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."

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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.

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.