1. I have never understood Purcell's explanation of the Hanbury Brown Twiss effect saying that the correlation they measured is only due to the clumping of the bosons; that the pure shot effect would not yield any correlation. Why not? 2. I was reminded of this by Purdy's recently announced observation of the Heisenberg uncertainty principle on a macroscopic object. He only talks about shot effect fluctuation. Shouldn't he see a slightly larger fluctuation due to the contribution of photon clumping?