Posted on 11/16/2006 7:22:01 PM PST by Jedi Master Pikachu
Dark energy - the mysterious force that is speeding up the expansion of the Universe - has been a part of space for at least nine billion years.
That is the conclusion of astronomers who presented results from a three-year study using the Hubble Space Telescope.
The finding may rule out some competing theories that predict the strength of dark energy changes over time.
Dark energy makes up about 70% of the Universe; the rest is dark matter (25%) and normal matter (5%).
"It appears this dark energy was already boosting the expansion of the Universe as much as nine billion years ago," said co-investigator Adam Riess from the Space Telescope Science Institute in Baltimore, US.
"That's out of a Universe which we think is about 13.7 billion years old - most of the way back."
The findings are consistent with the idea of dark energy behaving like Albert Einstein's cosmological constant. The cosmological constant describes the idea that there is a density and pressure associated with "empty" space.
In this scenario, dark energy never changes; it has the same properties across the age of the Universe.
Repulsive force
Einstein first conceived of the notion of a repulsive force in space in his attempt to balance the Universe against the inward pull of its own gravity, which he thought would ultimately cause the Universe to implode.
His cosmological constant remained a curious hypothesis until 1998, when astronomers used observations of supernovae from ground-based telescopes and Hubble to show that the expansion of space was accelerating.
These findings suggested there really was a repulsive form of gravity in space, a force that was shortly dubbed "dark energy".
There have been many attempts to explain the nature of dark energy.
One of these is that it behaves like the cosmological constant. Another is that dark energy behaves like a field that changes over time. The third proposes changes to our theories of gravity to explain the mysterious force.
The latest data from Hubble contradict theories that dark energy might have behaved differently billions of years ago to how it behaves now, or might not even have been present. Some astronomers had thought that dark energy might mimic whatever was the dominant force in the Universe at the time, such as matter for example.
Previous Hubble observations of the most distant supernovae known revealed that the early Universe was dominated by matter whose gravity was slowing down the Universe's expansion rate.
The observations also confirmed that the expansion rate of the cosmos began speeding up about five to six billion years ago. That is when astronomers believe that dark energy's repulsive force took over from that of gravity.
'Tug of war'
"Imagine that you were having a tug of war and the other end of the rope disappears behind a curtain. Somebody else is tugging on the other end; we'll call that dark energy," said Dr Riess.
"In 1998, we saw that the thing behind the curtain was winning, it was pulling harder and the Universe was accelerating.
"In 2004, we showed that was not always the case. There was a time when you - ordinary matter - were winning. The Universe was decelerating. Now, we have shown that, even at that time, the thing on the other end of the rope was beginning to pull."
The discovery comes from observations of 23 exploding stars, or supernovae. Using Hubble to peer far across the Universe, the astronomers were able see back to a time when the cosmos was less than half its present size.
"These supernovae provide cosmic mile-markers that allow us to measure the growth rate of the Universe about nine billion years ago," said Adam Riess.
Mario Livio, of the Space Telescope Science Institute, added: "Understanding the nature of dark energy is arguably the biggest problem physics is facing today."
In October, the US space agency (Nasa) said that shuttle astronauts would be sent to service the Hubble Space Telescope, which will fail within two or three years without running repairs.
The timescale is off (as the universe is only some 6,000 years old, Earth-time), but an interesting article.
dark energy ping.
The "dark energy" they talk about is really the influence of Satan ...
You do know, of course, how Philip Jose Farmer made the universe both billions of years old AND but 6,000 years old ~
I wonder what the speed of DARK is?
What?
This statement can be interpreted as: "We ain't got the first effin' clue!"
I sounds more like Medieval "Scientists" trying to explain disease.
Not in the version of Genesis I read...
The stories he wrote about pocket universes are all quite entertaining. One is called "lava lamp world".
You seem to be arguing from a religious, rather than a scientific, perspective.
There is no credible scientific evidence for a 6,000 year old earth. There is an immense body of evidence for an earth on the close order of 4.5 billion years in age.
Based on what I've seen in the Olympics, ir is significantly faster than the speed of LIGHT...
What I've always wondered is why God brought all the animals and plants before Adam to name. Didn't God already know what they were called? And how did Adam get so smart ~ ?
The problem with that scientific theory is that it cannot count out the possibility that the earth was created 6,000 years ago with a 4.5 billion year history in place. That's how I would have created it...
But the 5% intractable force of light will always prevail:
alas...
Scientists Examine 'Dark Energy' of Antigravity
New York Times | November 16, 2006 | Dennis Overbye
Posted on 11/16/2006 7:27:32 PM EST by SunkenCiv
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