Theory 93/Cosmic/Supernova remnants
Remnants Scale With Ejecta
The claim
Supernova remnant size at a given age is set by the ratio of ejecta mass to ambient density, so the same explosion produces very different remnants in different media.
01Mechanism
Expansion is driven by ejecta and decelerated by swept-up material; the ratio sets the radius at each phase.
02Prediction
Radius should track the ratio.
03Refutation
Radius tracking age alone would remove the medium.