[ben_w]

> 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/

[exe34]

I'm confident that the physics is correct, but I hate when things are translated for the lay public:

> "In general, there's no way to "overlay" light beams on each other, because the whole system has to be reversible".

Behold, my two torches.

[appplication]

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]

You may have been thinking of this one instead https://what-if.xkcd.com/141/ . Maybe we should put Randall on the supervillain watchlist.