Axis of Evil in the universe?
Going my way? The CMB quadrupole (top left), octopole (top right), and the next two multipoles. The red dots mark their symmetry axes, which appear to line up.
CREDIT: NASA/WMAP SCIENCE TEAM
The multipole moments mentioned in the caption are just the way that the full map was broken down, as a sum of progressively finer undulations. The courses is the dipole, which splits the map in two, then the quadrupole (four), octopole (eight) and so on. The coincidence is that the largest moments have their symmetry axis lined up. The question is whether this is just a coincidence or something more meaningful, and it's really hard to say which. The problem is that we only have on universe to look at, and we can't really make the assumption that this isn't just a fluke. And so far the efforts to explain it are seriously flawed, not matching up with other data.
This might end up being a big deal because if it's more than just a coincidence one of the sacred assumptions of the universe, that there's no preferred direction, is totally wrong. That would have deep implications, some conservation laws (energy, momentum, and angular momentum) are the result of assumptions about space, which could end up being wrong!
I have to be honest, I think this is probably just a mirage. Adding a preferred direction to the universe would be quite revolutionary, and it just doesn't sit well with me. I know that's not a good reason to ignore new data, but this hasn't been proved yet. If the universe ends up having an axis, then so be it, but I doubt it does.