Doug's Darkworld

This post would more appropriately be called “The Universe Turns Upside Down,” since there is a recent discovery that may very well change our understanding of the Universe in fundamental ways. I am of course talking about “dark flow,” one of the most inexplicable discoveries in astronomy ever.  More perplexing than even the CMBR Dipole Anisotropy. What the hell is “dark flow?” It’s not easy to explain, but explaining things is my stock in trade, so here goes:

OK, imagine that the visible universe is a sphere about 27 billion light years across.  (There’s a helpful illustration at the bottom of this link, our galaxy is part of the Virgo Supercluster.) The reason it’s 27 billion light years across is because the Universe is only about 13.5 billion years old, so light from the most distant visible parts of the Universe has only had 13.5 billion years to travel. Now the Universe is about 156 billion light years across, so we can only see a small sphere inside of a much larger sphere. Yes, I know, the Universe isn’t really shaped like a sphere, but for our purposes here it’s easy to visualize that way. Think of the Universe as a huge dark mysterious place, but we can only see our own little illuminated clearing in the darkness.

OK, with me so far? Well, recently astronomers have been studying the apparent motion of distant galaxies in our little visible section of the Universe, and lo and behold , they discovered something very interesting. In the above image, the distant galaxy clusters studied are shown in white. And they are all racing towards the area shown in pink. And I mean racing, they are travelling at 3.2 kph (2 million mph.) And this is a problem for astronomers, because there is nothing in the visible Universe that can account for this speed. Astronomers have dubbed this mysterious movement dark flow, in keeping with the idea that they don’t have a clue what is causing it. And in keeping with dark energy, and dark matter, two other mysterious but better understood aspects of the Universe.

Which leads to the obvious deduction, if there’s nothing we can see in the visible Universe that is making these galaxy clusters move, then there must be something outside the visible Universe. And whatever it is, it’s big. Now I mean big both figuratively and literally. The point is, if what is outside the visible Universe was simply more stars and galaxies like what we see around us, it wouldn’t and couldn’t account for the dark flow we are observing. So whatever is going on outside the visible Universe, it’s utterly unlike anything in the visible Universe. Maybe there are structures of immense magnitude, or maybe space-time operates differently in some fundamental fashion outside the visible Universe. Oddly enough, there had been reason to believe that the invisible Universe might be different that the visible universe, there’s aspects of the Big Bang theory that predicted that. Few expected something as radical as whatever is causing dark flow though.

Now some news reports are saying dark flow is the discovery of  “alternate universes,” which is sort of true and sort of isn’t. It’s true in the sense that far away parts of the Universe are forever inaccessible to us, since the Universe is expanding faster than the speed of light on a grand scale. On the other hand, the visible and invisible parts of the Universe all originated in the same Big Bang, so they aren’t really “alternate universes” in the sense it’s usually thought of.  I mention this because I was a bit perplexed when I read some media reports on the discovery of dark flow. Though like so many things on the frontiers of science, dark flow is so hard for the common person to grasp, let alone be interested in, that the media mostly gives it a perfunctory nod and goes back to whatever the celebrity du jour is doing. Such is life.

So what does dark flow mean to the man or woman on the street? Well, basically, nothing. Even if we are part of the dark flow, it’s not going to have any effect on Earth during our lifetime or Earth’s lifetime even. The only consequence I can think of is that it may lead a better understanding of the Big Bang and the underlaying nature of the Universe. And while that may make cosmologists and perhaps astronomers very happy, it probably won’t make much difference in people’s daily lives. Of course that what’s they said about Einstein’s theories … which eventually led to nuclear weapons.

Sleep tight everyone.

(The above image is claimed as Fair Use under US copyright law. It’s not being used for profit and is central to illustrating the post. It came from this fine site and may be the work of the author, Clara Moskowitz.)