Dark flow: Proof of another universe?

[Ichingcarpenter]

FOR most of us the universe is unimaginably vast. But not for cosmologists. They feel decidedly hemmed in. No matter how big they build their telescopes, they can only see so far before hitting a wall. Approximately 45 billion light years away lies the cosmic horizon, the ultimate barrier because light beyond it not has not had time to reach us.

So here we are, stuck inside our patch of universe, wondering what lies beyond and resigned to that fact we may never know. The best we can hope for, through some combination of luck and vigilance, is to spot a crack in the structure of things, a possible window to that hidden place beyond the edge of the universe. Now Sasha Kashlinsky believes he has stumbled upon such a window.

Kashlinsky, a senior staff scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, has been studying how rebellious clusters of galaxies move against the backdrop of expanding space. He and colleagues have clocked galaxy clusters racing at up to 1000 kilometres per second - far faster than our best understanding of cosmology allows. Stranger still, every cluster seems to be rushing toward a small patch of sky between the constellations of Centaurus and Vela.

Kashlinsky and his team claim that their observation represents the first clues to what lies beyond the cosmic horizon. Finding out could tell us how the universe looked immediately after the big bang or if our universe is one of many. Others aren't so sure. One rival interpretation is that it is nothing to do with alien universes but the result of a flaw in one of the cornerstones of cosmology, the idea that the universe should look the same in all directions. That is, if the observations withstand close scrutiny.

All the same colleagues are sitting up and taking notice. "This discovery adds to our pile of puzzles about cosmology," says......>>>>snip

http://www.newscientist.com/article/mg20126921.900-dark-flow-proof-of-another-universe.html

[panader0]

1. Cool. I hope we get to find out when we die.

[enlightenment]

2. I wish I was smart enough to understand even a fraction of

this stuff, because reading it creates some real neat mental images that I'm sure are so far off base they're in a different ball park.

I tried out the 'multiple bubbles' floating in a multiverse, but it looked too much like a Mr. Clean advert, so I thought about the galaxies all 'racing' toward one spot in the 'sky' and decided that I prefer the look of multiple streams (rivers/etc) of universes flowing through a multiverse - maybe even crossing over occasionally and mixing up with each other. If we can only see 45 billion light years, then there's nothing to suggest that the 'sides' of our universe can't be narrower than the 'ends' . . .

okay. Sounding totally idiotic now. Sorry.

Very, very cool article, though. Thank you for posting it. I'll go back to history books now . . .

[laconicsax]

3. How can we observe anything farther away than 13.7 billion light years?

It is 13.7 billion years since the big bang, so light now reaching us cannot have started its journey longer ago than that. Yet the most distant object we could conceivably see today lies further away than 13.7 billion light years. That's because throughout the life of the universe, space has been expanding. Taking this into account, cosmologists calculate that the edge of our observable universe is now approximately 45 billion light years away.

Am I correct in thinking that even if we're able to observe something that's potentially 45 billion light years away, we're seeing it as it was when it was only 13.7 billion light years away? How is that any different than looking at a picture of a 14 year-old kid and saying it's a picture of a 45 year-old adult?

[bsiebs]

5. Hyper-expansion

I recall reading about hyper-expansion at the beginning of the bang... expansion faster than light... this could be part of the reason...

Edit:

OK...the thing about expanding faster than the speed of light bothered me. I found an explanation at this site:

http://www.astronomybuff.com/how-can-we-see-galaxies-47-billion-light-years-away-when-the-universe-is-only-13-billion-years-old/

From the site:

A somewhat simpler way to think of the expansion rate of the universe is that it expands at roughly the age of the universe to the 2/3 power: AgeOfUniverse^(2/3). Unfortunately, it’s not simply a plug and chug formula, since the expansion is occurring continuously, you need to apply some calculus.

The expansion formula (see linked website page) just takes the ratio of elapsed expansion time to the age of the universe raises it to the 2/3 power and does this over the entire time the expansion is occurring.

What all of this means is that whenever you discuss the size of the universe, you need to apply a scale factor that is relevant TO THE TIME you are interested in. The issue of when is very important because the size of the universe, and the rate at which it was expanding has changed since the universe began.

So, for RIGHT NOW, the size of the universe has expanded to roughly 46.5 billion light years since the Big Bang.

Let’s break down the above integral into some smaller intervals and watch what happens. Let’s use 13 billion years as the age of the universe and let the universe expand for an average of five billion years at three different points in time: 2, 7, and 12 billion years after the Big Bang:

At age of universe = 2 billion light years: the universe has expanded by a factor of (13/2)^2/3 = 3.48
At age of universe = 7 billion light years: the universe has expanded by a factor of (13/7)^2/3 = 1.51
At age of universe = 12 billion light years: the universe has expanded by a factor of (13/12)^2/3 = 1.08
So combining these scale factors over the two intervals above, the universe has expanded to a size of:

(average distance light travels over interval of interest) * (sum of all scale factors).

Plugging in the numbers (we used an elapsed time interval of 5 billion years):
(5 billion light years) * (3.48+1.51+1.08) = 30.37 billion light years.

The 5 billion light year number above is the average distance light traveled in 5 billion years so the units are in light years.

Now, this is a discreet example, taking only three points in time, but already we have a number bigger than 13 billion light years. Since the universe is expanding continuously, we actually need to do the integral above and when you do that, the answer approaches 47 or so billion light years.

[laconicsax]

7. I'm not sure that answers my question.

I may be reading your response incorrectly, but it seems to be an explanation of how we arrive at 47 billion light years. I understand that aspect. What I'm not clear on is how we can see anything that is more than 13.7 billion years old since the light hasn't existed for longer than that.

When we observe a point in space that is now 47 billion light years away, aren't we limited to observing it as it was when it was much closer? The light entering our telescopes can't be any older than 13.7 billion years, so how could it be a observing something farther than 13.7 billion light years? When we say we're looking at an object that's 47 billion light years away, are we just looking at that object as it was when it was 13.7 billion light years away and keeping in mind that it's currently much farther away?

Cosmology is not my strong suit.

[Random_Australian]

8. Ah, to explain I just need to focus on two words in that last post.

What wasn't explained in that last post is what the 'scale factor' is. Without going into a really long explanation, if you were to measure the distance between two stars, double the scale factor, and measure it again, you would get twice the result the second time. In other words, increasing the scale factor represents space itself expanding.

The expansion of the scale factor is actually why they say "space started with the big bang". Because it did.

So you have light moving along at c, but the distance it has travelled is continuously expanding as well!

So it travels more than 13.7 gLy in 13.7 gy

And if you do the math in some detail, it comes out to ~47 gLy.

[laconicsax]

9. Gotcha, thanks.

I think I get it.

[Ichingcarpenter]

6. Is the 45 billion like the horizon?

as compare to a man's observation on earth?

Isn't 45 billion much older than the universe?

I really need to digest this article a little.

[Dead_Parrot]

10. Try this for an analogy

Imagine an ant walking along a rubber band, at 1 cm per second: after 1 second, it's walked 1 cm, after 2 seconds it's walked 2cm, and so on.

Now imagine you are stretching the rubber band while the ant is walking along, doubling the size every second: after 1 second, the ant has walked 1 cm, but is 2 cm from it's starting point. After 2 seconds, it's walked 2 cm, but is now 6 cm from its start point, and so on. (It's too damn early here to actually do the math right, but I hope you get the idea).

Same thing with light: After 13-odd billion years, it's now 47 billion years from where it's started because the universe has stretched in the meantime.

[DrDan]

4. malarky - anything beyond 6000 years is pure malarky

[tridim]

11. All rational people are witches.

That's the only explanation. :)

[pokerfan]

12. If it's finite, then what lies beyond the finite?

Doesn't really matter if it's 10³⁰ particles or 10⁷² or 10⁸⁷ or 10¹⁰⁰. What else is there?