An astronomer says he may have found an important clue to one of the most profound mysteries in the universe: Why the stars in the sky are moving away from us at an ever increasing pace. Some scientists have suggested that the vacuum of space is filled with a weird force, called "dark energy." ... To everyone's surprise, they found that the material isn't just coasting away from us in space, as expected in the aftermath of an explosion. It's actually picking up speed as it goes.
"Something out there is pushing the universe, making it expand, making it speed up and we don't know what this is really," says Bradley Schaefer, the Louisiana State University astronomer who presented the results.
"It's been given a name, dark energy, and you can say this dark energy is pushing the universe, pushing the acceleration," he says.
A leading notion is that dark energy is something that pervades what was thought of as empty space. It's sometimes called "quantum vacuum energy" or the "cosmological constant."
The idea is that it's a constant through all space and through all time. Schaefer decided to test this idea by probing deeper back in time, to see if the constant was the same way back then.
They go on to say if his data holds up then the idea of a constant pervading dark energy must be thrown out, deepening the mystery and making physicists look for novel new explanations for why expansion is accelerating.
On the radio broadcast today, Schaefer himself reminded listeners that "extraordinary claims require extraordinary evidence" and that more study is needed to confirm his findings. That's science!
It should be noted that these results do not cast doubt on the Big Bang origin of the universe.
Also, don't confuse dark energy with "dark matter," another name for the mystery that visible (luminous at any wavelength) matter only accounts for about 10% of the apparent mass of galaxies.
Posts: 1900 | Location: U.S. | Registered: 06-03-02
Also, don't confuse dark energy with "dark matter," another name for the mystery that visible (luminous at any wavelength) matter only accounts for about 10% of the apparent mass of galaxies.
Mass and energy are merely different forms of each other. I suspect dark matter and dark energy bear the same relationship as per E = mc squared. As I ponder this mystery, and with Hawking and M-Theory as my guide, I have become more and more convinced that Dark Matter and Dark Energy come from other Universes that exists beyond the ordinary dimensions of space-time, making its presence known to us through the mysterious gravity wave which is the only form of energy/matter small enough (like I mean a wicked small wavelength in the order of the Planck Length)to be able to penetrate the 'brane' that separates the Universes. See Hawking, Stephen "The Universe in a Nutshell", chapter entitled "A Brane New World".
(Edited Note:I want to clarify my use of the term "Dark Energy". The Dark Energy to which Prof referred, used to be called "Vacuum Energy" until about 5 years ago, when somehow the name got changed to its present term and common usage. The Dark Energy that I refer to may not be the same, so I have perhaps mislabeled the term. The dark energy I refer to is the energy associated with the yet to be discovered gravity wave, specifically, the ultra short wavelength variety of which would exist within black holes, as noted by Hawking, and be capable of penetrating the higher order domensions (something which light and even gamma rays can not ever do, unfortunately, because this makes the dark matter forever invisible.
This message has been edited. Last edited by: gerry,
Posts: 625 | Location: Boston | Registered: 06-13-02
Is this something to do with the Higgs Field? I was reading about it recently and struggling to make sense of it.
It seems (I think) that the Higgs Field (yet to be actually detected but confidently predicted by current theory) has, unlike electromagnetic fields, some intrinsic positive energy - it can't naturally fall to zero. (I'm not at all clear on why.) It's the 'non-zero value' of the Higgs field that gives the push to a universe with accelerating expansion.
I realise that my terminology - and maybe the whole summary - are probably horribly wrong, but is that anywhere near one current explanation of what might be going on?
You may have hit the nail on the noggin'! The fundamental hypothetical particle of the Higgs Field, the force carrier known as the Higgs Boson, remains as mysterious as the fundamental hypothetical boson particle of the Gravitational Field, the carrier of the gravity force called the Graviton. Both have yet to be detected, although the advent of the high energy particle accelerator/collider being built at CERN may offer some chance of their discovery within the next few years. The Higgs Boson is distinct from the Graviton in that the former has mass, and is postulated to be the particel responsible for the inertial mass of all other particles (with mass)in the universe (this would exclude the massless photon and graviton). The Graviton may be responsible for gravitational mass, as opposed to inertial mass, but don't ask me to explain the difference. As you noted, the process of the birth of all matter appears to be from the quirk of fate (or Divine Intervention, if you choose to go that route) that allowed the Universe's positive energy to win the battle over its negative energy , otherwise the sum total of Positive and Negative Energy would be zero {(+1) + (-1)= 0}, and we would have essentially Nothing, nothing at all. Instead, matter is created from Nothing , thanks to the Higgs Boson, perhaps. Now here's the kicker: Einstein tried in vain to unify the Universe's Four forces....Electromagnetic, Strong Nuclear, Weak Nuclear, and Gravity....but he couldn't figure out the Gravity part, the 'force' that curves spacetime and compels all matter and even light (and all electromagnetic waves)to follow that curve. The gravity wave, however, may be the exception, and find its way via black holes to Universes (Brane New Worlds)that may exist beyond the known dimensions of spacetime. Now comes the Higgs Boson, a carrier of a Fifth Force...Einstein's cosmological constant if you will...that may very well be the culprit that is responsible for the accelerating expansion of our Universe to Infinity....and beyond.
Posts: 625 | Location: Boston | Registered: 06-13-02
And yet, according to what I'm struggling through at the moment, the Higgs Field theory can't be the whole answer. It proposes a field that gives us a kind of reference grid across all space/time - and Einstein's theory of relativity demonstrated how that idea (the Newtonian one of a fixed background to everything) doesn't describe our universe.
Sorry to be absent from a topic I started. Thanks for responding, gerry & n3. I'm away from my personal library where I would find books and articles I've read. This was bad timing on my part. Wikipedia helps me out (disclaimer).
Only about 4% of the total mass in the universe (as inferred from gravitational effects) can be seen directly. About 23% is thought to be composed of dark matter. The remaining 73% is thought to consist of dark energy, an even stranger component, distributed diffusely in space, that probably cannot be thought of as ordinary particles.
The exact nature of this dark energy is a matter of speculation. It is known to be very homogeneous, not very dense and doesn't interact strongly through any of the fundamental forces other than gravity. Since it is not very dense—roughly 10−29 grams per cubic centimeter—it is hard to imagine experiments to detect it in the laboratory (but see the references for a claimed detection). Dark energy can only have such a profound impact on the universe, making up 70% of all energy, because it uniformly fills otherwise empty space. The two leading models are quintessence and the cosmological constant...Other ideas for dark energy have come from string theory, brane cosmology and the holographic principle, but have not yet proved as compelling as quintessence and the cosmological constant.
The universe was predicted to either keep expanding though ever more slowly (the flat model), or to reach a brief pause after which increasing contraction would gather all the mass together again, presumably to end eventually in a 'big crunch' or, in a model discussed by Hawking, a 'big bounce'. The article on cosmological constant takes the story further:
quote:
Einstein abandoned the cosmological constant and called it the "biggest blunder" of his life. Ironically, the cosmological constant is still of interest, as observations made in the late 1990's of distance-redshift relations indicate that the expansion rate of the universe is accelerating. These observations can be explained very well by assuming a very small positive cosmological constant in Einstein's equations. There are other possible causes of an accelerating universe, such as quintessence, but the cosmological constant is in most respects the most economical solution.
I interpret "most economical" to mean it follows the principle of Ockham's Razor: the simplest explanation is the most convincing.
Gravitational attraction between masses resembles electrostatic attraction between opposite electric charges, both 1/R2 laws, albeit 40 orders of magnitude weaker. But where electric charge may be positive or negative, there is no kind of mass that repels other masses. (No, not even flubber or cavorite. ) However, there's a gravitational pushing force arising (I'm not sure why) from energy in empty space -- space otherwise devoid of known particles and fields. This is the dark energy, aka vacuum energy, such that what we take to be zero energy may actually be a false zero or local minimum above true zero, much as a mountain lake may be far above sea level.
But this Higgs field is supposed to be constant and all-pervasive.
The NPR story in my original post says
quote:
Early results from Schaefer's study of the movements of gamma-ray bursts suggest that dark energy is different far out in space, and therefore way back in time...[Schaefer:]"The first result of this new method happens to be pointing toward the direction of this cosmological constant not being constant"
If confirmed by more observation, then the "most economical" model bites the dust.
I hope to contribute more on this topic later.
Posts: 1900 | Location: U.S. | Registered: 06-03-02
) However, there's a gravitational pushing force arising (I'm not sure why) from energy in empty space -- space otherwise devoid of known particles and fields. This is the dark energy, aka vacuum energy, such that what we take to be zero energy may actually be a false zero or local minimum above true zero, much as a mountain lake may be far above sea level.
