Image: NASA, ESA, E. Jullo (JPL/LAM), P. Natarajan (Yale) and J-P. Kneib (LAM)
A new study of one of the universe's fundamental constants casts doubt on a popular theory of dark energy, scientists say.
Dark energy is the name given to whatever is causing the expansion of the universe to accelerate. One theory predicts that an unchanging entity pervading space called the cosmological constant, originally suggested by Albert Einstein, is behind dark energy. But a popular alternative, called rolling scalar fields, suggests that whatever's causing dark energy isn't a constant, but has changed through time.
If that were true, though, it should have caused the values of other fundamental constants of nature to change, too. And a new measurement of one such constant, the ratio between the mass of the proton and mass of the electron, shows that this constant has remained remarkably steady over time.
The proton and the electron are two fundamental particles that make up the atoms inside stars, galaxies and people. Recently, a team of astronomers used the German Effelsberg 100-meter radio telescope to observe alcohol molecules in a distant galaxy, and found that the protons and electrons in those molecules' atoms weigh about the same as the ones right here on Earth.
Because the galaxy they studied lies 7 billion light-years away, its light has taken that long (7 billion years) to travel to Earth, and thus we are seeing it as it was half the universe's lifetime ago. (The universe is thought to be about 13.7 billion years old.) The observations strongly suggest that this fundamental constant has remained mostly unchanged over the past 7 billion years. [The Big Bang to Now in 10 Easy Steps ]
Building on that finding, which was detailed in the Dec. 14 issue of the journal Science, University of Arizona astronomer Rodger Thompson calculated how much the proton-to-electron mass ratio would change over time if the rolling scalar fields theory were true. He found that the predictions did not match the data.
That result supports the idea of Einstein's cosmological constant. "Basically, it says alternatives to Einstein's theory are really running out of room here," Thompson said Jan. 9 during a press conference at the 221st meeting of the American Astronomical Society (AAS) in Long Beach, Calif., where he presented his work. "This puts some very serious constraints on these rolling scalar field cosmologies."
However, the cosmological constant theory isn't ideal, either. The expected value of the constant, based on known physics, is a number more than 10 to the power of 60 (one followed by 60 zeros), which is too large to explain the universe as we see it.
And the new findings don't drive nails into the coffins of other dark energy explanations, either.
"Rolling scalar fields are not dead," Thompson said. Rather, "they may be more complicated than those original models expected."
The new study is the second in about a week to back up Einstein. Another project, also presented at the AAS meeting, offered support for the idea that space-time is fundamentally smooth, as predicted by the early 20th-century genius, as opposed to foamy.
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26 Comments
Add CommentSince inflation theory posits that the Universe has at times expanded faster than the speed of light, doesn't that mean that light from objects that are, for example, 7 billion light years away, could, in fact, be showing the state of something less than 7 billion years "old"?
Reply | Report Abuse | Link to thisMy understanding is that Einstein, unaware at the time of cosmic expansion and assuming the universe was in a steady state, simply employed an ad hoc constant to explain the fact that the universe hadn't collapsed from mutual gravitation long ago. But later, he considered this to be a big mistake. It's not like he derived dark energy from theory.
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Reply | Report Abuse | Link to thisThere is nothing wrong with considering "exotic" ideas, especially if they are testable, but the following should be borne in mind.
An alternative way to understand dark energy and dark matter is as follows:
A. Dark matter is composed of primordial black holes.
B. Dark energy is a result of inhomogeneities in an inhomogeneous fractal cosmos.
This alternative solves both of the enigmas in a far less fanciful way than "rolling scalar fields", "axions and Peccei-Quinn fields" or other tooth fairy ideas of theoretical physics.
Black holes are known to exist.
The recent discovery of an galactic cluster with dimensions of 500 Mpc by 1200 Mpc (way beyond the homogeneous LCDM's predicted "largest structures") argues empirically for an inhomogeneous cosmos.
Maybe yet another layer of exotic physics is not required to understand the cosmos. All one needs is Einstein, Maxwell and fractal self-similarity.
Robert L. Oldershaw
Discrete Scale Relativity/Fractal Cosmology
http://www3.amherst.edu/~rloldershaw
Postulates:
Reply | Report Abuse | Link to this1. The expansion of the universe is accelerating.
2. The most distant objects in the universe are accelerating from a speed (relative to us) less than the speed of light, to one greater than the speed of light.
3. Objects travelling faster than light are not detectable, and thus do not contribute to the total mass of the detectable universe.
Resulting Supposition/Question:
- The detectable mass of the universe is reducing over time because the force toward expansion (dark energy or cosmological constant or, for all I know, centrifugal force of a spinning universe) is counterbalanced by the gravity of the total mass of the detectable universe.
(I can't help thinking that this is a crank theory, even if it is my own, but I would dearly like to know what is wrong with it).
I agree - How can Einstein's long abandoned cosmological constant 'fudge factor', cause all other fundamental constants to be variable? This article is full of tripe!
Reply | Report Abuse | Link to thisThe late 1990s studies that identified a discrepancy between the distances derived from type Ia supernovae peak luminosity and those derived from galactic redshift using the then current standard cosmological models simply tweaked available model parameters to make the disparate distance estimates agree. Actually, they not only changed the cosmological constant parameter from zero to positive but also changed the 'deceleration' parameter from positive to _negative_! That does not mean that the deceleration of expansion do to increasing entropy no longer decelerates expansion or that entropy is now decreasing, but that the net effect of it and some separate, recent, unidentified acceleration effect has shifted to positive.
Despite the use of the so-called cosmological constant model parameter it has never been suggested that the acceleration of universal expansion has been a constant effect.
What does the inset image artistically altered to illustrate the existence of dark matter that seems to be inferred by gravitational lensing produced by the imaged galaxy cluster have to do with the acceleration of universal expansion?
As I understand, the use of Einstein's gravitational constant in cosmological models to (in part) represent the acceleration of universal effects does not imply that any that any specific physical effect causes the apparent acceleration of expansion - it only (contributes) to the production of a temporally dependent acceleration effect in the model's results.
I still have no idea what the "popular" rolling scalar fields theory is. Perhaps this article might have explained a bit... I did find the Thompson, et al., research report freely available at:
http://mnras.oxfordjournals.org/content/428/3/2232.abstract
I also found an apparently undated unpublished research report from someone:
http://www.physics.princeton.edu/~steinh/prit4.pdf
As near as I can tell, "rolling scalar fields" isn't really all that popular outside of certain academic circles...
IMO, the simplest explanation for the apparent temporal increase in the rate universal expansion is the result of growing enormous regions voided of matter by the combined effects of universal expansion and localizing gravitation. I suspect that expansion is less opposed by gravitational effects in the growing voids, increasing the effective rate of universal expansion.
Reply | Report Abuse | Link to thisI think your #3 is wrong on both counts.
Massive objects do not travel faster than the speed of light in agreement with special and general relativity.
Even if matter were to move beyond our light horizon it seems unlikely that its gravitational influence would suddenly be cancelled. We may not be able to observe it directly, but its presence could influence the physics within our local Hubble Bubble.
Decades ago, Hubble used a period-luminosity relation for variable stars to establish distances, in what we call Hubble's law, in that galaxies display a linear relation between distance and redshift. I think that photons are really bits of matter and also bits of energy. So, when bits of matter travel at the speed of light, as photons, they must emit gravitational waves, and so we get a redshift in photons that travel billions of years in space. Therefore, the expansion of space, I think, is an illusion. We should realize that photons lose energy because they emit gravitational waves, since photons are really bits of matter traveling at the speed of light. And, we should remember that light is bent by gravity because photons do have gravity. And, since light travels forever thru space, its gravity explains the extra gravity in the universe. In billions of years, much matter has become photons, but its gravity is still present although it is invisible as it travels in space.
Reply | Report Abuse | Link to thisWhile electrons lose some electromagnetic energy when they emit photons, the electromagnetic force carrier, they do not lose mass. Photons have zero rest mass. No gravitational waves have ever been detected.
Reply | Report Abuse | Link to thisLight is effectively bent by gravitational energy as it obliquely traverse a gravitational field of sufficient magnitude - described by the dimensional curvature/contraction of spacetime. The amount of curvature imparted to light is solely a function of the object producing the gravitational effect.
I have read something on this effect somewhere, but can't recall exactly right now. There was some concern that photons could "decay" over time, being that they were billions of years old and traveling all that time at light velocity, and that would cause the red shift. They probably do have some mass, and actually quantum theory says, if you think that they are little particles, then that's what they are.
Reply | Report Abuse | Link to thisI think there was some finding that they actually maintained their stability as good as new from the day they originated.
They can't be dark matter though, since they are light.
Perhaps there is some opposite or mirror particle, a dark photon.
This is all quite interesting, that they have said the majority of the mass of the universe is dark matter, and that galaxies wouldn't rotate properly without it. Now they are saying there's no such thing.
Reply | Report Abuse | Link to thisI think probably there is some kind of dark matter, meaning there is some gravitational effect from it, although we can't see it. That is different from black holes, which we can't see either, but they are definitely there from their gravitational signature.
Possibly the cosmological constant is established by a balance of light (present universe) and dark (invisible but gravitational) matter.
If the universe originated from dark matter, essentially "popping out" rather than "Big Bang" then there may be a consequent balance between the light and dark matter, causing a stable cosmological constant.
The dark matter may be left out from the initial event, and will never be able to get into the party, although if the party ever is over, the light might "turn off".
Steven & R.Blakely, please see http://en.wikipedia.org/wiki/Tired_light
Reply | Report Abuse | Link to thisProving that photons are massless is hard. For example, photons have momentum. Also, since photons are attracted by gravity, photons must have gravity, which is more evidence that photons have mass. Can we prove that photons do not have gravity? I think photons have gravity, and so photons must lose energy as they travel at the speed of light for billions of years. Photons are like bullets. While bullets produce shock waves while traveling at the speed of sound, photons traveling at the speed of light, lose energy in the form of gravity shock waves.
Reply | Report Abuse | Link to this"Can we prove that photons do not have gravity?"
Reply | Report Abuse | Link to thisIMO, that light inherently propagates in a vacuum at the maximum possible velocity, while other particles with rest mass cannot - even when enormous energy is applied (as in the LHC), is compelling evidence that photons have no rest mass. That gravitational effects are produced proportionally to the collective mass of an object is compelling evidence that mass is necessary to produce gravitational effects.
Please see:
http://en.wikipedia.org/wiki/Photon#Experimental_checks_on_photon_mass
It notes an interesting effect:
"Photons inside superconductors do develop a nonzero effective rest mass; as a result, electromagnetic forces become short-range inside superconductors."
This demonstrates that light cannot perpetually propagate at c when photons, under conditions of extreme electromagnetic force effects, acquire rest mass. In that case, they do "have gravity".
"This demonstrates that light cannot perpetually propagate at c when photons, under conditions of extreme electromagnetic force effects, acquire rest mass"
Reply | Report Abuse | Link to thisStrictly speaking, that only proves photons acquire some extra mass in superconductors, not that photons are currently massless.
About photons losing energy in the long journey, perhaps that´s the reason we can not see further than 14,000 or 15,000 light-years? It´s hard to believe that photons could travel ANY distance without ever being disturbed by matter interactions or magnetic fields or, you know.
IMO, the _effective_ rest mass exhibited by photons within a superconductor demonstrates that photons with rest mass cannot perpetually propagate at c - thus in more ordinary conditions, where they _do_ perpetually propagate at c, they must _not_ have any even effective rest mass.
Reply | Report Abuse | Link to thishttp://en.wikipedia.org/wiki/Photon#Experimental_checks_on_photon_mass
"It´s hard to believe that photons could travel ANY distance without ever being disturbed by matter interactions or magnetic fields or, you know."
Reply | Report Abuse | Link to thisThe statement was not that photons exhibit effective mass when interacting with magnetic fields - only when they are within a superconductor. "... Superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics."
http://en.wikipedia.org/wiki/Superconductivity
It _is_ almost certain that photons of intergalactic light are _never_ contained within a superconductor.
I don't know what "matter interactions" you refer to - can you be more specific? What "matter interactions" would cause photons to acquire rest mass?
Just a matter of linguistics: the article, when speaking about how the ratio of the mass of a proton and the mass of an electron remained says it was: "remarkably steady" "about the same" "mostly unchanged", but as an ignorant in physics, I'd like knowing if the conclusions or statements in the article would have been different if the expressions were: "steady", "the same", "unchanged", without qualifiers, and what would have been the scenario in this last case; we know all matter decays, but don't know if the decay of particles is thru an slow loss of mass. Salut +
Reply | Report Abuse | Link to thisInteresting points.
Reply | Report Abuse | Link to thisThis article erroneously suggests that describing the acceleration of universal expansion using the cosmological constant model parameter necessarily makes the acceleration constant, whereas describing using "rolling scalar fields, suggests that whatever's causing dark energy isn't a constant, but has changed through time."
It then goes on to state:
"If that were true, though, it should have caused the values of other fundamental constants of nature to change, too. And a new measurement of one such constant, the ratio between the mass of the proton and mass of the electron, shows that this constant has remained remarkably steady over time."
I don't know if or why any theoretical physicists might think that a varying dark energy would require that fundamental constants would also necessarily change, but I do know that observational analyses that led to the conclusion that universal expansion is accelerating used the cosmological constant (and 'negative deceleration') to describe its varying effects, beginning about 5 billion years ago.
All that being said, the new observation supposedly then conflicting with the very idea of varying 'dark energy' is that the relative mass of protons and electrons don't change.
All that being said, while some grand unified theories predict proton decay, it's never been observed. Moreover, if and when any fundamental particle decays, it's transformed into other particles (each of less or no mass and with a loss of total particle mass-energy), so a decayed proton would not be relevant to the proton-electron mass relation. Please see:
http://en.wikipedia.org/wiki/Particle_decay
I suspect you're thinking of nuclear decay - please see:
http://en.wikipedia.org/wiki/Radioactive_decay
(continued)
Reply | Report Abuse | Link to thisAfter a little searching, I found the research report that was presumedly the principal basis for this article:
S. A. Levshakov, M. G. Kozlov, and D. Reimers, (2011), "METHANOL AS A TRACER OF FUNDAMENTAL CONSTANTS,"
http://dx.doi.org/10.1088/0004-637X/738/1/26
The full research report is freely available at:
http://iopscience.iop.org/0004-637X/738/1/26/pdf/0004-637X_738_1_26.pdf
Subsequent research has used the measurement method described to more accurately constrain any possible variability in the "electron-to-proton mass ratio." Apparently all the hemming & hawing ( "remarkably steady" "about the same" "mostly unchanged") in the SA article was because the new measurements can't definitively determine that no variability has occurred throughout the history of the universe, only reduce the amount of any possible variation.
After all the article's confusion, the bottom line is that all dimensionless physical constants remain, by observation, 'almost absolutely' constant. Please see:
http://en.wikipedia.org/wiki/Dimensionless_physical_constant
A photon at rest would not be a photon. A photon is a wave that causes mass to appear from the ether, but only when a photon travels at the speed of light.
Reply | Report Abuse | Link to thisProving that photons have gravity, and thus mass, should be easy since photons must attract each other, which means that a beam of photons should expand less than predicted by theory. Such an experiment is important because it could supply more evidence that the universe is not expanding.
IMO, it's important to specify when speculating or using a conjecture when making statements - in order to avoid confusion. I presume you're describing your own personal views here, since you refer to an ether medium and assert that the universe is not expanding?
Reply | Report Abuse | Link to thisEinstein expressed his own views as well. Without actual proof, he predicted that light would be "attracted" by gravity. Similarly, what is wrong with the view that the universe is not expanding, based upon the fact that photons have gravity, and so they must lose energy as they travel great distances?
Reply | Report Abuse | Link to thisPossibly, a better method to prove that photons have gravity is to send two photons, as laser beams of light, a great distance, for example, to the reflector on the moon, and obtain a return signal that has the two photons closer together, which would prove that gravity acts between the photons. Such proof would avoid the need to modify cosmological constants.
I don't think we have to worry about dimensionless physical constants changing. To better understand, _please_ see:
Reply | Report Abuse | Link to thishttp://en.wikipedia.org/wiki/Dimensionless_physical_constant
An expanding universe can be shown to be an illusion by simply proving that photons lose energy as they travel in space. A redshift for photons traveling billions of years in space is easy to observe, but a redshift for photons traveling only a second is more difficult. Such a small redshift could be interpreted as a change in the orbit of the moon, for example. But if the orbit of the moon is included in the calculations, a photon sent to the moon and reflected back to Earth, should have a very small redshift that is twice the redshift observed in light that the moon naturally emits. Averaged over a long time interval, the observed redshift in reflected laser light should show that light does lose energy as it travels in space.
Reply | Report Abuse | Link to thisEinstein considered time as something mathematically instead of connecting it to real physical processes. Near mass the unit of lenght gets smaller and distances become bigger. There the atom shrinks and electrons rotate faster then, which means that the second becomes shorter near mass. This is in agreement with the principle of least action: the photon passing mass tries to make as big steps (oscillations of low frequency) as possible and a minimum of these, which is possible in a parabolic route. If Einstein were right a hyperbolic track had to be observed. Accellerated expansion is based on the general theory of relativity dating from before quantummechanics got known. In the expanding universe the speed of light becomes smaller as it seems to be related to the potential of the total mass of the univere (Vasily Yanchilin: The Quantum Theory of Gravitation, 2003). If the supernovae standard Ia is corrected for faster c in the past then accellerated expansion disappears and the Nobel prize 2011 has to be returned. Likewise a cosmological constant, inflation, dark energy and black holes are phantasy. Wikipedia boycots the new theory of Yanchilin, except the spanish version.
Reply | Report Abuse | Link to thisActually, my point was that one should be clear when expressing personal views that these are opinions or suggestions or proposals, etc., rather than making simple declarative statements representing only the commentator's personal views as if they were established facts.
Reply | Report Abuse | Link to thisIMO, that is...