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Einstein's Biggest Blunder That Wasn't
jose parinas writes "The genius of Albert Einstein, who added a "cosmological constant" to his equation for the expansion of the universe but later retracted it, may be vindicated by new research.
The enigmatic "dark energy" that drives the acceleration of the Universe behaves just like Einstein's famed cosmological constant, according to the Supernova Legacy Survey (SNLS). Their observations reveal that the dark energy behaves like Einstein's cosmological constant to a precision of 10%."
The cosmological constant is an extra term in Einstein's equations of general relativity which physically represents the possibility that there is a density and pressure associated with "empty" space. The inclusion of this vacuum energy term can greatly effect cosmological theories.. html
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http://super.colorado.edu/~michaele/Lambda/lambda
http://en.wikipedia.org/wiki/Cosmological_constan
Can anyone explain the idea behind dark matter and dark energy ? I mean if it is just a mathematical problem or has some experimental justification as well.
In astronomy (and other fields) you often have to live with large errors. That doesn't mean the science isn't valid. If the errors on your data are 10% and your theory is within the 10% error of your data, then fine, you have not invalidated the theory. On the other hand, if your error is 5% and the discrepancy with the theory is 10%, then you have something to think about.
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That's what I thought. However a quick scan of the article suggests that the increase in the rate of expansion can be explained better by a Cosmological constant (which is a constant unlike Hubble's constant which is not) rather than the alternative Quintessence hypothesis where the repulsive force is not constant.
So yes this story is new and possibly important.
Scientists did not prove anything. Some merely published a theory. It is not in anyway proven. Science is not like engingeering where it either works or doesn't. The scientific process takes a while, and dark matter and dark energy are still a vital theory in explaining expansion of the universe. So please don't tell me Dark Energy doesn't matter, because if that's true, I'm wasting a lot of my time.
dark matter anymore as per this past story.
Granted, it's unproven at this point, but Occam's Razor and all, I vote for the theory that makes sense with matter and energy as-is and doesn't require some exotic matter/energy that exists only as speculation to fill an unknown.
He doesn't mean the Hubble Space Telescope, he means Ediwn Hubble, the astrophysicst who the HST was named after.
Albert Einstein 1879-1955
Edwin Hubble 1889-1953
Hubble Telescope 1990-2003^H^H^H^H2007^H^H^H^H2009^H^H^H^Hwhatever
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Consider a spherical mass of uniform density. If an observer stands at the surface, the gravitational vectors sum to a unit vector from surface to center. If the observer stands at the center of the mass, the gravitational vectors sum to zero (all vectors cancel). If the observer stands at any location in between the first and second position, the gravitational vectors can be given as two sums, zero (canceled) for an equidistant radius from the observer's position to the surface and towards the center, and a distance vector from the observer's position and the residual (uncanceled) mass.
The distance vector between the observer and the residual center of mass is constant at any point between the surface and the center of the mass. The residual mass decreases linearly as the observer descends towards the center. The gravitational force on the observer decreases linearly to zero over this domain. The radius of the sphere is the radius of maximum gravitation.
Gravitational force may cause the radius of the sphere to contract. As the radius shrinks, it approaches the center of mass and therefore increases the gravitational force upon an observer standing at the radius as the inverse square of the change in radius until it relativistically approaches a point at which escape velocity equals the speed of light. To an external observer, the radius will seem to shrink more and more slowly until it seems to stop as it approaches this point. Likewise for the internal observer, but neither mass nor energy can now escape from inside the radius to the outside, so we cannot communicate with him unless we shift our perspective to his.
Staying with our external perspective for the moment, however, we can measure the gravitational force at some distance from the radius, and observe how it acts upon other masses. Nearby matter may get swept into this gravity well, adding to the total mass of our system and increasing its externally determinable radius. But by appearing to slow down and stop at a radius greater than that of our original mass, it would not seem to reach the original radius at all.
Now let's depart our external universe and try to figure out what's going on with our inside observer. First of all, he's not seeing any in-falling matter because his frame of reference is also much slower than that of the radius, in fact he'd have to wait infinitely long before anything like that would happen, so let's just say it doesn't. But that doesn't mean that he cannot observe any effects at all.
What our man on the inside discovers is that there is intense energy, in the form of pressure, being applied to his little micro-universe. This pressure continues to build and build, charging our little spherical mass like a battery, until maximum energy density is reached. But the pressure continues, so the mass does what it has to do, it inflates.
Our mass isn't just expanding in space; it is expanding "space." As pressure energy continues to pour in, the inflation continues until certain physical properties of matter and energy begin to assert themselves; and the inflation proceeds outwards and away from the original mass -- into the new universe.
This is one possible explanation of how our universe may have begun. In searching for evidence of such a hypothesis, one might hope to find some sort of inflationary pressure which seems to operate against gravity. Since this "dark energy" seems probably, this may be a feasible cosmology.
Peace and love, y'all
"Affect"... "Can greatly affect"... 'effect' is a different word, with a different usage.
An informative post, and I'll accept moderator punishment for grammar nazi-ism.
"It's overkill, of course. But you can never have too much overkill." - Anonymous Slashdot Coward
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Everyone forgets to mention Hubble's 'associate', Humason.
His work was what Hubble's Law is actually founded out, he and Hubble worked together, and he was the one that 'observed' the red shift.
Sagan always took time to credit Humason, but very few other prominent people give him the recognition.
Despite the theoretical blunder of a few (I find it doubtful that anyone would use Newtonian mechanics to calculate cosmological problems anymore), most people are using GR for their calculations, and this is a real effect. There is an acceleration that, if the data on redshift vs. distance is correct, can only be explained within GR by adding a repulsive term to the equations.
Remember, these publications are peer reviewed. If the mistake were that simple, the reviewers should have caught it.
You are talking about dark matter
This article is talking about dark energy
These are different things.
Personally I would suspect that, similar to dark matter, dark energy will come in time to be derided as an unnecessary mathematical kludge introduced to paper over problems introduced by an oversight we made somewhere else. However, this hasn't happened yet.
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
That turns out not to be the case. And I was far from the only poster to point that out. Please read the Slashdot comments for critical analysis, not just the blurbs.
Besides which, dark matter has nothing to do with dark energy.
Not exactly. Einstein was all over quantum physics and was one of the biggest contributors in the early days. You are right that he never accepted the probablistic aspects of quantum **MECHANICS**. In other words, he didn't like the math. There are a lot of people in the field who still agree with Einstein. i.e that probabilty is just a convenient way of predicting the outcome of quantum events, but does not reflect what is **REALLY** going on at the quantum level...
These stories always say it was Einstein's great blunder and it has been vindicated, but it really hasn't. The reason Einstein put it in was that he couldn't find any solutions to his equations that resulted in a static universe. (At the time, Hubble's revolutionary results on the recession of distant galaxies had not been completed, so it was thought the universe must be static) All of his model universes were expanding or contracting. So he added the constant to balance out the contraction in his favoured model (which was also closed, another historical assumption in cosmology that has been disposed of).
OK, but the cosmological constant we see now is being used to explain the _acceleration_ of the universe, nothing like what Einstein put the constant in for. His blunder wasn't really the constant, it was the assumption that the universe was static, which turned out to be totally wrong.
But you have to admire Einstein - out of pure thought and mathematics he produced a theory which is still held up as a foundation of modern physics, even though practically every cosmological observation was made years after he published it (and all the observations have supported the theory to great accuracy). Compare this to, say, quantum mechanics, where many theorists struggled for decades to explain observations that had already been made, and Einstein's one-man theory is truly impressive.
There is the theory of the Moebieus: a twist in the fabric of space, where time becomes a loop. Where time becomes a loop. Where time becomes a loop. Where time becomes a loop. Where time becomes a loop...
-- Worf
They don't have mass (any zero mass particle travels at the speed of light) but they do have energy (E=mc^2 doesn't work for a photon...)
The photon energy is taken into account, but it's currently a tiny fraction of the total energy (most of which is dark energy, the rest mostly dark matter - which does obey E=mc^2). If i recall corrrectly, currently the photons (namely the cosmic microwave background) contribute 0.004 of the total energy (starlight probably contributes less, but I could be wrong). In the past, however, photons dominated the energy (photons cooled over time due to redshifting, so they were very hot and energetic in the past).
The world is everything that is the case