had choosen mass-energy, as opposed
to the more correct stress-energy, to more easily be understood by the
current audience. I also included a pressure comment to keep the door to
larger concepts open. So you are right that in this example pressure
plays the major role.

But I don't know if I am comfortable saying the mass of the system does
not increase. I feel if I left out the box completely, and the "system"
was just the two (antiparallel) photons it would still have mass.

But given the box is closed, you don't know what's inside. You can
measure the mass of the system. Weight it, or try to accelerate it. In
either case, it exhibits mass. Calling it mass, or calling it "pressure
radiation manifesting itself as a measurable force" seem just two ways
of looking at the same thing due to equivalence.

Would you call the "mass without mass" of Wheeler's geon due to pressure
radiation? I wouldn't. Would radiation thrown down a black hole increase
it's radiation pressure component? or does it just become "mass".

So I don't see the mirrored box as a terribly bad example, just one
complicated by the presence of the mirrored box, to make it is easier to
conceptualize two photons as a system. The mirrors help us imagine them
remaining in close proximity.

--
Randy M. Dumse

Caution: Objects in mirror are more confused than they appear.

I thought a lot about it, I think that I much prefer "pressure
radiation". Let me ellaborate a little, in the case of the "didactical"
"mirrored box" I have done the calculations and it is an added force
(tangential to the walls of the box) that acts as "increased inertia".
In fact it acts as an internal FRICTION force that opposes WHATEVER
external forces trying to move the box in WHATEVER direction. That is,
the internal pressure radiation, generates such an internal friction
force ANYTIME one tries to move the box.The direction of the force
coincides with the direction of the external forces and the sense is
always opposite, exactly like friction. In the absence of any external
forces applied to the box the photons introduced in the box are
UNDETECTABLE.
The "friction" due to pressure radiation can also happen in the ABSENCE
of an external gravitational field, this is why I object to having it
made equivalent to gravitational mass.All you need is an arbitrary
external force in order for the photons to "show up" in the form of
internal friction.

.

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