Is Dark Energy Getting Weaker?? Your views

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xXTheOneRavenXx

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I found this article (which was released yesterday) while browsing through some of my favorite websites. If this is information proves to be true, what does this mean for our understanding of the universe?

Rachel Courtland from NewScientist.com":3seinkj8 said:
AFTER billions of years of runaway expansion, is the universe starting to slow down? A new analysis of nearby supernovae suggests space might not be expanding as quickly as it once was, a tantalising hint that the source of dark energy may be more exotic than we thought.

For more than a decade, astrophysicists have grappled with evidence of a baffling force that seems to be pushing the universe apart at an ever-increasing rate. Exactly what constitutes the dark energy responsible for this cosmic speed-up is unknown, says Michael Turner at the University of Chicago. "The simplest question we can ask is 'does the dark energy change with time?'"

So far, the evidence has suggested that dark energy is constant, though its effect on the universe has become stronger as the universe has expanded and the gravitational force between objects weakens with distance.

Now an analysis of supernovae suggests dark energy may actually be on the wane. In a paper on the physics preprint website, a team led by Arman Shafieloo at the University of Oxford examined a newly released catalogue of supernova explosions, including a number of relatively recent blasts nearby (http://www.arxiv.org/abs/0903.5141). They found that the new data made the best fit with a universe in which dark energy is losing strength. "It seems acceleration is slowing down," says Shafieloo.

The first evidence of dark energy emerged in 1998, when two teams of astronomers spotted distant supernova explosions that appeared dimmer than expected, and so further away. The find suggested the exploding stars were receding from Earth faster than anticipated, and therefore so was the rest of the universe. "Dark energy" was invoked to explain the apparent anomaly. Since then more supernovae have been catalogued to help build up a picture of how the universe has expanded over time.

The biggest set of supernova data was released earlier this year by the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. It includes data on 147 supernovae that exploded in the last billion years, more than half of them newly discovered (http://www.arxiv.org/abs/0901.4787). The Harvard team analysed the new supernovae assuming that dark energy has remained unchanged.

Shafieloo, however, dropped the requirement that dark energy be constant over the universe's history. Together with Varun Sahni of the Inter-University Centre for Astronomy and Astrophysics in Pune, India, and Alexei Starobinsky of the Landau Institute for Theoretical Physics in Chernogolovka, Russia, Shafieloo used an approach he says is particularly sensitive to rapid changes in the universe's rate of expansion.

Beginning with factors like red shift - a measure of how much the expansion of space has stretched the light from each explosion - they calculated a representative number for the epoch in which each supernova occurred. After plotting all of these numbers, they found that the best fit was a scenario in which dark energy has weakened over the last 2 billion years, causing cosmic acceleration to slow down. Shafieloo cautions that their result is preliminary, but adds that it could be time to begin revisiting other models of dark energy.

"Their approach is reasonable," though the effect is slight, says cosmologist Dragan Huterer of the University of Michigan, Ann Arbor. "If that is really the case it would be a tremendous discovery."
The effect is slight, but if true it would change our ideas about the source of dark energy

Indeed, it would change our ideas about the source of dark energy. Until now, all signs have pointed to the cosmological constant as the simplest explanation for the accelerating expansion of the universe. This constant is an unchanging energy that arises from quantum fluctuations in the vacuum of space. "The cosmological constant is the only thing that makes any sense to particle physicists right now," says Huterer.

Yet if dark energy is changing, the cosmological constant could not be the driver. Instead, it would suggest far more exotic physics at work. It might even mean dark energy does not exist at all (see "We don't need the stuff"). One example of an exotic origin is "quintessence", a theoretical quantum field that permeates space like the as-yet-unidentified field thought to have driven inflation right after the big bang. This field could be dissipating and losing energy, eventually causing the universe to decelerate and collapse back on itself.

A more likely explanation for the team's result is a slight bias in the new supernova data, Huterer says. Robert Kirshner, a member of the Harvard team, agrees. "I think these are serious people whose analysis should be taken seriously, but there can be more than one cause for the apparent effect," he says.

For example, a potential bias could have been introduced thanks to dimmer objects being easier to see if they are nearby. It is possible that the Harvard team happened to catalogue a disproportionate number of nearby supernovae that were faint or obscured by dust. Astronomers must correct for the dimming effect of dust and other subtleties in order to estimate a supernova's true peak brightness. But the team may have overcompensated in this correction, producing a catalogue of nearby supernovae that are slightly too bright for their distance. That would create the illusion that the universe's acceleration has been slowing.

New observations from other groups need to be examined to look for the same effect, Kirshner says, though determining whether dark energy really is changing could take a while. The fine details of so many supernovae have been recorded that the so-called "systematic floor" has been hit - a scenario in which everything from subtle differences between supernova explosions to the warp of a telescope mirror can skew results, Huterer says.

Upcoming "precision projects" like the Dark Energy Survey, which will mount a supersensitive 500-megapixel camera on a 4-metre telescope at the Cerro Tololo Inter-American Observatory in Chile, aim to reduce some of the sources of uncertainty. One of the project's aims is to measure some of the universe's most recent history, by recording about 2000 supernovae that have exploded in the last 7 billion years.

Other probes that will push the limit in sensitivity are still in early planning, including two space probes - the US's Joint Dark Energy Mission and Europe's Euclid. Some astronomers suspect a partnership will be forged between these missions to send up a single international probe instead.

It is practically impossible to definitively discover if dark energy is constant. "There isn't a target to shoot for," says cosmologist Sean Carroll of Caltech. "As we narrow down the error bars and get closer and closer to perfectly constant, there's no point at which you say 'OK. We're done. Dark energy is constant.'"

However, the next burst of effort could reveal in glowing detail if dark energy has been changing. "It would be a surprise if we found that dark energy were varying with time," says Carroll, "but it would be so hugely important that it's still worth looking."
 
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DrRocket

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xXTheOneRavenXx":3uvk8cyc said:
I found this article (which was released yesterday) while browsing through some of my favorite websites. If this is information proves to be true, what does this mean for our understanding of the universe?

Interesting article.

Since you are soliciting opinions, here is my opinion (opinions are not facts).

1. Our understanding of the unverse is rather primitive. There is a lot more that we don't understand regarding the origins and expansion of the universe than we do understand.

2. The data supporting an expanding universe is rather compelling. Expansion seems to fit rather well with redshift data and with general relativity. Other data also supports it.

3. The data for an accelerating expansion is relatively recent, and is based on more subtle analysis of experimental data. The more complicated an analysis, and the more it relies on statistical techniques, the more likely it is to be wrong. That data for accelerating expansion is generally pretty good, but not nearly as compelling as the data for expansion itself. It suggests a need for entirely new physics, a new form of energy conveniently labeled "dark energy". The evidence for dark energy is strong but not compelling, at least to me. It can be modeled with a cosmological constant in the Einstein field equations, but there is no clear reason for such a constant beyond the the hypothesis tha the expansion is accelerating.

4. This new information seem to be a result of analysis of relatively new data using even more subtle statistical analyses. That makes it more prone to error than either the analysis suggesting an expanding universe or the data suggesting the expansion to be accelerating. To model this effect (basically a third derivative) you have to hypothesize that the cosmological constant (or dark matter) is not constant at all by varies in time. That brings up the additional kicker that time itself is not a well-defined global parameter in a curved space-time.

5, Now we are baclk to point 1. Our ignorance of the working of the universe on a large scale is profound. This piece of work serves to emphasize just how profoundly deep that ignorance is.

My experience is that research of a theoretical nature proceeds in cycles. First one obtains a body of experimental facts or considers a number of simple examples that illustrate, hopefully, an underlying unifying theory. Second theorists consider the available evidence and develop a solid mathematical model that explains the data or examples, and that work continues until the theory becomes somewhat abstruse and disconnected from experience. Then more data and examples are developed and inadequacies or incompleteness in the theory is exposed. Explanations in terms of ad hoc ides or "patches" to existing theories are considered, until the patchwork simply starts to look silly. Then the theorists take over again and develop new theories and extensions of the old ones replacing the patchwork with a new and unified new theoretical construct. This exemplified by Einstein's development of relativity to replace classical Newtonian mechanics or the replacement of classical Maxwellian electromagnetic theory with quantum electrodynamics.

We seem now to be in the position where we have a lot of data that is not explainable by means of the available theory. It is time for some serious theoretical work and the development of really new theoretical concepts, not simply applying patches to the old ones. The patchwork is starting to look ridiculous.
 
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xXTheOneRavenXx

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DrRocket":2hbyg2va said:
xXTheOneRavenXx":2hbyg2va said:
I found this article (which was released yesterday) while browsing through some of my favorite websites. If this is information proves to be true, what does this mean for our understanding of the universe?

Interesting article.

Since you are soliciting opinions, here is my opinion (opinions are not facts).

This is really what I'm looking for here. I have to agree with everything you said Dr. Rocket. Our understanding of the universe is pretty minimal. We can do all the calculations and still come up with unexplainable phenomena. Look at the Dark Flow for one example. How it "should" work is that the motion of galaxy clusters with respect to the cosmic microwave background should be randomly distributed in all directions, however the study of the Dark Flow found evidence of a common motion of at least 600 km/s toward a 20-degree patch of sky between the constellations of Centaurus and Vela. How is that possible given what we currently know?

Perhaps in our study of the universe we will encounter even more puzzling discoveries that will without a doubt will cause a change in our current way of thinking.

Could this also indicate a concentrated "flow" of Dark Energy causing this phenomena? If it were gravity causing this then wouldn't a mass be required to attract these bodies?

Is there any other indications besides this article that Dark Energy might be weakening?
 
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DrRocket

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xXTheOneRavenXx":3kd30gar said:
This is really what I'm looking for here. I have to agree with everything you said Dr. Rocket. Our understanding of the universe is pretty minimal. We can do all the calculations and still come up with unexplainable phenomena. Look at the Dark Flow for one example. How it "should" work is that the motion of galaxy clusters with respect to the cosmic microwave background should be randomly distributed in all directions, however the study of the Dark Flow found evidence of a common motion of at least 600 km/s toward a 20-degree patch of sky between the constellations of Centaurus and Vela. How is that possible given what we currently know?

Perhaps in our study of the universe we will encounter even more puzzling discoveries that will without a doubt will cause a change in our current way of thinking.

Could this also indicate a concentrated "flow" of Dark Energy causing this phenomena? If it were gravity causing this then wouldn't a mass be required to attract these bodies?

Is there any other indications besides this article that Dark Energy might be weakening?

Maybe but I am skeptical. I am of the opinion that this "dark flow", a rather new observation, needs a bit more time to be studied and verified before it is accepted. I think there has been a bit too much hype surrounding this notion so far. I would not get too excited about it just yet. Let the pros digest and challenge the data a bit longer. Then see if it still looks real.

Either all of this "dark stuff" represents a tremendous gap in our understanding of fundamental physics, or else there is problem with the data or the interpretation of that data. I am personally a bit skeptical of oversensationalized accounts of both new data and unproven new theories. I think it is time for some serious, sober, research at a fundamental level and out of the spotlight of sensational reporting. More content, less hype.

Think about it. You ask a reasonable question, based on recent reports from popular science articles as to whether dark energy is getting weaker. No one has shown that dark energy even exists, let alone whether or not it is getting weaker !
 
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xXTheOneRavenXx

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Yes, I know the story on this is still being scrutinized. Astrophysicist Ned Wright even challenged this discovery on a few points. So far the discoverers only answered a few of his challenges.

DrRocket":1ry4eyf7 said:
Think about it. You ask a reasonable question, based on recent reports from popular science articles as to whether dark energy is getting weaker. No one has shown that dark energy even exists, let alone whether or not it is getting weaker !

That is absolutely true, and of course I am aware of speculation. Of course Dark Energy is just a theory at the moment and is widely accepted as a possibility. I know it would take some time, but maybe the true astrophysicists should go back over the years of formulas that were developed and come up with "New Age" theorems. It's as you said before, old formulas have been patch worked to a great extent over the years. I don't think they are "wrong", but rather it would surely increase accuracy and help with explanations of these new discoveries.
 
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DrRocket

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xXTheOneRavenXx":39ldqww2 said:
DrRocket":39ldqww2 said:
Think about it. You ask a reasonable question, based on recent reports from popular science articles as to whether dark energy is getting weaker. No one has shown that dark energy even exists, let alone whether or not it is getting weaker !

That is absolutely true, and of course I am aware of speculation. Of course Dark Energy is just a theory at the moment and is widely accepted as a possibility. I know it would take some time, but maybe the true astrophysicists should go back over the years of formulas that were developed and come up with "New Age" theorems. It's as you said before, old formulas have been patch worked to a great extent over the years. I don't think they are "wrong", but rather it would surely increase accuracy and help with explanations of these new discoveries.

That depends on what you mean by "New Age" theorems. There is a lot of "New Age" "science" out there these days -- all crap.

There is also a lot of work going on at the foundations of physics. But there has been way too much hype and reporting in the popular press. It has gotten to the pont where conjectures are being treated as fact, even by some professionals who ought to know better.
 
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xXTheOneRavenXx

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DrRocket":2d9bmlbp said:
That depends on what you mean by "New Age" theorems. There is a lot of "New Age" "science" out there these days -- all crap.

There is also a lot of work going on at the foundations of physics. But there has been way too much hype and reporting in the popular press. It has gotten to the pont where conjectures are being treated as fact, even by some professionals who ought to know better.

What I mean by "New Age" is the review of all the old formulas at the foundations of physics (good choice of words btw) and rebuild them. It's like patching up the body of an old car. You can only apply so many patches. Eventually you will need to build a new body. The car may look the same in the end, but it's make up is stronger.

I noticed that as soon as someone mentions a possibility of a new discovery, even the news media jumps all over it now a days; if it seems interesting enough. I think it's also a part of these new researchers trying desperately to make a name for themselves. Like trying to "out do" their predecessors.
 
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DrRocket

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xXTheOneRavenXx":286x7o7s said:
I noticed that as soon as someone mentions a possibility of a new discovery, even the news media jumps all over it now a days; if it seems interesting enough. I think it's also a part of these new researchers trying desperately to make a name for themselves. Like trying to "out do" their predecessors.

That is probably part of it. I am a bit more cynical and, having observed that some people who already are well known are writing books that put forth speculative cuttiing edge ideas as "truth", think that money and ego may be bigger factors.
 
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xXTheOneRavenXx

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DrRocket":10wb7vff said:
xXTheOneRavenXx":10wb7vff said:
I noticed that as soon as someone mentions a possibility of a new discovery, even the news media jumps all over it now a days; if it seems interesting enough. I think it's also a part of these new researchers trying desperately to make a name for themselves. Like trying to "out do" their predecessors.

That is probably part of it. I am a bit more cynical and, having observed that some people who already are well known are writing books that put forth speculative cuttiing edge ideas as "truth", think that money and ego may be bigger factors.

Of course, money always talks. I would hope accurate information in the science world would be their priority.
 
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