Why String Theory Still Offers Hope We Can Unify Physics

http://www.smithsonianmag.com/science-nature/string-theory-about-unravel-180953637/?no-ist

Evidence that the universe is made of strings has been elusive for 30 years, but the theory's mathematical insights continue to have an alluring pull



By Brian Greene
Smithsonian Magazine January 2015:


In October 1984 I arrived at Oxford University, trailing a large steamer trunk containing a couple of changes of clothing and about five dozen textbooks. I had a freshly minted bachelor’s degree in physics from Harvard, and I was raring to launch into graduate study. But within a couple of weeks, the more advanced students had sucked the wind from my sails. Change fields now while you still can, many said. There’s nothing happening in fundamental physics.

Then, just a couple of months later, the prestigious (if tamely titled) journal Physics Letters B published an article that ignited the first superstring revolution, a sweeping movement that inspired thousands of physicists worldwide to drop their research in progress and chase Einstein’s long-sought dream of a unified theory. The field was young, the terrain fertile and the atmosphere electric. The only thing I needed to drop was a neophyte’s inhibition to run with the world’s leading physicists. I did. What followed proved to be the most exciting intellectual odyssey of my life.

That was 30 years ago this month, making the moment ripe for taking stock: Is string theory revealing reality’s deep laws? Or, as some detractors have claimed, is it a mathematical mirage that has sidetracked a generation of physicists?

Unification has become synonymous with Einstein, but the enterprise has been at the heart of modern physics for centuries. Isaac Newton united the heavens and Earth, revealing that the same laws governing the motion of the planets and the Moon described the trajectory of a spinning wheel and a rolling rock. About 200 years later, James Clerk Maxwell took the unification baton for the next leg, showing that electricity and magnetism are two aspects of a single force described by a single mathematical formalism.

The next two steps, big ones at that, were indeed vintage Einstein. In 1905, Einstein linked space and time, showing that motion through one affects passage through the other, the hallmark of his special theory of relativity. Ten years later, Einstein extended these insights with his general theory of relativity, providing the most refined description of gravity, the force governing the likes of stars and galaxies. With these achievements, Einstein envisioned that a grand synthesis of all of nature’s forces was within reach.

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Will the Large Hadron Collider’s ATLAS proton-smasher detect signs of strings? (Rex Features via AP Images)



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VIDEO: What Is String Theory? Brian Greene Explains




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http://phys.org/news/2014-01-scientists-theory.html

Scientists find a practical test for string theory
January 6, 2014

(Phys.org) —Scientists at Towson University in Towson, Maryland, have identified a practical, yet overlooked, test of string theory based on the motions of planets, moons and asteroids, reminiscent of Galileo's famed test of gravity by dropping balls from the Tower of Pisa.

String theory is infamous as an eloquent theoretical framework to understand all forces in the universe —- a so-called "theory of everything" —- that can't be tested with current instrumentation because the energy level and size scale to see the effects of string theory are too extreme.

Yet inspired by Galileo Galilei and Isaac Newton, Towson University scientists say that precise measurements of the positions of solar-system bodies could reveal very slight discrepancies in what is predicted by the theory of general relativity and the equivalence principle, or establish new upper limits for measuring the effects of string theory.



Read more at: http://phys.org/news/2014-01-scientists-theory.html#jCp

 

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http://m.iopscience.iop.org/article...D28DDF2F9FAF7803F46.c2.iopscience.cld.iop.org

PAPER
Expanded solar-system limits on violations of the equivalence principle
James Overduin1,2, Jack Mitcham1 and Zoey Warecki1

Published 14 November 2013 • 2014 IOP Publishing Ltd • Classical and Quantum Gravity, Volume 31,

Abstract
Most attempts to unify general relativity with the standard model of particle physics predict violations of the equivalence principle associated in some way with the composition of the test masses. We test this idea by using observational uncertainties in the positions and motions of solar-system bodies to set upper limits on the relative difference Δ between gravitational and inertial mass for each body. For suitable pairs of objects, it is possible to constrain three different linear combinations of Δ using Kepler's third law, the migration of stable Lagrange points, and orbital polarization (the Nordtvedt effect). Limits of order 10−10–10−6 on Δ for individual bodies can then be derived from planetary and lunar ephemerides, Cassini observations of the Saturn system, and observations of Jupiter's Trojan asteroids as well as recently discovered Trojan companions around the Earth, Mars, Neptune, and Saturnian moons. These results can be combined with models for elemental abundances in each body to test for composition-dependent violations of the universality of free fall in the solar system. The resulting limits are weaker than those from laboratory experiments, but span a larger volume in composition space.

 

While some reputable professionals appear to have written off String theory and/or one of its many derivitives, the final potential outcome and goal, will still see equally reputable and respected experts continuing their search for the holy grail of physics/cosmology.

 

This is the type of articles which suggest that science journalists also deserve the name "presstitutes". Ok, a new test of the equivalence principle is certainly something interesting and useful. And, ok, in a purely formal the claim that this would give new upper limits for effects of string theory is correct too - simply because it gives new upper limits of whatever violations of the EP, thus, upper limits of whatever different theory.

Say, if what is tested are violations of the Strong EP, I could as well say that this is a practical test for my ether theory, simply because in my ether theory the SEP does not hold, and only the weaker Einstein EP holds. So, testing the EP is fine, but has nothing to do with string theory.

Unfortunately, given that there are essentially no nontrivial predictions of string theory, to have something one can sell as a "test of string theory" is a nice propaganda idea. And so we see this line in the header, in an article about an experiment which has nothing to do with string theory.

 

You could well say, and have said at every opportunity any excuse to raise your hypothetical paper...I expected nothing less [Is that another adhom?

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Let me say that while your posts against string are predictable, they are also shallow.

No one is forcing you, or anyone, to “accept” string theory, although the facts stand as unchallenged that we still have a lot of brilliant minds that are choosing to continue work in this regard.
They are putting their shoulders to the wheel and their collective talent to the best use possible in solving the issues at hand, and there is absolutely no sane reason why anyone should complain.
They are not presenting string theory or any of its derivitives as fact, and it is silly to say that they are, but in particular your own apparent zealous opposition to it, seems to present a motive for such zeal.
In actual fact the brilliant minds that are still working on it, do so because of the incredible, promising although as yet unproven goal of the whole excersise.

And BTW, I feel the same way about QLG [Quantum Loop Gravity]
So please Schmelzer, stop trying to tear down and confuse the goals of string theory, and continue on your own self appraised individualistic path that you have chosen.
And of course your predicted unevidenced opposition to strings will be treated with the contempt it deserves.

 

In relation to my previous post and what I said, the following paper is very interesting. I have highlighted in red the short, and sweet crux of the matter and the brief summarised answers.......
http://arxiv.org/pdf/0908.0333.pdf

Introduction String theory is an ambitious project. It purports to be an all-encompassing theory of the universe, unifying the forces of Nature, including gravity, in a single quantum mechanical framework. The premise of string theory is that, at the fundamental level, matter does not consist of point-particles but rather of tiny loops of string. From this slightly absurd beginning, the laws of physics emerge. General relativity, electromagnetism and Yang-Mills gauge theories all appear in a surprising fashion. However, they come with baggage. String theory gives rise to a host of other ingredients, most strikingly extra spatial dimensions of the universe beyond the three that we have observed. The purpose of this course is to understand these statements in detail. These lectures differ from most other courses that you will take in a physics degree. String theory is speculative science. There is no experimental evidence that string theory is the correct description of our world and scant hope that hard evidence will arise in the near future. Moreover, string theory is very much a work in progress and certain aspects of the theory are far from understood. Unresolved issues abound and it seems likely that the final formulation has yet to be written. For these reasons, I’ll begin this introduction by suggesting some answers to the question: Why study string theory?
Reason 1. String theory is a theory of quantum gravity
Reason 2. String theory may be the theory of quantum gravity
Reason 3. String theory provides new perspectives on gauge theories
Reason 4. String theory provides new results in mathematics
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

To put it as plainly as possible, and before anyone can misconstrue what I'm saying, research should certainly continue into all derivatives of string theory as well as QLG, because of the ultimate goal that may possibly be achieved.
This should continue at least and until a whole new far more promising model/physics is established.
There is no sane reason why this should not continue.
I also hold the same view as far as other scientific endeavours are concerned such as controlled Nuclear Fusion.

 

http://arxiv.org/abs/hep-ex/0008017

Introduction to Superstring Theory
John H. Schwarz
Abstract
These four lectures, addressed to an audience of graduate students in experimental high energy physics, survey some of the basic concepts in string theory. The purpose is to convey a general sense of what string theory is and what it has achieved. Since the characteristic scale of string theory is expected to be close to the Planck scale, the structure of strings probably cannot be probed directly in accelerator experiments. The most accessible experimental implication of superstring theory is supersymmetry at or below the TeV scale.

 

Hm, you have made 4 posts with the obvious "agenda" of string propaganda, added even two more by now, but I have answered only one. And, note, it was not even an attack against string theory, but an attack against a particular presstitute, who has presented a test of the EP as a test of string theory.

And the attack against the presstitute was supported with evidence - the evidence from the article itself, that what is really done is to test the equivalence principle, a test which would be reasonable and useful, and probably done even if nobody would have invented string theory.

And, let me add further evidence: String theorists are not stupid, so they know that string theory violates the EP, but also know how big these violations can be. So, they also know the order of magnitude of these violations, and can compare them with the order of magnitude accessible to experiments. So, we would have heard about this possibility if it would exists. So, what we can reasonably expect is that, formally correct, the observation will give upper bounds for the EP violations, and these would formally be upper bounds for string theory effects too, but they would be as relevant as, say, an upper bound of the size of the Everest would be for an effect expected to be of atomic size.

 

Another exercise in trying to get out from under.
My articles are posted to re-enforce the proposition that string theory research should continue and with the logical assumption that you would add your usual semantic bullshit and ether agenda.

 

If those who like would continue to study string theory as their hobby, nobody would have a reason to object.

In reality, they are nicely paid by taxpayer's money. Thus, in principle, taxpayers may have doubts if this is a reasonable investigation. I doubt.

But this makes sense, of course, only in democratic propaganda. In reality, once the taxes are in the hands of the state, they are lost anyway. And we can be happy if those who are paid with them are harmless string theorists, instead of "moderate rebels" who like to cut heads and eat human livers. From this point of view, I would be in favor of spending much much more money on string theory. I would support to spend the whole american defense budget on string theory. This would certainly allow the string theorists to show the real power of string theory.

 

That's nice...so why all the angst?

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More of the stupid conspiracy claims and obvious crazy rantings that alternative nuts so often fabricate to gouge some credibility for their own scientific and political agenda.
And an answer to my first question.

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Not entirely, Brian.

When someone sets out to produce a general template from which they can provide mathematical support for virtually any theory or assertion, that might be a problem. I'm not saying that it necessarily is; only that it could be.

When the universe is reduced to discrete math and probabilities, and all anyone ever thinks or cares about is calculating more discrete math and probabilities, that's a problem. A MATH problem, not necessarily a PHYSICS problem.

The uncertainty principle will undoubtedly be expanded and exploited more than ever from this day forward, but it should never be used as a justification to give up any science other than math. The parts of String theory that have done that will need some strings trimmed.

For the record, TOWSON UNIVERSITY is one of the reasons I chose not to be a teaching intern. They drilled the Common Core Curriculum propaganda into our heads like it was the only way to teach. That much, I believed.

 

Which angst? They are losers, their only chance is ignorance and state money.

 

And for the record, I'm retired and not receiving a pension yet. I'm on no one's payroll.

 

And the total unevidenced conspiracy crap continues.
Do better.

 

Worth noting that in Professor Steinhardt's Q and A in Scientific American, he also said......
Steinhardt: "I share Edward’s view that string theory represents our best hope at present for a unified theory. However, I think success requires that the string landscape issue be resolved and that we find some empirical evidence for supersymmetry".

http://blogs.scientificamerican.com/cross-check/physicist-slams-cosmic-theory-he-helped-conceive/