Say you drilled a hole down to the magma layer. Hot lava emits light. From what I've seen lava is red(?) hot. Then if you put some fibre optic cables down into the magma layer maybe protected at the bottom with a diamond layer to protect them from melting. Could you capture that light and bring it to the surface, in order to provide things like indoor lighting or even convert the light to electricity using solar panels?

(There is a place in Iceland where they are attempting to drill down to the magma).

What colour would the light be?

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    $\begingroup$ Well, theoretically you could, but it would be much more efficient to convert the heat into electricity and then use the electricity to power a light bulb. $\endgroup$ – Thorondor Feb 28 '19 at 15:51
  • $\begingroup$ @Throndor are you sure? Isn't that magma already converting the heat into light? A lightbulb is just heating up a filament, why would this be more efficient than taking the light from the hot lava? $\endgroup$ – zooby Feb 28 '19 at 17:10
  • $\begingroup$ Several reasons. Magma converts heat into light very inefficiently because most of the heat energy is lost to conduction and convection. At the temperature of the mantle, most blackbody radiation is IR, not visible light. And finally, fiber optic cables do not transmit light perfectly; most of the light would be absorbed and lost while traveling from the mantle to the surface. $\endgroup$ – Thorondor Feb 28 '19 at 17:28

Any object that has a temperature emits light via blackbody radiation. A relatively cool object at room temperature emits mostly in the IR part of the spectrum, and is not luminous enough to detect with human eyes. A much hotter object (like the sun) emits primarily in yellow light, and is bright enough to be detected by human eyes.

So yes, magma emits light. Technically blackbody radiation is all colors (blackbody radiation is emitted across all wavelengths). The color of greatest intensity would depend on the temperature of the magma. As the comment to your question mentions, in terms of usefulness, this would not be the most efficient light source, but if we don't want to be constrained by practicality and usefulness, I don't see why your proposal wouldn't work (engineering barriers aside).

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  • $\begingroup$ would not magma melt the diamomg? At best one would need a cavity with a magma pool at the botom I think. $\endgroup$ – anna v Feb 28 '19 at 16:06
  • $\begingroup$ Seems like it would. I'm ignoring the actual feasibility of accomplishing this task. Let an engineer to figure out a solution. $\endgroup$ – Bob Mar 1 '19 at 15:34

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