Over the holiday period, the physics arxiv blog is re-running the most popular blogs (by page views) of 2007.

The incredible galactic foxtrot
30 August

Ya’ll know the laws of physics are symmetrical–they have no preferred direction. The speed of light (and more or less everything else) is the same whichever way it is pointin’, right?

So it’d be surprisin’ if the universe turned out to be asymmetric, shockin’ if it had a prefered axis and stunnin’ if it had a direction in which things were different.

But it’s beginning to look that way. Two years ago, you could hear astro-jaws dropping all over the planet when a couple of upstarts suggested that data from a giant space-thermometer called the Wilkinson Microwave Cosmic Anisotropy Probe or WMAP looked as if it were aligned in a certain direction.

A-babblin and a-brayin, critics pointed out that the alignment matched the galactic co-ordinate system and so was probably an imprint of the Milky Way. Subtract this properly and the alignment would go away.

But it didn’t. And that left theorists a-scratchin their heads and a-rubbin their chins in amazement.

Now they gotta do a whole lot more a-broodin and a-worryin. Michael “Bongo” Longo at the University of Michigan has spotted another kind of alignment by a-meterin and a-measurin the orientation of 200,000 elliptical galaxies. That’s a lotta galaxies and it turns out they’re all aligned in the same direction too. We just ain’t noticed before now.

That’s put a ‘gator in the pool.

So what’s been causin this cosmic foxtrot? Ain’t nobody sure but we’re gonna be hearin a lot more about it in the weeks and months to come. Betcha!

Ref: arxiv.org/abs/0708.4013: The Axis of Opportunity: The Large-Scale Correlation of Elliptical Galaxies

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