# three great solutions to GR

10 Apr 2019every textbook on relativity discusses three great solutions for general relativity: the Schwarzschild solution with the scale \(r_S=2GM/c^2\), the FLRW solutions with the scale \(\rho_\mathrm{crit}=3H_0^2/(8\pi G)\) and the gravitational waves - why donâ€™t they have an associated scale?