Cosmic Variance is a collaborative weblog discussing physics, astrophysics, and other topics, written by JoAnne Hewett, Mark Trodden, Sean Carroll, Risa Wechsler, Julianne Dalcanton, John Conway, and Daniel Holz. It is the successor to Carroll's earlier blog Preposterous Universe, which began in early 2004 and ran through much of 2005. The blog's name comes from the cosmology concept of cosmic variance.