[lightarrow]

You're forgetting the relationship E = mc² which means that whatever has inertial energy E has inertial mass m and what has inertial mass m has inertial energy E.

And with this do you think to have proved that a photon (which has an energy E) warps spacetime?

[Pmb]

And with this do you think to have proved that a photon (which has an energy E) warps spacetime?

Since I've just spent an inordinate amout of time in another thread where all I did was to post proofs and you to claim they weren't correct. Homey don't play that game no more.

This time around please just state whether it will or won't and what it means to warp spacetime and what that has to do with the subject at hand. Then I might respond. Then answer me this. If a pulse of light could generate a gravitational field could a photon?

The reason I ask is because there is no well accepted theory of quantum gravity, hence the reason I never bothered to learn any of it. Since a photon is a quantum particle one needs quantum gravity to properly answer it. Instead let's talk about a pulse of light of energy E and momentum p and thus has a proper mass of zero.

Tell me lightarrow - Does it generate a gravitational field? If yes, then why. If no, then why not?

[AndroidNeox]

I'm going to say this one more time and only one more time - Please stop confusing the fact of whether a photon has mass or not.

Perhaps this would be a good topic for a FAQ list? Maybe include half a dozen links to good explanations (your ArXiV posting would should be on the list, I think: http://arxiv.org/pdf/0709.0687v2.pdf)... sometimes one explanation will "click" for one person but not another. For example, I often need to convert equations to physical models to understand how something works.

[Pmb]

Good idea. There are a few more pages to add.

http://www.phys.ncku.edu.tw/mirrors/physicsfaq_old/Relativity/SR/mass.html
http://home.comcast.net/~peter.m.brown/sr/inertial_mass.htm
http://home.comcast.net/~peter.m.brown/sr/invariant_mass.htm
http://home.comcast.net/~peter.m.brown/sr/long_trans_mass.htm
http://home.comcast.net/~peter.m.brown/gr/active_grav_mass.htm

I was going to make another one for passive gravitational mass but never got around to it. The first link is the best one.

[lightarrow]

And with this do you think to have proved that a photon (which has an energy E) warps spacetime?

Since I've just spent an inordinate amout of time in another thread where all I did was to post proofs and you to claim they weren't correct. Homey don't play that game no more.

This time around please just state whether it will or won't and what it means to warp spacetime and what that has to do with the subject at hand.

It has to do with the subject because it was AndroidNeox to write that "Light has no rest mass, but it has momentum. Momentum is what generates gravity", and he was answering me about photons.

Then I might respond. Then answer me this. If a pulse of light could generate a gravitational field could a photon?

Do you still believe a photon is a "corpuscle localized in spacetime"? It's something very different.

The reason I ask is because there is no well accepted theory of quantum gravity, hence the reason I never bothered to learn any of it. Since a photon is a quantum particle one needs quantum gravity to properly answer it.

At last you have written it. But not that I hade any doubt you knew it, it's only that you don't seem aware of how people could get confused, because they so easily make the association "photon = corpuscle".

Instead let's talk about a pulse of light of energy E and momentum p and thus has a proper mass of zero.
Tell me lightarrow - Does it generate a gravitational field? If yes, then why. If no, then why not?

If that energy were continuously present, as in the case of a continuous light beam, I know it generates gravity, but in the case of a pulse, I actually don't know.
I'm tempted to say yes, because when the pulse crosses a specific volume of space, the energy and momentum temporarily present inside that region should do it:

 = 8 and in the tensor there are terms which refers to energy, momentum, ecc:
http://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor

But actually I don't know.

[lightarrow]

Maybe?
Are you defining a single photon/lightquanta as having a spectrum Lightarrow?

Exactly. How broade its spectrum is, depends on how short was the time interval of its emission: a photon emitted by an axcited atom's electron which returns in its fundamental state in t seconds has a spectrum which broadness is proportional to 1/t. Lasers use electronic transitions called "metastables" because they are so stable the transition occurs in a much longer time; this means that the spectrum is very monocromatic

That should be from a wave perspective if so, right? As you say it has what we call Spin/polarization but thinking of it, all of those definitions come from treating photons as waves, don't they?

To say "treating them as waves" is very restrictive; you should say "treating them quantomechanically" (which is the only way to treat photons, at least to me, but this is still under discussion  [] ).

You made me think, and wonder, some more there Lightarrow
How many photons does it take to measure a linear polarization? 

Photons never stop to amaze me too...