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One of the most exciting ideas in modern physics is that gravity is not a traditional force, like electromagnetic or nuclear forces. Instead, it is an emergent phenomenon that merely looks like a traditional force.
This approach has been championed by Erik Verlinde at the University of Amsterdam who put forward the idea in 2010. He suggested that gravity is merely a manifestation of entropy in the Universe, which always increases according to the second law of thermodynamics. This causes matter distribute itself in a way that maximises entropy. And the effect of this redistribution looks like a force which we call gravity.
Much of the excitement over Verlinde’s idea is that it provides a way to reconcile the contradictions between gravity, which works on a large scale, and quantum mechanics, which works on a tiny scale.
The key idea is that gravity is essentially a statistical effect. As long as each particle is influenced by a statistically large number of other particles, gravity emerges. That’s why it’s a large-scale phenomenon.
But today, Archil Kobakhidze at The University of Melbourne in Australia points to a serious problem with this approach.
He naturally asks how gravity can influence quantum particles.
Kobakhidze argues that since each quantum particle must be described by a large number of other particles, this leads to a particular equation that describes the effect of gravity.
But here’s the thing: the conventional view of gravity leads to a different equation.
In other words, the emergent and traditional views of gravity make different predictions about the gravitational force a quantum particle ought to experience. And that opens the way for an experimental test.
As it happens, physicists have been measuring the force of gravity on neutrons for ten yeas or so. And…wait for the drum roll… the results exactly match the predictions of traditional gravitational theory, says Kobakhidze.
“Experiments on gravitational bound states of neutrons unambiguously disprove the entropic origin of gravitation,” he says.
That’s an impressive piece of physics. It’ll be interesting to see how Verlinde and his supporters respond.
Ref: arxiv.org/abs/1108.4161: Once More: Gravity Is Not An Entropic Force.
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originally posted by: neoholographic
a reply to: Diablos
No it's not and that's a paper from 2011 that was answered by Verlinde. There will always be questions and challenges and there should be there's still questions about SR and GR as well as quantum mechanics but every question doesn't mean a theory is refuted this is just the scientific process.
originally posted by: neoholographic
a reply to: Diablos
This is why support for this idea is growing and Verlinde just updated his findings and it shows from the basic idea of information theory you can derive the exact equations of GR and also get Newton's laws of gravity. This also ties into the entropy of entanglement and it's growing connection to gravity.
originally posted by: neoholographic
a reply to: Diablos
So questions have been asked and they should be because this is the scientific process but nothing has been refuted.
The AdS/CFT correspondence provides quantum theories of gravity in which spacetime and gravitational physics emerge from ordinary non-gravitational quantum systems with many degrees of freedom. Recent work in this context has uncovered fascinating connections between quantum information theory and quantum gravity, suggesting that spacetime geometry is directly related to the entanglement structure of the underlying quantum mechanical degrees of freedom and that aspects of spacetime dynamics (gravitation) can be understood from basic quantum information theoretic constraints. In these notes, we provide an elementary introduction to these developments, suitable for readers with some background in general relativity and quantum field theory. The notes are based on lectures given at the CERN Spring School 2014, the Jerusalem Winter School 2014, the TASI Summer School 2015, and the Trieste Spring School 2015.
Counterfactual quantum cryptography (CQC) is used here as a tool to assess the status of the quantum state: Is it real/ontic (an objective state of Nature) or epistemic (a state of the observer's knowledge)? In contrast to recent approaches to wave function ontology, that are based on realist models of quantum theory, here we recast the question as a problem of communication between a sender (Bob), who uses interaction-free measurements, and a receiver (Alice), who observes an interference pattern in a Mach-Zehnder set-up. An advantage of our approach is that it allows us to define the concept of "physical", apart from "real". In instances of counterfactual quantum communication, reality is ascribed to the interaction-freely measured wave function (ψ) because Alice deterministically infers Bob's measurement. On the other hand, ψ does not correspond to the physical transmission of a particle because it produced no detection on Bob's apparatus. We therefore conclude that the wave function in this case (and by extension, generally) is real, but not physical. Characteristically for classical phenomena, the reality and physicality of objects are equivalent, whereas for quantum phenomena, the former is strictly weaker. As a concrete application of this idea, the nonphysical reality of the wavefunction is shown to be the basic nonclassical phenomenon that underlies the security of CQC.
originally posted by: neoholographic
Verlinde could be right when he says Gravity is an emergent property and not a fundamental force. Verlinde's model explains the motion of objects at large scales without the need for dark matter and his theory supports the universe as a hologram.
Erik Verlinde just released the latest installment of his new theory of gravity. He now says he doesn’t need dark matter to explain the motions of stars in galaxies.
Theoretical physicist Erik Verlinde has a new theory of gravity, which describes gravity not a force but as an illusion. The theory says gravity is an emergent phenomenon, possible to be derived from the microscopic building blocks that make up our universe’s entire existence. This week, he published the latest installment of his theory showing that – if he’s correct – there’s no need for dark matter to describe the motions of stars in galaxies.
Verlinde, who is at the University of Amsterdam, first released his new theory in 2010. According to a statement released this week (November 8, 2016):
… gravity is not a fundamental force of nature, but an emergent phenomenon. In the same way that temperature arises from the movement of microscopic particles, gravity emerges from the changes of fundamental bits of information, stored in the very structure of spacetime.
earthsky.org...
Wow!
So everything is a construct of information. This is essentially the holographic principle. There's no volume and everything we see as 3D is really a projection of information on a 2D surface area. Here's more:
New theory explains gravity better than Einstein's relativity
But now there's a new theory on the block that's based on the idea that the universe is a hologram, and it doesn't require dark matter or its elusive cousin, dark energy, to explain gravity on a larger scale, reports Phys.org.
So if gravity is emergent, like temperature is, that means it must be emergent from something. But from what? This is where Verlinde borrows from the holographic principle. His theory suggests that gravity is emergent from fundamental bits of information that are stored in the fabric of spacetime itself.
www.mnn.com...
So what he's saying is, Gravity emerges when these fundamental bits that are stored in the fabric of spacetime change. This is very interesting as Gravity is also being tied to the entropy of entanglement.
In this instance, entropy can be seen as the amount of information contained in an area of spacetime. Any change in this information can increase entropy and gravity emerges. So gravity is an entropic force that emerges instead of a fundamentel force of nature.
From idea of information entropy, you can derive Einstein’s equations of general relativity exactly.
So our universe is processing and projecting vast amounts of information on a 2D surface area. Here's a good discussion on this topic from Leonard Susskind.
I didn't say that. Diablo said that. I said "Verlinde's own comments about his own idea are some of the most problematic, such as that where he is saying that he hasn't defined his idea very precisely".
originally posted by: neoholographic
a reply to: Arbitrageur
You said:
However, it is inconsistent with current experimental data:
Sometimes a wave function will specify a deﬁnite position (all the amplitude at one position).
But often it will specify multiple positions (nonzero amplitude at many positions).
Then the particle is in a superposition of different positions.
Background: Observation in quantum mechanics[edit]
In the orthodox Copenhagen interpretation, quantum mechanics predicts only the probabilities for different outcomes of pre-specified observations. What constitutes an "observer" or an "observation" is not directly specified by the theory, and the behavior of a system upon observation is completely different than its usual behavior: the wavefunction that describes a system spreads out into an ever larger superposition of different possible situations. However, during observation, the wavefunction describing the system collapses to one of several options. If there is no observation, this collapse does not occur, and none of the options ever become less likely.
It can be predicted using quantum mechanics, absent a collapse postulate, that an observer observing a quantum superposition will turn into a superposition of different observers seeing different things. The observer will have a wavefunction which describes all the possible outcomes. Still, in actual experience, an observer never senses a superposition, but always senses that one of the outcomes has occurred with certainty. This apparent conflict between a wavefunction description and classical experience is called the problem of observation (see: Measurement problem).
The only form of interactionist dualism that has seemed even remotely tenable in the contemporary picture is one that exploits certain properties of quantum mechanics. There are two ways this might go. First, some [e.g., Eccles 1986] have appealed to the existence of quantum indeterminacy, and have suggested that a nonphysical consciousness might be responsible for filling the resultant causal gaps, determining which values some physical magnitudes might take within an apparently "probabilistic" distribution… This is an audacious and interesting suggestion, but it has a number of problems… A second way in which quantum mechanics bears on the issue of causal closure lies with the fact that in some interpretations of the quantum formalism, consciousness itself plays a vital causal role, being required to bring about the so-called "collapse of the wave-function." This collapse is supposed to occur upon any act of measurement; and in one interpretation, the only way to distinguish a measurement from a no measurement is via the presence of consciousness. This theory is certainly not universally accepted (for a start, it presupposes that consciousness is not itself physical, surely contrary to the views of most physicists), and I do not accept it myself, but in any case it seems that the kind of causal work consciousness performs here is quite different from the kind required for consciousness to play a role in directing behavior… In any case, all versions of interactionist dualism have a conceptual problem that suggests that they are less successful in avoiding epiphenomenalism than they might seem; or at least they are no better off than [naturalistic dualism]. Even on these views, there is a sense in which the phenomenal is irrelevant. We can always subtract the phenomenal component from any explanatory account, yielding a purely causal component.[7]
— David Chalmers, "The Irreducibility of Consciousness" in The Conscious Mind: In Search of a Fundamental Theory
originally posted by: Arbitrageur
I didn't say that. Diablo said that. I said "Verlinde's own comments about his own idea are some of the most problematic, such as that where he is saying that he hasn't defined his idea very precisely".
originally posted by: neoholographic
a reply to: Arbitrageur
You said:
However, it is inconsistent with current experimental data:
Can you imagine if Einstein had published his general theory of relativity but said "sorry but it's not really a theory and I don't have the math"?
But he didn't, he had a theory and the math and no idea from Verlinde or anybody else stands to replace relativity without both the theory and the supporting math, meaning he needs to precisely define his idea.
Inflation from extra dimensions
J H Yoon and D R Brill
Abstract
In Kaluza-Klein theory it is known that the dimensional reduction induced by an n-dimensional (non-Abelian) isometry group G is consistent with (4+n)-dimensional general covariance. With the isometry group as the fiber it is shown that the scalar sector of the theory defined by the Einstein-Cartan-Hilbert action in (4+n) dimensions can drive a successful inflation in a cosmological setting, if one identifies the conformably transformed metric as the new physical space-time metric and assumes non-vanishing torsional bilinear. The vacuum, which has vanishing gauge and scalar fields, is found to be a four-dimensional Minkowski space with the Cartan-Killing metric on the group space for a compact group G.
originally posted by: Arbitrageur
I didn't say that. Diablo said that. I said "Verlinde's own comments about his own idea are some of the most problematic, such as that where he is saying that he hasn't defined his idea very precisely".
Can you imagine if Einstein had published his general theory of relativity but said "sorry but it's not really a theory and I don't have the math"?
But he didn't, he had a theory and the math and no idea from Verlinde or anybody else stands to replace relativity without both the theory and the supporting math, meaning he needs to precisely define his idea.