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Author Topic:   GRAVITY PROBLEMS -- off topic from {Falsifying a young Universe}
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 151 of 205 (253052)
10-19-2005 12:07 PM
Reply to: Message 122 by simple
10-16-2005 3:52 PM


Re: limits
simple
Right, more than the things that you said people were brain bleeding over
Yes but if you recall I was responding to this statement of yours
The question remains, however, what is the 'universe'? Is it just time and space, and what we have discovered, or is there more?
I was sensing,perhaps wrongly, that you were hand-waving aside the vast amount of understanding that is present in science concerning the boundaries of knowledge. that there is more to what people are bleeding brain cells over is just additional effort on the part of real thinkers.
I'll ask you as well, do you know what time is exactly? If not, there goes one of the two. In the veiw of some scientists, even the space bit needs to go, so whats that leave you?
That depends on what level of knowledge you are willing to acquire.
Time is simply a measure of a property of the universe. It is a dimension ,one among others that define the structure of that in which we find ourselves.
Now this is an exact accounting of what time is.However,there are subtleties that are at first not apparent but further study only reveals the details of the structure not a different nature of what time is.
Now,I will not argue the "view of some scientists" because you have not presented to me either their names nor,at least,their arguement that I might understand what this means.
"Most perplexing of all, spin nets and spin foam cannot be thought of as existing in space and time. They reside on a more fundamental level, as a deep structure that underlies and gives rise to space-time.
Certainly. That there is a deeper level is understood in science. The mathematics of quantum field theory required that there be a vacuum energy in order for the Heisenberg uncertainty principle to operate. There is,if you were to remove all matter and forces from the universe a "virtual" background of particles that flit into and out of existence continuously and constitute an enormous energy "potential". However because these particles exist for less than the Planck time they do not interact as such with our world. however the energy is measureable underthe proper conditions. This energy is extraordinary. A cubic meter of this zero point energy is capable of boiling the oceans of Earth.
As for you energy, I think it was you who gave simple the link that admitted it also is not known what it really is. Add gravity to the list, although some claim they know, in the elite higher knowledge of advanced math, but it would take years to explain! With all these limits to our actual knowledge, I think that those who portray a high priest attitude, and pretense of knowing everything (not that you do) should be taken to task, and knocked down a few pegs. I never sensed that attitude much from einstein, or Feynman, or many others, but some, on this forum wreak of it. Yet, would likely be the first to decry things like the unseen forces on earth at work and known by most men since time began. Making a few thousand loaves and fishes from a couple little loafs, and a fish are taboo, but making a universe from nothing, and expanding from less than the size of a proton, to a grapefruit in a fraction of a billionth of a second is science.
Energy is not known because the nature of it is purely mathematical and gives no hint of the mechanism by which it manifests itself. Gravity is well known because we can study the force of gravity and tie it to the structure of the universe. It is intimately tied in with the geometry of the universe and these things are well known in that we can make predictions of what it should do under given conditions and these predictions have always matched observed phenomena when we get the model correctly.
You also must understand the level of confidence that is portrayed within the mathematics and how the understanding we have of the fundemental forces allow us to say with what may appear to be "high priest" attitude {which I am sure does actually go on in some people} that certain things like walking on water or making more food from a given limited amount are not possible.
Like Martin Gardners carpenter puzzle when you understand the answer you immediately realize that there can be NO OTHER solution to the condition observed.
Evidence of what kind? The kind you could practice math on? The kind you could fit in a tube? Surely you have heard there have been evidences of more than the natural among most people on earth? Besides, I could give yo evidence of energy, time gravity, etc., does this mean you can explain it?
Evidence that can be replicated and experimented upon to determine that it is an actual phenomena and not the all too human propensity for error. As Feynman once said "The first principle is that you must not fool yourself - and you are the easiest person to fool."
This is why logic and math and careful reasoning are needed to winnow out the actual from the plausible,from the border line, from the mistakes,from the experimental errors,from the statistically insignificant, from the delusional,from the absurd,from the lies,from the attention seeking and from the impossible.
Feynamn also said that "Science is the belief in the ignorance of experts. "
Good, you admit that there is a restriction of understanding. As for any new physics, we really don't know if or what they will be, replace, or cause a rethink to anyhow. I wouldn't hold my breath
Restrictions of understanding nowadays is in the details and not in the general overview.The replacement of "old physics" with new alters only our way of looking at things which is artificial anyways. However, the phenomena themselves are what they are and follow rules regardless. These rules do not change as we study them deeper but are refined to reveal the next layer which also follows the rules of the higher level but add complementary rules that govern their level.
How would you know? Get by the restrictive bottlenecks, and get a grip on the core concepts. like time, and then maybe you can tell us something. It would be better to say something like 'our current understanding, or lack therof, of nature, indicates it is so complicated, it would take years to explain, and it could,'t be in english anyhow'.
The problem here is that you are not communicating to US what it is that we are failing to explain to YOU. If you do not know the question you are trying to ask how can you expect us to know an answer or to even postulate one. What is it that you do not understand that science is failing to give you reasonable means by which to inquire on your own?
So have you found the it that took nothing and produced the hot soup that gave us our universe?? Have you found the real nature and cause of many forces, like time, etc? Have you determined the finiteness or not of the universe, or many other things? Yet, what, you think you can turn around, and tell us that say, ghosts are not real? What even is 'real'? A universe from nothing is real, but something like non physical entities seen actually by millions are not real? Why, because you can't touch them? Can you touch a quark, or a Plackt unit?
But that is the point of the investigation and discovery. We find that "nothing" is different from our intuition about nothing, the vacuum energy of the universe which science has revealed is nothing and as a consequence the universe has a underlying structure that is different from the physical world we occupy.The world is subtle and requires that we give up our pre-concieved notions about it that we form through our senses because they are quite simply inadequate for understanding the real workings of the world.
Yes we have a good understanding of the interrelationships of many things and no we do not understand it all but what we do understand precludes the possibility of things like ghosts as ghost stories present themselves to us. Look ,a ghost that appears to a person,if it is real, is interacting with the structure of the eye which means it is using the electromagnetic force to produce the light which the structure of the eye physically responds to. That "light" can be measured and verified and recorded and we never find this to be the case do we?
I see no evidence that there is nothing else besides a physical universe at all, do you? If there is, we haven't scratched the surface of what wonders we may yet explore, somewhere, over the rainbow.
I see no evidence against invisible,immaterial things forever beyond our investigation? We can conjecture on that all we want but it cannot ever interact with us for then it would become physical with all the attendent restrictions and evidence.
This message has been edited by sidelined, Sun, 2005-10-23 10:14 PM

But I realize now that these people were not in science; they didn’t understand it. They didn’t understand technology; they didn’t understand their time.

This message is a reply to:
 Message 122 by simple, posted 10-16-2005 3:52 PM simple has not replied

  
Son Goku
Inactive Member


Message 152 of 205 (253460)
10-20-2005 3:50 PM
Reply to: Message 128 by simple
10-16-2005 4:12 PM


Re: long way to go
General Relativity and Quantum Field Theory, tell us things about the world we couldn't have ever made up in our strangest fictions
Yes, too bad they don't agree.
Actually they do agree.
It is possible to construct a Quantum Field Theory on a Curved background and it is possible to generate a classical spacetime from a Quantum Mechancial Stress-Energy Tensor.
It is not a case that they don't agree.

This message is a reply to:
 Message 128 by simple, posted 10-16-2005 4:12 PM simple has not replied

Replies to this message:
 Message 153 by JustinC, posted 10-21-2005 1:39 PM Son Goku has replied

  
JustinC
Member (Idle past 4844 days)
Posts: 624
From: Pittsburgh, PA, USA
Joined: 07-21-2003


Message 153 of 205 (253701)
10-21-2005 1:39 PM
Reply to: Message 152 by Son Goku
10-20-2005 3:50 PM


Re: long way to go
So what exactly is the conflict between these two theories? Is it just that gravity doesn't quantize?

This message is a reply to:
 Message 152 by Son Goku, posted 10-20-2005 3:50 PM Son Goku has replied

Replies to this message:
 Message 154 by Son Goku, posted 10-21-2005 2:03 PM JustinC has not replied
 Message 155 by cavediver, posted 10-21-2005 6:54 PM JustinC has not replied

  
Son Goku
Inactive Member


Message 154 of 205 (253705)
10-21-2005 2:03 PM
Reply to: Message 153 by JustinC
10-21-2005 1:39 PM


Re: long way to go
It is simply that General Relativity doesn't quantize.
This isn't truly a conflict, the two can still be used together.
It's just a case that you have to get conditions from one and then use the other.
The whole "General Relativity and Quantum Field Theory" issue is simply that they aren't one single conceptual entity.
This message has been edited by Son Goku, 10-21-2005 02:05 PM

This message is a reply to:
 Message 153 by JustinC, posted 10-21-2005 1:39 PM JustinC has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 155 of 205 (253844)
10-21-2005 6:54 PM
Reply to: Message 153 by JustinC
10-21-2005 1:39 PM


Re: long way to go
Just to add to SG's comments:
It is simply that General Relativity doesn't quantize.
It does in d=2
And it should be pointed out that "quantize" means to take a classical theory and use it to extrapolate the quantum theory. It does not mean that there is not a quantum theory of gravity, just that our usual prescriptive (and rather crude) methods of getting a quantum theory from a classical theory do not work.

This message is a reply to:
 Message 153 by JustinC, posted 10-21-2005 1:39 PM JustinC has not replied

Replies to this message:
 Message 156 by Son Goku, posted 10-21-2005 7:08 PM cavediver has replied

  
Son Goku
Inactive Member


Message 156 of 205 (253850)
10-21-2005 7:08 PM
Reply to: Message 155 by cavediver
10-21-2005 6:54 PM


Re: long way to go
quote:
It does in d=2
Is that just the Turaev-Viro model in Loop Quantum Gravity or is standard QFT able to do it when d=2 as well?
quote:
And it should be pointed out that "quantize" means to take a classical theory and use it to extrapolate the quantum theory. It does not mean that there is not a quantum theory of gravity, just that our usual prescriptive (and rather crude) methods of getting a quantum theory from a classical theory do not work.
Would your personal opinion be that we need a new method of quantization or do we just need to start at the quantum level?

This message is a reply to:
 Message 155 by cavediver, posted 10-21-2005 6:54 PM cavediver has replied

Replies to this message:
 Message 157 by cavediver, posted 10-21-2005 7:26 PM Son Goku has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 157 of 205 (253853)
10-21-2005 7:26 PM
Reply to: Message 156 by Son Goku
10-21-2005 7:08 PM


Re: long way to go
is standard QFT able to do it when d=2 as well?
Yes, in a cheating sort of way, becasue there are no dynamical degrees of freedom in d=2 GR, so the quantisation is essentially "trivial"... great word This is what's so great about topological gravity, in that you "twist" out all of the dynamical dof and you're left with an exact quantum theory even in d=4. Topological field theory is an awesome subject...
But I'm going to bed, so if you want to talk more about it you'll have to wait
Would your personal opinion be that we need a new method of quantization or do we just need to start at the quantum level?
Almost certainly the latter... but this is essentially string, M and loop. It's bound to be M as M could be anything!

This message is a reply to:
 Message 156 by Son Goku, posted 10-21-2005 7:08 PM Son Goku has replied

Replies to this message:
 Message 158 by Son Goku, posted 10-21-2005 7:31 PM cavediver has not replied
 Message 159 by Son Goku, posted 10-24-2005 6:53 PM cavediver has replied

  
Son Goku
Inactive Member


Message 158 of 205 (253856)
10-21-2005 7:31 PM
Reply to: Message 157 by cavediver
10-21-2005 7:26 PM


Re: long way to go
quote:
Topological field theory is an awesome subject...
But I'm going to bed, so if you want to talk more about it you'll have to wait
Cool, thanks.
I actually have a one or two things to ask, but I'll wait till tomorrow.

This message is a reply to:
 Message 157 by cavediver, posted 10-21-2005 7:26 PM cavediver has not replied

  
Son Goku
Inactive Member


Message 159 of 205 (254537)
10-24-2005 6:53 PM
Reply to: Message 157 by cavediver
10-21-2005 7:26 PM


Re: long way to go
Right, my questions are, if you have the time to answer:
1)Your personal opinion of String Theory and Loop Quantum Gravity?
2)Do you believe we should put more attention into trying to find the electronuclear/G.U.T. force?
3)Opinions on how we'll do in the next few years when it comes to finding exact solutions of GR and QCD?

This message is a reply to:
 Message 157 by cavediver, posted 10-21-2005 7:26 PM cavediver has replied

Replies to this message:
 Message 160 by cavediver, posted 10-29-2005 5:17 PM Son Goku has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 160 of 205 (255507)
10-29-2005 5:17 PM
Reply to: Message 159 by Son Goku
10-24-2005 6:53 PM


Re: long way to go
Sorry, a little late on these...
Your personal opinion of String Theory and Loop Quantum Gravity?
I don't know, what day is it?
To be honest, I'll side with string. I don't really believe we can understand gravity without involving everything else. In other words, QG is also our TOE. Loop tries to quantise gravity in the absence of anything else. I'm not sure that is the right approach. I think the presence of the other gauge and matter fields is critical.
Think just how incredible is the Einstein-Hilbert action. Imagine something just as elegant that gives rise to all fields... this was the goal of SUGRA and dimensional reduction. String gives us an avenue into this.
That said, it may not matter. The "fundemental" analogue of the EH action may be over some other space, more "real" than our 3+1 or 10+1 "target space". But that still wouldn't explain the reason behind why Langrangian mechanics works (classical and quantum)! That's my BIG question.
Do you believe we should put more attention into trying to find the electronuclear/G.U.T. force?
Yes, but not that's for the particle guys. Quadruple the theorists' budget and you may have dented the experimentalists' coffee budget We need to find clues to glue-balls, SUSY, X bosons, Higgs, etc. The standard model does need firming up. This should all point towards GU.
Opinions on how we'll do in the next few years when it comes to finding exact solutions of GR and QCD?
Exact of GR is no big deal... finding useful ones is a different matter! I think we've probably got all the easy stuff. QCD is pretty much impossible at our energy levels. More lattice work until we can get the proton mass within say 0.1% would be nice.
I don't think focussing on GR or QCD is going to help with the deeper questions.

This message is a reply to:
 Message 159 by Son Goku, posted 10-24-2005 6:53 PM Son Goku has not replied

  
Son Goku
Inactive Member


Message 161 of 205 (255548)
10-29-2005 9:24 PM


Sorry, a little late on these...
It's very kind of you to take the time at all, so thanks very much.
I don't really believe we can understand gravity without involving everything else. In other words, QG is also our TOE...
I see what you mean. I suppose the Field Equation says that itself in a way.
That said, it may not matter. The "fundemental" analogue of the EH action may be over some other space, more "real" than our 3+1 or 10+1 "target space". But that still wouldn't explain the reason behind why Langrangian mechanics works (classical and quantum)! That's my BIG question.
"Why Lagrangian Mechanics works?"
That has given me a lot of food for thought, thank you.
I'd gotten a bit too used to just thinking of the Lagrangian as a tool.
Exact of GR is no big deal... finding useful ones is a different matter!
The plight of Numerical Relativity.
I don't think focussing on GR or QCD is going to help with the deeper questions.
I'm a little bit of a phenomonology guy, so I like it when "wierd" things turn up in certain solutions, like Closed Timelike Curves, e.t.c.
However you're probably right in that it won't help with post-Standard Model physics.

Replies to this message:
 Message 162 by cavediver, posted 10-30-2005 4:49 AM Son Goku has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 162 of 205 (255589)
10-30-2005 4:49 AM
Reply to: Message 161 by Son Goku
10-29-2005 9:24 PM


I'd gotten a bit too used to just thinking of the Lagrangian as a tool.
That's certainly the image you get classically... but it still doesn't explain why it works. Why minimise? And what do you minimise? Hilbert wrote down the EH action because it was the simplest thing you could write down. But you could also use R_ab R^ab or R_abcd R^abcd etc, etc. But GR is just R.
But as Feynman realised, QM is simply allowing all trajectories, not just those minimising the action. Now the action weights the contribution of each trajectory. This is where things get really Platonistic! If all elements of the Lagrangian contribute, then the Lagrangian itself must in some sense exist. It is no longer a tool/method to reach the classical solution... every part of it represents a facit of reality.
so I like it when "wierd" things turn up in certain solutions, like Closed Timelike Curves, e.t.c.
CTCs are great Some of my first work was on wormholes and wormhole "billiards". If pushed though, I have to admit that CTCs are probably restricted to pure solutions. I can't really believe of a scenario where a CTC can be stable to matter perturbations. Unless you can guarentee there will be no trapped trajectories, a single electron will destroy the whole thing.
This though brings to light the glaring problem with GR. It is purely undynamical 4d, where as we are blatently dynamical 3d. Until we understand the reason behind "time evolution", we are going to struggle. It's funny, becasue "everyone" harps on about the role of conciousness in QM, but that's largely irrelevant. The question is what role does conciousness have in the 3d / 4d dichotomy. This is the real "problem of time" as I see it. Barbour is one guy who spends a lot of time on this - did you read the thread on him a while back? That may be where we are forced to go... an evolution through a moduli space, with time emerging from this evolution. We already see hints of this behaviour in soliton/monopole dynamics.

This message is a reply to:
 Message 161 by Son Goku, posted 10-29-2005 9:24 PM Son Goku has replied

Replies to this message:
 Message 163 by Son Goku, posted 11-02-2005 1:48 PM cavediver has replied

  
Son Goku
Inactive Member


Message 163 of 205 (256268)
11-02-2005 1:48 PM
Reply to: Message 162 by cavediver
10-30-2005 4:49 AM


This though brings to light the glaring problem with GR. It is purely undynamical 4d, where as we are blatently dynamical 3d. Until we understand the reason behind "time evolution", we are going to struggle. It's funny, becasue "everyone" harps on about the role of conciousness in QM, but that's largely irrelevant. The question is what role does conciousness have in the 3d / 4d dichotomy. This is the real "problem of time" as I see it. Barbour is one guy who spends a lot of time on this - did you read the thread on him a while back? That may be where we are forced to go... an evolution through a moduli space, with time emerging from this evolution. We already see hints of this behaviour in soliton/monopole dynamics.
You see, this is what always "screws with your head" when you're talking about General Relativity.
You can think about and discuss static 4-D geometry very easily (once you've broken the conceptual barriers obviously) yet your "thinking" and "discussing" are dynamic 3-D processes.
I'll often explain the whole thing of the Universe as a static 4-D Lorentzian surface to somebody and while explaining it realise, that while it is true for large scale structures, me and the person I'm talking to are definitely 3-D and time evolved.
In short big things are more comfortable with (4), smaller things with (3+1).
I brought this up with a few philosophers I know and they were shocked that physics contained such an interesting idea.

This message is a reply to:
 Message 162 by cavediver, posted 10-30-2005 4:49 AM cavediver has replied

Replies to this message:
 Message 164 by cavediver, posted 11-02-2005 2:15 PM Son Goku has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 164 of 205 (256271)
11-02-2005 2:15 PM
Reply to: Message 163 by Son Goku
11-02-2005 1:48 PM


In short big things are more comfortable with (4), smaller things with (3+1).
And that in short is the QM/GR problem. They have totally different mindsets.
I brought this up with a few philosophers I know and they were shocked that physics contained such an interesting idea.
Yeah, it's funny how ignorant the world is of this stuff... you certainly see that here on this site, with good levels of intellectual ability and understanding, yet a "shocking" lack of knowledge of this area at any real depth.
To be honest, I think popular science gets in the way far too much, presenting a very fake picture. I have seen actual papers written by good physicists on why QCD will prevent the formation of "classical" black holes, and I had demolished their argument before the end of their opening paragraph.
You get the impression that because everyone has heard of Einstein, GR, and black holes, that everyone has at least some understanding. This is completely false This subject is just as opaque to everyone as every other field: evolutionary biology, geology, etc, etc. This field just has more popular books and science fiction films!
This message has been edited by cavediver, 11-02-2005 02:15 PM

This message is a reply to:
 Message 163 by Son Goku, posted 11-02-2005 1:48 PM Son Goku has not replied

Replies to this message:
 Message 165 by madeofstarstuff, posted 11-23-2005 10:53 AM cavediver has replied

  
madeofstarstuff
Member (Idle past 5929 days)
Posts: 47
Joined: 08-12-2005


Message 165 of 205 (262670)
11-23-2005 10:53 AM
Reply to: Message 164 by cavediver
11-02-2005 2:15 PM


Understanding
I really enjoy peaking in on your (cavediver and SonGoku's) conversations and I hate to intrude here but I am overcome with wonderment. I read a lot of pop science books on these topics and am always left feeling a little empty on any true understanding on the topics discussed. You have always said that a lot is lost in the translation and perhaps it sometimes does a little more damage than good in these books to laymanize these topics, but I just want a little guidance to point me in the right direction to having a proper mathematical understanding.
I am still young, 28, but am in school and almost done with a Bachelor's and work full time. My area of study isn't related to these topics but is in engineering so I have some mathematical background. My mentioning of my age has more to do with the fact that I feel I have time to try to teach these things to myself given the proper direction and free time once I am done with my degree. It isn't practical for me to change my major to physics as I have already looked into it and it doesn't make financial sense for a person with a family considering how far behind in the game I would already be.
It seems to me that you feel that without proper schooling, knowledge about space and time in regards to general relativity is basically overwhelmingly esoteric. I have up to differential equations but not including linear algebra as my formal education in mathematics. I have also had two calculus based intro physics courses that basically went up to special relativity. My question is whether or not I (obviously you don't know me or my potential, this is just generally speaking) have the capability of taking time myself to learn these ideas mathematically and where I should start.
Anyone can get textbooks and you have mentioned "Gravitation" before, but all of the books I have seen in my schools library on relativity seem to be further along than I am. I haven't found a copy of Gravitation that I can look through (would like to before forking out all that dough, mostly for shipping ) does it start at the ground floor, or is there another recommended starting point for me like linear algebra, or some other mathematics that explain Riemannian/Minkowski/Lorentzian/etc. concepts and the like? I realize that it takes really smart people like yourself years to even intially understand these ideas, let alone a decade or so to be totally fluent in them. Am I doomed to failure and frustration trying myself or do I stand an outside chance at success?
Thanks for any input you can give. I will not have to ask silly layman questions anymore if I am pushed in the right direction.

This message is a reply to:
 Message 164 by cavediver, posted 11-02-2005 2:15 PM cavediver has replied

Replies to this message:
 Message 166 by Son Goku, posted 11-24-2005 1:26 PM madeofstarstuff has not replied
 Message 167 by cavediver, posted 11-26-2005 7:56 AM madeofstarstuff has replied

  
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