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baywax
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This looks like the full story, PDF
http://www.ptep-online.com/index_files/2011/PP-24-05.PDF
http://www.ptep-online.com/index_files/2011/PP-24-05.PDF
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czes said:So it’s not necessarily crazy, even if still very speculative, to suppose that thermodynamics and information will serve as the bridge for bringing gravity and quantum physics together. Einstein’s equations link energy to matter and matter to gravity, and the new work connects matter and energy to information and entropy. These links imply that Einstein’s equations are more about information than energy, the physicists write. “In other words, information might be a more profound physical entity than matter or field.”
http://www.sciencenews.org/view/feature/id/63190/title/A_New_View_of_Gravity
czes said:The gravity may be emergent from the vacuum energy disstribution.
The change of refractive index of the vacuum caused by the presence of matter has exactly the same effect on the path of light as the curvature of space in Einstein's General Relativity.
http://arxiv.org/abs/gr-qc/0604009
If a particle absorbs more information from the vacuum than emits, it is accelerating toward the source of the information (“denser vacuum”). The massive object creates the vacuum around due to the Compton wavelength of its rest mass particles. If the emission is faster than the absorption the particle decelerates then (Davies-Unruh effect). So the vacuum is transformed into a real, detectable thing.
http://www.calphysics.org/articles/chown2007.html
The vacuum as a volume is an illusion made of relation between the information on a flat screen.
Also the non-local process of producing a holographic reconstruction is explained purely in terms of interference and diffraction. Thus, someone looking into the hologram "sees" the objects even though they are no longer present. The hologram is not an image, but an encoding system which enables the scattered light field to be reconstructed. Images can then be formed from any point in the reconstructed beam either with a camera or by eye.
May be we are a part of an Holographic Universe ?
http://www.hologram.glt.pl/
baywax said:What is the quantum state or "microcosmic world" a product of? Does it all emerge from energy?
czes said:There are many evidences that quantum state and energy emerge from the quantum information relation.
Bekenstein's topical overview "A Tale of Two Entropies" describes potentially profound implications of Wheeler's trend in part by noting a previously unexpected connection between the world of information theory and classical physics. Bekenstein summarizes that "Thermodynamic entropy and Shannon entropy are conceptually equivalent: the number of arrangements that are counted by Boltzmann entropy reflects the amount of Shannon information one would need to implement any particular arrangement..." of matter and energy. The only salient difference between the thermodynamic entropy of physics and the Shannon's entropy of information is in the units of measure; the former is expressed in units of energy divided by temperature, the latter in essentially dimensionless "bits" of information, and so the difference is merely a matter of convention.
czes said:In 2008, Fermilab particle astrophysicist Craig Hogan made waves with a mind-boggling proposition: The 3D universe in which we appear to live is no more than a hologram.
Now he is building the most precise clock of all time to directly measure whether our reality is an illusion.
http://www.symmetrymagazine.org/bre...s-to-test-hypothesis-of-holographic-universe/
The Compton wave seems to be a fundamental unit of which our Observable Universe is built. The proton's Compton wavelength is a basic lattice and other particles have to correspond with the proton's wavelength. It is a question now.
Hogan wants to measure the quantum states made of the Compton wavelength of the proton (10^-15 m)
baywax said:In layman's terms what you're saying is that you can't have one without the other when it comes to gravity, matter and energy. So there is no causal relationship here, where phenomena can arise from one microsystem, moreover, these seemingly separate properties are all one and the same since none can exist independently. Is that why it's hard to determine if they are emergent or not?
atyy said:No, I meant that in general relativity, gravity=spacetime is not emergent.
Within general relativity, it always makes sense to talk about gravity=spacetime, even in extreme circumstances like black holes (let's ignore the singularity for now). So in general relativity, gravity=spacetime is not emergent, although it is curved by matter.
Of course general relativity could be wrong, and perhaps it doesn't make sense to talk about gravity=spacetime under all conditions. The AdS/CFT conjecture is an example of a theory in which gravity is emergent.
atyy said:No, I meant that in general relativity, gravity=spacetime is not emergent.
To me, an emergent property is one of which it makes sense to talk about sometimes, but not all the time. For example, when we study resistors and capacitors, it makes sense to talk about resistance, Ohm's law and all that. However, resistance is not a fundamental property. If we blow the resistor up into its individual atoms, then we have to use atomic physics or something other than Ohms law. So Ohmic resistance is emergent.
Within general relativity, it always makes sense to talk about gravity=spacetime, even in extreme circumstances like black holes (let's ignore the singularity for now). So in general relativity, gravity=spacetime is not emergent, although it is curved by matter.
Of course general relativity could be wrong, and perhaps it doesn't make sense to talk about gravity=spacetime under all conditions. The AdS/CFT conjecture is an example of a theory in which gravity is emergent.
StevieTNZ said:How does gravity arise?
dimension10 said:Different theories have different answers.
Finbar said:or do they...?
Nearly all theories of quantum gravity seem to imply that spacetime emerges from an effectively two dimension theory either by starting from two dimensional degrees of freedom, in string theory or LQG, or by predicting that spacetime is two dimensional on small scales e.g. CDT, asymptotic safety or Horava gravity. So two dimensions seems to be an input or an output in all the top theories of quantum gravity. The reason for this is very simple; two dimensions is the dimension in which Newton's constant is dimensionless. The problem for strings and LQG is to get from the two dimensional degrees of freedom to the standard model. In strings one has to compactify the extra dimensions in a clever way whereas LQG faces the problem of recovering classical GR from its highly non-perturbative and non-standard stating point.
CDT and AS are much more conservative and have both already shown that they have classical spacetime as an appropriate limit. The challenge for these theories is to understand the underlying microscopic degrees of freedom that they seem to be uncovering.
marcus said:Opinions can of course differ but offhand I would say the situation with Loop is more comparable with CDT on that score (than you suggest) and less comparable with String.
baywax said:Is space-time (re: distance) an emergent property?
atyy said:In general relativity, gravity=spacetime, so that is the same question as the original.
When the gravity=spacetime identification is made, it is assumed that there is matter, or at least test particles, clocks and rulers.
baywax said:Ha! Very good, thank you. Is beer an emergent phenomenon?! (or part of the foam?!)
atyy said:Beer is fundamental. Foam is emergent.
baywax said:Pretty interesting. Is anyone subscribed to this site?
Cahill is not a scientist.alt said:Cahill is an interesting Aussie scientist.
zhermes said:Cahill is not a scientist.
I certainly appreciate the detective work; I was trying to imply an obvious finality to the statement. I still can't say I understand why it even needs to be backed.alt said:Who said elsewhere of another contributor ..
All of your definitions here are just tautologies, effectively: 'a scientist is an 'ist' of science'.alt said:[/U]a person who studies or practises any of the sciences or who uses scientific methods
Cahill, in my opinion, is in no way searching for knowledge. Often, on physicsforums (e.g.), people post wild ideas to explain already solved problems. They're not looking for 'knowledge', they're looking for gratification. Cahill does the same, on a larger scale. Instead of learning the 'knowledge' of science, he attempts to fabricate it. What Reginald T. Cahill does is an insult to ever true scientist, or person who authentically strives to be a scientist, out there.alt said:A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method.[1] The person may be an expert in one or more areas of science.
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zhermes said:I certainly appreciate the detective work; I was trying to imply an obvious finality to the statement. I still can't say I understand why it even needs to be backed.
All of your definitions here are just tautologies, effectively: 'a scientist is an 'ist' of science'.
The key is that what Cahill does, is far from science. Ignoring all evidence in desperate reaches for overly forced explanations is a far cry from any type of scientific method. Every one of his ideas is systematically built on conjecture and---I'd dare say---a personal desire for a particular solution, instead of physical motivation.
But, as you already pointed out, this is flimsy and subjective. More objective is that most of his work isn't rigorously (if at all) peer-reviewed. In just about all of his 'articles' his only citations are to his other articles. He never has coauthors who behave any differently. He never has a single shred of empirical evidence to motivate his standpoint as apposed to a simpler, more accepted explanation. (While 'accepted' doesn't mean correct, Occam's razor suggests that he needs to work a little harder when he's fighting against 'accepted'--he doesn't).
Cahill, in my opinion, is in no way searching for knowledge. Often, on physicsforums (e.g.), people post wild ideas to explain already solved problems. They're not looking for 'knowledge', they're looking for gratification. Cahill does the same, on a larger scale. Instead of learning the 'knowledge' of science, he attempts to fabricate it. What Reginald T. Cahill does is an insult to ever true scientist, or person who authentically strives to be a scientist, out there.
baywax said:Is all that we can observe/calculate and imagine emergent?
Feullieton said:I guess the question here is about the correct way of talking about physical properties.
In the age of alchemy they didn't refer to formulas of chemical reacions, instead is was all about the reaction and how it appears to us. When we use formulas, we say that what appears as chemical reaction is actually emerging from more fundamental interactions of molecules. We write these interactions as chemical formulas. Still, the first thing we know is the apearance - that what we observe.
In general science goes like this: after we have made observation, we propose our hypothesis. Then using our hypothesis we calculate to predict further observations and observe again to test that. If all goes as planed and predictions succeed, we have developed a theory, which states law. And now we say: our observable phenomena is emerging from this law, which we call law of nature.
So referring to our general thread question, gravity is emergent as far as we are working with consistent theory which derrives gravity from more fundamental phenomena.
My personal point of view is that gravity as emergent phenomena is a road worth pursuing. We have spent too much time stuck with two inconsistent theories of nature, without any good success making sense out of it. So unless they find graviton particle, it would be favourable to see consistent and rigorous research in gravity emerging from universe entropy or quantum statistics.
baywax said:Very interesting! My understanding of the unit "graviton" is that it is just that, a unit of measurement designed to make the study of the phenomenon gravity easier. This is much the same as the unit "photon".