Dark Flow??

I do a lot of reading on the subject of cosmology. I find the field fascinating for a variety of reasons, not least because it includes aspects of quantum mechanics, General Relativity, high-energy physics, thermodynamics, astrophysics, and a heap of other stuff. If you read about, say, quantum chromodynamics, all you get is quantum chromodynamics, but if you read about cosmology, you get the whole enchilada.

And it's so weird.

At first we thought that all there was in the universe was matter and radiation. Then it turned out that there wasn't enough matter to explain the behavior of stars in galaxies, so we had to postulate the existence of "dark matter". Nobody knows what dark matter really is, but it seems almost a given that is has to exist, even though we can only guess at most of its properties. Then it turned out that the expansion of the universe was not slowing down, as one would expect, but actually speeding up. So we had to postulate the existence of "dark energy" to explain this accelerating expansion. Thus far nobody has any idea what dark energy really is, and there doesn't even seem to be much agreement on what observations we might make that would give us insight into its nature.

And now we have something new - "dark flow". Analysis of great heaps of data from the Sloan Digital Sky Survey and the Wilkinson Microwave Anisotropy Probe suggest that a fairly sizable chunk of the observable universe (the Local Group, the Virgo Supercluster and perhaps even the Great Attractor) all demonstrate a fairly uniform peculiar velocity (the term "peculiar velocity" refers to the velocity being directed in an actual direction with respect to the cosmic microwave background, rather than just being the recessional velocity that the Hubble Constant implies). This peculiar velocity is called "dark flow", maybe just because it sounds creepy.

It seems that us, the Local Group, the Virgo Supercluster and the Great Attractor are all being drawn toward something. But what? Something hugely massive, surely, but as far as we've been able to see, there's nothing out there that fills the bill. One theory is that it's something hugely massive that lies beyond the rim of the visible universe - not because our telescopes aren't good enough to see it, but because light from this sinister thing out there hasn't had time to reach us even though it's been traveling at the speed of light since the beginning of the universe.

I don't know if that's actually the case. Some theorize it's gravitational attraction from a parallel universe, or perhaps from a sub-universe that split off from ours during the period of superluminal inflation, or... But whatever it is, it fascinates me.

Cosmology can be kind of a bummer, because none of the theorized "ends of the universe" are at all appealing. The Big Crunch is bad. The Big Rip is bad. The Big Bounce is bad, but maybe not quite as bad. Universal heat death is just plain depressing. (I can fully understand why physicists like Fred Hoyle might have preferred the Steady State theory, which at least offers an eternal lifetime and doesn't require that the universe be obliterated in one way or another. Though I accept the Big Bang on intellectual grounds, a part of me pines for the comforting eternity of the Steady State model.)

But the presence of this unseen thing out there that causes dark flow might open the door for other outcomes. Maybe we really are headed somewhere special, and maybe the universe isn't just a really big, really long-playing exercise in the conservation of energy. Or maybe I just find ideas like the Big Rip or the Big Crunch spiritually unrewarding and hope for some other outcome because I find futility depressing.