If Photons Have no Mass......

[peter]

How come their path can be bent by gravity? What happens to them when you turn off the light (where do they go)? Could you (theoretically) capture light inside a one hundred percent efficient totally internally reflective sphere?

[Zarathustra]

Gravity curves space. Light is following a "straight" path through curved space. I assume light is absorbed, reflected, diffused by the surfaces it hits. So turning off the light just stops the production of more photons. But all the rest have already been absorbed etc. I don't know about the sphere idea. I assume there's no such thing as a 100% reflective anything.

[Vraith]

In the reflector, I'm pretty sure that even in the most perfect situation, Compton scattering will cause photon energy loss until eventually your sphere mirror and light universe reaches a heat-death state.
[[I think.]] So, yea, it's trapped in there...but ain't shit you can do with it.

[peter]

Yes but 'the rest have already been absorbed etc' - what does that mean? Photons travel at the speed of light don't they? It's that or nothing in the photon game as I understand it. And when I turn off my bedroom light surely the walls and sundry stuff in my room just don't hoover up all of the photons into the nuclei of their material - what would these photons do in there? Spin around at light speed knocking into things, cease to exist, get absorbed into the protons and neutrons of the above ( most likely I guess, but what effect does that have on the absorbing particle)?

[Vraith]

Yes but 'the rest have already been absorbed etc' - what does that mean? Photons travel at the speed of light don't they? It's that or nothing in the photon game as I understand it. And when I turn off my bedroom light surely the walls and sundry stuff in my room just don't hoover up all of the photons into the nuclei of their material - what would these photons do in there? Spin around at light speed knocking into things, cease to exist, get absorbed into the protons and neutrons of the above ( most likely I guess, but what effect does that have on the absorbing particle)?

They pass through, and/or get absorbed, and/or devolve to heat. You might think that would take a long time...
But you have to remember that, in a standard [u.s.] sized bedroom, the photon will reach a wall surface MORE than 50 MILLION times in a second. And even while that is happening, most of them...the ginormous majority of them, even the ones in the visible spectrum, will leave you totally in the dark---because they will never, ever, even indirectly/on the rebound interact with your eye.

[Wosbald]

+JMJ+

And when I turn off my bedroom light surely the walls and sundry stuff in my room just don't hoover up all of the photons into the nuclei of their material - what would these photons do in there?

They hang out. Have a few brewskis. Do photony things.

If they're not gettin' all up in my bidniz, I'm not gonna pry into theirs. Let the photons be, I say.

[peter]

I'll buy that Woz! ..........(but only after this) ..........

I've got to try to nail this V, what does 'gets absorbed' mean here? If I get it right a photon is a particle - a gauge boson ( I just checked ) - and particles interact with each other. I have trouble with the idea of photons just being sucked up by other particles and nothing happening to the latter as a result. Is this a case where the physicality of the photon and the energy it represents are simply one and the same thing (so that in absorbing the photon the absorbing particle simply jumps to a higher energy state). ie Mass and energy down at this level really are just the same thing (rather than being interconvertable)?

[Vraith]

I'll buy that Woz! ..........(but only after this) ..........

I've got to try to nail this V, what does 'gets absorbed' mean here? If I get it right a photon is a particle - a gauge boson ( I just checked ) - and particles interact with each other. I have trouble with the idea of photons just being sucked up by other particles and nothing happening to the latter as a result. Is this a case where the physicality of the photon and the energy it represents are simply one and the same thing (so that in absorbing the photon the absorbing particle simply jumps to a higher energy state). ie Mass and energy down at this level really are just the same thing (rather than being interconvertable)?

Things do happen.
Some photons don't hit shit, and just go on by. [you want a perfect reflector, but you can't have one. Sorry.]
But even if you did...when the photon interacts, totals must remain the same---but SOME is transferred. Kinda like billiard balls [kinda].
The "reflected" one is lower energy/wavelength.
Times 50 million per photon per second.
In reality, your reflector simply cannot reflect perfectly...it re-radiates in all directions, not just back in even IF it "intercepts" all photons and reflects all energy/wavelengths which it also cannot do.
A [near] perfectly reflective room would get dark much more slowly [at least from a photon point of view] but it would endarken [[you might perceive it as "boy it's getting dark...but I gotta take off this sweater in certain ranges/situtations]]
[[btw...absorption (why does absorb become ption not btion? I'll have to look that up. ) wavelength, re-radiation is EXACTLY why more CO2 in the atmosphere means warmer planet]]

[[and I'm sure there's lots of other crap going on in your sphericalmirrorverse, too]]

[peter]

Indeed V, could you but know........

[Skyweir]

Things do happen.
Some photons don't hit shit, and just go on by. [you want a perfect reflector, but you can't have one. Sorry.]
But even if you did...when the photon interacts, totals must remain the same---but SOME is transferred. Kinda like billiard balls [kinda].
The "reflected" one is lower energy/wavelength.
Times 50 million per photon per second.
In reality, your reflector simply cannot reflect perfectly...it re-radiates in all directions, not just back in even IF it "intercepts" all photons and reflects all energy/wavelengths which it also cannot do.
A [near] perfectly reflective room would get dark much more slowly [at least from a photon point of view] but it would endarken [[you might perceive it as "boy it's getting dark...but I gotta take off this sweater in certain ranges/situtations]]
[[btw...absorption (why does absorb become ption not btion? I'll have to look that up. ) wavelength, re-radiation is EXACTLY why more CO2 in the atmosphere means warmer planet]]

[[and I'm sure there's lots of other crap going on in your sphericalmirrorverse, too]]

great example - and great coverage. I am loving this forum - I have passed it by thinking its probably coding and computer stuff ..

Enjoying these threads a lot!
Cheers - everyone!