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Sorry, this is wrong. Please don't "explain" your misunderstanding as if you know the answer; ask questions instead. If we imagine a full sphere of inward-poin

by tbabb 8y ago

Sorry, this is wrong. Please don't "explain" your misunderstanding as if you know the answer; ask questions instead. If we imagine a full sphere of inward-pointing fibers, each one "looking" at the moon, then we see moon-surface in all directions from within this contraption. We are in a thermal bath of moon-temperature. We will not get hotter than the moon. And fibers are not needed to create this circumstance. The same situation ("moon visible in all directions") could be created with a few lenses and mirrors.

sandworm101 8y ago
Not the system i was talking about. None of the fibers would "look at the moon". Fiber isnt the same as lenses. Note too that i said match. Getting tiny bit of a matchhead hot enough to decompose isnt the same as burning an ant. A matchhead on the surface of the moon would probably ignite just fine (150*+o2).
- amluto 8y ago
  Fiber is very much the same as lenses. (Well, the fiber you’re thinking of is. Fluorescent fiber is not, but that’s another story.)
- tbabb 8y ago
  Again you are "explaining" when you should be asking. > None of the fibers would "look at the moon". Fiber isnt the same as lenses. I think you meant to ask "how is a fiber different from a lens?" instead of asserting "fiber isn't the same as lenses," which turns out to be completely wrong. To a physicist, a lens is a shaped piece of refractive medium-- that is exactly what a fiber is. There is no magic inside the fiber; it does not add any photons. You are looking through a shaped piece glass, through which you will see a (possibly very distorted) image of what's on the other side. In this case, it's the moon that is on the other side. The most you could do is surround your match/ant/whatever with fibers/lenses which are showing the moon on the other side of them. And from this fact it is unavoidable that you cannot make your surrounded subject hotter than the surface of the moon. If you are trying to say anything to the contrary, I'm sorry, but you are Flat Wrong. Any other configuration of fiber would give you less moonlight than completely surrounding the subject, so it's not going to improve the odds of starting a fire. > Note too that i said match. Getting tiny bit of a matchhead hot enough to decompose isnt the same as burning an ant. I think you meant to ask "does the material or shape change anything?" instead of asserting "it isn't the same," which again, in the context of this question, turns out to be completely wrong. The maxiumum temperature that can be imparted by a lens/mirror system doesn't depend on what it's focused on at all. In the long run, the ant/match/whatever will reach that maximum temperature and not get hotter. From a thermodynamics perspective, it is like putting an object in an oven of a particular temperature-- It doesn't matter if you put in a brick, or a cake, or match, or an ant; eventually they will all be 250 degrees if the oven is set to 250 degrees. In this case, the "oven" is the moon, and it's set to about 120C. A match combusts at about 600C. There will be no combusting of the match by putting it in the moon-oven. Sorry. End of story. And if I can give some advice: If what you're hearing doesn't make sense to you, it is always safer to ask a question than to blindly assert your gut-guess of how you think it is. Someone who thinks they're an expert but spouts nonsense looks like a fool. Someone who asks a question, though, looks curious, which is smart. These two people have the same degree of knowledge, but one comes off looking much worse than the other. That's why asking questions is better, especially when you don't know the knowledge of the people who are listening.
wrycoder 8y ago
The point is interesting. A CO2 laser at 10 microns can melt steel, which emits a whole lot of 0.5 micron photons. The problem with sunlight reflected off the moon is that it's like having a very low transmittance ND filter in the optical path. There aren't a whole lot of photons entering the aperture, and as the material begins to heat, there are more photons and overall probably more energy going out. (I'm not giving an answer here, just some thoughts.)
- AlexCoventry 8y ago
  What's ND?
  - nkurz 8y ago
    Neutral Density: https://en.wikipedia.org/wiki/Neutral-density_filter https://en.wikipedia.org/wiki/Neutral-density_filter
felipemnoa 8y ago
Just collect all the photons from the moon using solar panels (moon panels?) Store the energy in a battery. When you have a big enough charge use it to light whatever you want. Sure, it isn't practical and it is not what you guys are really talking about, but you can definitely make something hotter than the moon, as long as you are willing to cheat.

by tbabb 8y ago

sandworm101 8y ago

Not the system i was talking about. None of the fibers would "look at the moon". Fiber isnt the same as lenses. Note too that i said match. Getting tiny bit of a matchhead hot enough to decompose isnt the same as burning an ant. A matchhead on the surface of the moon would probably ignite just fine (150*+o2).

amluto 8y ago
Fiber is very much the same as lenses. (Well, the fiber you’re thinking of is. Fluorescent fiber is not, but that’s another story.)
tbabb 8y ago
Again you are "explaining" when you should be asking. > None of the fibers would "look at the moon". Fiber isnt the same as lenses. I think you meant to ask "how is a fiber different from a lens?" instead of asserting "fiber isn't the same as lenses," which turns out to be completely wrong. To a physicist, a lens is a shaped piece of refractive medium-- that is exactly what a fiber is. There is no magic inside the fiber; it does not add any photons. You are looking through a shaped piece glass, through which you will see a (possibly very distorted) image of what's on the other side. In this case, it's the moon that is on the other side. The most you could do is surround your match/ant/whatever with fibers/lenses which are showing the moon on the other side of them. And from this fact it is unavoidable that you cannot make your surrounded subject hotter than the surface of the moon. If you are trying to say anything to the contrary, I'm sorry, but you are Flat Wrong. Any other configuration of fiber would give you less moonlight than completely surrounding the subject, so it's not going to improve the odds of starting a fire. > Note too that i said match. Getting tiny bit of a matchhead hot enough to decompose isnt the same as burning an ant. I think you meant to ask "does the material or shape change anything?" instead of asserting "it isn't the same," which again, in the context of this question, turns out to be completely wrong. The maxiumum temperature that can be imparted by a lens/mirror system doesn't depend on what it's focused on at all. In the long run, the ant/match/whatever will reach that maximum temperature and not get hotter. From a thermodynamics perspective, it is like putting an object in an oven of a particular temperature-- It doesn't matter if you put in a brick, or a cake, or match, or an ant; eventually they will all be 250 degrees if the oven is set to 250 degrees. In this case, the "oven" is the moon, and it's set to about 120C. A match combusts at about 600C. There will be no combusting of the match by putting it in the moon-oven. Sorry. End of story. And if I can give some advice: If what you're hearing doesn't make sense to you, it is always safer to ask a question than to blindly assert your gut-guess of how you think it is. Someone who thinks they're an expert but spouts nonsense looks like a fool. Someone who asks a question, though, looks curious, which is smart. These two people have the same degree of knowledge, but one comes off looking much worse than the other. That's why asking questions is better, especially when you don't know the knowledge of the people who are listening.

wrycoder 8y ago

The point is interesting. A CO2 laser at 10 microns can melt steel, which emits a whole lot of 0.5 micron photons. The problem with sunlight reflected off the moon is that it's like having a very low transmittance ND filter in the optical path. There aren't a whole lot of photons entering the aperture, and as the material begins to heat, there are more photons and overall probably more energy going out. (I'm not giving an answer here, just some thoughts.)

AlexCoventry 8y ago
What's ND?
- nkurz 8y ago
  Neutral Density: https://en.wikipedia.org/wiki/Neutral-density_filter https://en.wikipedia.org/wiki/Neutral-density_filter

felipemnoa 8y ago

Just collect all the photons from the moon using solar panels (moon panels?) Store the energy in a battery. When you have a big enough charge use it to light whatever you want. Sure, it isn't practical and it is not what you guys are really talking about, but you can definitely make something hotter than the moon, as long as you are willing to cheat.