BlargenBlog

I decided to get my science fix today and stumbled upon this article from Space.com:

Mysterious New ‘Dark Flow’ Discovered in Space
By Clara Moskowitz
Staff Writer
posted: 23 September 2008
12:46 pm ET

As if the mysteries of dark matter and dark energy weren’t vexing enough, another baffling cosmic puzzle has been discovered.

Patches of matter in the universe seem to be moving at very high speeds and in a uniform direction that can’t be explained by any of the known gravitational forces in the observable universe. Astronomers are calling the phenomenon “dark flow.”

The stuff that’s pulling this matter must be outside the observable universe, researchers conclude.

When scientists talk about the observable universe, they don’t just mean as far out as the eye, or even the most powerful telescope, can see. In fact there’s a fundamental limit to how much of the universe we could ever observe, no matter how advanced our visual instruments. The universe is thought to have formed about 13.7 billion years ago. So even if light started travelling toward us immediately after the Big Bang, the farthest it could ever get is 13.7 billion light-years in distance. There may be parts of the universe that are farther away (we can’t know how big the whole universe is), but we can’t see farther than light could travel over the entire age of the universe.

Mysterious motions

Scientists discovered the flow by studying some of the largest structures in the cosmos: giant clusters of galaxies. These clusters are conglomerations of about a thousand galaxies, as well as very hot gas which emits X-rays. By observing the interaction of the X-rays with the cosmic microwave background (CMB), which is leftover radiation from the Big Bang, scientists can study the movement of clusters.

The X-rays scatter photons in the CMB, shifting its temperature in an effect known as the kinematic Sunyaev-Zel’dovich (SZ) effect. This effect had not been observed as a result of galaxy clusters before, but a team of researchers led by Alexander Kashlinsky, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md., found it when they studied a huge catalogue of 700 clusters, reaching out up to 6 billion light-years, or half the universe away. They compared this catalogue to the map of the CMB taken by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) satellite.

They discovered that the clusters were moving nearly 2 million mph (3.2 million kph) toward a region in the sky between the constellations of Centaurus and Vela. This motion is different from the outward expansion of the universe (which is accelerated by the force called dark energy).

“We found a very significant velocity, and furthermore, this velocity does not decrease with distance, as far as we can measure,” Kashlinsky told SPACE.com. “The matter in the observable universe just cannot produce the flow we measure.”

Inflationary bubble

The scientists deduced that whatever is driving the movements of the clusters must lie beyond the known universe.

A theory called inflation posits that the universe we see is just a small bubble of space-time that got rapidly expanded after the Big Bang. There could be other parts of the cosmos beyond this bubble that we cannot see.

In these regions, space-time might be very different, and likely doesn’t contain stars and galaxies (which only formed because of the particular density pattern of mass in our bubble). It could include giant, massive structures much larger than anything in our own observable universe. These structures are what researchers suspect are tugging on the galaxy clusters, causing the dark flow.

“The structures responsible for this motion have been pushed so far away by inflation, I would guesstimate they may be hundreds of billions of light years away, that we cannot see even with the deepest telescopes because the light emitted there could not have reached us in the age of the universe,” Kashlinsky said in a telephone interview. “Most likely to create such a coherent flow they would have to be some very strange structures, maybe some warped space time. But this is just pure speculation.”

Surprising find

Though inflation theory forecasts many odd facets of the distant universe, not many scientists predicted the dark flow.

“It was greatly surprising to us and I suspect to everyone else,” Kashlinsky said. “For some particular models of inflation you would expect these kinds of structures, and there were some suggestions in the literature that were not taken seriously I think until now.”

The discovery could help scientists probe what happened to the universe before inflation, and what’s going on in those inaccessible realms we cannot see.

Holy shit.  First off, to think of the known universe in terms of light is new to me, but also to think that what we know exists could be infinitely larger–we just can’t see it yet.

You may have heard of the “pulsing universe” theory (can’t remember the exact name) in which the universe expands and contracts constantly.  The Big Bang would be an expansion.  What this article seems to suggest might be a contraction.  Or an expansion.  It really doesn’t say whether we’re moving towards something or away from it, only that there is a “flow.”

Or, perhaps we’re in either a contraction or expansion as a whole, but this has nothing to do with it.  We could just be hurling towards some gigantic center of mass we just can’t see yet, itself being pulled in a contraction or propelled in an expansion.  The fact that it is currently impossible to see that far since the light hasn’t reached us yet is a very telling testament to just how big the universe is… as well as the fact that we have no friggin’ clue.

Try to imagine how many atoms are in baseball.  What if the vast amount of space we can see is, comparatively, the size of one of those atoms, whereas all the other atoms in the baseball are what we can’t see.

What if the object were larger or more dense?  What if it was a diamond the size of the moon?  Does it need to stop there?  What if it doesn’t?

It’s been awhile since I tried to comprehend “infinity” or the size of the universe.  Once I walked from the town square in Washington, IL, to Avanti’s in East Peoria.  Yeah, it just happened that way.  Anyway, to keep my mind occupied, I was trying to imagine the distance to the moon in footsteps.

I couldn’t do it.  I can look at estimates that place it as 250,000 miles away, but to mentally comprehend it in immediate, spatial terms, comparing the distance you travel every day or the size of your body compared to all that space?  It blows my mind.  Pile onto that the distance between here and the Sun, or the size of the solar system.  Add to that the realization that there are billions of stars in this galaxy, and there are billions of galaxies in the known universe, and the distinct possibility that comparing the size of our universe to a drop in the ocean may be the most incredible understatement in existence…  it’s incredible, and if you think about it too long, your head will hurt.

Maybe this would be a good time to mention how wonderful it is to be part of a species which is capable of encumbering such thoughts, yet still retain and utilize the ability to define our own purpose.