Posted on 11/16/2006 9:07:52 PM PST by NormsRevenge
NEW YORK - The Hubble Space Telescope has shown that a mysterious form of energy first conceived by Albert Einstein, then rejected by the famous physicist as his "greatest blunder," appears to have been fueling the expansion of the universe for most of its history.
This so-called "dark energy" has been pushing the universe outward for at least 9 billion years, astronomers said Thursday.
"This is the first time we have significant, discrete data from back then," said Adam Riess, a professor of astronomy at Johns Hopkins University and researcher at NASA's Space Telescope Science Institute.
He and several colleagues used the Hubble to observe 23 supernovae — exploding white dwarf stars — so distant that their light took more than half the history of the universe to reach the orbiting telescope. That means the supernovae existed when the universe was less than half its current age of approximately 13.7 billion years.
Because the physics of supernova explosions is extremely well-known, it is possible for the astronomers to gauge not just their distance, but how fast the universe was expanding at the time they went off.
"This finding continues to validate the use of these supernovae as cosmic probes," Riess said.
He and his colleagues describe their research in a paper that is scheduled for publication in the Feb. 10 issue of Astrophysical Journal.
The idea of dark energy was first proposed by Einstein as a means of explaining how the universe could resist collapsing under the pull of gravity. But then Edwin Hubble — the astronomer for whom the NASA telescope is named — demonstrated in 1929 that the universe is expanding, not a constant size. That led to the big-bang theory, and Einstein tossed his notion on science's scrap heap.
There it languished until 1998, when astronomers who were using supernova explosions to gauge the expansion of the universe made a shocking observation. It appeared that older supernovae, whose light had traveled a greater distance across space to reach the Hubble telescope, were receding from Earth more slowly than simple big-bang theory would predict. Nearby supernovae were receding more quickly than expected. That could only be true if some mysterious force were causing the expansion of the universe to accelerate over time.
Cosmologists dubbed the force "dark energy," and ever since they've been trying to figure out what it is.
"Dark energy makes us nervous," said Sean Carroll, a theoretical physicist at the California Institute of Technology who was not involved in the supernova study. "It fits the data, but it's not what we really expected."
Answers may come once NASA upgrades the Hubble Space Telescope in a space shuttle mission scheduled for 2008. NASA and the Department of Energy are also planning to launch an orbiting observatory specifically designed to address the mystery in 2011.
Dark energy could be some property of space itself, which is what Einstein was thinking of when he proposed it. Or it could be something akin to an electromagnetic field pushing on the universe. And then there's the possibility that the whole thing is caused by some hitherto undiscovered wrinkle in the laws of gravity.
BTW no more rants please. I may know more than you think.
Er, no. Quantum field theory and General Relativity don't appear to mix because a quantized spin-2 (read: gravitational) field can't be renormalizable (read: finite) in four dimensions. That's a mathematical fact that's independent of the value of the cosmological constant.
Which side are you on out of curiosity?
Extra dimensions. I believe QFT and GR are both correct. There is experimental evidence of the quantized nature of the gravitational field. If all that is the case, it implies that there are more dimensions than the four we measure.
Maybe, but there are others reading the thread who don't.
Re post #24. Yes, you are absolutely right.
Maybe that's when the first advanced civilization in the Universe decided it was time to reverse the collapse.
Quantum physics has yet to offer us gravitational equations, does it not?
As for General Relativity, the gravitational equations will not hold up under higher values, will they?
So what's your angle? Over-unity energy generation? Faster-than-light relativity skeptic? 6,000-year-old universe? New-age quantum consciousness...stuff? Just curious.
Chimps considering a Rolex Watch as to what it is?, where it came from?, what it's good for?, and is it good to eat?...
And since no chimp ever yet thought of God.. will never find out..
If ever there was a group that needed to be on the wrong side of an event horizon, it's this bunch.
Quantum field theory and General Relativity don't appear to mix because a quantized spin-2 (read: gravitational) field can't be renormalizable (read: finite) in four dimensions.
There is experimental evidence of the quantized nature of the gravitational field.
my uninformed spectulation is as follows.
Most everything in the universe seems to be in discrete packets or quanta.
I speculate that even time comes in discret packets and it ticks like an old fashioned clock.
The acceleration in the expansion, may simply be a result of a "clock" that is "ticking" faster across the universe.
The first would require a treatise. I'll see if I can search up a cogent link tomorrow.
As for the second, here's an old FR thread about an underappreciated demonstration of the quantum nature of gravity.
Specifically is a field or a wave quantized?
I don't really understand the question "is a wave quantized"; I might recommend that you read up on "particle/wave duality". As for fields, we know that the electromagnetic field, the weak nuclear field, and the strong nuclear field are all quantized, meaning that they can be modelled as the exchange of "force particles". We don't know mathematically how to do that with gravity, yet.
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