descenterace on 12/7/2006 at 06:37
The sticking point is visualisation, AM. They can't visualise a ten-dimensional topology and therefore can't reconcile it with the three dimensions we perceive. Visualisation is limited by perception, and our perception is limited by our experience and senses.
Applying mathematics to a problem such as this renders perception irrelevant. Of course it's not going to be possible to visualise that many dimensions. That does not mean that the theory is wrong; it just means that we are very limited creatures.
It doesn't automatically mean the theory is right, either, but String Theory has so far stood the test of time quite well and is one of the only cutting-edge tools we have in the field of particle physics.
String Theory first appeared sometime back in the 70s, but didn't catch on immediately because it didn't come close to matching the results. At the time it was being applied to hadrons only.
When other bosons were incorporated, it became more accurate and finally matched experimental data. It became Bosonic String Theory and described a 26-dimensional universe.
When bosons were mathematically linked to fermions (a link known as supersymmetry), Superstring Theory was born.
In the mid-eighties, physicists found that Superstring Theory could explain all particle and field interactions. Previously, each particle family had its own theories to describe its behaviour. Superstring is simpler, more general, and at least as accurate as that which came before. It is a better theory. It dealt with a ten-dimensional universe (necessary to fully describe the way in which the strings moved).
However, there were five different, irreconcilable (within the constraints of ten dimensions), but equally valid Superstring variant theories out there. All
In the 90s, those theories proved to be limits of one eleven-dimensional theory later called M-Theory. Another simplification, generalisation, and refinement. A better theory.
Superstring and M-Theory are just theories. Bosonic String Theory involved 26 dimensions; are we to assume that the universe is 26-dimensional? It was a requirement of the mathematics. The important point is that the theory simplified with generalisation and did not lose accuracy in the process. It is an elegant mathematical description of everything we know about the very basis of our universe.
Whether or not the fundamental particles actually are n-dimensional strings and branes is irrelevant; their behaviour is currently best described as if they were, and that's the point of a mathematical model.
Superstring is not the only cutting-edge theory, and at the moment the standard particle model is adequate for our needs. The interesting thing about it is that it is a Unified Theory and it predicts some amazing things about the Universe. It will likely be made or broken in the next thirty years.
Raven on 12/7/2006 at 09:30
Quote:
and at the moment the standard particle model is adequate for our needs
yeah, but it i soooo messy. It is akin to the big bang theory of cosmology - sticking on more bits till it fits your results is not good science okay!
Pyrian on 12/7/2006 at 22:39
String Theory has never made an experimentally verified prediction. So far, it fails to be falsifiable. Statements like "there are quantum phenomena,
measureable quantum phenomena, that 3-dimensional models cannot explain" strike me as grossly premature.
If it made the same predictions as the standard model but did so with a simpler theory, that could well be regarded as worthwhile. However, that too is an overstatement: many of the predictions of string theory have never been solved, and they certainly aren't known for being simple! More unified, yes, but is that really a function of the theory or just a function of its proponents' hopes? I.e., until it becomes vastly more testable, we can't really know if it provides a GUT or turns out to be just as messy as everything else... And if I were a betting man, I'd lay money on messy.
Quote:
...but String Theory has so far stood the test of time quite well...
So has god, and for much the same reason: it appears to explain things and it's not possible to prove it wrong.
Now, don't get me wrong, there's a lot of interesting hypotheses in String Theory and I suspect some of them
will be borne out... And many of them will not. Physicists have always sought to explain disparate phenomena with common rules, and while many fascinating breakthroughs have come of such work, I'm not holding my breath for a GUT.
Deep Qantas on 12/7/2006 at 22:47
Quote Posted by descenterace
It doesn't automatically mean the theory is right, either, but String Theory has so far stood the test of time quite well and is one of the only cutting-edge tools we have in the field of particle physics.
Hmm. I actually thought String Theory was a new hip and cool in-the-works and incomplete thing. I mean they can't even agree on the number of dimensions yet, can they?
In any case, I'm just saying this because that's the image I got. I really haven't been following the latest in quantum mechanics.
Agent Monkeysee on 13/7/2006 at 01:44
Quote Posted by Pyrian
String Theory has never made an experimentally verified prediction. So far, it fails to be falsifiable. Statements like "there are quantum phenomena,
measureable quantum phenomena, that 3-dimensional models cannot explain" strike me as grossly premature.
I think you're mixing up explanation vs. prediction. It is a quite simple fact that there are quantum phenonema that just arbitrarily *are* under the Standard Model but are actually provided an explanation in String Theory. However String Theory doesn't predict these phenomena, we've already known of them before String Theory.
The sort of things String Theory *does* predict are thus far outside our ability to experimentally verify, which makes it, practically speaking, unfalsifiable and therefore not a
true scientific theory.
descenterace on 13/7/2006 at 06:23
At the moment it's liitle more than a mathematical theory, rather than a physical theory. The maths is correct, but we don't know if it's a usable model of the Universe. IIRC the only verifiable stuff it predicts is handled easily by other theories.
It's been around for twenty years and has certainly opened up new avenues of thought, so even if it turns out to be wrong it will have had some value.
Pyrian on 13/7/2006 at 22:31
Quote Posted by Agent Monkeysee
I think you're mixing up explanation vs. prediction.
I think that explanation in the absence of predictive value isn't an explanation at all.
Quote Posted by Agent Monkeysee
It is a quite simple fact that there are quantum phenonema that just arbitrarily *are* under the Standard Model but are actually provided an explanation in String Theory.
An explanation which itself rests on things that just arbitrarily are... I will now repeat myself: "I.e., until it becomes vastly more testable, we can't really know if it provides a GUT or turns out to be just as messy as everything else... And if I were a betting man, I'd lay money on messy."
Agent Monkeysee on 14/7/2006 at 01:18
Quote Posted by Pyrian
I think that explanation in the absence of predictive value isn't an explanation at all.
String Theory doesn't lack predictive value; it makes plenty of predictions, we just can't test for them. I realize that sounds like a difference without a distinction but it's a big deal. Given two equally arbitrary explanations the one that provides measureable predictions, even if only theoretically, is superior to one that provides no predictions.
String Theory provides explanatory power for phenomena that the Standard Model doesn't. It suggests directions to take research. The fact that we don't have the technology to do it isn't a mark against the theory unless we come up with something else with equal or better explanatory power and makes predictions that we can test now. But until then the choice is between String Theory and *nothing*. Clearly String Theory is superior.
Quote Posted by Pyrian
An explanation which itself rests on things that just arbitrarily are... I will now repeat myself: "I.e., until it becomes vastly more testable, we can't really know if it provides a GUT or turns out to be just as messy as everything else... And if I were a betting man, I'd lay money on messy."
I've never claimed otherwise.
thefonz on 15/7/2006 at 20:20
Where the hell is Steven Hawking when we need him?
Probably off shagging his nurse in ten dimensions!
oh god, i'm sorry - the man is a genius and suffers a heck of alot.
frozenman on 17/7/2006 at 06:17
What the hell does it mean if the universe is curved or torus-shaped? If you walk all the way past the left edge of the screen you pop out on the right?
