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Fayvitt
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Message 40468 - Posted: 17 Jun 2010, 9:15:39 UTC

And the fish in the water swims around casually believing water is the only world there is. Just keep swimming.

That's all very well to have your own opinion. As all the mathematicians must be playing a fun game with M-theory. Seems like an awful lot of funding for a mathematical game, wouldn't you say?

Last i saw experimental/observational evidence for that was zero, nada, zilch, zip. Let's get some membranes out, and make a loaf universe!!

And if Wiki is your source of info, please find a more serious, scientific one. The people who correct/quote/contribute are all on board with mainstream science and have little time for others who wish to challenge their view.

Wiki = popular opinion, not fact.

The philosophy you are invoking is the God theory i believe. In the beginning.....

springing out of nothingness into something. Something from nothing. A 'point' that sprang from nothingness to something, within nothing. Spontaeneous creation.

Mr Physik, theology doesn't belong here.
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Vid Vidmar*
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Message 40469 - Posted: 17 Jun 2010, 9:22:33 UTC - in response to Message 40468.  

And the fish in the water swims around casually believing water is the only world there is. Just keep swimming.

That's all very well to have your own opinion. As all the mathematicians must be playing a fun game with M-theory. Seems like an awful lot of funding for a mathematical game, wouldn't you say?

Last i saw experimental/observational evidence for that was zero, nada, zilch, zip. Let's get some membranes out, and make a loaf universe!!

And if Wiki is your source of info, please find a more serious, scientific one. The people who correct/quote/contribute are all on board with mainstream science and have little time for others who wish to challenge their view.

Wiki = popular opinion, not fact.

The philosophy you are invoking is the God theory i believe. In the beginning.....

springing out of nothingness into something. Something from nothing. A 'point' that sprang from nothingness to something, within nothing. Spontaeneous creation.

Mr Physik, theology doesn't belong here.


On the contrary... I think that only place(and time) left for theology in our universe is at it's beginning. From there on, it's pure science.
BR
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Message 40470 - Posted: 17 Jun 2010, 9:33:13 UTC - in response to Message 40469.  
Last modified: 17 Jun 2010, 9:34:46 UTC

Thanks for making my point Vid. Most appreciated.

How can you know where the universe is going, if you don't know where it's been? The 'point' or 'singularity' of the big bang, well, it came from somewhere.
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Message 40471 - Posted: 17 Jun 2010, 9:44:56 UTC - in response to Message 40468.  
Last modified: 17 Jun 2010, 9:46:22 UTC

And the fish in the water swims around casually believing water is the only world there is. Just keep swimming.

But the fish *could* detect that there is more. And the world outside his lake/ocean influences his world, so there is some causal connection.
It is a bit different with our universe where nothing outside can influence our universe. That is identical to say that there is nothing outside.

That's all very well to have your own opinion. As all the mathematicians must be playing a fun game with M-theory. Seems like an awful lot of funding for a mathematical game, wouldn't you say?

Yes ;)

And if Wiki is your source of info, please find a more serious, scientific one. The people who correct/quote/contribute are all on board with mainstream science and have little time for others who wish to challenge their view.

Uhmm, what would it help if I cite the original work of Andrej Linde who "invented" the buble universum. I just had a look to his publications (in real scientific journals if you mind) an he writes specifically of "causally disconnected regions of the universe". That's basically the same as I cited from Wikipedia and he even states that those bubbles are only subregions of our universe. Your point was what?

The philosophy you are invoking is the God theory i believe. In the beginning.....

I don't see where God entered the discussion. I definitely didn't throw him to the conversation ;)

What I know as "God theory" is quite rubbish in my opinion. There is nothing what can't be "explained" (it's actually not an explanation, just a stating of basic facts with very simple logic) with the (weak) anthropic principle.
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Message 40472 - Posted: 17 Jun 2010, 9:57:10 UTC
Last modified: 17 Jun 2010, 10:09:10 UTC

Ok, so the fish would 'notice' how things affected his world. Just like we notice something is affecting our world.....an expanding universe, but you swear black and blue it must be from inside the universe based on.....your hunch? Based on a theory of dark energy? that can't be detected? like dark matter? like a higgs boson? Purely hypothetical explainations?

Did God tell you there was no medium into which our universe came into existence?

Explain to me what the universe is expanding into...that is, the event horizon of the universe. What's on the other side of the wall? Strings? Angels? Ahhh, i've got it, nothing! The universe is growing into nothing.

So, it started infinitely small, surrounded by....nothing. Grew to the size of a pea, compared to what? There is no frame of reference as there is nothing.

Why is the expansion not uniform? what's stopping it from expanding uniformly? What "outside" force is opposing it? Certainly can't be gravity from the inside, it's too weak.

Lay your wisdom upon me.
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Message 40473 - Posted: 17 Jun 2010, 10:15:03 UTC - in response to Message 40472.  
Last modified: 17 Jun 2010, 10:18:49 UTC

Did God tell you there was no medium into which our universe came into existence?

There is no god. He told me! ;)

Explain to me what the universe is expanding into...that is, the event horizon of the universe. What's on the other side of the wall? Strings? Angels? Ahhh, i've got it, nothing! The universe is growing into nothing.

You are making the common mistake of trying to look at the universe from the outside. But this doesn't make any sense as a hypothetical observer outside would be completely disconnected from our spacetime inside (remember the hypothetical vaccum fluctuation which inside growed into our universe while it simply disappered in the other spacetime?). You can only look at the universe from the inside. If you see our universe, you are in our universe. Otherwise it wouldn't be a universe (hint: think what universe means).

So, it started infinitely small, surrounded by....nothing. Grew to the size of a pea, compared to what? There is no frame of reference as there is nothing.

Correct. That is why you can't measure a universe from the outside ;) See above. There is a reason I wrote that there is not even an outside.

Why is the expansion not uniform? what's stopping it from expanding uniformly? What "outside" force is opposing it? Certainly can't be gravity from the inside, it's too weak.

What do you mean with uniform?
Expansion is at least almost isotropic. One thinks that only some random fluctuations in the early universe disturbed it a very tiny amount. One needed great efforts to measure the anisotropy of the cosmic background for instance (which is a direct consequence of the expansion).
And how do you come to the conclusion that gravitation is far to weak to influence the expansion? There is experimental evidence for about 27% of the mass needed to asymptotically stop the expansion. The open question is if we find the missing 73% or if those are comprised of the still hypothetical dark energy.
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Message 40474 - Posted: 17 Jun 2010, 10:35:16 UTC - in response to Message 40470.  

Thanks for making my point Vid. Most appreciated.

How can you know where the universe is going, if you don't know where it's been? The 'point' or 'singularity' of the big bang, well, it came from somewhere.


Yes, if you take my statement generally, however in context of debate over the beginning of universe (which I got impression this thread was turning to) here and now could also be a place for theology.
I will admit (and I in no sense believe in God in any traditional way; I am not religious), that the beginning of universe may be the sole act of God, God's will if you like.
One more thing all this reminded me of, and it is also connected to cosmology, beginning of universe and even more mundane everyday things is time.
One day, couple of years ago, I had a talk with a family friend, a professor of mathematics, about how I came to conclusion that time is probably running in discrete intervals rather than continuously. My reasoning was the following: After the big bang, up to a certain time things are not only undefined, but also undefinable (at the moment). That is called planck's time. Therefore if time ran continuously, it would be no problem to "calculate" the state of universe down to arbitrarily short time interval, even to the beginning itself. To my amazement, he agreed. And just now, when I checked if I spelt "planck" right, I noticed, that some more established scientists think likewise (wow! :D ).
Nevertheless I would also be interested in others views. Are we ticking or running smooth?
BR

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Message 40476 - Posted: 17 Jun 2010, 12:05:08 UTC - in response to Message 40473.  

You are making the common mistake of trying to look at the universe from the outside. But this doesn't make any sense as a hypothetical observer outside would be completely disconnected from our spacetime inside (remember the hypothetical vaccum fluctuation which inside growed into our universe while it simply disappered in the other spacetime?).


Like us looking at the hypothetical fish in the water? The universe by definition, as all that we know. Are you claiming we now know everything that there is to know?

There is a reason I wrote that there is not even an outside.


So, answer the question. When i peer through the event horizon, what do i see? What do i travel into? The ocean with the fish in it?

And how do you come to the conclusion that gravitation is far to weak to influence the expansion? There is experimental evidence for about 27% of the mass needed to asymptotically stop the expansion. The open question is if we find the missing 73% or if those are comprised of the still hypothetical dark energy.


You answered your own question.
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Message 40477 - Posted: 17 Jun 2010, 12:24:13 UTC - in response to Message 40472.  

Explain to me what the universe is expanding into...that is, the event horizon of the universe. What's on the other side of the wall?

To add something to my above post, there is no "wall" in a material sense. The "event horizon" of the universe defines only the visible part of the universe, or in another sense the part of the universe which can possibly affect us right now. Depending on the way the universe expands (or shrinks), it is allowed for instance that matter virtually "disappears" at the edges of the visible universe in case of an accelerated expansion. It simply means that some part of the universe which was formely within our visible universe (moves slower than the speed of light away from us) is now faster than light (the horizon always moves away with the speed of light from you and that since the Big Bang).
One can get picky and say that it will look like it is only approaching that limit, but the fact remains that only the light emitted up to a certain point in time (where it leaves our visible universe, but remains in our universe) will ever be able to reach us, it will be stretched over longer and longer periods.
And before someone starts with the argument that nothing can move faster than light, that is not violated. In fact, the far away galaxies are not really moving away, it is the space itself which expands (which looks like distant objects are moving away). If the space between two points expands faster than the speed of light, it only means that no information can be exchanged between those two points, i.e. they don't belong to the same visible universe anymore (but that was likely the case earlier in time).

That all may sound confusing first, but after thinking a bit, it started to make some sense.
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Message 40478 - Posted: 17 Jun 2010, 12:29:00 UTC
Last modified: 17 Jun 2010, 12:36:03 UTC

I don't believe in god, but on the same token i don't believe in the big bang. I find it difficult to fathom basing the current fate of the universe whilst only knowing a % of the whole picture.

The Hartle and Hawking No-Boundary Proposal

Hartle and Hawking's new theory treated the universe like a quantum particle. As a result, they created a wave function that describe all possible universes. The wave function is assumed to have a large value for our own universe, and small, non-zero values for an infinite number of other possible, parallel universes. The other universes are expected to have different physical constants than our universe and are believed to be devoid of life.

The problem with Hartle and Hawking's theory is that it predicted the universe is "closed." Consider a closed universe to be the surface of an inflating balloon. Objects such as galaxies on the surface of the balloon would move away in one direction as the balloon inflates, and eventually end up at their initial positions. In addition, the concept of a closed universe implies that the universe will one day stop expanding, and collapse under the force of its own gravity.

Observations suggest that there is insufficient matter in the universe to create enough gravity to recollapse it. In fact, there is evidence predicting the universe to be expanding at a faster rate than the inflationary theory predicts. Thus, observations favor the idea of an "open" universe, a universe that will continue to expand.


The same idiot that gave us singularities and big bang's. First he comes up with multiple universes, then we get 1 from a big bang.

Where did the initial big bang 'singularity' suddenly appear from? Not there 1 microsecond, expanding exponentially the next.
I atleast give M-Theory a rap for having a go at explaining it, whilst current science palms it off to philosophers to debate over. Puts it in the too hard basket as it interferes with their current theory.

Matter can't be created or destroyed? Law of some sort? ;) 'Big bang' energy came from....
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Message 40479 - Posted: 17 Jun 2010, 12:42:19 UTC - in response to Message 40476.  

The universe by definition, as all that we know. Are you claiming we now know everything that there is to know?

No, the universe is all that is. It doesn't matter if we know it, it only has to be ;)

There is a reason I wrote that there is not even an outside.

So, answer the question. When i peer through the event horizon, what do i see? What do i travel into? The ocean with the fish in it?

You are not able to go through the horizon of your visible universe. The universe will always look spherical with you in the center and the horizon moves away from you with the speed of light in all directions, always. It doesn't matter how fast you travel or where you are. It also means that for a hypothetical guy at the left edge of your visible universe and another one at the right edge the universe will look different and they possibly don't see each other.
If you ask what is outside of your visible universe, the answer is all the remaining parts of the universe. We can only see an infinitesimal part of the total universe. As I said, the event horizon of the visible universe isn't material in any way. It is simply defined as moving away with the speed of light under all circumstances since the Big Bang.

And how do you come to the conclusion that gravitation is far to weak to influence the expansion? There is experimental evidence for about 27% of the mass needed to asymptotically stop the expansion. The open question is if we find the missing 73% or if those are comprised of the still hypothetical dark energy.

You answered your own question.

I wouldn't consider a factor of 4 or less significant or a major hurdle. Only 40 years ago we've known only 2% of the necessary mass. We found already a factor of 10 or so in the meantime ;)
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Message 40480 - Posted: 17 Jun 2010, 13:00:43 UTC

So, Mr Physik, there is part of our universe beyond what we can see. I get that from what you're saying. But it doesn't explain this..

[url] http://en.wikipedia.org/wiki/Galaxy_formation_and_evolution[/url]
In 2007 the Keck telescope, a team from California Institute of Technology found six star forming galaxies about 13.2 billion light years (light travel distance) away and therefore created when the universe was only 500 million years old.
Damn, i'm using evil Wiki.

Of the oldest observable light, our universe is 13.7 billion years old. But what about the part of the universe we can't see, beyond the horizon? I assume it's still part of our 'universe' by your own definition.
So how, with any accuracy, can we predict when galaxies first formed? There could be 20 billion light years worth of creation beyond our horizon. Well, that could mean we don't really know squat about what formed and when. Correct?
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Message 40481 - Posted: 17 Jun 2010, 13:02:40 UTC - in response to Message 40478.  
Last modified: 17 Jun 2010, 13:25:47 UTC

If something 'logically' follows on from GR, why does it become complicated? It either is..or isn't.

If that were true, science wouldn't be nearly as difficult as it is. I highly recommend looking into emergent behavior and chaotic behavior - a good place to start would be the simple experiment of a double pendulum. I was going to recommend a very readable text I was given as part of a physics course, but unfortunately I haven't been able to find it online.

Where did the initial big bang 'singularity' suddenly appear from? Not there 1 microsecond, expanding exponentially the next.

A microsecond is a unit of time, and time is subject to relativity. The closer you get to the big bang, the bigger the concentration of mass and the more time slows down - although the singularity itself is not understood by current theories (much like black holes), you could say there -was- no 'before' the big bang, as time itself was started off by it. But I should add that some theories of quantum gravity propose a 'big bounce' instead, where the big bang is not a singular event (but that begs the question of why our universe will keep expanding unlike earlier incarnations).

So how, with any accuracy, can we predict when galaxies first formed?

In essence we just look at how fast the universe is expanding and calculate back to when all the matter we see was bunched together into a single point. Since we can look 'into the past', we can check to see if the rate of expansion then agrees with our calculations. Of course, it really depends on your definition of 'accurate', since there is still a lot of uncertainty in the age of the universe. These calculations -are- based on the assumptions that space is both isotropic and homogeneous at the largest distance scales. That is, we've no reason to assume that our solar system is in some sort of great galactic void and throwing off our calculations, or that the rate of expansion would be different beyond the visible universe. Now, if we ever did find light with a greater redshift than the calculated age of the universe should allow, scientists would have some explaining to do (in one way, the smoothness of the Cosmic Microwave Background is such a problem, and we need theories of Inflation to solve it).
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Message 40482 - Posted: 17 Jun 2010, 13:09:52 UTC - in response to Message 40478.  

I find it difficult to fathom basing the current fate of the universe whilst only knowing a % of the whole picture.

That is called science. If we would know the complete picture, one wouldn't need to think about it any further ;)

The Hartle and Hawking No-Boundary Proposal

In the current state, all that stuff is mostly just some theorization without supportive evidence from observations. A nice gimmick if you want.

The same idiot that gave us singularities and big bang's. First he comes up with multiple universes, then we get 1 from a big bang.

Looks like you mix up now quite some stuff. Hawking had nothing to do with the Big Bang idea for instance and he didn't invented the singularities either.

Where did the initial big bang 'singularity' suddenly appear from? Not there 1 microsecond, expanding exponentially the next.

It does not matter, as it has no influence on our universe. Even when it may be possible to solve this scientifically (one idea would be the vacuum fluctuation I mentioned already (at the end)), I don't see the scientific value. We may want to ask this question for our own curiosity because one may see it as the the ultimate question of life, the universe, and everything, but strictly speaking the answer has no real value, just like "42" ;)

I atleast give M-Theory a rap for having a go at explaining it, whilst current science palms it off to philosophers to debate over. Puts it in the too hard basket as it interferes with their current theory.

M-theory won't explain how the universe came to existence. Furthermore, it first has to grow into a consistent theory (which it isn't currently).

Matter can't be created or destroyed? Law of some sort? ;) 'Big bang' energy came from....

There is some concept named energy conservation which is generally fullfilled except on very short time scales. That is where the vacuum fluctuations come into the game. And by the way, the total energy of the universe may be zero ;)
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Message 40483 - Posted: 17 Jun 2010, 13:23:18 UTC - in response to Message 40480.  

it doesn't explain this..

http://en.wikipedia.org/wiki/Galaxy_formation_and_evolution
In 2007 the Keck telescope, a team from California Institute of Technology found six star forming galaxies about 13.2 billion light years (light travel distance) away and therefore created when the universe was only 500 million years old.
Damn, i'm using evil Wiki.

Of the oldest observable light, our universe is 13.7 billion years old. But what about the part of the universe we can't see, beyond the horizon? I assume it's still part of our 'universe' by your own definition.
So how, with any accuracy, can we predict when galaxies first formed? There could be 20 billion light years worth of creation beyond our horizon. Well, that could mean we don't really know squat about what formed and when. Correct?

No. The universe as a whole came into existence about 13.7 billion years ago. We know that, because no light older than that had the chance to reach us so far. That is simply defined by the size of the visible universe and the speed of expansion one can measure. Because this process (and the whole universe) is so isotropic, there is simply no reasonable explanation how some parts of the universe could have existed somehow earlier than other parts. One would be able to detect that through a far greater anisotropy in our universe as observed.
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Message 40484 - Posted: 17 Jun 2010, 13:49:14 UTC

No. The universe as a whole came into existence about 13.7 billion years ago. We know that, because no light older than that had the chance to reach us so far.


Didn't you say though that there's part of the universe beyond our viewable range? Please be consistent.

Looks like you mix up now quite some stuff. Hawking had nothing to do with the Big Bang idea for instance and he didn't invented the singularities either.


Penrose penned (pardon the pun) the singularity, Hawking 'borrowed' it as the source of the big bang. Yep, i'm the Mix Master!

M-theory won't explain how the universe came to existence. Furthermore, it first has to grow into a consistent theory (which it isn't currently).


If it does become viable (i hope not), they already have a model for the big bang.

There is some concept named energy conservation which is generally fullfilled except on very short time scales. That is where the vacuum fluctuations come into the game. And by the way, the total energy of the universe may be zero ;)


Vacuum fluctuations? Theory? No facts? Not provable but invented to fill a knowledge gap? We aren't talking gravitons are we? Of course not. We're quoting Hawking again. The man that gave us the unworkable multiple universe theory. Well, he thought it worked anyway.

http://www.braungardt.com/Physics/Vacuum%20Fluctuation.htm
It is possible to settle the issue by a simple calculation. Astronomers can measure the masses of galaxies, their average separation, and their speeds of recession. Putting these numbers into a formula yields a quantity which some physicists have interpreted as the total energy of the universe. The answer does indeed come out to be zero within the observational accuracy.


That's Hawking's zero energy. But that doesn't account for our dark matter or dark energy, does it? So is Hawking wrong, or wrong?
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Message 40486 - Posted: 17 Jun 2010, 15:04:58 UTC - in response to Message 40484.  

Vacuum fluctuations? Theory? No facts? Not provable but invented to fill a knowledge gap?

Check out the Casimir effect.
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Message 40487 - Posted: 17 Jun 2010, 15:30:51 UTC
Last modified: 17 Jun 2010, 15:37:12 UTC

So, is this electromagnetism explained in another way?

As the gap between the plates is narrowed (to a few nanometers), fewer waves can contribute to the vacuum energy and so the energy density between the plates falls below the energy density of the surrounding space. The result is a tiny force trying to pull the plates together – a force that has been measured and thus provides proof of the existence of the quantum vacuum.


Just asking. Walks like a duck, quacks like a duck, so let's call it a rabbit?
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Message 40489 - Posted: 17 Jun 2010, 17:09:19 UTC - in response to Message 40484.  

No. The universe as a whole came into existence about 13.7 billion years ago. We know that, because no light older than that had the chance to reach us so far.

Didn't you say though that there's part of the universe beyond our viewable range? Please be consistent.

There is no inconsistency.

Looks like you mix up now quite some stuff. Hawking had nothing to do with the Big Bang idea for instance and he didn't invented the singularities either.

Penrose penned (pardon the pun) the singularity, Hawking 'borrowed' it as the source of the big bang.

Uhmm, no. The origin of the idea with the Big Bang starting from a very dense state is Georges Lemaître who formulated that idea already in 1927.
Penrose and Hawking have only proven (much later) that there are no solutions of Einsteins field equations completely without singularities.
By the way, singularities are in fact only mathematical constructs which should give a strong hint to every physicist that some part of the theory is still missing. So in fact they have proven that Einstein's equations are no complete theory (which is a well known fact).

There is some concept named energy conservation which is generally fullfilled except on very short time scales. That is where the vacuum fluctuations come into the game. And by the way, the total energy of the universe may be zero ;)

Vacuum fluctuations? Theory? No facts? Not provable but invented to fill a knowledge gap? We aren't talking gravitons are we? Of course not. We're quoting Hawking again. The man that gave us the unworkable multiple universe theory. Well, he thought it worked anyway.

Again, only because Hawking has written something about it in his "Brief history of time" doesn't make him the original source of the idea. Vacuum fluctuation were known long before (they are in a sense a consequence of the Heisenberg uncertainty principle formulated also already in 1927). And the vacuum fluctuations have measurable and proven consequences (you may look up the Lamb shift), even as some details are not fully understood yet (there are for instance some problems when one tries to calculate the Casimir effect from vacuum fluctuations, there are also competing interpretations of the Casimir effect which may be a better fit).

http://www.braungardt.com/Physics/Vacuum%20Fluctuation.htm
It is possible to settle the issue by a simple calculation. Astronomers can measure the masses of galaxies, their average separation, and their speeds of recession. Putting these numbers into a formula yields a quantity which some physicists have interpreted as the total energy of the universe. The answer does indeed come out to be zero within the observational accuracy.

That's Hawking's zero energy. But that doesn't account for our dark matter or dark energy, does it? So is Hawking wrong, or wrong?

No, that's not "Hawking's" zero energy. The gravitational potential of some masses is known for some hundred years now, the same is true for the kinetic energy. Only for Einstein's E=mc² we had to wait a little bit longer. But summing all up is hardly a breakthrough. The total energy of an isolated system (as our universe) is known to be conserved and constant for ages now, one should learn this latest at College if not already in the high school. It is a common quantity to characterize a physical system.
By the way, it doesn't matter which kind of energy/matter our universe consists of, that calculation should work always.
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Message 40490 - Posted: 17 Jun 2010, 17:34:36 UTC - in response to Message 40487.  
Last modified: 17 Jun 2010, 17:35:25 UTC

So, is this electromagnetism explained in another way?

No, it's the Casimir effect ;)
It was predicted in 1948 and measured 8 years later.

The vacuum fluctuations happen not only with an electromagnetic field but for everything. The textbook experiment is only designed to measure the electromagnetic part as it is the easiest (lowest energies and the longest wavelengths). But is has proven and measured implications also for the strong(*) interaction between quarks for instance.

(*):
There are 4 fundamental forces in the universe which possibly unify at very high energy scales. The electromagnetic, the weak, the strong interaction, and finally gravitation. The unification of the electromagnetic and the weak interaction can be considered theroetically understood and experimentally more or less proven up to the still pending detection of the Higgs particle. Theories for three forces (Grand Unified Theories, GUTs) are being developed, but hard experimental checks are probably far far away. The "holy grail" would be to embed some sort of quantum gravitation for a unification of all 4 forces.
That may show how far we are currently away from such stuff, as it is not really possible to check even the GUTs (there are a lot of competing ones) and we are still struggling to find the last pieces of the puzzle for the electroweak unification. That's why I said earlier that such advanced theories are currently not much more than playing around with some advanced mathematics without any factual base.
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