Today Megan Bedell (Flatiron) and I called Jan Rybizki (MPIA) to discuss his nucleosynthesis (or chemical-evolution) models for the abundances Bedell sees in her Solar twin stars. His fits are not great—the yield tables from nuclear astrophysics don't do a good job explaining the Sun yet—but he can build a model that is best-fit under his assumptions. The realization we had today is that Bedell's abundances are referenced to the Solar abundances in the real world; and so if we are using Rybizki's model, we should reference her abundances to the Solar abundances in Rybizki's world! That should make everything work better and permit us to come to conclusions.
All this assumes that Rybizki's model is better at getting relative element abundances than absolute abundances. That remains to be seen! However, this also connects to the constant refrain on my blog that we need to do inference in the context of models we know to be wrong! That can't be helped; so what is the epistemological status of conclusions based on wrong models? Scientific inferences are only correct in the context of specific and questionable assumptions. But we still learn a lot and know a lot.