Roger Penrose's explanation of quantum behavior

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captdude

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The links below are followed by short segments of his article. The article is fairly lengthy so the first link takes you to the beginning and the second link gets to the main point. I thought it was quite interesting and wanted to share it with the community.

Beginning of Article: http://discovermagazine.com/2005/jun/co ... :int=0&-C=
Heart of the article: http://discovermagazine.com/2005/jun/co ... :int=2&-C=


There are four fundamental forces in the universe: electromagnetism; the strong force, which binds atomic nuclei together; the weak force, which is responsible for radioactive decay; and gravity. Gravity is the only one of the forces that physicists have been unable to explain in quantum terms. To Penrose, the failures are a clue that physicists are on the wrong path. Most believe that quantum theory is fundamentally sound but that our understanding of gravity must change. Penrose says that rather than seeking to change Einstein’s theory of gravity, we should study how gravity affects an object small enough to exist in the borderland between the quantum world of atoms and the human world of visible objects.
Penrose is convinced that conventional quantum theory seems absurd because it is incomplete. Specifically, it ignores the effects of gravity. On atomic or subatomic scales, gravity is so weak compared with the other forces that most physicists see no problem with leaving it out of the picture. But in Penrose’s view, the only way to understand the quantum world is to consider all the forces that act on it. To do that, he is combining Einstein’s relativity with quantum physics in a way nobody has considered before.
In Einstein’s theory, any object that has mass causes a warp in the structure of space and time around it. This warping produces the effect we experience as gravity. Penrose points out that tiny objects—dust specks, atoms, electrons—produce space-time warps as well. Ignoring these warps is where most physicists go awry, he believes.
If a dust speck is in two locations at the same time, each one should create its own distortions in space-time, yielding two superposed gravitational fields. According to Penrose’s theory, it takes energy to sustain these dual fields. The stability of a system depends on the amount of energy involved: The higher the energy required to sustain a system, the less stable it is. Over time, an unstable system tends to settle back to its simplest, lowest-energy state—in this case, one object in one location producing one gravitational field. If Penrose is right, gravity yanks objects back into a single location, without any need to invoke observers or parallel universes.
How long the process takes depends on the degree of instability. Electrons, atoms, and molecules are so small that their gravity, and hence the amount of energy needed to keep them in duplicate states, is negligible. According to Penrose, they can persist that way essentially forever, as standard quantum theory predicts. Large objects, on the other hand, create such significant gravitational fields that the duplicate states vanish almost at once. Penrose calculates that a person collapses to one location in a trillion-trillionth of a second. For a dust speck, the process takes nearly a second—long enough that it might be possible to measure.

To read about his proposal to measure this effect click on one of the links above
 
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Gravity_Ray

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Re: Robert Penrose's explanation of quantum behavior

Simply brilliant. I had to read the meat of the article several times for it to stick. I think he is really on to something. I hope that they can run some of his proposed experiments to confirm his ideas.

His experiment is a perfect example of the kind of thing, NASA should be spending money on. He needs to do a major experiemnt that really can not be done on Earth. So why not put a fraction of the money ONE space shuttle mission needs and find out once and for all if we can tie the four forces of nature together or not.

Thanks for posting the article.
 
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darkmatter4brains

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Re: Robert Penrose's explanation of quantum behavior

This actually seems somewhat similar to M-theory to me, which also says that on small scales gravity may be doing something different than we thought. The idea there is that gravity is leaking into higher dimensions. These higher dimensions are extremely small so we can't see them, and there are technical reasons why the other three forces aren't effected by them. But, if we could measure gravity on scales roughly as small as the size of these extra dimensions we would find that the inverse square law would be violated, that gravity actually becomes stronger on these scales.

Penrose seems to have possibly found a way to mess with gravity on the small scale without appealing to higher dimensions. But, what's with the "dual" field? There must be details missing here, or perhaps I should have read the whole article. :lol: You can very easily say let's cut a 3rd slit in the board and then the electron would appear to be in 3 places at once, or 4 slits and say it was in 4 places at once, ad nauseum, until you reach infinity. Then, you would have something much more complex than just a dual gravitional field.
 
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darkmatter4brains

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Re: Robert Penrose's explanation of quantum behavior

ah, I read the rest of that article. Sounds like he's basically saying the traditional interpretation that a particle is in a superposition of states before the act of measurement, has been essentially incomplete. Gravity itself can break that superposition, forcing a particle to settle on a specific location, in a fashion somewhat similar to how the act of measurement forces a particle to take a stand. These superimposed states are no longer permanently stable in his view, with the degree of stability being dependenent upon the size of the object in question. The whole dual field thing appears to have just been a specific case to use as an example and as a way to test the theory.

But, it still sounds more like a way to finally bridge the two worlds, of the very small and the very large, basically providing the details of how and when and why quantum effects come into play. I'm unclear as to how this helps complete an actual quantum theory of gravity based on the graviton, or am I missing something? One or two spots in the article seem to say that it does, for example .... "Gravity is the only one of the forces that physicists have been unable to explain in quantum terms. To Penrose, the failures are a clue that physicists are on the wrong path. "
 
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yevaud

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Re: Robert Penrose's explanation of quantum behavior

FYI, it's Roger Penrose, not Robert.
 
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kelvinzero

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Re: Robert Penrose's explanation of quantum behavior

I have a physicist friend near to getting tenure at some american university, whose recent papers have been about how classical physics emerges from quantum physics. Mainly he talks about connecting small quantum systems to a 'bath' and simulating what happens. I think a bath just means something so complex that it should behave classically.

The point is that they do, without having to postulate an observer. This leaves me a bit confused as to what this article is about. Quantum mechanics may have some problem integrating with gravity but I thought it did not have a problem explaining why these quantum weirdnesses become less apparent as systems become more complex.
 
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captdude

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My apologies to ROGER Penrose

It is Roger (not Robert) Penrose.
 
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ramparts

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Re: My apolagies to ROGER Penrose

Great. Now please apologize to the word "apologies" :cool:
 
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darkmatter4brains

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I guess not all quantum weirdness was created equal, with some of it being weirder than others.

One that jumps to mind that is not quite so weird is the quantum harmonic oscillator whose energy states are discrete and go something like E_n= hbar*w*(n+1/2), where n is the nth discrete energy state. Since hbar is so darn small, in the classical macroscopic world we just don't detect these discrete energy states and it looks like a continuum.

So that makes sense. But what is weirder and more along the lines of what that article is trying to address ( I think ) is the fact that before a measurement a particle is seemingly in a superposition of states. In the classical world, when we measure that a large beach ball is spinning in a clockwise direction, we can confidently say that before the measurement the beachball was spinning in that direction then too. But, in the quantum world, before the measurement a particle would be spinning in both the clockwise and counterclockwise directions. Now, that anology is somewhat of a stretch, but it does illustrate how weird it is to think that something can be in a superposition of multiple states. This is really weird stuff. The electron going through two slits at the same time, would be analogous to you walking through two diffferent doors at the same time.

Another thing this article made me think about was quantum computers. Qbits rely and work upon the fact that quantum objects are in a superposition of states. If these states are no longer permanent (per Penrose) seems like it could possibly complicate designing these computers.
 
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kelvinzero

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Right.. but something being in two states isnt the weird part, if we kept seeing that in our everyday life we would be used to it. The weird part was how microscopic particles were meant to do this all the time, but observing it forced it to collapse into 'normal' classical behavior, as if a conscious observer has some special property.

But as I understand it there is no mysterious property of an observer. you can demonstrate the same collapse, straight from the theory, when an isolated quantum system in superposition is connected to a more complex system.

As I understand, it hasnt been easy to confirm until recently that complicated quantum systems produce all the expected properties of a classical system because you need very powerful supercomputers to model that many interactions.
 
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captdude

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Could it be possible that the wave form aspect of a quantum particle oscillates through its various "probabilities" while interacting with higher dimensions? Then, at the moment of measurement, the wave form collapses into a particle with the properties inherent to that moment of its oscillation – and by collapsing - it is now "imbedded" into our 3-D space/time.
Wouldn’t this remove the roll of a conscious observer in the workings of quantum mechanics? It also seems to me that it would fit in nicely with string theory.
P.S. I have no one to bounce ideas off of, am completely obsessed with cosmology and quantum physics and am very grateful to have found this forum and the views of its community.
CaptDude

:? All I am is what I know and all I know is what I am
 
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darkmatter4brains

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kelvinzero":32iq2ww8 said:
Right.. but something being in two states isnt the weird part, if we kept seeing that in our everyday life we would be used to it. The weird part was how microscopic particles were meant to do this all the time, but observing it forced it to collapse into 'normal' classical behavior, as if a conscious observer has some special property.

But as I understand it there is no mysterious property of an observer. you can demonstrate the same collapse, straight from the theory, when an isolated quantum system in superposition is connected to a more complex system.

As I understand, it hasnt been easy to confirm until recently that complicated quantum systems produce all the expected properties of a classical system because you need very powerful supercomputers to model that many interactions.

Well, I guess if you kept seeing anything in everyday life, it would then cease to be weird, but I definitely agree with you that this is also weird - the role of the observer.

I, however, always had my suspicions of that being short sighted in some way or another. I mean there are quantum processes that happen out in deep space where there is apparently nobody around? However, this just led some people to the conclusion that the entire Universe is driven by consciousness (i.e. God)

Apparently, back in the day, John Von Neumann did some mathematical "proof" that showed that the cause of the collapse of the wave function has to be the observer. There was a name for the math/proof that he used but I can't seem to recall at the moment. I've always meant to look into this more, but never did. If these new theories turn out to be right, I suppose that makes JVN wrong.

btw, for anybody that might be interested, there is a great book out there that goes over the differeing viewpoints and interpretations of quantum mechanics that have existed over the course of the formation of the theory. Quantum Reality by Nick Herbert. He's also the guy that is credited with the shortest proof to Bell's Theorem.
 
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undidly

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Re: My apologies to ROGER Penrose

captdude":2h35nfcw said:
It is Roger (not Robert) Penrose.

I think he will forgive you.

The Reverend Spooner would called him Podger Renrose.
 
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captdude

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Roger Penrose, by any other name, would still smell out sweet theories.
 
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captdude

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It really is pretty cool how his theory explains the mechanisms of quantum mechanics WITHOUT the need for a conscious observer to be involved.
 
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