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This is a snippet from Scientific American, October 1993, 50 and 100 years ago: October 1893: "It now does not seem improbable that, when by the power of thoug

This is a snippet from Scientific American, October 1993, 50 and 100 years ago: October 1893: "It now does not seem improbable that, when by the power of thought an image is evoked, a distant reflex action, no matter how weak, is exerted upon certain ends of the visual nerves, and, therefore, upon the retina. Helmholtz has shown that the fundi of the eyes are themselves luminous, and he was able to see, in total darkness, the movement of his arm by the light of his own eyes. This is one of the most remarkable experiments recorded in the history of science, and probably only a few men could satisfactorily repeat it, for it is very likely that the luminosity of the eyes is associated with uncommon activity of the brain and great imaginative power. It is fluorescence of brain action, as it were." --Nikola Tesla, in a paper read before the Franklin Institute Can anyone - uh - shed some light on it?

duskwuff 4y ago
For context, it's important to remember that Tesla was an accomplished experimental scientist, but he was prone to wild claims and flights of fancy which weren't based in scientific reasoning, even by the standards of the day. Not everything he said or wrote was literally true. > Helmholtz has shown that the fundi of the eyes are themselves luminous... This is erroneous -- no part of the eye emits light. Some animals, like cats and dogs, have retroreflective surfaces within the eye, and I wouldn't be surprised if that's what got Helmholtz (or possibly Tesla in quoting him?) tripped up. > ... and he was able to see, in total darkness, the movement of his arm by the light of his own eyes ... If this experiment occurred, it's far more likely that there were low levels of light present in the room, and/or that the experimenter was imagining the position of his arm as sensed through proprioception. > ... it is very likely that the luminosity of the eyes is associated with uncommon activity of the brain and great imaginative power And this is one of the flights of fancy I was talking about. :) There's no basis for this claim.

duskwuff 4y ago

For context, it's important to remember that Tesla was an accomplished experimental scientist, but he was prone to wild claims and flights of fancy which weren't based in scientific reasoning, even by the standards of the day. Not everything he said or wrote was literally true. > Helmholtz has shown that the fundi of the eyes are themselves luminous... This is erroneous -- no part of the eye emits light. Some animals, like cats and dogs, have retroreflective surfaces within the eye, and I wouldn't be surprised if that's what got Helmholtz (or possibly Tesla in quoting him?) tripped up. > ... and he was able to see, in total darkness, the movement of his arm by the light of his own eyes ... If this experiment occurred, it's far more likely that there were low levels of light present in the room, and/or that the experimenter was imagining the position of his arm as sensed through proprioception. > ... it is very likely that the luminosity of the eyes is associated with uncommon activity of the brain and great imaginative power And this is one of the flights of fancy I was talking about. :) There's no basis for this claim.