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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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When Albert Einstein was working on his equations for the theory of general relativity, he threw in a cosmological constant to bring the universe into harmonious equilibrium. But subsequent observations by Edwin Hubble proved that the universe was not static. Rather, galaxies were flying apart at varying speeds. Einstein abandoned the concept, calling it the biggest blunder of his life's work.
Observations in the 1990s, however, proved that the universe was not only flying apart, it was doing so faster and faster. This seemed to point to a dark energy filling space that actually repelled ordinary matter with its gravity, in contrast to all other known stuff, including dark matter. A number of theories have been developed to explain what this dark energy might be, including Einstein's long discarded cosmological constant.
Now new observations from an international team of astronomers seem to show that dark energy is like the cosmological constant, unvarying throughout space and time. By measuring the distances to 71 far-off supernovae, the scientists were able to ascertain with a high degree of confidence that the effect dark energy exerts on supernovae light does not vary with distance. The researchers also plugged this data into a so-called equation of state, which measures the relationship between pressure and density, and found that dark energy must be less than -0.85--awfully close to Einstein's cosmological constant at -1. "Our observation is at odds with a number of theoretical ideas about the nature of dark energy that predict that it should change as the universe expands and, as far as we can see, it doesn't," says team member Ray Carlberg of the University of Toronto. The results will be published in a future issue of Astronomy & Astrophysics.
The 71 supernovae observations are the results of just one year of an ongoing Supernova Legacy Survey being carried out using telescopes throughout the world, such as the Canada-France-Hawaii Telescope in Hawaii and the Very Large Telescope in Chile. Data collected over the next four years should improve the precision of the finding and help researchers determine more about the enigmatic nature of dark energy that seems to constitute at least 70 percent of the universe.
But the finding brings to the fore another question: the so-called cosmological coincidence. Observations like this one seem to prove that regular matter and dark energy have similar densities at precisely this moment in time, even though the density of matter has been declining steadily since the big bang. Even Einstein couldn't answer why that would be.
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12 Comments
Add CommentExpanded Universe Perspective
Reply | Report Abuse | Link to thisThe perception of an accelerating universe may have arisen from our limited observational perspective. While light from distant galaxies may seem to represent current conditions near the spatial periphery of the observed universe, it actually represents the more ancient conditions of the developing universe. Since light emitted 10B years ago indicates greater expansion than light emitted 5B years ago, it must be concluded that universal expansion actually decelerated. Only this temporal interpretation produces results consistent with fundamental laws of physics.
From this perspective, distant galaxies did not begin to more rapidly recede away from our own galaxy about 5B years ago, but rather, in the earlier universe all galaxies more rapidly receded away from all other galaxies. Observed more distant galaxies are further away than expected because, long ago, our own galaxy very rapidly receded away from their approaching light emissions. More recently, galaxies have less rapidly receded away from these ancient light emissions as well as the more recent emissions of nearer galaxies.
The redshift of distant light indicates the relative velocity of the emitter and receiver, physically imparted to the wavelength of light by the relative velocity of its emitter as it is emitted and the receiver as it is received. The actual distance light traverses is determined by the separation distance of the emitter and receiver at emission and any subsequent relative motion of the receiver throughout the observed light's transit. The receiver's actual relative velocities, varying throughout the transit of observed light, are not reflected in its redshift but are reflected in its traversal distance, as indicated by diminishment of its observed luminosity. The discrepancy between redshift and distance is produced by temporal variation in the velocity of the receiver.
Events producing the observed characteristics of light from other galaxies:
1. As all galaxies receded away from each other in the earlier universe, their emitted light was redshifted by the relative velocity of the then current rate of spacetime expansion.
2. As light emitted from other galaxies in the direction of our own galaxy independently traversed expanding spacetime, our galaxy continued its recession, initially at the relative velocity indicated by the emission redshift but varying over time.
3. When the light from other galaxies is eventually received it is again redshifted by the now current recession velocity.
4. Distant light's actual traversal distance, derived from type Ia supernovae observed peak luminosity, disagrees with the relative velocity indicated by observed redshift. This discrepancy is proportionate to the variance of our own galaxy's recession velocity from emission to reception. This process produces the observed distant light characteristics.
In a decelerating universe, the receiver has moved farther during the observed light's transit than is indicated by its relative velocity at reception. This is consistent with observations, as more distant galaxies have been determined to be more distant than expected based solely on redshift.
The apparent universe consisting of innumerable galaxies surrounding our own, now rapidly receding away from us, is an illusion of our own relativistic motion. It is our own galaxy that has rapidly receded away from the ancient light emissions of all observed distant galaxies. While all distant galaxies recede away from each other, we directly observe only their ancient light emissions. Observation results originally understood to indicate an accelerating universe actually confirm a decelerating universe, complying with the second law of thermodynamics.
Given we are also expanding within the expanding universe we are part of, how is it we are experiencing anything different from what is observed. We speed along in the so called expansion. If the indicators are we are excelerating, how can we separate our relative motion from what we perceive?
Reply | Report Abuse | Link to thisWhy should Einstein be able to solve the problem? He was not even able to describe light propagation correctly and made a light speed isotropy postulate that led to the wrong theory of special relativity which he implemented into the General Theory of Relativity. Since this theory combines Newtons gravitational theory and special relativity it is wrong, too.
Reply | Report Abuse | Link to thisWhy should Enstein be able to solve this problem? He did not even formulate correctly light propagation by developing a wrong theory called "Special Theory of Relativity". Then he added Newton's gravitational laws to special relativity and called it "General Theory of Relativity", which, of course, is wrong, too.
Reply | Report Abuse | Link to thisCould you explain what is wrong with Einsteinincorrestly formulating light propagation, given the lack of equipment available at the time. And how is Newton's gravitational laws not compatible with the General theory?
Reply | Report Abuse | Link to thisSorry about the bad spell check. Should read,
Reply | Report Abuse | Link to thisCould you explain what is wrong with Einstein incorrectly formulating light propagation, given the lack of measuring devices available at the time. And how is Newton's gravitational laws not compatible with the General theory? Gravitation remains a mystery, and Einstein knew this.
There were a lot of things that were not fully understood at the moment which made it diffucult for Einstein to correctly formulate his theories and much less solve the still not solved mystery of gravity. But what do you mean by "wrong theory"?
Reply | Report Abuse | Link to thisThe expansion of the Universe is predicated on the assumption that cosmological red shift is a Doppler shift. However there is no direct evidence that this is actually happening. It is much more likely that the red shift results from a gravitational interaction of the photons with the masses the photons pass in space. Because a photons frequency is affected by mass, which has been proven by experiment beyond a doubt, they must lose energy when they pass a mass. This is because they dive up out of a deeper well past a mass than they dove into on account of the fact that their trajectory bends in toward the mass. You may see this concept developed in detail in http://charles_w.tripod.com/red.html .
Reply | Report Abuse | Link to thisTherefore an expanding Universe is not necessary to explain the red shift. Each shell of mass around the photon would have an equal affect on the photon as the shell inside it or outside it, because while gravitys force declines with the square of the distance, the amount of mass in the shell increase with the square of the radius of the shell.
So, "Dark Energy" is a defunct concept supporting the interpretation of an accelerating, expanding universe. The universe is decelerating. The observed "red shift" only confirms the deceleration, at different rates, of emitter and receiver...yes?
Reply | Report Abuse | Link to thisWow! I'm impressed! Not one, but two different, non-standard theories explaining why (a) there is no acceleration in cosmic expansion and (b) there's no need to invent "dark energy" - which would be much more comfortable to our physical intuitions (no guarantee of course that it's any the better a theory for that).
Reply | Report Abuse | Link to thisBiggest mistake of modern science is assumptions of NEWTON and EINSTEIN particularly of unchanging laws and constants and isotropic universe with limiting limiting speed maximum to light speed. cASIMIR EFFECT PROVED CONCLUSIVELY THAT VACUUM HAS ENERGY.No accelerating universe is required to prove dark energy and red shift does not prove accelerating universe. NOBEL PRIZe for physics in year 2011 is wrongly awarded. NOBEL COMMITTEE SHOULD BE MORE CAREFUL. If you believe universe is non isotropic then you do not know how far is supernova as speed of light is changing from sender to receiver . WAVE LENGTH IS DEPENDING ON DARK ENERGY FIELD DENSITY. So varying wave length can not judge whether accelerating or receding. ALL OUR PRESENT PHYSICS REQUIRE MAJOR REVISION. DURGADAS DATTA published a paper--MISJUDGEMENT BY NEWTON in ASTRONOMY.NET in year 2002 where he said that EINSTEIN IS WRONG and ether exists as dark energy in a non isotropic variable dark energy universe. His balloon inside balloon theory of matter and antimatter universe on opposite entropy path clearly says that dark energy is produced at the common boundary by annihilation matter and antimatter and injected into our universe as dark energy causing expansion,swirls and whirls so that galaxies ,stars, rotate giving gravity and other laws due to five god particles in it --four for four forces and one for mass creation. If you apply modified NEWTON EQUATION F=P.G.M.m/R.R Where P is permeability as in coulombs law then , you will see that amount of dark matter may not be so much as we think today.--durgadas.ddatta@gmail.com.
Reply | Report Abuse | Link to thisSorry to have missed you questioning so long ago.
Reply | Report Abuse | Link to thisReviewing my comment from now well over two years ago, I now must correct my original statement:
"While light from distant galaxies may seem to represent current conditions near the spatial periphery of the observed universe, it actually represents the more ancient conditions of the developing universe. Since light emitted 10B years ago indicates greater expansion than light emitted 5B years ago, it must be concluded that universal expansion actually decelerated."
That statement was incorrect, in that the observations of consistent type Ia supernovae, to precisely determine their distance from their consistent peak period luminosity, has not been sufficiently sampled for SNe more than about 5 billion light years away. As I understand, only SNe about 5 billion light years away have been determined to have been receding from us at apparent velocities that exceed those derived from the redshift of the SNe's host galaxy's light using standard cosmological models.
For those SNe observations that emitted their light about 5 billion years ago and contradicted the distance estimates of cosmological models presuming standard parameter values, researcher found that they could produce distance estimates that were in agreement by adjusting their model parameters to presume that, at that time, the expansion of the universe was accelerating rather than decelerating as had been presumed, and by specifying a positive cosmological constant parameter. Note that their may have been other parameters that could have yielded similar adjustments to the cosmological models' estimated distance.
The observations of SNe that emitted their light less than about 3 billion years ago did not produce model distance estimates that conflicted with those derived from SNe luminosity. It is thought that that is a sensitivity issue with the models rather than a valid indication that more recent light emissions do not exhibit any indications of accelerating expansion...
Since, as I understand, there have not been sufficient calibrations of type Ia SNe luminosity to host galaxy redshift for SNe emitting light more than about 5 billion years ago, researcher can only conclude that the expansion of the universe began accelerating about 5 billion years ago - more ancient and more recent evidence has not been determined. It is apparently only presumed that, prior to 5 billion years ago, the expansion of the universe was decelerating as had been previously expected, in accordance with the 2nd law of thermodynamics.