GaiaCal, day four

Tne theme of this short meeting has been that things we thought were real astrophysical parameters just might not be. Soderblom continued along this path when he showed that it is impossible to measure effective temperature to better than something on the order of 100 K. That limits the precision of model comparisons, even in the absence of modeling uncertainties (which are currently large). I argued that perhaps we should just give up on these ersatz "physical" parameters and go to predictions of observables. I was shouted down.

Finkbeiner showed unreal comparisons between SDSS and PanSTARRS photometry, with each survey synthesizing the other. He can show with enormous confidence which survey is responsible for which photometric residuals, just by projecting the residuals onto the sky or into the focal planes of the two instruments. This is an interesting kind of "causal inference". It is incredibly convincing; I must discuss it with Schölkopf next month.

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