NOVA Reminder - String Theory

[tracer]

the Quantum Cafe, in particular, was very cool.

Yeah, but it was soooo cheesy! "Disco String Theory" indeed.

Heck, this episode of Nova had more simplistic science in it than the PBS show about Einstein's first wife that followed. Come on! This is Nova, for crying out loud! If I wanted dumbed-down science I'd watch the Discovery Channel.

 

[Diamond]

So tell us all, does this theory actually tell us how long a piece of string is?

 

[Ziggurat]

Re: When will people learn there is no 'final description'?

The 'Newton came up with the theory of gravity after an apple fell on him' is probably one of those lovely myths of science.

Yes, this probably is a myth, but it's a pet peeve of mine that people still get the myth wrong. The way you phrase it, it just doesn't make any sense, but the "real" version of the myth does make sense, even if it's not what happened. So here's the story: Newton was sitting under a tree, and an apple falls on his head. He looks up and sees the moon. It's at that point that he realizes that the moon is ALSO falling, just like the apple. That is, terestrial gravity and celestial orbits are the same thing. THAT is what Newton discovered. The existence of terestrial gravity was obvious (he's not exactly the first person to see apples falling) and even mathematically understood by the likes of Galileo, and Kepler already had done a lot of work on celestial motion, but it's the connection between terestrial gravity and celestial mechanics that was Newton's great insight, and the typical retelling of the myth ignores the critical detail of the myth (the moon) that provides that connection. Without it the myth just doesn't make any sense, and really sounds stupid.

 

[CurtC]

I have to say that the book The Elegant Universe will be much more satisfying to anyone here than the show was. The show was too dumbed-down.

However, one thing kept coming up in the show. It also was my overall impression of the book. Did you notice how they kept saying "may," "might," "could," and other wishy washy words like that? It seems to me that String Theory is one possible TOE, out of some larger number of possibilities which we haven't quantified. After someone first noticed some cool aspects of it (similarity of some QM laws with vibrating string equations, the fact that something which looks like a graviton falls out of the equations), they ran into trouble with these "anomalies." Then someone noticed that if we work in ten dimensions, it becomes self-consistent. ST proponents treat this as if it's some fundamental insight, but it could also be viewed as a kludge to the theory to give it a somewhat longer life till we find the next thing wrong with it. Now I think they're up to eleven dimensions. What's next? 42?

It seems quite possible to me, even likely, that we have a bunch of the brightest minds working on a dead-end path. OTOH, it's the only path we know of at this time.

Some prominent physicists (one was on the show) complain that ST will never make a testable prediction. From what it looks like to us now, we would need colliders on a scale that they never will be practical to build (and I mean never). I just can't see this panning out in my lifetime.

 

[Michael Redman]

Very repetative. Saying the same thing over and over. Lots of redundancy. Very repetative
. . .

Did you notice that he said, "billions and billions"? More than once. Was that supposed to be some sort of homage to Sagan?

 

[T'ai Chi]

.., I urge just the opposite: Learn how the universe works! Don't waste your college career reading endless amounts of fiction!

Studying fiction certainly does not waste a career!

However, there might be quite a bit of fiction in 11 or whatever dimensions, or saying a theory is true when one can't even test it.

 

[bignickel]

Gosh, I'm not sure what everyone was expecting here in just 4 50 minute episodes. Professors explaining physics equations on a classroom backboard?

I thought that they explained them selves quite well. They had nay-sayers on who complained that ST was indistuingishable from philosophy; you think you'd see that on any theology program? On all the countless UFO programs that saturate the airwaves?

This program is an overview: it's not meant for people who chew physics books for breakfast. It's meant for people whose main hobby is not science; to give them an idea of what's currently being worked on in the field.

These days, too many people are grossly illiterate in the sciences. Many have heard about quarks or 'probability theory' in QT, and just shake their heads: at this point you get dangerously close to people shrugging off current science as professors debating how many bosons dance on the head of a pin. Is that where we're going right now? Science as being indististuingishable from magic? In our own lifetime, in our 1st world nations, with our own fellow citizens?

I don't think we want that: it's that kind of thinking that gets Creationists elected to school boards.

If the first program or so is an intro, let's see what #3 and #4 have to deliver.

 

[T'ai Chi]

They had nay-sayers on who complained that ST was indistuingishable from philosophy; you think you'd see that on any theology program?

Yes, I actually have seen that type of thing on a theology program before.

at this point you get dangerously close to people shrugging off current science as professors debating how many bosons dance on the head of a pin.

Nah, not on heads of pins, but in how many dimensions. Or how many times can we pretend we are at the 'end' of physics, just a step away from discovering The Equation?

I'm not terribly impressed by fancy graphics and loads of mathematical equations that only explain themselves and not the real world. When they can actually test their hypothesis (I hesitate to call it a theory), then it will be more interesting to me.

Don't get me wrong, it is fairly interesting and exciting to me as it stands, especially with its huge potential, it just isn't convincing me at all (who cares though, its just me). Last time I checked, potential theories of everything should be very convincing.

 

[CurtC]

T'ai Chi wrote:When they can actually test their hypothesis (I hesitate to call it a theory)...

I think "theory" is the right word - if it were a hypothesis, it would actually make testable predictions. But it's a theory, in that it offers a big-picture explanation for lots of data. And just because it's a theory, that doesn't mean it's true.

 

[bignickel]

Yes, I actually have seen that type of thing on a theology program before.
[/b]

Really? Could you point out the theology program where the minister says "You know, all this stuff in the Bible is pretty hard to believe. In fact, alot of the stories attributed to Jesus are just as easily attributable to other people at the time, such as Apollonius of Tynae. Since Occam's Razor is useful in so many things, I'd have to say that alot of our religion is highly unlikely and not tenable."

That's the differance between a science program and believe program: a science program needs to poke holes in it's own statements. A religion program would never do so.

 

[bignickel]

Wierd; it just occured to me how my current sig could be used to describe various elements of Quantum theory. Spooky action at a distance.... (just in time for Halloween)

 

[Walter Wayne]

However, one thing kept coming up in the show. It also was my overall impression of the book. Did you notice how they kept saying "may," "might," "could," and other wishy washy words like that? It seems to me that String Theory is one possible TOE, out of some larger number of possibilities which we haven't quantified. After someone first noticed some cool aspects of it (similarity of some QM laws with vibrating string equations, the fact that something which looks like a graviton falls out of the equations), they ran into trouble with these "anomalies." Then someone noticed that if we work in ten dimensions, it becomes self-consistent. ST proponents treat this as if it's some fundamental insight, but it could also be viewed as a kludge to the theory to give it a somewhat longer life till we find the next thing wrong with it. Now I think they're up to eleven dimensions. What's next? 42?

I noticed this seeming effort to continually "bend the math to make it fit" appeared to be going on. To me it sounds a bit like polynomial fitting, any set of data can be fit to a polynomial, you just have to find the right constants. Does that mean the underlying polynomial tells you anything. It sounds to me like they are just 'tuning' the strings until it fits the data. I wonder if the strings could be 'tuned' to any universe given the right number of dimensions.

Walt

 

[Tez]

However, one thing kept coming up in the show. It also was my overall impression of the book. Did you notice how they kept saying "may," "might," "could," and other wishy washy words like that? It seems to me that String Theory is one possible TOE, out of some larger number of possibilities which we haven't quantified. After someone first noticed some cool aspects of it (similarity of some QM laws with vibrating string equations, the fact that something which looks like a graviton falls out of the equations), they ran into trouble with these "anomalies." Then someone noticed that if we work in ten dimensions, it becomes self-consistent. ST proponents treat this as if it's some fundamental insight, but it could also be viewed as a kludge to the theory to give it a somewhat longer life till we find the next thing wrong with it. Now I think they're up to eleven dimensions. What's next? 42?

I think inserting such qualifiers is essential when discussing science with non-experts. When these guys are chatting with each other they don't do it! Would make the conversation somewhat dreary..

However from your comment I think that perhaps they didnt emphasize that the 3 constraints of
(i) relativity (no FTL signalling)
(ii) positive probabilities (make sure you dont predict something occurs with negative probability!)
(iii) positive energies
actually severely restricts the type of quantum mechanical theory you can devise for a non-pointlike particle. (i.e. These are the postulated ultimate physical restrictions that perhaps they werent making clear when talking about anomolies etc. ) In fact, we've found pretty much only one way of doing it, and that way is the construction we call M/string theory. Within that construction are lots of possible "particular examples" - one of which we hope corresponds to our universe. In a similar way (though not perfectly analogous) there is only one classical mechanics, we need to "fit the observations" to the specifics of the problems we want to tackle using it.

It seems quite possible to me, even likely, that we have a bunch of the brightest minds working on a dead-end path. OTOH, it's the only path we know of at this time.

This has the advantage of keeping them out of my work. ST has had a myriad of extremely useful results in many other areas of physics as well as mathematics, so it'll never be judged a complete waste of time...

Some prominent physicists (one was on the show) complain that ST will never make a testable prediction. From what it looks like to us now, we would need colliders on a scale that they never will be practical to build (and I mean never). I just can't see this panning out in my lifetime.

Personally I think this objection is bunk. If correct, ST in principle predicts things about the big bang that we should be able to observe the consequences of today. It in principle predicts the mass of the electron, which we have already observed. I say in principle, because it has proven too hard to extract such a prediction. However I doubt anyone working in ST genuinely thinks the theory will remain untested until we can build solar system sized colliders...

 

[epepke]

Gosh, I'm not sure what everyone was expecting here in just 4 50 minute episodes. Professors explaining physics equations on a classroom backboard?

At least one-quarter of the clarity of The Mechanical Universe would have been nice. Or Cosmos or The Standard Deviants or Bill Nye, the Science Guy, or even Donald Duck in Mathemagic Land, all of which rock.

I thought that they explained them selves quite well. They had nay-sayers on who complained that ST was indistuingishable from philosophy; you think you'd see that on any theology program?

The talking heads portion was one part that was done well. Except when the narrator became a talking head. That was just strange. But for most of them, they were appropriate comments, well edited. Some of the history was pretty good.

On all the countless UFO programs that saturate the airwaves?

I suppose that there is reason for an impulse to applaud just about any attempts to popularize science.

But still, it was disappointing.

 

[teddosan]

I noticed this seeming effort to continually "bend the math to make it fit" appeared to be going on. ... It sounds to me like they are just 'tuning' the strings until it fits the data. I wonder if the strings could be 'tuned' to any universe given the right number of dimensions.

That's what science is supposed to do. We constantly tune the theories to fit data. That's how progress is made. This is not something that is easy to do. They are trying to tune the theory to fit every piece of experimental data obtained. If there is one exception, then the theory must be tuned further or eventually thrown out. Both have been done to certain types of string theories a number of times. The idea is that we are closing in on one correct theory. It is important to note that if and when that is discovered, it is not the "end of physics" like some people on this thread have been labeling it.
Personally, I thought that the program last night was very good. The book goes into far more detail, but the show was designed for a wide audience. They did a great job of balancing betwen historical, scientific, and personal perspectives while keeping it entertaining. Also, for someone who is considered one of the greatest minds of our time, I was really impressed with Greene's personality. Seriously... I was expecting more of a Jarrod-from-the-Subway-commercials type...

 

[espritch]

I wasn’t too bothered with the dumbed down aspect of the show. Not being a physicist, I find these concepts rather hard enough to get my brain around, even in a dumbed down version.

I was however a little bothered by this being called a theory. I was under the impression that a theory in science isn’t just an educated guess (the "evolution is just a theory" version of the word that creationists like to drag out every so often). I was given to understand that something doesn't become a theory until it has withstood extensive testing. I am also under the impression that a valid theory should make at least some testable predictions. The thing that most struck me in the program is that String Theory doesn’t make any testable predictions. It can’t be falsified. If that is true, does it even warrant being called a theory?

 

[Tez]

I wasn’t too bothered with the dumbed down aspect of the show. Not being a physicist, I find these concepts rather hard enough to get my brain around, even in a dumbed down version.

I was however a little bothered by this being called a theory. I was under the impression that a theory in science isn’t just an educated guess (the "evolution is just a theory" version of the word that creationists like to drag out every so often). I was given to understand that something doesn't become a theory until it has withstood extensive testing. I am also under the impression that a valid theory should make at least some testable predictions. The thing that most struck me in the program is that String Theory doesn’t make any testable predictions. It can’t be falsified. If that is true, does it even warrant being called a theory?

Unfortunately common usage of the word "theory" in science does not conform to any of the standards that we'd like imposed when we're debating the True Believers! The problem is that we often construct "toy theories" - things that are meant to be self consistent/contained descritptions of some constrained (and imagined) universe. Then the word "toy" gets dropped (or is only ever understood implicitly). There are a bazillion examples of this physics - sine-Gordon Theory, Chern-Simons Theory. Sometimes the word "model" is used - this normally when the toy theory is some simplification of another theory designed to capture its essence.

Anyway, ST does make testable predictions, just not testable right now. I would rather call Evolution an empirical observation and Natural Selection a fundamental principle...

 

[CurtC]

teddosan wrote:
They are trying to tune the theory to fit every piece of experimental data obtained... The idea is that we are closing in on one correct theory.

No, my point was that the whole idea of String Theory may well be wrong, in which case all this fine-tuning it is not closing in on anything, but would be a very large waste of great minds.

However, as I admitted, it's the only good candidate we have right now. We have a bunch of bright minds in one corner of a dark parking lot, furiously looking for keys under the one street light we have.

 

[peptoabysmal]

The one point I got out of the show, in favor of string theory is that under the two current systems, the "fabric" of space is very dynamic and chaotic at very small sizes and very smooth at great big sizes. This can't be. So far, string theory is the only one which unifies the difference for gravity in both quantum mechanics and general relativity. Forgive my clumsy explanation here.

Until someone comes up with some sort of testable experiments for string theory, there will probably be lots of versions of string theory.

Personally, I think that the Inflationary Universe and String Theory folks are on to something that will lead to the real "theory of everything". I also think that one of the obstacles to progress is that many scientists can't get beyond the idea that instead of a small tangible particle, there might be just a bit of vibrating energy.

At the sizes and distances they are talking about it must be an extremely short wavelength of vibration, which I would think means a lot of energy per little "quark" or whatever. I can't help but wonder if anyone has calculated this out and found out if perhaps it is actually too much energy to match with the reality of an atom?

Anyone have a pointer to that Euler Gamma Function or whatever that sparked off the idea of String Theory? I couldn't find it earlier in a web search.

 

[Walter Wayne]

That's what science is supposed to do. We constantly tune the theories to fit data...

My problem is that I get the impression it could be attuned to any data. Like I said it is an impression, I am not well versed in the math be hand the theory. I may be wrong, but the assertion that something doesn't make a testable prediction seems to imply that it predicts anything if manipulated the right.

Walters Wave Theory
Any phenomenon can be described 2 data-points is a result of Waves intersecting and can be described by the equation below, find something that disproves my mystical waves. Any data that you come up with I can match by changing A_i and omega_i. This can be expanded to phenomenon that are described by numerous data-points but the equation begins to look messy.

I am not saying that String theory is equivalent to this, but my impression from the show was, if the theory fails, change some constants, and dimensions, change string size ... we'll curve fit it. If this is in fact the case with string theory, then I don't think it has anything more to do with the underlying mechanisms than my wave theory above.

Walt