Dark Energy May Be Changing

SpaceAdmiral writes "Nature is reporting that Dark energy, the hypothetical energy driving the universe's expansion, may not be as constant as previously thought. According to new research the strength of dark energy may be very different now than it was when the universe was young."

Comments

well no kidding

[User 956]

According to new research the strength of dark energy may be very different now than it was when the universe was young.

Indeed. Begun, this clone war has.

Lets hope..

[Anonymous Coward]

..that someone shreds some light on the matter.

"I too, sense a disturbance in the Force"

That's a pretty bold statement...

[numLocked]

...considering no one even knows if dark energy EXISTS.

Re:That's a pretty bold statement...

[schwanerhill]

Dark matter is required by looking at galaxy rotation curves. Essentially, the rotation speed of galaxies is too fast given the mass that can be seen, so there must be some mass that doesn't emit light as conventional, baryonic matter does. Dark matter was first hypothesized by Zwicky in 1933 and has been well accepted throughout the astronomical community for decades.

Dark energy is required by looking at Type 1a supernovae from the early universe. Astronomers and cosmologists use Type 1a supernovae, which have a well known intrinsic brightness (they are called a "standard candle"), to establish a cosmological distance scale and measure the expansion rate of the universe. If the universe is composed of ordinary matter and dark matter, the self-gravity of all the matter in the universe would cause the expansion rate to slow over time. A goal of these observations was to determine whether there is enough matter in the universe to stop it from expanding forever and ultimately cause it to collapse back on itself in a "big crunch."

In about 1998, the supernova observations were pinned down well enough to show that the expansion rate is actually increasing with time. Therefore, there must be some "antigravity" force that causes the expansion of the universe to accelerate. This is dubbed "dark energy."

The "cosmic energy budget" says that about 4% of the mass/energy in the universe is ordinary matter, 23% is dark matter, and 73% is dark energy. The matter and dark matter total mass is measured from observations of the cosmic microwave background.

All of this is pretty well supported by the best current observational evidence, although the physical nature of dark matter and dark energy are both poorly understood (and new observations can always change things, of course).

The new claim in the current article is that the effect of dark energy has changed over time. The fundamental problem is that the new evidence relies on gamma-ray bursts, which are not nearly as well established a standard candle as the Type 1a supernovae, so it's much harder to say with certainty what distance they are at. Note that the new claim was presented at the American Astronomical Society meeting in DC last week; it has not yet appeared in a refereed journal. (Nature news is merely reporting on the AAS presentation.) The author himself has an appropriate degree of skepticism of his claim.

(Yes, I am an astronomy grad student, although I don't do any work on cosmology.)

Re:That's a pretty bold statement...

[rodac]

Sigh. Ok, lets try it like this :

Physics is a science. Physics is not really a hard science in the same way as Math is a hard science. Physics is way harder science than Biology and Chemistry but still a lot softer than Math, which is the Queen of Science.

Since Physics is a "soft" science, they have "theories". Some of these theories are either incomplete, not fully understood or maybe incorrect. These theories are still very useful for Physicists, too useful too just discard just because they are not completely correct, complete or provable.
This is different from real hard science such as Math where there are no real "theories" per se and where statements that are not formally provable are worthless.

Anyway, some of these theories in Physics are to physicists too useful to just ignore just because they today are provably incorrect, or not currently provable correct which means :

There are certain theories that stipulate x + y = z.

The problem here is that there are legions of observations that can not be explained using that theory and that according to the theory leads to 1 + 1 = 3.

This is obviously not good since the observations show that the theory is provably incorrect (or lets say incomplete), sso instead of discarding this still useful theory one has "invented" an extra term that explains why the calculations come to the "wrong" number and which covers the errors in the theory : DARK ENERGY/MATTER so then the theory becomes :

1 + 1 + "unobservable dark xxx" = 3

and everyone is happy.


We hard scientists, i.e. mathematicians, find this very funny. You might not understand the joke unless you are a mathematician.

We mathematicians also find the "heat distribution equation in one dimension" hilarious as well since an obvious consequence of it is instant communications faster than light as long as you can construct a thermometer accurate enough.


(of course we have our share of "issues" as well as Mr Goedel was so very kind to show us)

Re:That's a pretty bold statement...

[AndersOSU]

Wow you seem to have a fundemental misunderstanding of the nature of science.

For starters mathematics isn't a science - it tells us nothing about the physical world, mathematics is a tool, nothing more, nothing less. I have the highest esteem for mathematics, but it's not science.

Secondly science has never proved anything. The requirement of the scientific method is that hypothesis be falsifiable. If its predicted results turn out to be reproducably observed you have the makings of a good theory.

I don't know what your gripe about "stub fields" is, but unfortunately kinematics and Newtonian ballistics have been pretty well explained, so physicists have been compelled to move into more arcane fields. Too bad they've never produced anything of value like the computer chip or GPS.

Anyhow this rant reminds me of a joke I heard once whose punchline was something like "When I went to college I learned that all sociologists are really psycologists, who are really biologists, who are really chemists, who are really physicist, who use mathematics - The mathematicians just think they're god."

Re:That's a pretty bold statement...

[Tim C]

You do not understand the scientific method, nor what a science is.

The problem is that using theories, that are just theories and not provably correct

No theory is provably correct. All you can do is fail to disprove them. All you can ever say is that a theory explains the observable results as we can measure them, and that we have been unable to make any observations that run contrary to the theory.

In time, it may be that we improve our measurement-making capacity and find that the theory is *not* correct - this is essentially what happened to Newtonian mechanics. At very small scales and/or very high velocities Newtonian mechanics is wrong, and we need quantum mechanics (for the small) and relativistic mechanics (for the fast).

At no point, however, do we get to sit back, relax, and say "that's that - this one is proven to be correct". Science just doesn't work like that. The closest we get is "this one has survived many attempts to disprove it, so we can be pretty confident in it, but who knows what the future may bring?"

Re:That's a pretty bold statement...

[thesandtiger]

They are only "required" if one insists that current theories are correct and complete.

Kind of like aether was "required." And phlogistion. And igneous fluid.

I'm not saying that dark matter and dark energy don't exist - I don't know, and neither does anyone else - but I am saying that they're not necessarily "required."

Re:That's a pretty bold statement...

[gutnor]

I guess it is obvious that there are some flaw at some level in our understanding of the universe.
It is even so obvious that in order to make the measures stick to the theory, we need to introduce 'patches' that have well known properties, but unknown 'physical' representation like the dark matter and dark energy.

That the way science works. Before having an absolute correct theory we still need any theory to start with, demontrates and experiment and maybe change it or even replace it later. It is easier to start with a theory we are more or less confident with ( by experimentation ) and patch it to make some progress than throw everything away and start from scratch.

Maybe in x years some guy(s) will find that 3 stars in a line of 100 lightyears produce the same effect as if there was an amount y of dark matter. And this guy will be able to demonstrate his theory because thanks to a patched theory during the previous x years, scientists have been able to measure very precisely the characteristic of this dark matter and are able to validate his results!

Now of course, I said 'start with a theory we are more or less confident with' and that's where people starts disagreeing...

Re:That's a pretty bold statement...

[selfsealingstembolt]

Sigh. Ok, let's try this.

Mathematics is not science. It is a very complex formal system. You could desribe it as the science of understanding that system, I guess. But I wouldn't. Although you are right, mathematics is somewhat purer, that does not invalidate physics. For example: Let assume we have a theory of space, time and gravity, that seems to be tremendously correct for all observations we made as of now (note that this is just an example, we do not have such a theory, but please bear with me). Now we observe some new event or something that was out of reach previously, which cannot be described with current theory, and seems to need not a small fix, but a complete rework of current theory. So, does this observation suddenly invalidate the usefulness of the existing body of theory? Does an apple on earth suddenly not fall with the same speed as before and does it not release the same amount of kinetic energy in impact?

What physics is about is one belief: That the world can be described in terms of a formal system (mathematics). That is the only 'faith' physicists have. We don't know (and probably never will) if that is true or not. All we know is that everything in nature that follows rules can be described with a formal system and if there is something that does not follow a set of rules, it cannot be predicted anyways.
Besides that, physics is just trying to find new insights and new systems to describe rule-abiding reality as accurate as possible, using mathematics as a tool. Physics does acknowledge, that it may never be complete. But the knowlege we have gained so far is correct and works, albeit only for the cases in which it has been tested. And no new insight will invalidate that. No machines will stop working, no buildings collapse, because of a new observation that cannot be described within the current body of theory. We may find a better, simpler or more complex theory, which gives for tested known and understood cases the same results as the old one AND describes previously unexplainable observations.

And if you want to start with "formally proveable", may I give you Gödel? Any system complex enough to reference itself (like mathematics) is by definition incomplete AND contains provably unprovable sentences which are nonetheless valid within this system.

Re:That's a pretty bold statement...

[jackbird]

Actually, the ancient Greeks knew the world was round, and made a pretty good stab at measuring it based on simultaneous observations around the mediterranean basin.

Later on, pretty much anybody dealing with sailing ships noticed that the mast came over the horizon before the rest of the ship did. It was the church, with its insistence on the literal veracity of biblical statements about the world, and its stranglehold on political power throughout Europe, that made the Earth's shape a dangerous topic to shout from the rooftops.

For a modern analogue, biology, rather than cosmology, would seem to be the place to look.

Re:That's a pretty bold statement...

[Anonymous Coward]

IIRC, the whole beauty behind Dark Matter is it is supposed to be some constant that solves the problems we have with understanding how the universe operates. If that constant is not constant, then doesn't that sort of ruin the value?

You're confusing dark matter and dark energy, and no, a non-constant dark energy doesn't ruin anything. The point of dark energy, like any theory, is to explain our observations. If our observations indicate that the universe is expanding in a weird way, we may need a weird explanation to account for it.

I'm just reminded of the tendency of science. We make an observation and derive a theory. The theory does not fit subsequent observations, so we try to force the observation to fit the theory.

No, we modify the theory to fit the observations. That's why we replaced a theory with no dark energy by a theory with dark energy, and may need to replace that with a theory involving time-varying dark energy. These modifications are driven by new observations.

Now, it is becoming scientific heresy to say there is no Dark Matter.

Nonsense. What is true is that more and more observations have proven to be consistent with dark matter, and so it is becoming harder and harder to come up with an alternative that is also consistent with all that evidence. That is exactly the process by which new theories become accepted.

Well, I for one do not put any salt in DM because it's unobservable.

You're joking, right? Dark matter is postulated precisely because it has a great many observable consequences. We observe it through gravity.

Sort of like a Devine creator--we can't observe him so we assume he does not exist. So, why do we assume there is DM?

Actually, we can attribute any of our observations to the actions of a divine creator, and thus "support" his existence. The reason why that's not considered scientific is because the divine creator hypothesis makes little in the way of specific, testable, and falsifiable predictions regarding independent phenomena. But dark matter, like all other good scientific theories, does.

An extraordinary Claim requires...

[helioquake]

...extraordinary evidence to support it. I'm not an expert on this
topic (will hear more about it from local experts for sure), but
it doesn't sound a statistically significant claim to me.

For the life of me I can't recall a false study about something...
I think it's about pulsars / neutron star. Astronomers found the
first few pulsars and found them to be aligned in a similar
orientation. This provoked a few new thoughs and fresh ideas
among the community...but later only to realize that the first few
detections happened to be a freak series of coincidence; further
observations revealed that other pulsars orient in many different ways.

Choosing random samples is important here. I'm not sure how carefully
that thought process has been applied here by this author (i.g., that
is what Adam Rees alludes to, I think).

We have to be careful since some people tend to see what they want
to believe in.

article wasn't very clear, but...

[heatdeath]

So...brighter means closer. Since that was the result that prompted us to think that the universe is expanding in the first place, I guess this means that the rate at which the universe is accelerating is accelerating.

http://en.wikipedia.org/wiki/Big_RipBig Rip.

Not THAT again...

[mcrbids]

Didn't we recently conclude that dark matter didn't really need to exist at all?

Re:Not THAT again...

[helioquake]

matter != energy.

Well, in this particular term that is.

I'm sure some nerds will bring in on Einstein reference that is E = mc^2.

He does not really believe in Dark Energy

[anandsr]

He is merely collecting data to disprove the current gravitational model.
He actually believes in Dr. Mannheims Conformal Gravity. An attempt to define
gravity in terms of Conformal Symmetry, which the other three forces observe.

In the theory Dark Energy is just a manifestation of the repulsive component of
gravity. And this force changes with the evolution of the universe. He has just
found proof of this. This would mean that they have discovered something that has
not yet been predicted by the standard model. They have been hard at work to come
up with something that they can predict something that can be proved based on the
observation. The only other significant difference from the standard model is that
in the theory universe is always expanding, and there was no contraction phase.
The observations are not yet conclusive enough on this point.

IANAP but...

[Goalie_Ca]

According to new research the strength of dark energy may be very different now than it was when the universe was young.

Maybe its just the engineer in me, but isn't it possible that we're just observing some other unknown effect. Something so complicated and exotic doesn't feel right. When it comes down to the math we juggle equations around, fit curves, and re-evaluate until the math yields a good approximation. Math juggling is one thing but I don't think there's a strong case for creating a physical entity for it.

Re:IANAP but...

[anandsr]

MOND cannot explain anything like this. It was designed to fit the galactic curves. It cannot do anything more. I wouldn't even place much faith in the theory designed around MOND, to come up with these results. Actually the result is alluding to Conformal Gravity by Dr. Mannheim. In this theory gravity has three components one like Newton, second that increases with distance and is felt at galactic distances, third that increases with the square of distance but is repulsive and is felt only at cosmological scales but does manifest itself as an extra attractive constant component at galactic scales.

In the theory repulsive component decays with the evolution of Gravity, and hence the Dark Energy which is what the repulsive component amounts to.

String Theory Fallout

[ObsessiveMathsFreak]

There's already a few comments openly questioning and in some cases deriding the concept of dark energy. I think this could well be fallout from String Theory's current fall from grace.

It's looking more and more like String Theorists are on the wrong track. I think this may have bred a new skeptisism in people with regard to the more "out there" physics theories.

The whole debate about Intelligent Design may also be playing a part. There's been a very public question about "what is science". String Theory has already come under fire from this, and it's understandable that some other theories such as Dark Energy might also be brought under the spotlight of a new skeptisism.

This might be stifling for scientists, paticularly those with more outlandish sounding, but still reasonable hypotheses. But ultimately I think it will be good for science. No one should blindly accept any scientific theory without sufficient evidence. And supplying that evidence can only further validate the theory. In this sense, skeptics are good for science.

more information

[anandsr]

This is the actual press release from Dr. Schaefer.
http://www.phys.lsu.edu/GRBHD/pressrelease/
It seems that the results are very damning to cosmological
constants.

Unfortunately there are no good web sites talking about
Mannheim's theory the only paper that explains a lot of
it is "Alternatives to Dark Matter and Dark Energy" which
can be accessed at http://arxiv.org/abs/astro-ph/0505266

Ob blackadder quote

[zmollusc]

So, what you're telling me, Percy, is that something you have never seen is slightly less blue than something else you have never seen.

Re:It is changing, but we don't know which way

[FhnuZoag]

It seems to be getting stronger.

An analysis: http://cosmicvariance.com/2006/01/11/evolving-dark -energy/

OMFG, COSMIC WARMING

[Rogerborg]

Now do you see the folly of driving huge SUVs?

Math != Science

[brunes69]

Mathematics is not a science. It is a tool (an important tool, but a tool nonetheless) that is used in science. Science (from Latin scientia - knowledge) refers to a system of acquiring knowledge - based on empiricism, experimentation, and methodological naturalism. Mathematics is not based on experimentation or empiricism, it is based on deduction and logic.

Also, I don't know how you could argue that physics is not a "hard" science. As the sciences go, one can argue that physics is the "hardest" science of them all, because at a fundamental level, all the other "hard" sciences (chemistry, biology, geology, etc) derrive from physics in one form or another.

Some astronomers doubt this result

[Wormholio]

A longer article on this in the NY Times says that other astronomers doubt this result.