At lunch, Fergus, Fadely, and I met with Brenner (AMNH) and Nilsson (AMNH) to discuss the P1640 data and analysis next steps. After lunch we all got into an argument about finding the location of the center of the
optical flow—the point from which the speckles expand with wavelength. I argued that this is not defined if you let the point itself be a function of wavelength; then you are in the situation of the expanding Universe, where everyone thinks he or she is at the center. Same for speckles in the focal plane: Every speckle can have a comoving, colocated
observer who thinks he or she is at the center of the focal plane! Of course there really is some center, because the telescope and camera have an axis, so the point is purely amusing.
In the afternoon, Keith Chan (NYU) defended his PhD (supervised by Scoccimarro) on understanding dark-matter simulations in terms of halo clustering and halo statistics. He has created a valuable piece of work and the defense was a pleasure.