On the largest scales — far bigger than any galaxy or galaxy cluster — the Universe is remarkably smooth and regular. Tiny irregularities in the early cosmos are what gave rise to all the structures we see today, including us, but there’s another irregularity covering the whole sky. The Universe appears to be ever-so-slightly lopsided, an anomaly facetiously known as the “axis of evil”. Cosmologists are concerned with trying to understand whether the anomaly is a significant challenge to our understanding of some of the laws of physics, or whether it can be understood either as a new astronomical source or a random fluke based on the fact that the whole cosmos is much larger than our observable Universe.

In my latest feature article at Ars Technica, I explored why the “axis of evil” could be a big deal and how some physicists are trying to understand it.

The lopsidedness is real, but cosmologists are divided over whether it reveals anything meaningful about the fundamental laws of physics. The fluctuations are sufficiently small that they could arise from random chance. We have just one observable Universe, but nobody sensible believes we can see all of it. With a sufficiently large cosmos beyond the reach of our telescopes, the rest of the Universe may balance the oddity that we can see, making it a minor, local variation.

However, if the asymmetry can’t be explained away so simply, it could indicate that some new physical mechanisms were at work in the early history of the Universe. [Read more….]

The mystery of the lopsided Universe