First we had "Dark Matter," then came "Dark Energy," and now we find "Dark Flow" ... sometimes I wish scientists would simple leave me in the dark...
Give me strength! Way back in 1933, astronomer Fritz Zwicky was studying the motions of galaxies in a galactic cluster. Fritz realized that there was not enough visible mass to keep the galaxies forming the cluster from flying apart. Further observations confirmed his findings, which led astronomers to come up with the concept of "Dark Matter". As the Wikipedia would have it:
Dark Matter is hypothetical matter that does not interact with the electromagnetic force, but whose presence can be inferred from gravitational effects on visible matter.
Later, in 1998, two independent teams of astronomers were searching for distant supernovae in order to measure the rate at which the expansion of the universe was slowing down. We can only imagine their surprise when they discovered that the expansion was actually speeding up. This led to the concept of "Dark Energy". Once again, the Wikipedia puts it in a nutshell:
Dark Energy is a hypothetical exotic form of energy that permeates all of space and tends to increase the rate of expansion of the universe.
So Dark matter is attracting things together, while Dark Energy is making them fly apart... and together they account for something like 70 to 95 % (depending on who you are talking to) of the total amount of mass-energy in the universe. Could it get any better than this?
Well, apparently so, because now we have the "Dark Flow". It seems that NASA has discovered a bunch of super-clusters (collections of 1,000 or so galaxies) that are all moving in the same direction. It's a bit difficult to wrap one's brain around all of this, but from what I can gather they are saying that there must be some HUGE mass outside of the portion of the universe that's visible to us that's attracting these super-clusters. For more info check out this, and this, and this, and this.
In fcat, as you'll see, some folks seem to be saying that this mass must be completely outside our universe... at which point I start to reach for another beer...
Questions? Comments? Feel free to email me – Clive "Max" Maxfield – at firstname.lastname@example.org). And, of course, if you haven't already done so, don't forget to Sign Up for our weekly Programmable Logic DesignLine Newsletter.