data-driven spectral models; Oort cloud

I spent a good chunk of the day at Stanford, chatting with Blandford and Strigari. Blandford had lots of good thoughts to contribute to my general ideas about how one might build empirical (data-driven) and yet physically interpretable models of stars from enormous amounts of high signal-to-noise, high resolution spectral data (like we have in APOGEE). In particular, he pointed out that we don't have to ignore what we know about atomic physics and quantum mechanics when we do it! Strigari is thinking about the Oort cloud and the comets that allegedly fill it: Do they really have to be in a fluffy cloud around every star, or could they instead be in a space-filling population not bound to any star? Or a mixture of the two? Radical! And, he hopes, testable.