> The temperature at the focal point may reach 3,500 °C

I thought this was interesting because it doesn’t really seem like an applicable top level claim, surely this is referring to a specific furnace, not all solar furnaces?

Then this got me thinking if there is some universal upper bound constraint to these temperatures. E.g. if I recall a telescope can’t make a source object brighter than it actually is, and this just seems like a thermal telescope, so I wonder if that principle applies here or not.

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ben_w 3 hours ago | parent [-]

> I wonder if that principle applies here or not

It applies, but also in practice the maximum temperature is lower than the theoretical upper bound.

https://what-if.xkcd.com/145/

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appplication 3 hours ago | parent [-]

Oh funny, my intuition when I was writing that was “there’s probably an xkcd what if about this”, but I imagined it be about surrounding the sun with mirrors. Same idea though in the end

	▲	cobbal 2 hours ago \| parent [-]
		You may have been thinking of this one instead https://what-if.xkcd.com/141/ . Maybe we should put Randall on the supervillain watchlist.