Fermilab Reports Dark Energy Not Needed

An anonymous reader writes "A Fermilab press release reports that the expansion of the universe may be explainable without the need for dark energy or a cosmological constant. Apparently, ripples from inflation in the early universe may account for the observed expansion rate of the universe."

Comments

Nothing for you to see here.

[brilinux]

Nothing for you to see here. Please move along.

Well, apparently the dark matter is still important on Slashdot.

But what about the Horizon problem?

[mr100percent]

But what about the Horizon problem?

From an earlier /.-linked article 13 things that do not make sense:

The horizon problem

OUR universe appears to be unfathomably uniform. Look across space from one edge of the visible universe to the other, and you'll see that the microwave background radiation filling the cosmos is at the same temperature everywhere. That may not seem surprising until you consider that the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old.

Nothing can travel faster than the speed of light, so there is no way heat radiation could have travelled between the two horizons to even out the hot and cold spots created in the big bang and leave the thermal equilibrium we see now.

This "horizon problem" is a big headache for cosmologists, so big that they have come up with some pretty wild solutions. "Inflation", for example.

You can solve the horizon problem by having the universe expand ultra-fast for a time, just after the big bang, blowing up by a factor of 1050 in 10-33 seconds. But is that just wishful thinking? "Inflation would be an explanation if it occurred," says University of Cambridge astronomer Martin Rees. The trouble is that no one knows what could have made that happen.

So, in effect, inflation solves one mystery only to invoke another. A variation in the speed of light could also solve the horizon problem - but this too is impotent in the face of the question "why?" In scientific terms, the uniform temperature of the background radiation remains an anomaly.

"A variation in the speed of light could solve the problem, but this too is impotent in the face of the question 'why?'"

Also, in the same article, Dark Energy is discussed:

9 Dark energy

IT IS one of the most famous, and most embarrassing, problems in physics. In 1998, astronomers discovered that the universe is expanding at ever faster speeds. It's an effect still searching for a cause - until then, everyone thought the universe's expansion was slowing down after the big bang. "Theorists are still floundering around, looking for a sensible explanation," says cosmologist Katherine Freese of the University of Michigan, Ann Arbor. "We're all hoping that upcoming observations of supernovae, of clusters of galaxies and so on will give us more clues."

One suggestion is that some property of empty space is responsible - cosmologists call it dark energy. But all attempts to pin it down have fallen woefully short. It's also possible that Einstein's theory of general relativity may need to be tweaked when applied to the very largest scales of the universe. "The field is still wide open," Freese says.

Re:But what about the Horizon problem?

[PureFiction]

If you read the article you would see they address this issue. The key is to realize that the horizon extends beyond what we can see (our cosmic horizon):

• It is widely believed that during the inflationary expansion early in the history of the universe, very tiny ripples in spacetime were generated, as predicted by Einstein's theory of General Relativity. These ripples were stretched by the expansion of the universe and extend today far beyond our cosmic horizon, that is over a region much bigger than the observable universe, a distance of about 15 billion light years. In their current paper, the authors propose that it is the evolution of these cosmic ripples that increases the observed expansion of the universe and accounts for its acceleration.
• 
  
  "We realized that you simply need to add this new key ingredient, the ripples of spacetime generated during the epoch of inflation, to Einstein's General Relativity to explain why the universe is accelerating today," Riotto says. "It seems that the solution to the puzzle of acceleration involves the universe beyond our cosmic horizon. No mysterious dark energy is required."

Re:But what about the Horizon problem?

[niktemadur]

While it is a generally accepted law that nothing WITHIN space can travel faster than light, this law may not apply to SPACE ITSELF, which could inflate at superluminous speeds if the correct conditions are present.

I know this sounds bizarre, and I'm no expert on the subject, but I'll try to give a simple example that even I can understand:

Let's say space is like a balloon.
Matter are the molecules within that balloon.
The matter within may not move faster than light by its' own means.
But the balloon may inflate faster than light, and the matter within goes along for the ride.
At the end of inflation, the matter has kept its' same relative position in space.

The correct condition for inflation to happen is known as supercooling. Here is an example that Alan Guth used to describe it: water that's below 32 degrees farenheit but retains its' liquid state. However, just gently tap the plastic mold and the water will abruptly crystalize into ice before your very eyes. Supercooled water.

Another example would be a beer in the freezer that's liquid, but turns to ice from the top down when you open the lid. Supercooled beer.

Accordingly, the universe would have to inflate at a certain speed (much faster than light) to re-attain its' appropriate state under specific conditions.

According to Alan Guth, most of the universe's matter cancelled itself out instants after the Big Bang, due to matter-antimatter collitions. In a super-excited state, the universe found itself almost empty, and had to readjust by inflation and a spontaneous burst of creation of matter. In fact, Guth said that with 28 pounds of matter under the right conditions, a universe just as massive as ours could be created. This is why Guth said that our universe could be the ultimate "free lunch".

How did the ripples get there?

[Dancin_Santa]

If there was nothing to push against, what would cause something to be held back and "ripple" as if there were some sort of repulsive force?

Let's say we've reached the edge of the universe, what happens when we step beyond that boundary? What is out there that would possibly hold back further expansion of our universe?

Inflation...

[ackthpt]

Apparently, ripples from inflation in the early universe may account for the observed expansion rate of the universe."

Hmm. Better check the exchange rates on Altairian Dollars, Flainian Pobble Beads and the Triganic Pu.

Has anyone contacted Alan Greenspan about this?

WWDVS?

[LokieLizzy]

(What would Darth Vader say?)

"Do not be so proud of this cosmological terror you have created. Its existence pales when compared to the power of the Dark Side."

Gravity leaks

[Tablizer]

I've read another hypothesis recently: that gravity slowly "leaks" into other dimensions so that over long distances it's attractive force diminishes, and that is why the universe is flying apart. The average distances between the galaxies has now reached a threashold where the leakage makes a big difference, giving the appearence of a relatively sudden expansion speedup.

Re:Difference?

[Pfhorrest]

The other responses to this thus far are completely off. Dark matter and dark energy are not (by any current theory at least) related anything like how normal matter and energy relate via e=mc^2.

Dark Matter is a hypothetical unknown "stuff" with normal mass just like regular matter but which we cannot observe with light; it doesn't appear to be emitting or noticably obscuring any kind of radiation. But we see the movement of galaxies in such a way that they appear to be responding to the mass of something that we can't see. Hence "dark matter" - we can't see it, but it seems to be some sort of matter. Think of it like leaves blowing in the wind - we can't see the wind, but we see the motion is causes.

Dark Energy is another hypothetical unknown "stuff" that seems to be adding, somehow, to the velocity of all objects in the universe. It is postulated because the universe appears to be accelerating in its expansion, which does not make sense given an empty, neutral vaccum and a bunch of matter in it. It should be slowing down or at best, expanding at a steady rate. Hence "dark energy" - we can't detect it, but some source of energy which is causing the expansion of the universe to accelerate.

Hope this helps.

That Einstein...

[Omniscientist]

"Whether Einstein was right when he first introduced the cosmological constant, or whether he was right when he later refuted the idea will soon be tested by a new round of precision cosmological observations," Kolb said.

So either way, Einstein was right. Damn you Einstein!!!

I believe in Dark Energy, and...

[LokieLizzy]

I'm not a scientist.

But I did stay at a Holiday Inn last night. And when the lights went out at midnight (power outage), I can assure you that there was more than a little energy going on in the room next door.

Enjoy Fermilab's work while you can

[stox]

Their budget has been slashed almost in half. After all, low quality bombs are far more important than high quality science. In fact, spending on basic research is dropping at an alarming rate through all the national laboratories. This does not bode well for our future.

Re:Enjoy Fermilab's work while you can

[stox]

Well, we could get into a very long and detailed discussion into the value of basic research. I'll point out just a few of the benefits we have received from Fermilab, and leave the rest to you.

1) Ever hear of a "computing farm"? I'm sure you have. The concept was pioneered at Fermilab.

2) Ask Bob Young, "Who made the most important confirmation of the value of Linux in the early days?" Couldn't be Fermilab, could it? ( Bob Young was one of the founders of RedHat, BTW. )

3) Who has done more basic research into superconductors? Who pioneered the use of superconductors? Fermilab.

4) How many lives have been saved through the use of radiation for treating cancer? Neutron therapy was pioneered at Fermilab.

5) Do you like American Buffalo? At one time, the only surviving herds were at Fermilab and Yellowstone. Fortunately, they have made a comeback.

6) Enjoy using the web? Fermilab was the third website on the planet, behind CERN and SLAC.

I'm sure I have missed a few, but I hope you get the point. We are lucky that our ancestors didn't take the same outlook as you. Some things need a horizon of lifetimes, not just your own. How long was the electron studied? Quantum theory? Radiation? Thankfully, many did, and have left us with a rich environment to live in. I hope the current generation, and those to follow, are wise enough to invest in the future with basic research.

As for my assertion that money devoted to basic research is dropping at a alarming rate, I will leave this as an exercise for the reader. The results of your studies will be quite enlightening, and quite possibly, terrifying.

Re:Not Funny, Insightful

[wanerious]

Insightful? What would you like to have happen? Publish fewer articles? Not research it so much? Sheesh.

This anti-intellectualism stain in /. responders is saddening. Basically it seems to be, "I don't understand what they're talking about, so I think I'll make fun of them" or "I don't understand the thousands of papers that have been published, so I'm going to shout something superior-sounding from the cheap seats". Dismissing a beautiful and maturing field of physics with "we don't really know anything, so give up" is a sophomoric and pretentious reaction.

Sure, there's a bunch that we don't understand, but please realize that this is the way science works. Nature is too subtle for us to have canned and precise answers for her behavior. Cosmologists are rightly invigorated by the new data, and ought to be encouraged to research and refute each other's ideas.

Re:And they call me crazy?

[dalyraptor]

No, something that does not appear possible or make sense in nature does not prove that god exists. You cannot put everything that you do not understand down to god, jesus christ!