No Shadow From the Big Bang?

ultracool writes "In a finding sure to cause controversy, scientists at The University of Alabama in Huntsville (UAH) found a lack of evidence of shadows from "nearby" clusters of galaxies using new, highly accurate measurements of the cosmic microwave background (WMAP). Other groups have previously reported seeing this type of shadows in the microwave background. Those studies, however, did not use data from WMAP, which was designed and built specifically to study the cosmic microwave background."

Comments

Re:Existensial?

[arun_s]

How can the big bang cast a shadow if there's nothing outside thereof on which to cast it?

Shadows require light, an object and an observer. The 'observer' is us here at the earth. The 'object' is this (from TFA):

Galaxy clusters are the largest organized structures in the universe.[snip] The gravity created at the center of some clusters traps gas that is hot enough to emit X-rays.
This gas is also hot enough to lose its electrons (or ionize), filling millions of cubic light years of space inside the galactic clusters with swarming clouds of free electrons. It is these free electrons which bump into and interact with individual photons of microwave radiation, deflecting them away from their original paths and creating the shadowing effect. This shadowing effect was first predicted in 1969 by the Russian scientists Rashid Sunyaev and Yakov Zel'dovich.

And the 'light' is the background microwave radiation, until now assumed to be from the edges of the universe, beyond these clusters.