A testable prediction about dark energy? Such is the promise of a new formulation from Sourish Dutta and Robert Scherrer (Vanderbilt University), whose dark energy model interacts with normal matter and has observable results, including a prediction about the expansion rate of the universe. Astronomical surveys in the next decade should be able to detect the slowdown in the expansion rate predicted by this model, if it exists.
Think ‘quintessence,’ a new field with the unique property that it can act like antigravity, forcing nearby objects to move away from each other rather than pulling them together. The quintessence field as developed by Dutta and Scherer likely went through a phase transition somewhere around 2.2 billion years after the Big Bang.
‘Freezing out’ as the universe cooled creates a scenario where the energy density of the field remained high until, with the phase transition, it dropped abruptly to a level it retains to this day. Another result: The release of some of the dark energy in the form of ‘dark radiation,’ undetectable by our instruments but observable through changes to the universe’s expansion. Those precise changes are what can be tested.
And how about this, from an online story about this work from Vanderbilt. Noting the possibility of detecting the dark radiation signature in the expansion rate, the article adds:
At the same time, new particle accelerators, like the Large Hadron Collider nearing operation in Switzerland, can produce energies theoretically large enough to excite the quintessence field and these excitations could appear as new exotic particles, the researchers say.
It’s fascinating to think that we may soon have the ability to detect particles produced by the dark energy field through existing instrumentation. Will implications for propulsion eventually crystallize out of this highly theoretical work? The paper is Dutta, Hsu et al., “Dark radiation as a signature of dark energy,” Physical Review D Vol. 79, 103504 (2009). Abstract online.
Hi; An arXiv preprint of this paper is available at arXiv:0902.4699v2 [astro-ph.CO] 6 May 2009
Tim, thanks!
Hi Paul;
I personally like to muze over the evolution of our universe over very cosmic scale time frames. I suspect that since we according to most models of the big bang evolution have already gone through 3 theoretically well articulated phase change symmetry breaking event: 1) the decoupling of the gravitational force from the electroweak-strong force, the decoupling or the grand unified field into the strong nuclear force and electroweak unified field, and then the decoupling of the electroweak force and the electromagnetic force and the weak nuclear force.
It is interesting to consider what huge energy releases might yet be in store for us as the universe ages over the coming relavant cosmic epochs. Predicting these catastrophic phase changes might help us adapt and transition our civilizations and our physical ontological makeup into the new cosmic eras.
In a way, each such future phase change is like a rebirth where new laws of physics, novel natural structures, and new and exotic lifeforms can develop including intellegent technologically advancable ones.
If indeed our universe is infinite in spatial extent, it is evidently still growing and perhaps at some impossibly remote time into the future, we will use concepts taken from the mathematics of Georg Cantor such as the concept of Aleph 1, the number of real numbers as opposed to the concept of Aleph 0, the infinity of the number of integers which is a much smaller set than Aleph 1, in order to describe the infinity of our universe. Note that the concept Aleph i includes value of i of 3, 4, …, all the way up to at least the the least infinite ordinal value.
Would be amazing if stufying the Dark Energy taught us how to manipulate the cosmological constant to create warp bubbles. For those who missed my blog on the latest bit of warp-drive news…
http://crowlspace.com/?p=397
…only takes 10,000 tons of mass-energy converted into cosmological constant energy to push a teeny-tiny warp-bubble around at lightspeed.
Adam: How does that jive with this work announced last month that seems to indicate that faster-than-light warp drives are impossible?
Are warp drives really interesting or viable if they’re only usable up to and including the speed of light? Wouldn’t other sorts of propulsion be more efficient under those constraints?
Found this press release which I found interesting:
http://www.baylor.edu/pr/news.php?action=story&story=58707
However for a reality check on the above:
http://www.math.columbia.edu/~woit/wordpress/?cat=8
Cheers, Paul.
Hi Folks;
Other forms of FTL travel might still present them selves.
Wormhole shortcuts through space time might still be viable.
A form of macroscopic quantum tunneling might present it self wherein an energy barrier of a precise shape, width, and hieght might be put in front of a space craft to cause the craft to tunnel macroscopic distances in one feld swoop or perhaps repeatedly perhaps enabling macroscopic tunneling over cosmic distances.
Higher spatial dimension short cuts m still present themselves as a option.
The production of space time region multiple connectivities might yet work perhaps through the manipulation of the eleactrodynamic aspects of the vacuum of space time.
Also, the inverse square of the product of epsilon naught and mu naught might be artificially increased by manipulation of the electrodynamic properties of the vacuum of space thus resulting in local incrrease of C.
And the list of FTL schemes goes on and on.
Warp drives are not FTL. Wormholes are not FTL. No so-called FTL mechanism will get you to your destination faster than with mundane sub-FTL travel. This topic comes up an awful lot here and elsewhere but I wonder how well everyone fully understands spacetime structure and its implications for spaceflight.
I’ve said this before: you can travel arbitrarily quickly from A to B without any type of FTL mechanism (which may not even be possible). The actual challenges for inter-stellar travel include the energy requirements and safety. Speculative mechanisms such as wormholes and warp drives do not resolve these challenges. Unfortunately.
Hi Ron S;
I think what most people mean by faster than light travel while refering to warp drives and wormholes is the ability to beat a light beam traveling to a distant body for cases where the light beam travels in a vacuum. Since such exotic travel means imply beating such a light beam to its destination, these forms of travel are effectively FTL travel and that is the reason why the term faster than light travel is used to describe such methods.
I feel there are likely numerous forms of travel that do not involve translational inertial travel through space, even methods that have not been dreamed up yet.
James, while I do appreciate your point, I don’t believe that it is a useful definition of FTL for our purposes. We are not in a race with photons.
If (and that is a big ‘if’) we can construct a wormhole we are restricted to which spacetime coordinates we can travel. That is, the *where* and *when* of the other end of the wormhole. There is no reason to believe you will arrive at some destination before a photon traversing the distance in the usual manner. For example, you cannot arrive at your destination before the other end exists. And even if you could, why? You are, perhaps, engaging in time travel, which is fine if that is the objective. Travel time is itself not necessarily shorter.
Of course, all discussion of this sort requires a whole bunch of assumptions regarding the construction and traversal of wormholes, much of which is speculative. There are also a bunch of causality issues which could destroy the wormhole whether or not it is put to use. It’s all very interesting, but speculative.
So far as I understand it, an Alcubierre-style warp drive will not get you to a destination faster than a photon. Even if you could, again, you are engaging in time travel and not faster travel time.
Finally, are we really aiming to outrace photons? I understand useful interstellar spaceflight to be about short travel times achieved with reasonable energy requirements and safety for the cargo.
Hi Ron;
Thanks for the above perspectives. It remains to be seen whether or not wormoles exist or can be constructed artificially and whether or not teleportation or multiple space time connectivities can be set up an utilized artificially. The arguments for and against such mechanisms have propenents within the theoretical physics community.
However, it is interesting to ponder the concept of achieving ever higher gamma factors if we are limited to sub-C space travel inertially and translationally through space; and space time warpage and other topological manipulations of macroscopic extent, are not possible.
The great endeavor of closing in on the speed of light ever more closely might from both an experimental and theoretical perspective help us define what travel really means and what would become manefest for observers some how managing to reach light speed assumming that the equations of special relativity begin to break down at extreme gamma factors in some unforseen manner. We might as a result need to evolve our mathematical and philosophical defintions of what space and time mean and what extended dimensionality means.
My guess is that the first step in this long road of progress will be fusion rocket systems that can at least initially be capable of 0.1 C and then faster as the specific impulse of fuel/rocket engine designs becomes more optimized.
It is, however, my hope and my expectation that we humans will one day travel among the stars and colonize ever further outward into this vast universe.
Hi Ron;
I hope I did not come accross as too dismissive of your ideas or too argumenative. Come to think of it, I really like the way you expressed the process of interstellar travel as in your statement, “…you can travel arbitrarily quickly from A to B without any type of FTL mechanism …”
The really cool thing is that even if good old special relativity holds immutably and we have no general relativistic space time topological or kinematical tricks to draw on, at least for the crew, effectively ever shorter transit times become possible for future star and galaxy fairing space craft, obviously due to relativistic time dilation.
I have become a champion of ever higher gamma factor inertial travel through space since that at least we know we can do in theory. As you might have guessed, I hope we can do wormhole travel, however like you mentioned issues of casuality and instability can result which may make wormhole travel impossible.
Either way, the prospects of some how improved ISR space craft intregue me and I do not think that the final chapters on interstellar ram jets have been written yet.
I also as you can see like to muze on what we may discover about the meaning of travel and dimensional extension as we refine our physics over the comming centuries. My hope is that perhaps there are some tricks that will make wormholes and FTL seem like tinkertoys in comparison. But as I tend to speculate into fantasy some times, I just don’t know.
Regards;
Jim
Risking kicking in an open door in this discussion: my hope, maybe even beyond rational expectation, for a FTL type propulsion system is primarily focused on a breakthrough with some kind of ‘anti-gravity drive’, ref. Heim/Dröscher/Häuser, and/or Tajmar and/or Chiao.
See for instance the recent tantalizing article: “If superconducting sheets reflected gravitational waves…” in Technology Review, referring to Raymond Chiao’s articles “Do Mirrors for Gravitational Waves Exist?” and “Laboratory-Scale Superconducting Mirrors for Gravitational Microwaves” in arXiv.org (both of March this year).
It seems to me the only realistic avenue for further research now.
Paul, would it be an idea to have an article/thread here some time with an update of state of affairs ref. the above-mentioned anti-gravity research, and also clarifying the essential differences between Heim et al. on the one hand and Tajmar/Chiao on the other. I know there are differences, but never quite understood them.
Ronald writes:
It’s a wonderful idea, Ronald, because there is a great deal of confusion about these approaches and they tend to be lumped together. This is understandable when you realize how early in the game we are. Heim theory is not yet producing lab results discussed in peer review journals, whereas Martin Tajmar has been out there publishing his own extensive lab work and having his theories studied and his work replicated by other scientists. I’m working on the right source to write the comparative article and I hope we’ll have more on this in the not distant future.
In a recent lecture at the American Institute of Aeronautics and Astronautics (Sacramento, 13 March 2009), “Emerging Physics for Novel Field Propulsion”, Hauser and Dröscher indeed link Heim and Tajmar themselves. Or at least they extensively quote Tajmar’s work and connect it to Heim, by analyzing his work using Heim’s Extended Theory.
They don’t mention Chiao’s recent work.
James (and anyone else who may be interested in wormholes, their relationship to FTL, quantum theory, and especially FTL and time travel), see:
http://blogs.discovermagazine.com/cosmicvariance/2009/05/14/rules-for-time-travelers/
None of this directly addresses inter-stellar travel using exotic means, but it very nicely lays down the rules for moving about in spacetime under known physics, and then draws the speculative boundaries with probable and improbable physical laws. Read all the comments as well for some excellent commentary.
Hi Ron;
Thanks for posting the above link. I found reading through the 10 sections very informative.
From a purely sociological perspective with no attempt being made to promote faith-based agendas or spiritualism, I tend to be a “God does not throw dice kind of guy” with respect to what is true or what was true. Thus, the discussion at the above link that there are no time travel paradoxes is re-assuring to me.
Regarding C, some modern theorists proposed that C in vacuu might not be a single well defined applied everywhere constant but might depend subtly on EM wavelength. Such a effect would be immeasurably small over ordinary EM photon energies but would become much more pronounced for photon energies approaching the Planck Energy and higher energies if such energies are even possible.
Certain observations from distant gamma ray bursts (which seem to be supernova) and supernova in general suggest a small lag time between the arrival of lower frequency EM radiation and gamma rays with the gamma rays arriving a few seconds after the lower visible frequency EM radiation. An idea has surfaced that perhaps the gravitational potential acting between the gamma rays and any finite disecreetization of the fabric of space time at the Planck Space and Planck Time levels might be causing the gamma rays to propagate more slowly over macroscopic distances.
However, any effects of photon propagation based on highly speculative theories such as Doubly Special Relativity wherein the photon velocity approaches infinity in the limit as the frequency of a photon approaches infinity might still be operative wherein the energy dependent drop in photon velocity at ordinary gamma ray energies is simply a shallow minima. Moreover, there might be additional minima, local maxima, and inflection points in the curve of C verses photon frequency due to unforseen mechanisms.
While I do not hold Doubly Special Relativity to be Gospel Truth, I feel it has to be considered now that predictions of such a theory have been lexocographically formulated.
A few provoking relations between dark energy, dark matter and pions
Authors: Dragan Slavkov Hajdukovic
(Submitted on 7 Aug 2009)
Abstract: I present three relations, striking with their simplicity and fundamental appearance; the first one connects the Compton wavelength of a pion and dark energy density of the Universe; the second one connects Compton wavelength of a pion and the mass distribution of non-baryonic dark matter in a Galaxy; while the third one relates mass of a pion to fundamental physical constants and cosmological parameters. All these relations are in excellent numerical agreement with observations.
Subjects: General Physics (physics.gen-ph)
Cite as: arXiv:0908.1047v1 [physics.gen-ph]
Submission history
From: Dragan Hajdukovic [view email]
[v1] Fri, 7 Aug 2009 13:08:23 GMT (42kb)
http://arxiv.org/abs/0908.1047
‘Big Wave’ Theory Offers Alternative to Dark Energy
By Clara Moskowitz, Staff Writer
posted: 17 August 2009, 05:56 pm ET
This story was updated at 2:40 p.m. on Aug. 18.
Mathematicians have proposed an alternative explanation for the accelerating expansion of the universe that does not rely on the mystifying idea of dark energy.
According to the new proposition, the universe is not accelerating, as observations suggest. Instead, an expanding wave flowing through space-time has caused distant galaxies to appear to be accelerating away from us.
This big wave, initiated after the Big Bang that is thought to have sparked the universe, could explain why objects today appear to be farther away from us than they should be according to the Standard Model of cosmology.
“We’re saying that maybe the resulting expanding wave is actually causing the anomalous acceleration,” said Blake Temple of the University of California, Davis. “We’re saying that dark energy may not really be the correct explanation.”
The researchers derived a set of equations describing expanding waves that fit Einstein’s theory of general relativity, and which could also account for the apparent acceleration.
Temple outlines the new idea with Joel Smoller of the University of Michigan in the Aug. 17 issue of the journal Proceedings of the National Academy of Sciences.
While more research will be needed to see if the idea holds up, “the research could change the way astronomers view the composition of our universe,” according to a summary from the journal.
To convince other cosmologists, the new model will have to pass muster with further inquiry.
Full article here:
http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html