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Do We Live in a Giant Cosmic Bubble?
by Space
Thanks to Chipshotz for the link.
http://www.space.com/scienceastronomy/080930-st-universe-void.html
Do We Live in a Giant Cosmic Bubble?
By Clara Moskowitz
If the notion of dark energy sounds improbable, get ready for an even more outlandish suggestion.
Earth may be trapped in an abnormal bubble of space-time that is particularly void of matter. Scientists say this condition could account for the apparent acceleration of the universe's expansion, for which dark energy currently is the leading explanation.
Dark energy is the name given to the hypothetical force that could be drawing all the stuff in the universe outward at an ever-increasing rate. Current thinking is that 74 percent of the universe could be made up of this exotic dark energy, with another 21 percent being dark matter, and normal matter comprising the remaining 5 percent.
Until now, there has been no good way to choose between dark energy or the void explanation, but a new study outlines a potential test of the bubble scenario.
If we were in an unusually sparse area of the universe, then things could look farther away than they really are and there would be no need to rely on dark energy as an explanation for certain astronomical observations.
"If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were."
Scientists first detected the acceleration by noting that distant supernovae seemed to be moving away from us faster than they should be. One type of supernova (called Type Ia) is a useful distance indicator, because the explosions always have the same intrinsic brightness. Since light gets dimmer the farther it travels, that means that when the supernovae appear faint to us, they are far away, and when they appear bright, they are closer in.
But if we happened to be in a portion of the universe with less matter in it than normal, then the space-time around us would be different than it is outside, because matter warps space-time. Light travelling from supernovae outside our bubble would appear dimmer, because the light would diverge more than we would expect once it got inside our void.
One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special. When Nicholas Copernicus argued that it made much more sense for the Earth to be revolving around the sun than vice versa, it revolutionized science. Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.
"This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."
Clifton, along with Oxford researchers Pedro G. Ferreira and Kate Land, say that in coming years we may be able to distinguish between dark energy and the void. They point to the upcoming Joint Dark Energy Mission, planned by NASA and the U.S. Department of Energy to launch in 2014 or 2015. The satellite aims to measure the expansion of the universe precisely by observing about 2,300 supernovae.
The scientists suggest that by looking at a large number of supernovae in a certain region of the universe, they should be able to tell whether the objects are really accelerating away, or if their light is merely being distorted in a void.
The new study will be detailed in an upcoming issue of the journal Physical Review Letters.
http://www.space.com/scienceastronomy/080930-st-universe-void.html
Do We Live in a Giant Cosmic Bubble?
By Clara Moskowitz
If the notion of dark energy sounds improbable, get ready for an even more outlandish suggestion.
Earth may be trapped in an abnormal bubble of space-time that is particularly void of matter. Scientists say this condition could account for the apparent acceleration of the universe's expansion, for which dark energy currently is the leading explanation.
Dark energy is the name given to the hypothetical force that could be drawing all the stuff in the universe outward at an ever-increasing rate. Current thinking is that 74 percent of the universe could be made up of this exotic dark energy, with another 21 percent being dark matter, and normal matter comprising the remaining 5 percent.
Until now, there has been no good way to choose between dark energy or the void explanation, but a new study outlines a potential test of the bubble scenario.
If we were in an unusually sparse area of the universe, then things could look farther away than they really are and there would be no need to rely on dark energy as an explanation for certain astronomical observations.
"If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were."
Scientists first detected the acceleration by noting that distant supernovae seemed to be moving away from us faster than they should be. One type of supernova (called Type Ia) is a useful distance indicator, because the explosions always have the same intrinsic brightness. Since light gets dimmer the farther it travels, that means that when the supernovae appear faint to us, they are far away, and when they appear bright, they are closer in.
But if we happened to be in a portion of the universe with less matter in it than normal, then the space-time around us would be different than it is outside, because matter warps space-time. Light travelling from supernovae outside our bubble would appear dimmer, because the light would diverge more than we would expect once it got inside our void.
One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special. When Nicholas Copernicus argued that it made much more sense for the Earth to be revolving around the sun than vice versa, it revolutionized science. Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.
"This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."
Clifton, along with Oxford researchers Pedro G. Ferreira and Kate Land, say that in coming years we may be able to distinguish between dark energy and the void. They point to the upcoming Joint Dark Energy Mission, planned by NASA and the U.S. Department of Energy to launch in 2014 or 2015. The satellite aims to measure the expansion of the universe precisely by observing about 2,300 supernovae.
The scientists suggest that by looking at a large number of supernovae in a certain region of the universe, they should be able to tell whether the objects are really accelerating away, or if their light is merely being distorted in a void.
The new study will be detailed in an upcoming issue of the journal Physical Review Letters.
Comments 1 - 44 of 44 |
Reload Comments | Back to Top | Page Numbers2. Comment #257681 by Quetzalcoatl on October 1, 2008 at 12:51 am
Hmm. The article doesn't mention how big this "void" is supposed to be. Given that there are a few galaxies relatively close to us (in size-of-the-universe terms), I presume they're talking in the order of billions of light-years.
It does seem to violate the principle that we, or rather the galaxy of which we are a part, is not anything special. I wonder if they have a theory as to what could cause an area to have so much less matter?
Other Comments by Quetzalcoatl
3. Comment #257691 by reedbraden on October 1, 2008 at 1:09 am
I'm deeply intrigued. But if we live in a relative void, why does that make us special? There could be billions of these voids. Hell, the entire universe could be a particularly matter-free bubble in the midst of trillions of other universes with more matter, but that doesn't mean it's special. Other Comments by reedbraden
4. Comment #257693 by GaryHeron on October 1, 2008 at 1:19 am
If we are in a void then does this mean that our observations that indicate that the density of matter in the universe will cause the universe to be flat are wrong and that the density is greater than we think, making the universe closed?
Since the idea of inflation is used to explain a flat universe, would a closed universe mean we have to reconsider the idea of inflation?
Other Comments by GaryHeron
5. Comment #257695 by Quetzalcoatl on October 1, 2008 at 1:21 am
GaryHeron-
A closed universe would have problems for inflation. But there are other observations that we would expect if the universe was closed that we do not see, so in all likelihood the universe is open.
Other Comments by Quetzalcoatl
6. Comment #257697 by Quetzalcoatl on October 1, 2008 at 1:23 am
GaryHeron-
This article on the subject of the shape of the universe might be helpful:
http://en.wikipedia.org/wiki/Shape_of_the_universe
Other Comments by Quetzalcoatl
7. Comment #257699 by Sargeist on October 1, 2008 at 1:26 am
damn all these articles about cosmology. The part of physics about which I know the least.Oh well, back to books, I suppose.
Other Comments by Sargeist
8. Comment #257717 by dvespertilio on October 1, 2008 at 2:39 am
I've been living in my own bubble universe for a long time. Doesn't everyone?Other Comments by dvespertilio
9. Comment #257720 by Steve Zara on October 1, 2008 at 2:52 am
Comment #257695 by QuetzalcoatlInflation has no problems with the universe being closed. It simply makes the universe very, very, very big.
Other Comments by Steve Zara
10. Comment #257722 by Quetzalcoatl on October 1, 2008 at 2:56 am
I stand corrected. Other Comments by Quetzalcoatl
11. Comment #257727 by Steve Zara on October 1, 2008 at 3:00 am
Comment #257722 by QuetzalcoatlYou actually highlighted interesting issues with inflation. It has been messed about with to ensure it fits all kinds of possible shapes of universe.
Other Comments by Steve Zara
12. Comment #257730 by moopet on October 1, 2008 at 3:07 am
I have a tiny problem with science writing like this: regardless of the big issues, they often get the trivia wrong. Is it nit-picking to point out that she says in a dark-energy-universe light gets dimmer as it travels through space and in a void-universe it only diffuses at the interface? The target audience absorbs a lot of the minor details without thinking much about them. Other Comments by moopet
13. Comment #257754 by Oystein Elgaroy on October 1, 2008 at 4:28 am
These "bubble" models are different from the standard Big Bang-models, so the concepts of "open" and "closed" geometries don't apply straighforwardly. As far as I know, it has not been shown how to combine a "Hubble bubble" with inflation. But what has been shown is that we have to live very close to the center of a bubble, otherwise the cosmic microwave background would look very different from what it does. To my mind, at least, dark energy seems like a simpler explanation of the observations. Other Comments by Oystein Elgaroy
14. Comment #257946 by Old Sarum on October 1, 2008 at 9:26 am
The difficulty with the Copernican principle is that we know that there are many locations within the observable universe that are more "special" - in the sense of being more empirically restricted - than ours. And in many of these locations, there's no reason why observers shouldn't arise, & have to discover & comprehend the "special" nature of their own perspective of the cosmos, before they have any hope of making sense of it.Most of this "specialness" is associated with the scale on which observers function. We are fortunate in being born into an environment that is reasonably transparent, on the scale of our Hubble volume. But it's becoming increasingly probable that our Hubble volume is but a tiny fragment of a much bigger picture, stretching back into histories that are never likely to be fully traceable.
After decades of cosmological over-confidence, we might once again have to become accustomed to "mystery" as one of the fundamental properties of the broader universe, on a human scale.
Other Comments by Old Sarum
15. Comment #257949 by NewEnglandBob on October 1, 2008 at 9:28 am
13. Comment #257754 by Oystein Elgaroy:Thanks Oystein. Your statement seems the most rational explanation to me. If we were close to the middle of a bubble, that would put us back to the 'center of it all' which has been discounted for hundreds of years now.
Other Comments by NewEnglandBob
16. Comment #257987 by ggab7768 on October 1, 2008 at 10:11 am
Ummm....
Me like big words and sciency stuffs.
Some of this is over my head, but I think I'm getting it. I love that you cats are always here to help.
Thanks you big brained bastards (bows and kisses many rings).
Other Comments by ggab7768
17. Comment #258009 by Old Sarum on October 1, 2008 at 10:42 am
how much if any of the universe is outside of our observable part?
According to recent studies of the data from WMAP (Wilkinson Microwave Anisotropy Probe), cosmologists Douglas Scott & J.P. Zibin say "...we can say that there are at least 21 patches out there the same volume as (our observable universe), at 95% confidence. Moreover, even if the precision of our cosmological measurements continues to increase, density perturbations at the particle horizon size limit us to never knowing that there are more than about 10^5 patches out there."
Their PDF paper can be downloaded through here:
http://arxiv.org/abs/astro-ph/0605709
Other Comments by Old Sarum
18. Comment #258012 by Oystein Elgaroy on October 1, 2008 at 10:44 am
Comment #257967 by Ultraviolet G Question: if the age of the universe is approx. 13.7 billion years: and the observable universe is approx 90 billion lightyears across, how much if any of the universe is outside of our observable part? beyond *that*, do we get nothing? or do we get other bubbles with possibly different physical laws?
First of all, the kind of bubble they talk about in the article has a radius of a few billion light years, so it is smaller than the observable universe. Then you have the kind of bubbles you get in inflationary scenarios. The exact size of these bubbles depends on the details of the inflation model, but they are typically much larger than the observable universe. What the conditions are like outside the observable universe is again hard to tell. There might be different "physical laws", at least for those laws where the details were determined by events taking place after inflation. And outside our bubble, the laws may be very different.
Other Comments by Oystein Elgaroy
19. Comment #258019 by dvespertilio on October 1, 2008 at 10:57 am
"Double, double toil and trouble; fire burn and cauldron bubble." Much ado about bubbles. Maybe the cosmos exist in a giant champagne bubble? Seriously, though, most of this stuff is way beyond me. I think "they" publish it just to keep us in the dark, so to speak.Other Comments by dvespertilio
20. Comment #258030 by amalthea on October 1, 2008 at 11:14 am
As I understood the whole concept of inflation, post-Big Bang, the spread of matter would be random, not even (it's not like it was engineered to impress, like, say a firework) and so I would naturally expect some random patches of concentration and, conversely, of void. I wouldn't really see ourselves as special by being in a 'void'. We just happen to be where we are.
Looking at what we can in the near universe, there seems to be a definite lack of uniformity, so it also seems reasonable to expect clumps and big gaps, or voids.
Then again, I'm a biologist, so what do I know?
Other Comments by amalthea
21. Comment #258047 by Oystein Elgaroy on October 1, 2008 at 11:36 am
Comment #258030 by amalthea As I understood the whole concept of inflation, post-Big Bang, the spread of matter would be random, not even (it's not like it was engineered to impress, like, say a firework) and so I would naturally expect some random patches of concentration and, conversely, of void. I wouldn't really see ourselves as special by being in a 'void'. We just happen to be where we are.
Looking at what we can in the near universe, there seems to be a definite lack of uniformity, so it also seems reasonable to expect clumps and big gaps, or voids.
It is true that the universe had small inhomogeneities after inflation, and that these have grown to the large-scale structures we see in the universe today. But in most models for inflation you would not expect to produce underdense bubbles of the size we are talking about here, of the order of a billion light years.
Other Comments by Oystein Elgaroy
22. Comment #258058 by prettygoodformonkeys on October 1, 2008 at 11:51 am
Are we talking 6,000 light years close? Because I know of some folks who would LOVE that!
Close = young = Feeling Special Again!
Other Comments by prettygoodformonkeys
23. Comment #258061 by Oystein Elgaroy on October 1, 2008 at 11:54 am
Comment #258058 by prettygoodformonkeys Are we talking 6,000 light years close? Because I know of some folks who would LOVE that!
More like 6 billion. I am afraid that science lets those folks down once again. But they don't care anyway.
Other Comments by Oystein Elgaroy
24. Comment #258090 by aprocess on October 1, 2008 at 12:16 pm
I've been thinking along similar lines for years!The universe is like a Cadbury's Crunchie, with each bubble being empty space created by its own Big Bang. Our BB could have pushed the already existing matter so far away we can only see its gravitational effects. It could be that, while we think its getting bigger, the Universe is collapsing.
Other Comments by aprocess
25. Comment #258092 by Swordmaiden on October 1, 2008 at 12:18 pm
Blimey, I wish I wasn't such a thicky!
I find all this so interesting but Im not clever enough to understand it....can someone please write Science and Space for Dummies?
I would love to cut through the long words and just visualize it all in laymans terms.
(just a dumb blonde but I bake a nice cake).
Other Comments by Swordmaiden
26. Comment #258094 by decius on October 1, 2008 at 12:19 pm
Comment #258090 by aprocessIt could be that, while we think its getting bigger, the Universe is collapsing
I think it would result in blueshifted as opposed to redshifted doppler effect, if that were the case.
Other Comments by decius
27. Comment #258099 by Steve Zara on October 1, 2008 at 12:25 pm
Comment #258094 by deciusI don't think that is necessarily true. A local bubble of space could have redshifted photons from outside the bubble, even if space was collapsing in that region.
Other Comments by Steve Zara
28. Comment #258100 by decius on October 1, 2008 at 12:26 pm
Comment #258092 by Swordmaiden Try this one.
Other Comments by decius
29. Comment #258108 by decius on October 1, 2008 at 12:30 pm
Comment #258099 by Steve ZaraYes, but he said 'universe'.
Other Comments by decius
30. Comment #258109 by aprocess on October 1, 2008 at 12:31 pm
Comment #258094 by decius: I think it would result in blueshifted as opposed to redshifted doppler effect, if that were the case.I'll clarify a bit more:)
The visible universe is expanding it's just in the minority compared to the rest of the 'crunchie'
A crunchie is a honeycomb sweet made of millions of bubbles, its made when you put cream of tartar into boiling sugar.
Sorry Decius I should have used local bubble instead ;)
Other Comments by aprocess
31. Comment #258112 by Steve Zara on October 1, 2008 at 12:33 pm
Comment #258108 by deciusIndeed, but all we could see of the universe was the view from within our bubble, which may be distorting things.
Other Comments by Steve Zara
32. Comment #258125 by aprocess on October 1, 2008 at 12:51 pm
In the 'Crunchie' model there is likely to be an electromagnetic wave of trillions the magnitude of the entire output of the know universe heading towards us from the shell of the bubble. The only time we would sense it would be when the entire night sky goes white and the Earth is vaporised:(Other Comments by aprocess
33. Comment #258132 by Oystein Elgaroy on October 1, 2008 at 12:54 pm
A model of the universe where we live in an expanding region surrounded by a collapsing one could possibly be constructed. It would be fun, but I can't see what it would help us to explain.
Other Comments by Oystein Elgaroy
34. Comment #258146 by Ty_Webb on October 1, 2008 at 1:24 pm
First of all, the kind of bubble they talk about in the article has a radius of a few billion light years, so it is smaller than the observable universe. Then you have the kind of bubbles you get in inflationary scenarios. The exact size of these bubbles depends on the details of the inflation model, but they are typically much larger than the observable universe. What the conditions are like outside the observable universe is again hard to tell. There might be different "physical laws", at least for those laws where the details were determined by events taking place after inflation. And outside our bubble, the laws may be very different.
Are we really able to detect supernovae at further away than a billion light years? I got the impression from the article that the light got more diffuse when it crossed into our "bubble". Or is this just while it passes through the bubble area, so closer ones would be affected as well. If it's the latter, how did we set our baseline? If supernovae look dimmer than predicted, why do our predictions expect a denser area of space when the area around us is the one that we're "used to"? Sorry for all the questions. I don't really understand and I find this stuff fascinating.
As an aside, the observable universe is presumably getting larger (by around 1 light-year per year). Does that mean that at some point in the future, the entire universe would become visible (assuming it's not expanding)? And, does it mean that new things (if they're moving towards us from outside the observable universe) will pop into view over time?
Other Comments by Ty_Webb
35. Comment #258150 by aprocess on October 1, 2008 at 1:26 pm
It may account for the missing Dark Matter as well as the faster outer Galaxies, because it influences the matter from our Big Bang through gravitation only. It also allows the potential for a more cumulative creation theory.Other Comments by aprocess
36. Comment #258154 by decius on October 1, 2008 at 1:32 pm
Comment #258146 by Ty_Webb Are we really able to detect supernovae at further away than a billion light years?
Yes, they normally outshine the galaxy that contains them.
Some have been detected as far away as 11 billion ly (thus equally old).
Other Comments by decius
37. Comment #258161 by Oystein Elgaroy on October 1, 2008 at 1:40 pm
Comment #258150 by aprocess It may account for the missing Dark Matter as well as the faster outer Galaxies, because it influences the matter from our Big Bang through gravitation only.
I doubt if it could account for the dark matter in the observable universe, since we haven't seen this blue shifted region yet. There is evidence for dark matter on the scales of galaxies, clusters of galaxies etc.
You would also need a funny matter distribution in order to make the collapsing region cause galaxies at the boundary of the observable universe to accelerate. For a spherical distribution of matter, if you consider a test particle at distance R from the center only matter inside r
Other Comments by Oystein Elgaroy
38. Comment #258202 by bachfiend on October 1, 2008 at 3:07 pm
Sigh....Whenever I read an article on cosmology in "New Scientist" I always complain that I understand every single word, it's just the sentences I don't understand. I read the article in the wikipedia about the shape of the universe and I must confess that I prefer the flat universe one, if only because I am a secret closet flat earth believer.Other Comments by bachfiend
39. Comment #258314 by LeeC on October 1, 2008 at 7:50 pm
I just don't buy... so I will wait for the evidence.Until then, I will just look at the pretty pictures WMAP gave us since in there I think I might see the problems with this new idea.
Lee
Other Comments by LeeC
40. Comment #258356 by Palli on October 1, 2008 at 10:46 pm
As a law student, I like these science articles where they make an effort to simplify things.They make me feel as if maybe I'm on the wrong track, I should be discovering things about the universe!
(as opposed to studying details about where responsibility lies when floor-boards get damaged in shipping)
Then I start to really dwelve into these astronomy subject... Which invariably leads to me picking up my torts books again.
Other Comments by Palli
41. Comment #258359 by Raiko on October 1, 2008 at 11:15 pm
Void = special?Why? Who says that the universe doesn't contain 20% voids, 20% super-density areas and 60% normal areas or so?
Why should a void be special?
bachfiend,
I dearly hope the universe is NOT flat. I can just see the outcry of catholics "YES! The entire universe is what was meant when the bible implied the world was flat! Look! It was in the bible all the time! This whole mumbo-jumbo was symbolic speech about the universe."
Other Comments by Raiko
42. Comment #258639 by aprocess on October 2, 2008 at 8:40 am
argh... typed for ages then it didn't register :(Comment #258161 by Oystein Elgaroy
So what is outside the bubble have no visible impact on what is inside?
I thought it might be a uniform effect until you get to the scale of Galaxies and clusters. Is it possible for the mass outside the bubble to create areas inside it where its outward gravity pull is lessened allowing the mass of the galaxy or cluster to take a greater influence on its own matter? It might account for why there is no electromagnetic interactions with Dark matter, it just isn't there. Does it have the potential to skew the results from Earth based experiments?
It sounded better the first time I typed it but I forgot what I typed:(
Other Comments by aprocess
43. Comment #258992 by j.mills on October 2, 2008 at 4:53 pm
Ty_Webb said: As an aside, the observable universe is presumably getting larger (by around 1 light-year per year). Does that mean that at some point in the future, the entire universe would become visible (assuming it's not expanding)? And, does it mean that new things (if they're moving towards us from outside the observable universe) will pop into view over time?
No to the first, because the inflated universe, combined with expansion, is too big for the light-horizon to catch up with before the whole universe fizzles out. (Or somebody will correct me...)
Yes to the second: every day the radius of the observable universe gets one light-day longer, and hundreds of previously unseen galaxies twinkle into being like fairy lights. :)
Other Comments by j.mills
44. Comment #259976 by PERSON on October 4, 2008 at 10:30 am
"The target audience absorbs a lot of the minor details without thinking much about them."Rather than not thinking about them, I think they tend to compare and try to make consistent the things they've picked up. If some of those are wrong, it makes it a lot harder for them to form a consistent model. Further, the comparisons may happen long after reading about them. This is not limited to laymen. A full and integrated understanding of a subject often comes long after it was studied.
"...that would put us back to the 'center of it all' which has been discounted for hundreds of years now. "
Not discounted, just made insignificantly probable.
"can someone please write Science and Space for Dummies?"
Assuming you're not being sarcastic, you could have a look at Bill Bryson's "A Short History of Nearly Everything". My wife liked it. She says she found the audio book version easier to take in after trying the dead trees version a couple of times. It's about the level of a Radio 4 programme, e.g. http://www.bbc.co.uk/radio4/science/chimpanatochimpanzee.shtml or anything else at http://www.bbc.co.uk/radio4/science/
"[Catholics will say] The entire universe is what was meant when the bible implied the world was flat!"
Where does the bible do that?
"44. Comment #258639 by aprocess on October 2, 2008 at 8:40 am
argh... typed for ages then it didn't register :("
The comments system is a bit rubbish. Always logs you out after a few minutes IME. I edit in a text editor, log in again, then cut and paste. A good habit for most comment systems, TBH. I've yet to encounter one that doesn't screw up from time to time.
Other Comments by PERSON
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1. Comment #257677 by GaryHeron on October 1, 2008 at 12:35 am
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