Mathematically, the Hubble constant H0 arises as an integration constant in the Friedmann equations once one assumes the Universe is isotropic and homogeneous. Thus, consistency demands that H0 is observationally a constant. Observationally, one either i) determines H0 in the local Universe without a cosmological model or ii) constrains H0 as a fitting parameter in a cosmological model. i) and ii) need not agree when one has a bad model. I will present preliminary results showing that the current standard model is a bad model. This supports a "Hubble tension" that is physical in origin. Restoring the angles, H0 should also not vary on the sky. I will argue that we are now at a precision where variations in H0 on the sky are evident. This has implications for the 100-year-old assumption that the Universe is isotropic and homogeneous. Cosmology appears to be on the cusp of another paradigm shift, but arguably a more cataclysmic rewrite than usual.