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Consider this: Say a light source has a T temperature resulting in X photons emitted. I redirect all the photons to a single point. I see arguments mentioning

by Drury 8y ago

Consider this: Say a light source has a T temperature resulting in X photons emitted. I redirect all the photons to a single point. I see arguments mentioning that that single point cannot be hotter than the source because there's no more photons to make it hotter. I now add a second light source of the same T temperature, that emits the same amount of photons and also focus all of them on that same point. I now have more photons, but temperature source of all photons is the same. How does adding more photons not make my point hotter?

URSpider94 8y ago
In order to truly move all of the photons from the emitter to the target, you need to effectively surround the target with lenses, such that it looks from the surface of the target as if the emitter is filling the sky. If that is the case, then there is no extra room to fit the optics to focus another source onto the target. If you shrink the optics enough to make room for another source, then you also aren’t delivering all of the photons from the original source (you can’t be, since you aren’t covering all incoming angles), and therefore it’s not the same temperature as the source.
Dylan16807 8y ago
> I redirect all the photons to a single point. For that to be possible with a blackbody light source, it has to itself be a single point. Which means a temperature of approximately infinity. For a real light source, one that has an area, you can at best focus it down to the same area. To get maximum light to a target, you either have to make the target almost touch the source, or you have to have it so no matter what direction you go from the target, you hit a lens that's bringing light from the source. Once you set either one of those up, there's nowhere to fit a new light source.
- speedplane 8y ago
  > For a real light source, one that has an area, you can at best focus it down to the same area. I'm not an optics expert, but this can't be true. You can clearly focus light emitting from an area into a smaller area (although probably not to an infinitesimally small area).
  - Dylan16807 8y ago
    You can focus 1/100 of the light onto 1/100 the area. Or 1/1000 of the light onto 1/100 the area. You can't increase the density of the light. You can't focus all of it onto a smaller area. Is that clearer?

by Drury 8y ago

URSpider94 8y ago

In order to truly move all of the photons from the emitter to the target, you need to effectively surround the target with lenses, such that it looks from the surface of the target as if the emitter is filling the sky. If that is the case, then there is no extra room to fit the optics to focus another source onto the target. If you shrink the optics enough to make room for another source, then you also aren’t delivering all of the photons from the original source (you can’t be, since you aren’t covering all incoming angles), and therefore it’s not the same temperature as the source.

Dylan16807 8y ago

> I redirect all the photons to a single point. For that to be possible with a blackbody light source, it has to itself be a single point. Which means a temperature of approximately infinity. For a real light source, one that has an area, you can at best focus it down to the same area. To get maximum light to a target, you either have to make the target almost touch the source, or you have to have it so no matter what direction you go from the target, you hit a lens that's bringing light from the source. Once you set either one of those up, there's nowhere to fit a new light source.

speedplane 8y ago
> For a real light source, one that has an area, you can at best focus it down to the same area. I'm not an optics expert, but this can't be true. You can clearly focus light emitting from an area into a smaller area (although probably not to an infinitesimally small area).
- Dylan16807 8y ago
  You can focus 1/100 of the light onto 1/100 the area. Or 1/1000 of the light onto 1/100 the area. You can't increase the density of the light. You can't focus all of it onto a smaller area. Is that clearer?