Also the basis of the least precise prediction made by a physics theory: https://en.wikipedia.org/wiki/Cosmological_constant_problem

> Depending on the Planck energy cutoff and other factors, the discrepancy is as high as 120 orders of magnitude

yes and no. physical theories always have a domain of validity where their prediction make sense and QFT and QM do not give an absolute value of energy (density). sure you can do QFT on curved spacetime (Hawking had some success w/ it) but comparing the QFT vacuum energy with the cosmological constant is sloppy at best.

but yeah, sure, it doesn't work for that :)

And then what about fluids? Are there other descriptions for things that look like that?

TIL superfluids have zero viscosity; and at that scale, galaxies are supposably superfluidic; at least one formulation of "superfluid quantum gravity" has Bernoulli's && GR and it supposably works.