Current Thoughts in String Theory

DrLudicrous writes "The NYTimes is running a nice little synopsis of the current ideas in string theory. Apparently, there is still quite a bit of disagreement about how to interpret the various theories, with some string theorists supporting a semi-deterministic worldview a la Einstein (God does not play dice), while others believe our universe is just one possibility among many, with respect to various physical parameters."

Fringe science, or valid?

Considering that we presently greatly lack the amount of energy required to test even the smallest of superstring theory claims, this debate is merely beginnning. Frankly, I still view superstring theory as a fringe science, considering the fact that it holds merit (many of it's hypothesis are built upon solid scientific foundations), but none of it's claims can yet be tested and verified.

Still, intriguing stuff.

Re:Fringe science, or valid?

I'm not sure I'd completely agree with that. True, that sort of test would be ideal. However, while it is true we can't synthetically test it, that's not always necessary for it to have scientific value.

Science isn't so much about finding the "material truth", it's about finding an appropriate "model". For instance, Newton wasn't wrong per se, his model was just incomplete. We still use his model for predicting the majority of practical behaviours outside of experimental physics. Einstein came up with a better model, but we know it isn't complete because relativity and quantum mechanics are not compatable. Still, those models work in their respective applications.

If superstring theory is able to work at predicting all behaviour we can observe, it doesn't really matter if the concept is correct. In other words, if two different phenomena (conceptually) always produce the exact same results, does it matter if our model is based on the "real" one or the ficticious one?

True, there is a desire to know the "truth" of a given situation, but a model that works for all observable phenomena is certainly sufficient for most reasons we use science. Requiring that we create a phenomenon that we can't normally observe is useful for testing the truth of the model, but not necessary its practicality.

Yes but no

You are correct in stating that we lack the energy to test string theory -- According to Hawking, one estimate of the (theoritcal) grand unification energy [wikipedia.org] would be a thousand million million million GeV. Further, he goes on to say that it would take something the size of a solar system to produce this. So you're right, we can't do it.

BUT, there could very well be places that do have this necessary energy and could be observed to exhibit traits that we can measure and confirm theories with. This has been how most of the more recent unification theories have been confirmed -- either by measuring very small things with very fine equipment or measuring very large things in space.

Re:Yes but no

Isn't the first experimental proofs of the relativity theory (special and/or general) came from astronomy? We don't necessarily need to do the experiment here on Earth... all we have to do is to find a place were the experiment is already taking place and observe it...

Re:Fringe science, or valid?

Well we have small galaxies. Now all we need is a particle accelerator the size of a small galaxy, according to the article.

Well that would require some sort of a Rebigulator which is a concept so ridiculous it makes me want to laugh out loud and chortle.

Re:Fringe science, or valid?

Enstein's theories were also empirically unprovable until recent advances in avionics, minaturization, and electronics.

Bollocks. Einstein's relativity could be readily tested at the time by measuring the bending of the light by Sun's gravity. That's exactly what made them so strong and actually respected by the experimentalists.

To an experimentalist a theory is just hot air until it can be tested in practise.

Re:Fringe science, or valid?

Curiously, three independent experiments were undertaken at the next suitable solar eclipse to look at starlight being bent round the sun. One failed (cloud?), one produced results broadly consistent with General Relativity, and one produced results broadly consistent with Newtonian gravity applied to light.

The conclusion at the time was that General Relativity was confirmed, because the likelihood of measurement or equipment error seemed to have been greater with the result consistent with Newtonian gravity.

Re:Fringe science, or valid?

Einstein's theories were also empirically unprovable until recent advances in avionics, minaturization, and electronics. It turns out, decades after he began to speak about 'Special Relativity', you can indeed fly an atomic clock around the world and measure that it has undergone relativistic time dialation.

Einstein's General Theory of Relativity provided an explanation for the motion of the perihelion of Mercury's orbit. Further, it correctly predicted the magnitude of this motion [bartleby.com]--all of about 43 seconds of arc per century. It's a small motion, but it had been observed, measured, and puzzled at by astronomers in the nineteenth century.

Aside: Many people cite the 1919 eclipse observations made by the Royal Astronomical Society (also mentioned in the link above) as a further early proof of relativity. Though this is the most popular early 'proof', it is tainted with uncertainties. More recent work suggests that the precision of the RAS' instruments was insufficient for the task--the good agreement with theory was likely largely coincidence. Indeed, contradictory results from later eclipses and other groups did follow in succeeding decades. (Measurements with modern instruments have, of course, borne out relativity.)

Re:Fringe science, or valid?

"Frankly, I still view superstring theory as a fringe science, considering the fact that it holds merit (many of it's hypothesis are built upon solid scientific foundations), but none of it's claims can yet be tested and verified."

This is why I prefer sillystring theory. You can easily prove or disprove the effects of sillystring in a great many environments. For example:

1) If I shoot sillystring at the hot blonde across the room, will she sleep with me, or slap me?
2) How slow must I drive on the freeway to enable me to shoot sillystring, and still have it maintain cohesion enough to obscure another driver's windshield completely?
3) If I replace my roommate's shaving cream with sillystring, how many times will he cut his face before he realizes the switch?

You see? Definite, provable, questions. None of thos "alternate universe" or "quintuple bajillion watts of energy" problems.

Free Link

Link [nytimes.com]

Mirror

In case the site is slow, or you don't have a stinking NYTIMES account, here [martin-studio.com] is a mirror.

Martin Studio Slashdot Policy [martin-studio.com]

Good Info on String theory

This site is maintained by a professor and has a great book on string theory. http://www.mkaku.org/ [mkaku.org]

Re:Good Info on String theory

Michio Kaku is a very brilliant man, he was on Big Thinkers and made a very interesting arguement about the String theory.

There is also a very interesting book called Elegant Universe. I really haven't seen anything that compared to it.

String Theory

Just use the StringTokenizer class, and leave the actual implementation to the virtual machine. That way, the best String theory can be used later, when it is derived, and you won't have to change a line of code.

Re:String Theory

The most important part of String theory is the null terminator%#@%(&(*(FA(EWUA(UF#(A@JI#J^IHITHAIUG(#A @U(T#@(*(^@U#IHTIAWHIHJT#(@AU&%(#@

God ?

(God does not play dice)

yep god is much more sophisticated, it's all decided through russian roulette.

Re:God ?

"God does not play dice with the universe. He plays an ineffable game of His own devising, which might be compared, from the perspective of any of the other players [i.e. everybody], to being involved in an obscure and complex variant of poker in a pitch-dark room, with blank cards, for infinite stakes, with a Dealer who won't tell you the rules, and who smiles all the time." (Terry Pratchett, Good Omens)

on pseudorandom oscillation

My housemate was recently developing a comprehensive theory of the oscillations of short bits of string, even comprising such philosophical points as whether they're inherent or caused by some bored unemployed minor god. Then I bought a laser pointer and now it's all refraction this and speckle that.

Cats are fickle.

Theory vs Reality

While various Theories of Everything are being proposed, a lot of them are not based on observation. They are just complex mathematical magic created to explain reality. It's like someone saying the earth is suspended in space on the back of a big turtle which is suspended on the back of another turtle, ad. infinitum. For a human who doesn't have any means of verification, the turtle theory can explain things as well as gravity. Similarly, there are currently no means to verify string theory. It is about as good as the turtle theory until then.

Re:Theory vs Reality

While various Theories of Everything are being proposed, a lot of them are not based on observation. They are just complex mathematical magic created to explain reality.

The observation is that there are two fields of physics that have been rigorously tested and widely accepted, but are only really valid in their own domains. The problem that faces modern physics is how to reconcile this disagreement. The difference between string theory and turtle theory is that string theory is reduces down to quantum theory and relativity when suitable constraints are placed on it. Stop me if I'm wrong, but I don't think turtle theory can do that. The fact that current technology is unable to verify the theory through experiment is a temporary situation (and a unique one. Through most of history, experimental observations have triggered theoretical research.)

String theory might be pushing the limits of science, and it might be completely wrong, but it has a strong foundation, and it attempts to address a big question, and that should be reason enough for scientists to keep working on it.

But...

..quantum physics probably doesn't exist...

wait..

From the article:The new calculations suggest that this dark energy cannot last forever, that it will disappear sometime in the far future

how can it disappear? does dark energy not follow the laws of conservation? (energy can neither be created, nor destroyed, only changed) any one have an answer?

Einstein quote

The theory yields a lot, but it hardly brings us any closer to the secret of the Old One. In any case I am convinced that He does not throw dice. --Einstein, writing to Max Born, 4 December 1926.

I think that quote (or rather, truncuated paraphrases thereof) is much abused. What Einstein is saying (which is much clearer in a fuller context) is that while the probabalistic equations that comprise much of quantum theory are valuable as descriptive and predictive tools, they do much less to further Einstein's cherished ideals of really understanding the fundamental basis of physical reality. The statement "I am convinced that He does not throw dice" is a statement that while the equations of quantum mechanics might behave like statistics, they did not mean that the underlying reasons for why these equations work were simply artifacts of random, statistical processes - mere throwing of dice. Our ongoing failure to connect all the dots of the various paradigms could indicate that he was on to something...

Re:Einstein quote

It should be pointed out that Einstein in addition to helping at the start of QM (the photoelectric effect and brownian motion) also did some major work in QM later on. Most of that work was to try and poke holes in the theory. Wherever he was able to the QM folks were able to patch them back up.

I will admit to not understaning much of the term of QM I had to take in my physics major

Re:Einstein quote

"I will admit to not understaning much of the term of QM I had to take in my physics major"

Leading us to another great misquote, "those who are not shocked when they first come across
quantum mechanics cannot possibly have understood it," Niels Bohr, which gets turned into something like, anyone who thinks they understand quantum mechanics doesn't, which is really a totally different statement. It's not that you can't "understand" it - it's that the implications of the theory are simply shocking.

Both your statements about Einstein are perfectly true though. The Brownian motion work tends to be overshadowed by the relativity, but its actually elegant and significant science that was later backed up with some baroque and inventive experiments. And no, he could never accept the quantum mechanics entirely - not its reliance on probabilities and not the world where things could have no precise position and momentum. But as you note, he was never able to build a case against it that had any traction.

I don't know if anyone but the true math-heads really understands quantum mechanics. I took a fair amount with physical chemistry, and while I could grasp what was presented to me by the teacher, it was pretty damn clear that I wouldn't ever be coming up with stuff like that on my own. I remember very clearly being taught the proof for Heisenberg's uncertainty principle. It was so elegant and undeniable - either this is the way it is or else our most fundamental definitions of matter and energy have to be scrapped. But I never would have figured it out on my own, and I can't really remember it now - it would be hours of unpleasant work with the calc book and scratch paper to take myself through the proof on my own. Ah well. Quantum nostalgia (o particle in a box, we hardly knew you!)

My Thoughts on String Theory

Strings are pretty cool. They make clothes (among other things), and when they vibrate, they make music. They're also good for fishing if you tie a hook at the end of it. String it up with two cans and you've got yourself a cool communication network!

I do have a theory on string cheese, though. I think it's a plot to tempt and destroy the lactose intolerant. So cheesy...so convenient...so stringy but oh so dangerous.

If particle man got in a fight with string man who would win? If he's underwater does he get wet or does the water get him instead? (They Might Be Giants)

A challenge?

Maybe god is like some kind of ubercoder, daring us to figure out his implementation.

And like most of them, he doesn't document.

Re:A challenge?

> Maybe god is like some kind of ubercoder, daring us to figure out his implementation.

> And like most of them, he doesn't document.

Worse yet, he writes in Perl! *ewwww!*

The Devil, however, codes in TurboPascal. :)

Re:A challenge?

Yes, but wouldn't reverse engineering God's code violate the DRM? :(

Deeper questions...

Is there a click through license when you are born? And does a C-section circumvent it?

No, no, ONE string walks into a bar

He hops up on a barstool and says "Bartender gimmee a bourbon on the rocks." The bartender says "We don't serve strings in this bar, git out!" So the string leaves, ties himself at one end and musses up the other. He walks back in and asks for a bourbon again. The bartender says, "Hey, aren't you that piece of string I just threw out of here?" And the pice of string says, "No, I'm a frayed knot."

Historical perspective

All long time readers of the rec.humor newgroups will recognize "the string joke". Apparently it was submitted so many times that it became a cliche for the "already heard joke", to the point that whenever somebody submitted what was thought to be an old joke, people would reply simply with the phrase "I'm afraid not". Ah, those were the good ol' days...

Elegant Universe

For anyone curious about string theory, I would highly recommend Brian Greene's "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory". He uses excellent writing style and plain, easy to follow examples to illustrate difficult concepts, and rather than going through lots of math and derivations, reserves that type of thing for the endnotes. It makes for a very approachable book that is particularly good for someone trying to learn new concepts rather than the struggle with the gory details of theoretical physics equations.

Fudge Factor

If Einstein's fudge factor is real after all, the universe will continue to expand faster and faster as space grows bigger and bigger, producing more and more repulsion.

Einstein's fudge factor is strikingly similar to Hershey's fudge factor, in which those unfortunate souls who are addicted to sugary goodness tend to expand faster and faster, producing more and more repulsion to members of the opposite sex.

Strings OMG!!

Einstein once wondered aloud whether "God had any choice" in creating the universe.In principle, strings can unite all the forces of nature, including gravity, in a single mathematical framework.

So what happens when God messes up on bounds checking, or memory allocation for strings?

Segmentation fault. Asteroid dumped *shudder*.

I guess we're lucky He decided to steer clear of pointers.

My physical parameters

"...our universe is just one possibility among many, with respect to various physical parameters."

I'd like to think there's at least ONE universe out there where I'm skinny and good look'n!

"No pain, no... pain." Why don't we just leave it at that?

Anti-Anthropic Sky God Freaks

It seems to me that all the desperate anti-anthropic people are frightened, at some deep existential level, by the undoubted, rational reality of there being no omnipotent Sky God watching over them. So ever-expanding universes, or universes where sudden phase changes in the structure of the dark energy destroy existing life, or universes with life-hostile substructural "laws" all make them feel too small, unloved, and insignificant against the vastness. Get used to it, we are cosmic dust. The simplest explanation is that there is no design, no Sky God, no plan, and no ordering. Sic transit gloria mundi.

Trade secret?

Am I the only one drawn to the inescapable conclusion that God has deliberately obfuscated the universe to prevent reverse engineering? Or maybe I've just been working too hard...

Existence of TOE

Has anyone ever stopped to think that there is no TOE? And not just that, that there is no valid description of possible universes either? Theoretical physicists are playing mathematical games to find the TOE, but are having lots of trouble. The TOE should produce all the physical constants from its principles, right? What if the TOE has constants? Worse, what if someone proved a Godel or Turing like theorem that says something to the effect of "There is no theory that can describe everything, because there will be at least one (universe|force|particle|whatever) that does exist, but cannot be described." This is the most likely outcome I think.

At best I think that if we find a TOE it will have extremely poor predictive value because it will be so generic that it tells us not too much more about our universe than we already know, and simply give physicists new universes to wank around in. Not to say we shouldn't research this... ya never know where you might find useful stuff.

My String theory

Two strings walk into a bar.

The first string says to the bartender, "Give me a beer." The bartender turns to the second string and says, "and what about for you?" To which the second string replies, "I would also like a beer#@a9101gb230b81;kajf3#$B89*#(&)*13!$%#@$" and goes on and on spewing gibberish.

The bartender, shocked, asks the first string, "What is your buddy's problem?"

The first string answers, "Oh, you'll have to excuse him, he isn't null terminated."

He does play dice...

His is just 20,000,000,000 sided instead of 20, and he gets +19,000,000,000 HP.

People with issues...

There are several overlooked points in the discussion. Someone above has already pointed out that the Einstein quote about divine gambling is over and misquoted.

String theory was proposed by Lord Kelvin, who started to investigate by developing a theory of knots, which was expanded by Reidmeister, and blossomed in the 20th century.

Einstein's special and general relativity were created to explain observed phenomenon that could not be explained by current theories. For special relativity, this was the constant velocity of the speed of light given by electromagnetism and confirmed by the Michaelson-Morley experiments. General relativity is a result of formulating Newtonian gravity in the field theoretic language used for unified electromagnetism. There were bits of data around indicating its necessity, though, such as errors in the perihelion of Mercury.

Quantum mechanics was similarly developed because of an incredible plethora of data. Thanks to Bell, we now know that (unless theory takes some really extreme turns), before an interaction with a "classical" apparatus, a quantum particle not only has unknown position and momentum, it actually doesn't have either. It's a subtle argument, but it's pretty well tested.

The motivation for string theory was to remove infinities in the fields which result from point-like particles. There is no physical motivation. String theory was not formulated as a theory of gravity or a grand unification theory. Those were bolted on afterwards as people noticed they could have sufficient degrees of freedom: you can build similar theories with straight up quantum field theory, and many people do for their life's work. So far the theory has produced one observable, which we already knew to far higher accuracy from quantum field theory. Pure number theorists get more physics as a by product than do string theorists. Supersymmetry and the Higgs boson are attempts to clean up mathematical holes, but they seem almost well motivated compared to the morass that is string theory.

String theory has driven a wedge between theorists and experimentalists in particle physics, and made it "unfashionable" to do serious theory that actually deals with reality. However, the popular press loves it: you can quote big sounding names and no one can nay-say them. Most areas of particle physics abjectly fail when it comes to explaining what you're doing to the layman.

Thankfully the pendulum seems to be swinging. At Caltech, their one phenomenologist has recently been absolutely swamped with pupils: string theory seems to be dying off at last.

I had a really good String theory

But then Schrodinger's Cat started to play with it.
Now all I have is a mess.

Everyone seems to be dying

But Dr. Max Tegmark, a cosmologist at the University of Pennsylvania, said, "I think this grand dream is basically dying."

Along with BSD, trinity and internet.....

BSD has been dying for over 10 years.

Trinity died even before reloaded could hit the screen.

Internet has been dying for sometime now.

Executive summary

The universe is tied up in knots. Figuring out just how has physicists tied up in knots
QED

Primer to get you up to speed on current theory

I know more about string and particle theory than 99% of the population, which means I'm still a comparative dumbass on the subject in relation to people who really know what they're talking about.

However, here's a spiffy chart of the current "standard model" [particleadventure.org] to help people get up to speed. Especially helpful for those who don't normally deal with Mesons and Antibayrons on a regular basis...

PBS Nova: The Elegant Universe homepage

The NY Times article mentions that Nova is doing an string theory episode this fall (Oct 28,2003 and Nov 4, 2003) based on Brian Greene's book The Elegant Universe. Turns out the homepage for this episode is already online with plenty of interviews and animations [pbs.org].

Superstring theory is not the only candidate

You may also be interested in reading about loop quantum gravity, an alternative theory of everything. I' not expert, better refer to this reference [livingreviews.org] that I looked up.