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Copernicus
2012-Sep-03, 10:34 PM
In the following article it states space may not be grainy. I guess my question is this. Haven't phycisist already ruled out graininess already less than 10^-35 meters. Isn't this nothing new?

Strange
2012-Sep-03, 10:41 PM
Which article?

This one? http://www.nature.com/news/cosmic-race-ends-in-a-tie-1.9768

Copernicus
2012-Sep-04, 12:12 AM
Which article?

This one? http://www.nature.com/news/cosmic-race-ends-in-a-tie-1.9768

Yeah, good work!

John Mendenhall
2012-Sep-04, 12:24 AM
In the following article it states space may not be grainy. I guess my question is this. Haven't phycisist already ruled out graininess already less than 10^-35 meters. Isn't this nothing new?

You are correct. And IIRC, the limit on time increments is well below the Planc interval. The Intelligent Designer had three martinis, sat down at his drawing board, and said 'Smooth, really smooooth.'

Copernicus
2012-Sep-04, 08:03 AM
In the following article it states space may not be grainy. I guess my question is this. Haven't phycisist already ruled out graininess already less than 10^-35 meters. Isn't this nothing new?

i miswrote, i meant Haven't physcisist already ruled out graininess of "greater" than 10^-35 meters.

http://www.msnbc.msn.com/id/48863290/ns/technology_and_science-science/t/have-three-little-photons-broken-theoretical-physics/

antoniseb
2012-Sep-04, 01:53 PM
It should be noted that 10-35 meters is still way larger than infinitesimal.
It should also be noted that the tests of graininess make some assumptions about the behavior of matter and energy as they pass from group of grains to group of grains (if there are grains)... so at best you can say some variations on some models have been ruled out.

Copernicus
2012-Sep-04, 03:56 PM
It should be noted that 10-35 meters is still way larger than infinitesimal.
It should also be noted that the tests of graininess make some assumptions about the behavior of matter and energy as they pass from group of grains to group of grains (if there are grains)... so at best you can say some variations on some models have been ruled out.

Agreed! Although 10-35 meters seems tiny, it is not infinitesimal.

VonBelmont
2012-Sep-05, 03:37 PM
Agreed! Although 10-35 meters seems tiny, it is not infinitesimal.

It's a clever experiment, but based on wrong presuppositions.

You see, about only 4.3-4.6% or so of the universe is made up of the stuff we recognize in daily life. If the experiment is basing the smoothness of spacetime by measuring the photons, then clearly the experiment is not accurate, since photons do not interact with either the dark energy or dark matter particles. If you try and dilute only 4% of all matter which does interact with it on universal scales, it should be no wonder photons appear to move in an almost non-grainy vacuum.

13 billion years ago, dark matter dominated. It covered over 60% of all the matter in the universe. Today, dark energy dominates, covering over 70% of all the energy in the universe. Neither of these massive chunks of the materials in the universe would effect a photons trajectory.

antoniseb
2012-Sep-05, 06:33 PM
... If the experiment is basing the smoothness of spacetime by measuring the photons, then clearly the experiment is not accurate, since photons do not interact with either the dark energy or dark matter particles....
You should read the article. It isn't talking about the smoothness of matter, or dark matter, or dark energy. This is a question about the scale and/or existence of Heisenberg foam.

VonBelmont
2012-Sep-05, 06:37 PM
You should read the article. It isn't talking about the smoothness of matter, or dark matter, or dark energy. This is a question about the scale and/or existence of Heisenberg foam.

Well, it says

'' In a simplified explanation, photons with the highest energies have wavelengths comparable to the Planck length, so are more likely to interact with and be slowed down by these 'lumps'. Although the slowing effect is minuscule, the difference is amplified as the particles journey for billions of years across the vast distances of the cosmos.''

To me this is questioning how smoothly a photon will move through matter. For billions of years, my point being, is that a photon doesn't even interact with most of the matter in the universe. Most of the matter, does not interact electromagnetically, so of course it will smoothly move through it. Spacetime can still be grainy in the presence of this stuff we don't detect.

antoniseb
2012-Sep-05, 07:00 PM
... To me this is questioning how smoothly a photon will move through matter. ...
You are misunderstanding it. I don't have time to try and figure out where you went wrong, but it isn't talking about matter.

VonBelmont
2012-Sep-05, 07:03 PM
You are misunderstanding it. I don't have time to try and figure out where you went wrong, but it isn't talking about matter.


The smoothness of spacetime is due to how flakey quantum fluctuations make it. All kinds of matter and energy are fluctuations. The vacuum is basically, quantum fluctuations.


Exactly, where do you think I have gone wrong?

VonBelmont
2012-Sep-05, 07:05 PM
I believe you have misunderstood the article. The article is talking about the graininess, or quantum makeup of the vacuum. The vacuum is made up of fluctuations which is what we call matter. I am explaining that photons only interact with a mere 4% of all matter in the universe, so no wonder their experiment turned up a near smooth vacuum.

Shaula
2012-Sep-05, 07:12 PM
The vacuum is made up of fluctuations which is what we call matter.
Nope. The flucutations can be bosonic too. Unless you call photons matter too?

VonBelmont
2012-Sep-05, 07:16 PM
Nope. The flucutations can be bosonic too. Unless you call photons matter too?

I refer you to post 36. I clearly note matter and energy are fluctuations. My reply was to Anton who states this is not talking about matter. However, both matter particles and energy particles make up quantum fluctuations.

VonBelmont
2012-Sep-05, 07:17 PM
http://faculty.washington.edu/smcohen/320/GrainySpace.html

A good reference to show what I am talking about.

VonBelmont
2012-Sep-05, 07:43 PM
Nope. The flucutations can be bosonic too. Unless you call photons matter too?

Also, how do you distinctly identify bosons with zero mass, may I ask?

Some Bosons have a mass... you know?

Shaula
2012-Sep-05, 07:44 PM
Of course the minor issue is that quantum fluctuations are not the same as quantum graininess...

VonBelmont
2012-Sep-05, 07:46 PM
Of course the minor issue is that quantum fluctuations are not the same as quantum graininess...


Well actually, the graininess of spacetime are fluctuations which are quantum particles.

VonBelmont
2012-Sep-05, 07:46 PM
You cannot separate the idea of quantum fluctuations and particles, which my link hints at as well.

VonBelmont
2012-Sep-05, 07:47 PM
what do you think it is?

From the article

''In the 1950's, the physicist John Wheeler suggested that the Planck length marked the boundary where the random roil of quantum mechanics scrambled space and time so violently that ordinary notions of measurement stopped making sense. He called the result "quantum foam."

Well, we all know what quantum foam is. It is the presence of quantum fluctuations at very very small levels.

edit/

Spacetime is not just a sheet. It is a violent activity of particles which gives rise to a graininess of the vacuum. This graininess is what we might associate a photon travelling through, however, as I have pointed out a few times now, a photon is only effected by 4% of all the matter in spacetime. The experiment is flawed in the OP, or at least, the assumptions brought forth.

headrush
2012-Sep-05, 08:43 PM
It's a clever experiment, but based on wrong presuppositions.

You see, about only 4.3-4.6% or so of the universe is made up of the stuff we recognize in daily life. If the experiment is basing the smoothness of spacetime by measuring the photons, then clearly the experiment is not accurate, since photons do not interact with either the dark energy or dark matter particles. If you try and dilute only 4% of all matter which does interact with it on universal scales, it should be no wonder photons appear to move in an almost non-grainy vacuum.

13 billion years ago, dark matter dominated. It covered over 60% of all the matter in the universe. Today, dark energy dominates, covering over 70% of all the energy in the universe. Neither of these massive chunks of the materials in the universe would effect a photons trajectory.

You seem to have a great deal of knowledge about something that has not been detected. Surely all what follows is ATM ?

VonBelmont
2012-Sep-05, 08:55 PM
You seem to have a great deal of knowledge about something that has not been detected. Surely all what follows is ATM ?


Is dark energy and dark matter a matter itself of ATM?

I will leave that to those who run the site on cosmology itself. Keep in mind, dark matter and dark energy are not ATM concepts.

antoniseb
2012-Sep-05, 09:22 PM
Is dark energy and dark matter a matter itself of ATM? ...
I believe that your statements about matter and quantum fluctuations is what Headrush was saying were unknown and unobserved, and hence all that follow must be ATM. Dark Matter and Dark Energy are fine topics until you say we know something about them that we don't know.

VonBelmont
2012-Sep-05, 09:26 PM
I believe that your statements about matter and quantum fluctuations is what Headrush was saying were unknown and unobserved, and hence all that follow must be ATM. Dark Matter and Dark Energy are fine topics until you say we know something about them that we don't know.

Not at all. Quantum foam is not ATM, it has been observed.

Have you heard of the Casimir Effect?

Tensor
2012-Sep-05, 09:32 PM
Well, it says

'' In a simplified explanation, photons with the highest energies have wavelengths comparable to the Planck length, so are more likely to interact with and be slowed down by these 'lumps'. Although the slowing effect is minuscule, the difference is amplified as the particles journey for billions of years across the vast distances of the cosmos.''

To me this is questioning how smoothly a photon will move through matter. For billions of years, my point being, is that a photon doesn't even interact with most of the matter in the universe. Most of the matter, does not interact electromagnetically, so of course it will smoothly move through it. Spacetime can still be grainy in the presence of this stuff we don't detect.

And this is where you are wrong. It's questioning how a photon will move through space-time. The lumps are lumps (or the graininess) of space-time, not matter. Nor are they lumps of energy. Unless, of course, you are equating the lumpiness of space-time with energy particles, are you? The article, is talking about Lorentz Invariance. At the scale the article (and the referenced papers) are talking about, high energy Gamma Rays will not travel at c because space-time will not be isotropic nor homogeneous, IOW, not Lorentz invariant. Of course, the experiments to date have not found any verifiable differences in the speed of high energy gamma rays, all they have done is constrained the size of the grains (or lumps) of space-time.

Tensor
2012-Sep-05, 09:38 PM
Not at all. Quantum foam is not ATM, it has been observed.

Have you heard of the Casimir Effect?

The Casimir effect has nothing to do with Quantum Foam and everything to do with Quantum Electrodynamics and charges and currents. You do not need a reference to zero point energies to compute the Casimir effect. See here (http://arxiv.org/pdf/hep-th/0503158v1.pdf)

VonBelmont
2012-Sep-05, 09:42 PM
And this is where you are wrong. It's questioning how a photon will move through space-time. The lumps are lumps (or the graininess) of space-time, not matter.

Am I just speaking to myself?

You do realize that the graininess of spacetime is due to quantum foam... right? You do know what quantum foam is... right?

Space and time is a sheet with what are called distortions. This is what causes the graininess.

VonBelmont
2012-Sep-05, 09:43 PM
The Casimir effect has nothing to do with Quantum Foam


So wrong it is beyond belief.

Quantum foam are quantum fluctuations. The Casimir Effect is due to quantum fluctuations.

VonBelmont
2012-Sep-05, 09:45 PM
You can check any good website for this information. The Casimir effect is due to quantum fluctuations. They are due to particles within the sheet of the vacuum. The vacuum is not a case of empty space, it is filled with virtual particles and antiparticles. Our normal everyday matter, interacts with a small proportion of this stuff.

VonBelmont
2012-Sep-05, 09:50 PM
Read this please

http://en.wikipedia.org/wiki/Quantum_foam

VonBelmont
2012-Sep-05, 09:51 PM
And for reference to quantum fluctuations being present for the Casimir effect

http://www.hep.caltech.edu/~phys199/lectures/lect5_6_cas.pdf

VonBelmont
2012-Sep-05, 09:57 PM
So... for one last time. I will explain, this experiment is bunk because it does not take into consideration that a photon only interacts with about 4% of all the matter in the universe. That is next to insignificant... not totally, but enough possibly to think spacetime is smooth since a photon will not interact with the rest of the energy or matter present in the vacuum.

In other words, spacetime may be very very grainy indeed. We just don't have the ''things'' which can detect it.

Shaula
2012-Sep-05, 10:01 PM
Spacetime is affected by dark matter and dark energy. Has to be really. So they will affect spacetime which will affect the photon. You are ignoring this indirect mechanism for some reason.

Tensor
2012-Sep-05, 10:02 PM
what do you think it is?

From the article

''In the 1950's, the physicist John Wheeler suggested that the Planck length marked the boundary where the random roil of quantum mechanics scrambled space and time so violently that ordinary notions of measurement stopped making sense. He called the result "quantum foam."

Well, we all know what quantum foam is. It is the presence of quantum fluctuations at very very small levels.
edit/

Not quite. Quantum Foam is the description given to the different shapes space-time can take (foam-like) due to the quantum fluctuations of the MANIFOLD (or in your words, sheet).


Spacetime is not just a sheet. It is a violent activity of particles which gives rise to a graininess of the vacuum.

Space-time is a sheet in GR(actually, it's a Lorentzian Manifold, but sheet is close enough). The quantum fluctuations that Wheeler talks about are the changes (or fluctuations) of the curvature and topology of the sheet due to quantum uncertainty and have nothing to do with particles. See pages Section 20.6, page 480; Section 43.4, pages 1190-1192; Box 44.2; and section 44.3 page, 1202 of "Gravitation". It's a bit different from most thoughts on exactly what Quantum Gravity is.


It is a violent activity of particles which gives rise to a graininess of the vacuum.

If you look up those references, you'll find that there are no particles involved. Particles can pop in and out of existence at that level, but it has nothing to do with space-time and everything to do with QED and QCD along with weak force.


This graininess is what we might associate a photon travelling through, however, as I have pointed out a few times now, a photon is only effected by 4% of all the matter in spacetime. The experiment is flawed in the OP, or at least, the assumptions brought forth.

Actually, it's your understanding of the assumptions that is flawed. Go look up those references from "Gravitation". After all, Wheeler was one of the authors of that tome, although Misner and Thorne were prophets of Wheeler's.

VonBelmont
2012-Sep-05, 10:08 PM
I don't know who you are, or where you came into this discussion, but I can assure you, you are wrong on many points. The Casimir effect is because of quantum fluctuations... did you even bother reading the paper I cited?

Tensor
2012-Sep-05, 10:11 PM
So wrong it is beyond belief.

Nope. Don't read websites or articles. Read actual papers and graduate level textbooks. Then tell me I'm wrong.


Quantum foam are quantum fluctuations.

Yea, of the topology and curvature of spacetime.


The Casimir Effect is due to quantum fluctuations.

Yes, quantum fluctuations as described by QED.

There are quantum fluctuations in various theories. Just because there is a quantum fluctuation in one theory doesn't mean it accounts for an effect in another theory.

VonBelmont
2012-Sep-05, 10:13 PM
Tensor

''Space-time is a sheet in GR(actually, it's a Lorentzian Manifold, but sheet is close enough). The quantum fluctuations that Wheeler talks about are the changes (or fluctuations) of the curvature and topology of the sheet due to quantum uncertainty and have nothing to do with particles. See pages Section 20.6, page 480; Section 43.4, pages 1190-1192; Box 44.2; and section 44.3 page, 1202 of "Gravitation". It's a bit different from most thoughts on exactly what Quantum Gravity is.

Well, actually spacetime is just a flat manifold, a sheet if you will. My terminology may make you puke, but I am trying to speak to all corners of the intellect here, unlike you. You don't seem to be aware that when a physicist talks about uncertainty in a vacuum, they are not talking about the vacuum per se, (well they are), but in a manner of speaking, they are talking about the dynamics happening in that vacuum, which is totally resultant from quantum particles, oscillations, or even fluctuations, call it what you will.

You have a very odd view of spacetime. Spacetime is what we call the ''particle.'' Take a small area of a Planck Space and what you will end up with something equivalent to this

\frac{\hbar \omega}{2}

All of spacetime is teeming with this material stuff. It is what we call quantum fluctuations or as it has been described as ''quantum foam.''

Please do not derail this thread any more, or I will report you.

Tensor
2012-Sep-05, 10:13 PM
And for reference to quantum fluctuations being present for the Casimir effect

http://www.hep.caltech.edu/~phys199/lectures/lect5_6_cas.pdf

And where exactly does your paper state anything about Quantum Foam?

Tensor
2012-Sep-05, 10:16 PM
I don't know who you are, or where you came into this discussion, but I can assure you, you are wrong on many points. The Casimir effect is because of quantum fluctuations... did you even bother reading the paper I cited?


Quantum Foam is the result of quantum fluctuations, not the fluctuations themselves.

VonBelmont
2012-Sep-05, 10:16 PM
Nope. Don't read websites or articles. Read actual papers and graduate level textbooks. Then tell me I'm wrong.



Yea, of the topology and curvature of spacetime.



Yes, quantum fluctuations as described by QED.

There are quantum fluctuations in various theories. Just because there is a quantum fluctuation in one theory doesn't mean it accounts for an effect in another theory.

Are you being dense intentionally? All particles interact with some kind of gravitational effects which cause curvature, this is not the case. Quantum fluctuations play the greatest part in theories concerning energy densities within the vacuum. Not to mention also, the Casmir effect is in fact a resultant cause of such interactions. In fact, as I have explained, the graininess spoke about in this case is the result of quantum fluctuations itself. One just needs to read the things I have cited to understand this.

If you don't read papers, I think you might be in the wrong place.

VonBelmont
2012-Sep-05, 10:17 PM
Quantum Foam is the result of quantum fluctuations, not the fluctuations themselves.


The Casimir effect, what you quoted me on, is the result of quantum fluctuations. I never said anything about quantum foam, but now you say it, quantum foam is the same thing as fluctuations. There is NO DIFFERENCE.

VonBelmont
2012-Sep-05, 10:18 PM
And where exactly does your paper state anything about Quantum Foam?

Go back, find the link about quantum foam. I have posted plenty links here in this thread. Only you are finding trouble in this, everyone else seems to have subsided.

Tensor
2012-Sep-05, 10:30 PM
The Casimir effect, what you quoted me on, is the result of quantum fluctuations. I never said anything about quantum foam,

From Post #25:


Not at all. Quantum foam is not ATM, it has been observed.

Have you heard of the Casimir Effect?

That certainly appears to me as if you are claiming Quantum Foam has been observed and the observation is the Casimir Effect. If this is not what you meant, could you please clarify.


but now you say it, quantum foam is the same thing as fluctuations. There is NO DIFFERENCE.

No, I said Quantum fluctuations of the manifold cause Quantum Foam. There is a difference.

VonBelmont
2012-Sep-05, 10:32 PM
I would like people to read, without the distractions, my point made in post 33.

Photons will appear to move in a smooth vacuum. Can anyone from reading this tell me why?

The reason is that we have basically, a vacuum in which 93% of it, (the rest of the material is known gasses) in which the photon does not interact. Indeed, this means that the vacuum will appear smooth.

VonBelmont
2012-Sep-05, 10:34 PM
From Post #25:



That certainly appears to me as if you are claiming Quantum Foam has been observed and the observation is the Casimir Effect. If this is not what you meant, could you please clarify.



No, I said Quantum fluctuations of the manifold cause Quantum Foam. There is a difference.

OF COURSE the quantum fluctuations have been observed. How many times do I need to repeat this? The fact we have observed the Casimir effect, is the result of such fluctuations.

And no, quantum fluctuations do not cause quantum foam exactly, quantum foam is the same thing as vacuum fluctuations. Particles are particles, such are ducks ducks.

VonBelmont
2012-Sep-05, 10:37 PM
If you place two plates close enough in the vacuum, we are talking about small plates, but nevertheless, small enough that the discharge of virtual particle are seen interacting. These are quantum fluctuations, they are the same thing as what is described as the quantum foam, a ''bubbling couldren of particles'' is how Wheeler described it.

Derail this with an intellectual dishonesty one more time, and I will report you. No more threats needed.

antoniseb
2012-Sep-05, 10:51 PM
I would like people to read, without the distractions, my point made in post 33. ...
I have no problem with your belief that the experiment is bunk... My concern is your rationale. That the high-energy photons of different energies traveling through 8 billion light-years of granular-or-not space arrive within moments of the same time depends on whether the matter in space is dark or not isn't the issue. When people discuss this experiment, the issue is that photons of sufficiently high energy have wavelengths small enough that the level of granularity has an impact on their apparent velocity, by giving them a slightly non-linear path.

You clearly have given all this some thought, but you are talking outside the thing it is hoping to measure, and substituting your own terminology as to what is implied by granularity, quantum fluctuations, and quantum foam. We are not talking about Dirac's sea of particle-antiparticle pairs. We are not talking about the Casimir effect. We are talking about quantum gravity and the granularity of spacetime.

In any case, we are talking about a measurement/observation that can be applied to confirming/refuting some models of quantum gravity only. There is no fact that one model of String Theory, is correct. We are finding observations that rule out classes of models... You are coming across as though you think these models have been worked out. That is the probable cause of friction in this thread.

VonBelmont
2012-Sep-05, 11:09 PM
I have no problem with your belief that the experiment is bunk... My concern is your rationale. That the high-energy photons of different energies traveling through 8 billion light-years of granular-or-not space arrive within moments of the same time depends on whether the matter in space is dark or not isn't the issue. When people discuss this experiment, the issue is that photons of sufficiently high energy have wavelengths small enough that the level of granularity has an impact on their apparent velocity, by giving them a slightly non-linear path.

You clearly have given all this some thought, but you are talking outside the thing it is hoping to measure, and substituting your own terminology as to what is implied by granularity, quantum fluctuations, and quantum foam. We are not talking about Dirac's sea of particle-antiparticle pairs. We are not talking about the Casimir effect. We are talking about quantum gravity and the granularity of spacetime.

In any case, we are talking about a measurement/observation that can be applied to confirming/refuting some models of quantum gravity only. There is no fact that one model of String Theory, is correct. We are finding observations that rule out classes of models... You are coming across as though you think these models have been worked out. That is the probable cause of friction in this thread.

''I have no problem with your belief that the experiment is bunk... My concern is your rationale. That the high-energy photons of different energies traveling through 8 billion light-years of granular-or-not space arrive within moments of the same time depends on whether the matter in space is dark or not isn't the issue. When people discuss this experiment, the issue is that photons of sufficiently high energy have wavelengths small enough that the level of granularity has an impact on their apparent velocity, by giving them a slightly non-linear path.''

Well, considering we live in a universe with a 4% matter dominated region in which photons only interact, I would not be surprised they arrive at the same time. It only adds to the theory that matter itself is truly distributed accordingly. Dark matter and energy becomes an issue when you consider how much vacuum it has had to move through. None of the shifting values between the dark and energy matter phases have altered this in one part of any billionth, trillionth ect. The only thing which will, is in fact the normal matter we see today which has obviously had normal effects and balanced effects, needless to say, to this day. They have measured a bunch of photons from two different sources. To be honest, it is not only difficult to say the photons came from the appropriate sources, but it is also difficult to say there is enough interference in the vacuum to allow the significant delays required to measure the graininess of spacetime.

''You clearly have given all this some thought, but you are talking outside the thing it is hoping to measure, and substituting your own terminology as to what is implied by granularity, quantum fluctuations, and quantum foam. We are not talking about Dirac's sea of particle-antiparticle pairs. We are not talking about the Casimir effect. We are talking about quantum gravity and the granularity of spacetime.''

I am not talking about Dirac's Sea of negatively charged particles. I am talking about your natural quantum vacuum, with natural occurring dynamics. It just so happens, that the Dirac Sea, mathematically speaking is not entirely compatible with current theories today, however, many theories ''like it'' exist. Fluctuations and Casimir effect are completely the same thing. You can't have one without the other. Quantum foam and oscillations are also the same thing when speaking about the quantum nature of particles. The granularity of spacetime is in fact due to quantum fluctuations, which is the same thing as saying there is a presence of the Casimir effect. You just need to read the reference I gave, or any good text to explain they are essentially the same thing.

''In any case, we are talking about a measurement/observation that can be applied to confirming/refuting some models of quantum gravity only. There is no fact that one model of String Theory, is correct. We are finding observations that rule out classes of models... You are coming across as though you think these models have been worked out. That is the probable cause of friction in this thread.''

I disagree, to a point. This is not about refuting models of quantum gravity, rather we are talking about quantum gravity at the ''quantized level.'' And no one said anything about a string theory. I don't like that theory and I feel is off-topic to even discuss it.

Swift
2012-Sep-05, 11:20 PM
<snip>

Are you being dense intentionally?

If you don't read papers, I think you might be in the wrong place.
VonBelmont,

Do not accuse other members of being dense, do not publicly express doubt about their intelligence, and do not accuse them of not participating "properly" in a thread. All of that is considered rude behavior here and is against our rules.

If you have not done so already, I strongly suggest you review the rules for CQ (http://cosmoquest.org/forum/showthread.php/32864-**-Rules-For-Posting-To-This-Board-**); in this case I suggest reviewing rule 2, part of which is quoted below:

Attack the ideas, not the person(s) presenting them. If you've got concerns with what someone is saying, feel free dismantle their arguments, but do not resort to ad hominem or personal attacks. Be mindful and respectful of others' feelings.

VonBelmont
2012-Sep-05, 11:25 PM
VonBelmont,

Do not accuse other members of being dense, do not publicly express doubt about their intelligence, and do not accuse them of not participating "properly" in a thread. All of that is considered rude behavior here and is against our rules.

If you have not done so already, I strongly suggest you review the rules for CQ (http://cosmoquest.org/forum/showthread.php/32864-**-Rules-For-Posting-To-This-Board-**); in this case I suggest reviewing rule 2, part of which is quoted below:

I am sorry, I never realized pointing out someones errors after being linked to informative sources was against the rules. I apologize and move on.

Tensor
2012-Sep-06, 12:47 AM
OF COURSE the quantum fluctuations have been observed. How many times do I need to repeat this? The fact we have observed the Casimir effect, is the result of such fluctuations.

And no, quantum fluctuations do not cause quantum foam exactly, quantum foam is the same thing as vacuum fluctuations.

I am quite aware that quantum fluctuations are the same thing as vacuum fluctuations. I am also aware that you can model the Casimir effect as the result of such fluctuations. (which are part of Quantum Electrodynamics, as I said in Post #27) and you can also model the Casimir effect as relativistic charges and currents, as I provided a link for, again in post #27. But Quantum Foam is not the same thing as the fluctuations. I provided references to quantum foam in "Gravitation". Here they are again: See pages Section 20.6, page 480; Section 43.4, pages 1190-1192; Box 44.2; and section 44.3 page, 1202 of "Gravitation". If you believe otherwise, please, provide a reference for such a claim. You provided a reference to Wikipedia in post #31. To quote from that source:


the energy of these fluctuations would be large enough to cause significant departures from the smooth spacetime seen at larger scales, giving spacetime a "foamy" character

My Bold. Note it says that the fluctuations CAUSE the departures from smooth spacetime which gives spacetime the "foamy" character. Nowhere in that reference is there any comment about fluctuations being the same as "Quantum Foam". Here's another one:


Quantum foam is theorized to be created by virtual particles of very high energy.....These "vacuum fluctuations" affect the properties of the vacuum.


Again, my bold. And, again, note that the quantum foam is created by or affected by the fluctuations, not the same as the fluctuations. These are from YOUR source.



Particles are particles, such are ducks ducks.

And, yet, you haven't pointed out in that paper on the Casimir effect anywhere that mentions Quantum Foam. Other than your assertion that fluctuations and quantum foam are the same thing. Even though the reference you linked to, show they are not.



You have a very odd view of spacetime. Spacetime is what we call the ''particle.''

You know, I've never heard of it put that way. Do you have a reference for that? I haven't seen it in "Gravitation", so it must be out there some where.

What I objected to was your claim that Quantum Foam was responsible for the Casimir effect and then your continued imprecise use of the phrase Quantum Foam. It has a specific meaning and you were using it in a non-standard way. You haven't presented anything that shows that fluctuations and the foam are the same. What you did present was a link that showed that the foam was just what I claimed. That the foam was the result of fluctuations. If you model the Casimir effect as fluctuations, then the fluctuations as described by QED are used, but that doesn't mean that the Casimir effect is the same thing as the fluctuations.

VonBelmont
2012-Sep-06, 07:26 AM
I am sorry but i have rapidly grown tired of this conversation.

VonBelmont
2012-Sep-06, 07:29 AM
You know, I've never heard of it put that way. Do you have a reference for that? I haven't seen it in "Gravitation", so it must be out there some where.

What I objected to was your claim that Quantum Foam was responsible for the Casimir effect and then your continued imprecise use of the phrase Quantum Foam. It has a specific meaning and you were using it in a non-standard way. You haven't presented anything that shows that fluctuations and the foam are the same. What you did present was a link that showed that the foam was just what I claimed. That the foam was the result of fluctuations. If you model the Casimir effect as fluctuations, then the fluctuations as described by QED are used, but that doesn't mean that the Casimir effect is the same thing as the fluctuations.

I will finish with this, but I will not continue this debate after this thread. What I mean by the vacuum is the particle, is that the vacuum is never absent of particles. There is no such thing as ''empty space''.

As for quantum foam, that is all it is. Quantum foam is the bubbling sheet of dynamic particles in a vacuum. That is the same stuff we attribute to the Casimir Effect.

headrush
2012-Sep-06, 03:42 PM
Is dark energy and dark matter a matter itself of ATM?

I will leave that to those who run the site on cosmology itself. Keep in mind, dark matter and dark energy are not ATM concepts.
As antoniseb observed, it's what follows on that I have issues with.
Maybe I was too quick to say ATM, but it is still highly speculative.

Speculation upon speculation in fact.

Copernicus
2012-Sep-06, 05:44 PM
I will finish with this, but I will not continue this debate after this thread. What I mean by the vacuum is the particle, is that the vacuum is never absent of particles. There is no such thing as ''empty space''.

As for quantum foam, that is all it is. Quantum foam is the bubbling sheet of dynamic particles in a vacuum. That is the same stuff we attribute to the Casimir Effect.

I can't agree that there are particles all over, nor that the vacuum is a particle, nor that there is no such thing as empty space. Don't know if this is ATM or not.

VonBelmont
2012-Sep-07, 01:20 AM
I can't agree that there are particles all over, nor that the vacuum is a particle, nor that there is no such thing as empty space. Don't know if this is ATM or not.

The vacuum is not a particle - I wasn't trying to say that at the time. I worded that terribly. However, there are particles all over. It's well known in physics, there is no such thing as empty space, every little square measurement of space is constantly filled with particles springing in an out of existence. Indeed, this is what quantum foam is, the presence of virtual particles fleeting in and out of existence.

Copernicus
2012-Sep-07, 01:30 AM
The vacuum is not a particle - I wasn't trying to say that at the time. I worded that terribly. However, there are particles all over. It's well known in physics, there is no such thing as empty space, every little square measurement of space is constantly filled with particles springing in an out of existence. Indeed, this is what quantum foam is, the presence of virtual particles fleeting in and out of existence.

Hi VonBelmont,

I did learn things about quantum foam theory from your discussion, but I am not aware that it is mainstream or that virtual particles are fleeting in and out of existence in every square space at every instant. But moreover, personally, I tend to think of particles as spherical and the packing as approximately 74 percent with remaining being empty space. Don't know that anyone could prove or disprove this packing theory at all. However, and I know he was only conjecturing, but I believe Buckminster Fuller stated space was a cuboctahedron structure, and this is what I believe will eventually be found as well.

VonBelmont
2012-Sep-07, 03:40 AM
Hi VonBelmont,

I did learn things about quantum foam theory from your discussion, but I am not aware that it is mainstream or that virtual particles are fleeting in and out of existence in every square space at every instant.

Yes, there are indeed particles fleeting in and out of existence at extremely small levels. Not one Planck Length of space is without such dynamics. In fact, at Planck Length it is very active. It is the uncertainty principle which allows this activity. The energy of virtual particles is very high as you shrink the size of the space you are dealing with. It even larger at sub-Planck lengths, but our theories cannot deal with lengths this small, so when we think of quantum foam, we tend to think of the dynamics of the very small but still theoretically measurable.

Copernicus
2012-Sep-07, 03:52 AM
Yes, there are indeed particles fleeting in and out of existence at extremely small levels. Not one Planck Length of space is without such dynamics. In fact, at Planck Length it is very active. It is the uncertainty principle which allows this activity. The energy of virtual particles is very high as you shrink the size of the space you are dealing with. It even larger at sub-Planck lengths, but our theories cannot deal with lengths this small, so when we think of quantum foam, we tend to think of the dynamics of the very small but still theoretically measurable.

I thought there were random quantum fluctuations, but I was never led to believe they were occuring everywhere all the time, even in space or deep intergalactic space. Is this part of quantum foam theory? Or certain quantum foam theories. I guess how would we know every Planck Length is without such dynamics? I am not aware of a way to detect anything at that length level.

VonBelmont
2012-Sep-07, 04:00 AM
I thought there were random quantum fluctuations, but I was never led to believe they were occuring everywhere all the time, even in space or deep intergalactic space. Is this part of quantum foam theory? Or certain quantum foam theories. I guess how would we know every Planck Length is without such dynamics? I am not aware of a way to detect anything at that length level.

Yes, even in the deep of space. You see, as you increase the space you deal with, you reach a transition which makes spacetime look smooth and without deform. Spacetime is not exactly smooth though when you go back to these small distances, rather than calling it ''graininess'' physicists are really talking about quantum foam. Quantum foam is the idea that particles are everywhere on the smallest levels, popping in and out of existence, like a bubbling cauldron.

We certainly don't have the ability to observe anything at the Planck Length yet, but assuming we are correct about how we treating the fabric of spacetime and that the uncertainty principle is equally fundamental, then we are reasonably sure then that this is what is happening at this level.

Shaula
2012-Sep-07, 08:08 AM
There are several possible things that could be part of the graininess, if we allow some of the more speculative models free rein. At larger length scales you have the effect of the quantum foam on spacetime (not the foam itself). Then you start getting down into the realm of loop quantum gravity, CDT and other theories which posit a structure to spacetime. The photons being dealt with here have nothing like the energy require to probe this level though so the graininess that we are looking for is primarily that due to quantum effects.

VonBelmont
2012-Sep-07, 08:42 AM
There are several possible things that could be part of the graininess, if we allow some of the more speculative models free rein. At larger length scales you have the effect of the quantum foam on spacetime (not the foam itself). Then you start getting down into the realm of loop quantum gravity, CDT and other theories which posit a structure to spacetime. The photons being dealt with here have nothing like the energy require to probe this level though so the graininess that we are looking for is primarily that due to quantum effects.

And therefore, still only 4% of the stuff in the universe actually interacts with particles of light. But forgetting this for a minute, the idea then that the photon cannot interact with quantum foam further adds to the argument, that the experiment doesn't prove anything. The vacuum could very well be grainy.

Shaula
2012-Sep-07, 10:14 AM
I am not arguing against the fact that photons only interact with a small proportion of matter in the universe. What I am arguing against is your repeated erroneous argument that this means that they only interact with a small percentage of the graininess in this work. The graininess is primarily warped spacetime, a consequence of quantum fluctuations but not the fluctuations themselves. Spacetime acts as a mediator which means that it is irrelevant to the photon if the things causing the warp is only weakly interacting. It may be true that only a small number of virtual particles produced by these fluctuations interact electromagnetically. Irrelevant. Their mass energy has an effect on spacetime and this is the graininess that is being probed.

VonBelmont
2012-Sep-07, 02:17 PM
The graininess is primarily warped spacetime, a consequence of quantum fluctuations but not the fluctuations themselves.


You're going to need to be clearer.


When you say, is a consequence of quantum fluctuations, not the fluctuations themselves, what are you saying exactly?... Gravity maybe?

Copernicus
2012-Sep-07, 02:36 PM
You're going to need to be clearer.


When you say, is a consequence of quantum fluctuations, not the fluctuations themselves, what are you saying exactly?... Gravity maybe?

I not really understanding the details here. I don't really have a problem with quantum fluctuations in everywhere but the vacuum, but is it mainstream or not. All I've heard about before is quantum fluctuations, but not everywhere all the time. What would be the average energy or momentum level of these fluctuations?

VonBelmont
2012-Sep-07, 02:46 PM
I not really understanding the details here. I don't really have a problem with quantum fluctuations in everywhere but the vacuum, but is it mainstream or not. All I've heard about before is quantum fluctuations, but not everywhere all the time. What would be the average energy or momentum level of these fluctuations?

Yes it is mainstream.

VonBelmont
2012-Sep-07, 02:47 PM
Practically no physicist would argue, in the concept of quantum foam. Our theories predict it. Indeed, many of our theories depend on it.

Copernicus
2012-Sep-07, 04:15 PM
Practically no physicist would argue, in the concept of quantum foam. Our theories predict it. Indeed, many of our theories depend on it.

So are these experiments about the magnitude of the quantum foam, and the magnitude is less than the Planck length?

VonBelmont
2012-Sep-07, 04:17 PM
So are these experiments about the magnitude of the quantum foam, and the magnitude is less than the Planck length?


There are no measurements which can obtain information below the Planck Range.

Copernicus
2012-Sep-07, 05:04 PM
There are no measurements which can obtain information below the Planck Range.

Can't find it now, but thought some tests ruled out quantum foam greater than 10^-45 meters or smaller yet.

Shaula
2012-Sep-07, 05:18 PM
Quantum foam is a consequence of trying to marry up gravity and QM. Gravity is described in terms of a curved spacetime metric which has a curvature dependent on the energy (technically the stress-energy tensor). The next effect of this is what we call gravity, and the coupling of it to everything with energy is why we see things like stars shifting their apparent position thanks to the gravity well of the Sun. Let me be upfront: Quantum foam is actually speculative. It is speculative because it is an extrapolation into the domain in which we know that our two best theories don't play that well together. We know that QM predicts energy fluctuations, we know it has no obvious limit (apart from maybe the Planck time, but even that is not confirmed) to how small a time they can happen over. We know that the largest energy fluctuations will have an effect on the spacetime of GR. So there is speculation that at these tiny scales spacetime is effectively granular, because below these scales spacetime stops being isotropic to photons passing through it. It has nothing to do with what the fluctuations 'are' and everything to do with their effect on what we understand GR to be based on.

To get a good idea what is going on we actually need a quantum theory of gravity - we can speculate now but that s all.


Indeed, many of our theories depend on it.
Name three.

Copernicus
2012-Sep-07, 11:27 PM
Quantum foam is a consequence of trying to marry up gravity and QM. Gravity is described in terms of a curved spacetime metric which has a curvature dependent on the energy (technically the stress-energy tensor). The next effect of this is what we call gravity, and the coupling of it to everything with energy is why we see things like stars shifting their apparent position thanks to the gravity well of the Sun. Let me be upfront: Quantum foam is actually speculative. It is speculative because it is an extrapolation into the domain in which we know that our two best theories don't play that well together. We know that QM predicts energy fluctuations, we know it has no obvious limit (apart from maybe the Planck time, but even that is not confirmed) to how small a time they can happen over. We know that the largest energy fluctuations will have an effect on the spacetime of GR. So there is speculation that at these tiny scales spacetime is effectively granular, because below these scales spacetime stops being isotropic to photons passing through it. It has nothing to do with what the fluctuations 'are' and everything to do with their effect on what we understand GR to be based on.

To get a good idea what is going on we actually need a quantum theory of gravity - we can speculate now but that s all.


Name three.

I was wondering if this the same type of thing as the fluctuations of the nucleus and nucleons except on a much smaller and faster scale.

VonBelmont
2012-Sep-08, 05:14 AM
Name three.

1) Well if our understanding of virtual particles is right, then our model predicts quantum foam.

2) Quantum foam itself a type of zero point energy. Again, it could be pivotal in explaining vacuum energy.

3) For advanced but still speculative formulations of general relativity, this level may also harvest wormhole activity. Of course, wormholes are perfectly valid solutions of GR.

Shaula
2012-Sep-08, 06:05 AM
So you cannot name a single theory which actually depends on it being there. Making your statement "Indeed, many of our theories depend on it" completely wrong. Please so not use statements like this to bolster your arguments.


I was wondering if this the same type of thing as the fluctuations of the nucleus and nucleons except on a much smaller and faster scale.
Try the wiki page (http://en.wikipedia.org/wiki/Quantum_fluctuation) as a starter - you see it really depends what you mean by fluctuations of the nucleus. I think, if I understand you correctly, that all the phenomena you talk about are driven by the same underlying principle (the Uncertainty principle).

VonBelmont
2012-Sep-08, 12:43 PM
So you cannot name a single theory which actually depends on it being there. Making your statement "Indeed, many of our theories depend on it" completely wrong. Please so not use statements like this to bolster your arguments.


Try the wiki page (http://en.wikipedia.org/wiki/Quantum_fluctuation) as a starter - you see it really depends what you mean by fluctuations of the nucleus. I think, if I understand you correctly, that all the phenomena you talk about are driven by the same underlying principle (the Uncertainty principle).

I'm not bolstering anything, if you had a working understanding of quantum mechanics, you would personally realize that vacuum fluctuations are at the core of our understanding of the universe and the vacuum.

I don't need to bolster anything. Quantum foam is predicted by our theories, those concerned with zero point energies, virtual particle fluctuations.