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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
IIRC, Einstein "fudged" his equations (i.e., introduced the cosmological constant) to stop them from predicting that the universe would expand. Subsequently, Hubble discovered that the universe was expanding after all. Still later, it was found that the rate of expansion was not in line with Einstein's un-fudged equations. Since then, the value of the cosmological constant has really depended on what value you measure for the expansion of the universe.
So, why is this news?
If he's so smart how come he's dead?
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Einstein put in the constant as a fudge because he wanted his equation to match the data. At the time people were not aware of the exanding nature of the universe. I don't think he ever liked using the constant, and was relieved when it turned out it wasn't necessary. Everything was neat again.
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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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.
In later years, studies will show that Einstein actually CREATED the universe in some kind of unconcious blunder, giving him the "Genius" over the universal equations we praise today.
What a fraud, and I would assume would be then, a god.
~--~
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Fair Warning: what follows is a really simplified version of reality, and at least a couple of points go beyond simplification to the point that they're arguably flat out wrong. If somebody wants to correct part or all of this, please feel free, but if you do so please try to keep with the spirit of actually explaining things so they're understandable.
The situation with dark matter is simpler than dark energy, so we'll start with that.
We've observed a certain amount of matter in the universe. Those observations lead to a rough estimate of what the total amount of matter in the universe might be.
Now, there was a certain amount of energy released in the big bang. For quite a while, it was assumed to be the primary reason that the universe was expanding. I.e. there as a big explosion, and matter went flying off in all directions (and we're basically just living on a bit of shrapnel from that explosion).
Now, if there was enough matter in the universe, the gravity between it would eventually slow it down, stop it, and finally start it contracting back together. That was a rather attractive idea -- that the big bang wasn't a one-time thing, but that we just happened to be seeing evidence of the most recent occurrence.
The problem was that our estimates of how much matter there was in the universe came out well below what was needed for there to be enough gravity to make the expansion stop and eventually reverse.
One answer that was postulated to that was dark matter -- a lot more matter out there that we couldn't see, so it wasn't being figured into our estimates of how much matter there was in the universe. Therefore, a lot of people spent a lot of time and energy trying to find ways to observe a lot more matter than we had previously. To some extent they succeeded -- better telecsopes, observing techniques, etc., have allowed us to observe quite a bit more than we had previously.
By this idea, however, almost regardless of the exact amount of matter in the universe, the gravity should act to slow down the expansion over time -- i.e. the energy pushing things apart was all expended during the big bang, and now gravity should be acting in the general direction of pulling things back together again or at least slowing down the rate at which they're moving apart.
That doesn't fit reality though. In reality, it appears that the expansion of the universe is actually accelerating. The original theory was that the expansion was due to energy released during the big bang. If that was the case, the expansion of the universe should basically just be "coasting", and there's no way it could be accelerating.
The obvious way for the expansion to accelerate is to figure that even though we generally think of the space beyond the edge of the universe as a complete vacuum, devoid of matter or energy, that there really is a little bit of something there afterall, and being a little bit of something (energy or mass) it has some gravitational pull on the matter that we think of as part of the universe, so it's more or less pulling the universe apart -- i.e. accelerating the outward movement.
Given that the expansion of the universe is accelerating (which certainly seems to be accepted as fact right now anyway), it seems to me that the existence of the cosmological constant isn't really the question. The primary questions are 1) what is its exact value, and 2) where exactly does it come from.
If you read the article from the University of Colorado cited elsehwere (for one example), you can find both some estimates of upper and lower limits on the value, and at least one possible explanation for its source. I've heard at least one person give what sounded (to me) like a different explanation of its source, but it wouldn't surprise me too much i
The universe is a figment of its own imagination.
"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.
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That's my take on modern cosmology. That there exists this one substance, the vacum substance, the stubstance of space-time itself. It can be imagined as a drop of water, or equally as a cloud of moisture. It contains volumes within it that are "denser" than other volumes. We say that there is "more space" (or less?) within those volumes. All "material" goods are then just some kind of configuration of this "space-time" stuff. I think also that based on quantum mechanics, and the "Beckenstein bound", material within a given volume can be realized in much the same way pictures are made up of "pixels" on a computer screen. Think of it. Your computer screen resolution determines all objects that are "realizable" within its resolution. The Beckenstein bound then formulates a given volume for space-time in which objects of a given size can fit. The relationship of the "density" of space-time then should directly influence the Beckenstein bound such that, if there is "more space", then there should be the possibility of a larger number of possible quantum states within the abstract volume of space-time.
If you had a glass sphere the size of a basketball, what are all the material objects that are realizable within that space? Well, we can put car keys, pens, small animals/insects, etc. But we cannot put a house inside a basketball right? Well maybe a doll house. But how would we go about putting a real house in a volume the size of a basketball? Simple, just increase the density of space-time within that abstract volume. That will increase the number of quantum states possible just like increasing the resolution of your computer screen. But what do we mean when we say "space is dense"? Since the vacum is matters "opposite", we would probably conclude that space would be "denser" where matter is not. So we might say that within a "black-hole" there is theoretically "no space". A black hole would then indeed be a hold within space-time, a tear in the fabric of reality for example. But this may not be the case. It could be that a black hole is a place were the density of space is so high as to be exactly "solid" space-time. In this respect matter flows into a black hole and then becomes converted to "space-time", which then slowly and inexorably flows outward. Space-time is being generated by a black-hole by the conversion of matter to space-time.
If space-time is a substance of some kind, and all matter is just some configuration of it, then that would explain why we cannot move faster than light. This would be the case if we were somehow made of configurations and vortices of "air". Since we being made of "air", we could not move faster than sound right? Of course doesn't the speed of sound vary with the density of air? Would not the speed of light vary with the density of space-time? Of course it does, this was Einsteins great find, that light travels along a space-time geodesic. The geodesic caused by the "density" of space-time.
Based on all these analogies, I don't see why we have to think about the fourth dimension at all. We just need to imagine space-time as a volume with varying densities. Within a high density of space-time, you can have more matter, and more quantum states. It is abstract I know, but for my mind it works. Is there a reason that these analogies can be viewed as "wrong"? I'm willing to take an alternate view.
I'll expand on the issue of dark matter a little. It's still rather simplified, but it is more to the point on the issue of dark matter particularly.
The original problem that lead to postulating dark matter involves observations of galaxies. Galaxies rotate and physics makes predictions about the orbital velocity of stars in a galaxy based on their distance from the centre of the galaxy. The problem is that these predictions don't square very well with observations. In general observations show stars distant from the center of the galaxy orbiting much faster than expected. You can express this in terms of rotation curves making the problem relatively clear. The proposed solution to this is to assume that there must be extra unobserved (hence dark) mass providing extra gravitational energy, and thus extra orbital velocity, to the more outlying stars.
There are other theories to explain the observations such as Modified Newtonian Dynamics, but they tend to run into their own problems, and currently aren't anywhere near as widely accepted as the dark matter solution.
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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.
The proposed solution to this is to assume that there must be extra unobserved (hence dark) mass providing extra gravitational energy, and thus extra orbital velocity, to the more outlying stars.
Just to expand on this a little, as people may not know the physics behind this...
The stars in question are gravitationally atrracted to the centre of the galaxy, just like the Earth is gravitationally atrracted to the Sun. Just like the Earth, they must either circle the gravitational source, or "fall" towards it. In order to remain in their orbit (rather than moving inwards or outwards) their centripetal acceleration must be equal to the acceleration they feel from the gravitational pull of the galaxy. (Centripetal acceleration is the acceleration required to keep them moving in a circle)
If the gravitational pull is too strong, they'll be pulled in towards the galactic centre; if it's too weak, they'll fly off into space.
Measuring their orbital speed allows us to calculate their centripetal acceleration, and thus the acceleration they feel due to the gravitational pull of the galaxy. This in turn allows us to calculate the mass that is producing the gravitational field that they are in:
v**2/r = GM/r**2
Where v**2 is the speed of the star, squared; r is the radius of the orbit of the star; G is the gravitational constant; and M is the mass of the galaxy producing the gravitational force.
This gives us an estimate of the mass of the galaxy of rv**2/G.
The problem is that working through the numbers gives us a mass that's significantly higher than we can account for from what we see. So, that leaves us with three choices:
1) our understanding of dynamics is flawed (and so v**2/r is wrong)
2) our understanding of gravity is flawed (and so GM/r**2 is wrong)
3) there's stuff out there that we can't (currently) detect by other means
1) would be pretty fundamental (that's some very basic physics indeed), as would 2). That only really leaves 3) as an attractive proposition (imho).
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I get tired of this description of the Big Bang as an explosion in the usual terms, as in things flying apart out into something, "matter flying off in all directions". It's popular science, and most people wouldn't know what the heck you were talking about if you described it any other way. But, it ought to be restated...
It's an expansion of space, everything that is in space is just going along for the ride.
A visual way to clarify that is to shoot down the idea people have that things cannot recede faster than light. That gets their attention, they all know about Einstein and c. Things cannot move through space faster than light, but space itself puts a distance between things that C can never outpace.