Lonely Tylenol
First Post
This one's for Nifft. Why Darkvision isn't based on radiation.
Normal sight is based on radiation. Light of various wavelengths bounces off objects and strikes a sensitive tissue, causing the sensation of vision. Darkvision is described as being just like regular vision, except it's in black and white, and works only in the dark.
If we assume darkvision is based on radiation as well, we have an important question to answer: Where does the radiation come from?
There has to be a source for the radiation, and there are three good candidates. The first is that it comes from the sun, like regular radiation. Secondly, it is projected by the darkvision-using creature. Thirdly, it is emitted by objects naturally.
If the radiation comes from the sun, we immediately run into a problem. Darkvision works underground, where light cannot penetrate. We can assume that darkvision radiation can penetrate objects, something like neutrinos or X-rays do, but that creates the problem that if it penetrates objects, it cannot be reflected by them. Reflection of the radiation from an object to the viewer's eye is necessary for vision to occur. We could say that, like X-rays, the radiation has a limited penetration, and does in fact bounce off objects some of the time (actually, X-rays are absorbed, but for the sake of argument...). However, that would mean that the effectiveness of darkvision would depend on how much matter there is between the viewer and the radiation source, since for each inch of matter the radiation passes through, there is a constant amount reflected/absorbed and a constant amount that can penetrate. Since there is no indication that darkvision works worse the deeper underground you go, we must discard this hypothesis. So much for the sun.
If darkvision radiation were projected by the darkvision-using creature, like a bat's sonar, it would function just fine, so long as it behaved something like light. However, this would cause every darkvision-using creature to stand out as a torch-like beacon, immediately apparent to every other darkvision-using creature. There is no indication that this is the case, and furthermore, it would be a pain in the butt for most darkvision-using creatures, because the presence of another darkvision-using creature would render them effectively blind, much in the same way as two people facing each other in the dark with flashlights can't see much else besides the flashlights. Also, forget ever sneaking up on a creature with darkvision if you use it yourself. So let's discard the creature as the source of the radiation.
If objects emit radiation, we should be able to see them, like a glow-in-the-dark object, right?. If darkvision works like normal vision, but in the dark, that means that every material there is emits radiation, otherwise it would be invisible. If only certain materials emit radiation, that means that it is possible for a darkvision-using creature to be in a situation in which his darkvision does not work the way it is described to. If placed in a box made of a non-radiating material, he would be unable to see in the dark, which is something that should not happen based on the description of the ability. So, if every object radiates light, we get two troublesome effects. First, if every object emits light the visual field will be a homogeneous glow, unsuitable for finding your way around. Object distances may be obscured, and the edges will be hard, if not impossible, to make out. Second, transparent materials like glass or water will emit light as well, obscuring whatever's behind them even if they can transmit the darkvision radiation as though it were light. That violates the "works like regular vision" rule. There's also the problem of matter in the air emitting light, causing a haze effect.
Since there is no potential source for radiation that doesn't fail to satisfy the necessary conditions for darkvision to work properly, we must conclude that darkvision is not based on radiation. There is actually no good explanation why darkvision works that doesn't just wave a hand and say "it's magic." Of course, since darkvision works in an antimagic field, it's not magic either. It just works, and that's the best we're going to get.
edit: I forgot to add that if all materials emit radiation, then the creature's own eyes will presumably emit radiation as well. In that case, it will be rendered blind.
Normal sight is based on radiation. Light of various wavelengths bounces off objects and strikes a sensitive tissue, causing the sensation of vision. Darkvision is described as being just like regular vision, except it's in black and white, and works only in the dark.
If we assume darkvision is based on radiation as well, we have an important question to answer: Where does the radiation come from?
There has to be a source for the radiation, and there are three good candidates. The first is that it comes from the sun, like regular radiation. Secondly, it is projected by the darkvision-using creature. Thirdly, it is emitted by objects naturally.
If the radiation comes from the sun, we immediately run into a problem. Darkvision works underground, where light cannot penetrate. We can assume that darkvision radiation can penetrate objects, something like neutrinos or X-rays do, but that creates the problem that if it penetrates objects, it cannot be reflected by them. Reflection of the radiation from an object to the viewer's eye is necessary for vision to occur. We could say that, like X-rays, the radiation has a limited penetration, and does in fact bounce off objects some of the time (actually, X-rays are absorbed, but for the sake of argument...). However, that would mean that the effectiveness of darkvision would depend on how much matter there is between the viewer and the radiation source, since for each inch of matter the radiation passes through, there is a constant amount reflected/absorbed and a constant amount that can penetrate. Since there is no indication that darkvision works worse the deeper underground you go, we must discard this hypothesis. So much for the sun.
If darkvision radiation were projected by the darkvision-using creature, like a bat's sonar, it would function just fine, so long as it behaved something like light. However, this would cause every darkvision-using creature to stand out as a torch-like beacon, immediately apparent to every other darkvision-using creature. There is no indication that this is the case, and furthermore, it would be a pain in the butt for most darkvision-using creatures, because the presence of another darkvision-using creature would render them effectively blind, much in the same way as two people facing each other in the dark with flashlights can't see much else besides the flashlights. Also, forget ever sneaking up on a creature with darkvision if you use it yourself. So let's discard the creature as the source of the radiation.
If objects emit radiation, we should be able to see them, like a glow-in-the-dark object, right?. If darkvision works like normal vision, but in the dark, that means that every material there is emits radiation, otherwise it would be invisible. If only certain materials emit radiation, that means that it is possible for a darkvision-using creature to be in a situation in which his darkvision does not work the way it is described to. If placed in a box made of a non-radiating material, he would be unable to see in the dark, which is something that should not happen based on the description of the ability. So, if every object radiates light, we get two troublesome effects. First, if every object emits light the visual field will be a homogeneous glow, unsuitable for finding your way around. Object distances may be obscured, and the edges will be hard, if not impossible, to make out. Second, transparent materials like glass or water will emit light as well, obscuring whatever's behind them even if they can transmit the darkvision radiation as though it were light. That violates the "works like regular vision" rule. There's also the problem of matter in the air emitting light, causing a haze effect.
Since there is no potential source for radiation that doesn't fail to satisfy the necessary conditions for darkvision to work properly, we must conclude that darkvision is not based on radiation. There is actually no good explanation why darkvision works that doesn't just wave a hand and say "it's magic." Of course, since darkvision works in an antimagic field, it's not magic either. It just works, and that's the best we're going to get.
edit: I forgot to add that if all materials emit radiation, then the creature's own eyes will presumably emit radiation as well. In that case, it will be rendered blind.
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