I'll see your blue hole and raise a "Blautopf" near where I grew up: https://en.wikipedia.org/wiki/Blautopf https://en.wikipedia.org/wiki/Blautopf Rayleigh sc

I'll see your blue hole and raise a "Blautopf" near where I grew up: https://en.wikipedia.org/wiki/Blautopf https://en.wikipedia.org/wiki/Blautopf Rayleigh scattering on nanoscale limestone particles!