I produced today a second draft of the chemical tagging paper. Boris Leistedt came by the SCDA and updated me on his SED and redshift model for photometric surveys. I hesitate to even call this “photometric redshifts” because the ambition is so much greater: It is to get the luminosity distribution, the redshift dependence, and the spectral energy distribution for every type of object on the sky, plus assign types and redshifts to all the sources in a multi-band survey (or collection thereof). We even talked about constraining cosmology with galaxy counts, as was first proposed by Hubble so many years ago: It is a generative model for all the redshifted objects on the sky, plus perhaps an admixture of stars in our own Galaxy. Ambitious! And, I think, not impossible, at least if we keep our early goals limited.