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Quantum Physics
Posted: 23 March 2007 04:30 PM   [ Ignore ]   [ # 31 ]
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[quote author=“Carbon based”]

He knows that it’s not scientific. That’s all he needs to know.

Aren’t you making a classic logical error?  Setting up Glashow as the authority, and only authority on string theory due to his nobel status?

No, not at all.  Science by definition involves actual observation of matter and testing.  If you remove empirical observation then it ceases to be science.

Superstring theory is merely a theory, divorced from the element of empirical observation which science depends on.

I could/would counter with: David Gross shared the 2004 Nobel Prize in Physics and is the director of the Kavli Institute for Theoretical Physics at the University of California at Santa Barbara.

Gross: The big bang theory is the idea that if we go back early enough in the history of the universe—and we can do this, of course, by looking at starlight coming to us from billions of years ago—we will see a very hot and dense period where the universe was much smaller, denser, and hotter. And that explosion or hot state left remnants that we can observe today in the microwave background. So we know that that aspect of the theory is true.

You see, now that sort of theorizing is scientific because actual observation is involved in the theorizing.  In otherwords, there is a healthy balance between theory and actual emprical observation.

If we push back even farther, that hotter or denser state becomes even hotter and denser. And if we extrapolate using Einstein’s theory of general relativity, we find total disaster. That is, we find a singularity, in which the forces that act on particles become infinitely strong. Things break down completely, and the theory no longer makes sense.

Our conclusion is not that the universe doesn’t make sense, but that the equations are wrong. They’re applicable maybe at later times, but they’re not applicable at the beginning of the universe. So we desperately need something like string theory appears to be—a theory that is consistent.

NOVA: Basically you need a theory that’s going to work under those conditions.

Gross: Yes, and one that can provide an answer to questions that with our present theories we can’t dream of answering, such as: How does the universe begin? What starts it off? What is the state of the universe at the beginning? Is that unique or arbitrary? Who fixes the initial conditions? There are questions that can’t be answered within the standard theory. We’re not sure that string theory, or any theory, could provide answers to the beginning of the universe, but it’s a goal that many of us are desperate to try to reach.

I would say desperate is a very apt word indeed to describe these people. Naive and lopsided would be a good way of putting it as well.  They are not acknowledging the fact that scientific instruments are not going to be able to determine whether or not the singularity causing the big bang was a seed among billions of seeds.  And sadly, as is typical of human nature, they are hoping that the singularity is the edge of the world, or the center of the universe. 

NOVA: And string theory can help provide these answers?

Gross: String theory is the best hope at the present. And the questions are some of the most interesting questions that we can ask. All of us would like to know: Is the universe arbitrary? Could it have been otherwise than it is? Could there have been different laws, different constants of nature? Has it begun only once, or is it cyclic? Was there beginning to time? Does time have any meaning before it began? These are wonderful questions, and we’re now in a position to address them. We have no guarantee that we will find the answers, of course, but the effort is as important as finding the answer.


Philiosophical enough for you?

No, not really.  I’m not impressed with people who think theorizing is enough.  I’m more impressed with people who assert the value of developing theories along side of accumulated data, and who think about the context and logical implications involved in attaining the sort of instruments and power required to peer back into the moment before the big bang, or the sorts of instruments and power required to observe the level that superstrings reside in. 


I’d like to address a comment Glashow makes in his interview about superstrings:

NOVA: If it’s not testable, how useful is it?

Glashow: It leads to many interesting ideas. It is important in mathematics. String theory has had an impact on modern mathematics. They may even have a practical impact some day, these things that string theorists do. One never knows, just as number theory, the most useless of the mathematical sciences, has given us cryptography and has given us a secure way to encode information. The string theorist may also produce something equally useful.

And this I agree to.  I am not condemning SS theory.  I’m just deflating what I see as a lot of naive hyperbole.

Here is another comment by Glashow:

It’s something that began to develop in the ‘80s, grew in the ‘90s, and today attracts many of the best and brightest physicists. It’s called superstring theory and it is, so far as I can see, totally divorced from experiment or observation. If not totally divorced, pretty well divorced. They will deny that, these string theorists. They will say, “We predicted the existence of gravity.” Well, I knew a lot about gravity before there were any string theorists, so I don’t take that as a prediction.

But in and of itself, it has failed in its primary goal, which is to incorporate what we already know into a consistent theory that explains gravity as well. The new theory must incorporate the old theory and say something more. String theory has not succeeded in this fashion. String theory has said something more, but it does not incorporate the details of the structure that preceded it, that is to say the standard theory of elementary particles. Until it does that, it is not yet physics in a conventional form.

[Troublingly] The best and the brightest young theorists, instead of being concerned about the experimental enterprise, are going off among themselves and doing their thing [in superstring theory] with the doors closed. Because no one else is interested in coming, they’re all making these secret signs to one another and putting incomprehensible formulas together that to them are, of course, central and simple and predictive and whatnot but to us are a little bit irrelevant.

Now, what happens if there are suddenly some major experimental discoveries? There is a big accelerator, the Large Hadron Collider, which is scheduled to be completed in another five years or so. That should make lots of discoveries. Who will be interested in trying to fit these discoveries into the theory? It will be people like me, except we may be dead by then or if not we’ll be rather old. Or it will be the young theoretical physicists, but the young theoretical physicists are doing string theory, and they ain’t interested in the results of the experiments. Not now, and not then. So who’s going to be there to continue the role of building a better theory of particle physics? That’s why it’s a problem.

To me, the interest in string theory by young people and their disintrest in actual raw data, reflects a certain laziness and a certain lack of restraint when it comes to being able to put aside what is most immediately gratifying, in order to do the hard work of developing a theory along side actual observation.

I also find the hope that the big bang singularity as the ultimate begining of everything to be rather anthropocentric, and reflects the human tendency to come to conclusions like: the world is flat and the edge of the horizon is where the world ends, the earth is the center, the sun is the center, etc, etc. 

Also could you please supply your source on the 1,000 light year accelerator.

  HERE

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Posted: 23 March 2007 04:45 PM   [ Ignore ]   [ # 32 ]
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Well if you had read all of the interviews you would of seen/read that string theory is testable.  There is a prediction called supersymtry: from the interview with Witten:

NOVA: It seems like the standard criticism of string theory is that it isn’t testable. How do you respond to that criticism?

Witten: One very important aspect of string theory is definitely testable. That was the prediction of supersymmetry, which emerged from string theory in the early ‘70s. Experimentalists are still trying to test it. It hasn’t been proved that supersymmetry is right. But there is a very precise relationship among the interaction rates of different kinds of particles which follows from supersymmetry and which has been tested successfully. Because of that and a variety of other clues, many physicists do suspect that our present decade is the decade when supersymmetry will be discovered. Supersymmetry is a very big prediction; it would be interesting to delve into history and try to see any theory that ever made as big a prediction as that.

NOVA: What are some of the other ways that string theory could be confirmed experimentally?

Witten: There are a lot of conceivable ways we could get experimental information that would help with string theory. Explorations of cosmology, studying the cosmic background microwave radiation and hopefully finding gravitational waves left over from the big bang and studying their properties are very plausible avenues for eventually testing string theory, although there isn’t yet to my thinking a satisfactory theoretical understanding of what to expect.

But it’s conceivable that the big bang could have produced a string so large that it would be present in today’s universe and visible in telescopes, perhaps discoverable by the satellites that are now mapping out the microwave sky. If that were discovered, it would be a dramatic confirmation of the existence of strings. Still, that’s a story that will develop over the next decade or two as the experiments progress and conceivably as the theory progresses.

NOVA: How likely do you think it is that string theory will be proven correct?

Witten: Well, I don’t have a crystal ball. You know, the theory of neutron stars was tested and the same is true of the theory of black holes and the theory of gravitational waves. A lot of the theories that were there in the ‘20s and ‘30s that looked like they were way beyond reach were eventually tested. They were tested because there were new technologies, there were new instruments, there were newer things found in the sky. Things happened that you couldn’t foresee. That’s what happens in science.

Since as Witten has pointed out string theory is testable (supersymmetry) and therefore falsafiable, which leads to string theory IS scientific.

Also I think your confussing the length an accelerator has to be with the energies it needs.

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Posted: 24 March 2007 04:45 AM   [ Ignore ]   [ # 33 ]
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[quote author=“Carbon based”]Well if you had read all of the interviews you would of seen/read that string theory is testable.  There is a prediction called supersymtry: from the interview with Witten:

NOVA: It seems like the standard criticism of string theory is that it isn’t testable. How do you respond to that criticism?

Witten: One very important aspect of string theory is definitely testable. 

It is only an aspect of symmetry.  Whether it’s important or not, really isnt the issue.  String theory as a whole is not testable, at least not now.  At best, experiments can provide only necessary but even ultimately insufficient evidence for mere components of string theory—such as supersymmetry.

If you confront string theorists about this fact, their reply is: “SS theory is testable but we do not have the right kind of equipment yet for this purpose.”

So when are we going to get our hands on this right equipment?

John Horgan put things nicely into perspective when he wrote: “The Superconducting Supercollider, the monstrous particle accelerator that Congress canceled in 1993, would have been 54-miles in circumference. Gaining access to the infinitesimal microscales where superstrings supposedly wriggle would require an accelerator 1,000 light years around. (The entire solar system is only one light day around.)”

Now, Carbon based, I know you don’t believe that, but it’s a fact that has been published and circulated around the scientific community for quite some time now without any objections. 

Here is a quote by David Gross, who, believe it or not is an aggressive proponent of String theory:

“We don’t know what we are talking about” The state of physics today is like it was when we were mystified by radioactivity” They were missing something absolutely fundamental. We are missing perhaps something as profound as they were back then.”

Now, lets consider the following quote by Witten:

“Supersymmetry is a very big prediction; it would be interesting to delve into history and try to see any theory that ever made as big a prediction”

hmmm, ok, so let’s try to delve into history and try to find a theory that made as big of a prediction….

Ah, how about, Einstein’s theory of Relativity?  The theory made some very important predictions which guided the scientists on how to test the theory. For example, the theory predicted that light rays are bent in the vicinity of massive stars; also predicted black holes and that the universe is constantly expanding, among many others. All these predictions have come true.

Whereas on the other hand, string theory fails to be “background-independent” meaning that it is based on a fixed geometry of the space. Einstein’s theory of general relativity showed that the space geometry is dynamic and changing in time. “this is a basic discovery and cannot be reversed, so any further theory must incorporate it. String theory doesn’t, so if string theory is valid, there must lie behind it a more fundamental theory, one that is background-independent.” (Lee Smolin)

And of course, the more fundamental theory is non-existent, as String theorists themselves don’t even completely know what string theory is in the first place, as there is still much to be worked out.

I have to agree with John Horgan , that the whole enterprise of SS theory seems based largely on aesthetic and religious impulses for unity, simplicity and beauty.

I think that speculation has it’s value, and that some good may come out of string theory.  But overall, I just agree with many critics, in that it’s over-hyped and ‘not even wrong’

I heard an amusing term used to describe SS physics - - “hollywood physics”.  It’s elitist, aesthetic and elegent, but ultimately hollow and shallow.

Feynman reportedly once said: ‘String theorists don’t make predictions, they make excuses.’

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Posted: 24 March 2007 05:31 AM   [ Ignore ]   [ # 34 ]
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Throughout the history of science for every major paradigm shift there have been nay-sayers, even Einstien scoft at QM (he later recanted).  So we will just have to wait and see won’t we.  :D

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Posted: 24 March 2007 04:04 PM   [ Ignore ]   [ # 35 ]
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Well, there comes a point where one eventually has to recant or concede sometimes, esp when presented with the better argument or evidence.  We can’t always be right or win them all.  It takes a big person to admit when they are wrong or what have you.

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Posted: 25 March 2007 03:52 AM   [ Ignore ]   [ # 36 ]
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[quote author=“Mriana”]Well, there comes a point where one eventually has to recant or concede sometimes, esp when presented with the better argument or evidence.  We can’t always be right or win them all.  It takes a big person to admit when they are wrong or what have you.

This is true, and as I’ve pointed out wait for 2009 for Cern to turn on the Large Hadron Collider.  I think with fundimental physics looking for quick answers is fruitless.  Lets see what string theory or some derivative of it produces.  The big problem with QM is that it ignores gravity, and string theory is looking to put ALL the forces together.

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Posted: 29 March 2007 05:22 PM   [ Ignore ]   [ # 37 ]
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[quote author=“Carbon based”]  I think with fundimental physics looking for quick answers is fruitless.  Lets see what string theory or some derivative of it produces.  The big problem with QM is that it ignores gravity, and string theory is looking to put ALL the forces together.

“Quick” answers? How about just answers?

QM doesn’t ignore gravity and GR doesn’t ignore QM, what therein lies is an anomaly that is waiting for all of physics to unify, and yes, that may or may not very well be string theory.

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Posted: 30 March 2007 06:04 PM   [ Ignore ]   [ # 38 ]
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[quote author=“Carbon based”]Throughout the history of science for every major paradigm shift there have been nay-sayers, even Einstien scoft at QM (he later recanted). 

Right up until his death Einstein was dissatisfied with Quantum theories that were content doing without hidden variables.  Einstein had a strong hunch that all things must be caused.  Me?  I know that it’s an absolute truth that all things are caused.

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Posted: 30 March 2007 06:32 PM   [ Ignore ]   [ # 39 ]
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http://en.wikipedia.org/wiki/Bohr_Einstein_debate

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Posted: 20 April 2007 02:54 AM   [ Ignore ]   [ # 40 ]
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Posted: 20 April 2007 03:18 AM   [ Ignore ]   [ # 41 ]
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This depends on a particular (and in my view, unwarranted) interpretation of QM (roughly, the “Copenhagen Interpretation”), it does not come from QM itself.

For example, the observation necessary to collapse the wave function in the two-slit experiment is made by a device of some sort. There is no reason why the “device” needs to be conscious or complex.

There are other interpretations of QM that do not require an “observer”, e.g., the many-worlds interpretation, or Bohm’s “pilot wave” interpretation, IIRC. I am sure there are others.

Indeed, if you consider the famous Schrodinger’s Cat thought experiment, it would seem to imply that without an external observer, the many-worlds interpretation of QM might be true ... i.e. there would be an infinity of different, equally true, universes, all “superposed” upon each other. But this is only the sheerest speculation.

(NB: this “many-worlds” interpretation of QM is different from the “logically possible worlds” discussed in the other threads on necessity and free will).

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Posted: 20 April 2007 04:06 AM   [ Ignore ]   [ # 42 ]
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Posted: 20 April 2007 04:28 AM   [ Ignore ]   [ # 43 ]
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[quote author=“George”]This whole QM stuff is making me dizzy.

Yep. And that’s no joke. The world is a very strange place.

[quote author=“George”]We are not only overdue for a pandemic, but also for the new Darwin/Einstein…and the music sucks too these days…

LOL  LOL

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Posted: 20 April 2007 06:50 PM   [ Ignore ]   [ # 44 ]
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I’m telling you guys, there’s just stuff we aren’t ever going to understand. If there were a god, he would probably think it’s cute how we keep trying to figure everything out. Like when a kindergartener decides to count “all the leaves in the whole world!” Still, that’s what I love about kindergarteners that school somehow squeezes out of them-unashamed curiosity about stuff they aren’t even close to being able to really grasp. Didn’t Milton say, ” Man’s reach should ever exceed his grasp, else what’s a heaven for?”

As someone largely mathematically challenged, I had one brief shining moment in undergraduate physics when an exceptional professor actually got me to see how and idea could be clearly expressed in mathematics, and completely impenetrable in ordinary language (something about how your mass varies with your velocity, I think). I suspect QM will always remain largley impenetrable to those of us unable to follow the mathematics that describe it. It doesn’t really lend itself to metaphors constructed out of the language of everyday experiences. And as suspicious as I am of relying on “authority” to tell me how reality is, I don’t know that I have much choice in this subject area.

Oh, and the music I listen to doesn’t suck!  :D

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Posted: 21 April 2007 01:24 AM   [ Ignore ]   [ # 45 ]
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I would add that what we do learn next may not unify anything but may just as likely overthrow all previous models.

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