String Theory

Alright, as I said in the Suggestions Thread, this is something that I have been interested in for just over a year now. I'm not going to try and explain the theory in detail in here as that would take too long and I wouldn't be able to do it justice, but instead I'll provide a brief overview for those who haven't heard of this or know little about it before getting to the points I wish to discuss.

Basically string theory is a relatively newish theory that is considered another contender to be the TOE (Theory of Everything). It operates on the basis that, unlike the point particles of quantum mechanics, all matter is made up of tiny, one-dimensional strings (hence the name) that oscillate in 11 different dimensions. While this may sound very far-fetched and crazy, there is actually quite a lot of supporting ideas and theories behind it that suggest this may very well be the case.

The main reason string theory has developed is because the two currently accepted theories of quantum mechanics and relativity have several flaws; the most notable being neither works on the others scale. For example, applying the rules and formulae of quantum mechanics to the macro-world delivers very unusual and often impossible results. It is this conflict between the two theories, and the fact that it is impossible to determine a point at which a clean transition from quantum to relativity takes place that led the scientific community to believe that these were not the TOE science was searching for.

As I said, I am merely providing a very brief summary of the whole topic. I highly recommend reading a book by Brian Greene entitled "The Elegant Universe". This particular book provides thorough and non-technical analysis of all of the theories I have mentioned already, as well as delving briefly into the evolving "M-Theory".

Now that I have got that out of the way, I would like to put down a few points of discussion I would like to stimulate. First of all of course is simply about string theory itself; do you think it is a feasible idea, do you disagree with it in any way, do you even think that it may be be the TOE? Also, I'd like to get some comparisons drawn between quantum mechanics/relativity and string theory; places where you might think one theory is superior to the other, where they disagree or even where they may in fact work together.



As for myself, I believe string theory could bring us as close as we have come to understanding the universe as it is, however there are several hurdles I believe that will prevent it from ever being accepted by the entire scientific community:

1. The fact that the strings are sub-Planck length, meaning that we will never be able to detect or observe them.
2. The fact that 7 extra, tightly curled and again sub-Planck length dimensions are required to get the theory to work.
3. The fact that at this stage all formulae behind string theory are approximations and as such no definitive calculations can be made, making progression very difficult.

That's simply my opinion on the whole thing, not necessarily the actual truth of it. If you would like an explanation of anything I've said in here I'd be willing to provide it, but as I said, Greene's book is by far the best and easiest to understand analysis of the whole lot that I have read.

Well, there we go. Discuss!

I recall watching that Nova about string theory a couple of times, and I have to say it's rather interesting stuff, though I hardly remember any of the details right now. >=|

Okay, so essentially, the subatomic level is not composed of subatomic particles, but subatomic strings instead? Am I getting that much right?

Also, are these strings all connected or just connected in their given unit of matter?

Yeah, now that graphic image really helps, but I'll probably need to understand physics a little better before I can really grasp this that well.

Still, it's an interesting theory, I think.

String theory has very little to do with time travel.

What it is really about is the very basic nature of the universe. String theory if correct can account for a great many things that physics can't otherwise account for. Including a possible origin for the universe otherwise known as the "M-Theory" Ajnidehs mentioned. One which dismisses the singularity theory since that theory unfortunately has a great many flaws in it.

If you're asking that question, then it's possible that you saw a Nova special on Quantum Mechanics and String Theory and perhaps got confused by a few mentions at the potential of time travel under these multiple sets of circumstances (this particular episode was alluded to earlier). While they do mention the theoretical methods of time travel, they are unrelated to String Theory and Quantum Mechanics (as Koloth pointed out).

At least, that was the case with me for a short while (I was terribly sleepy during that class). I have very limited knowledge on String Theory (and Quantum Mechanics, for that matter), but from what I have read and seen it does seem a reasonable theory, at least when compared to the flaws found in previously existing theories on Quantum Physics.

quote Foxtrot493

so are these strings supposed to be massless, dimensionless peices of the fabric of the space-time continuum, or are they massive, quantitative tangibles that can be measured, given the accurate technology?

They are one-dimensional strings that can exhibit both open ('straight' line) and closed ('circular' loop) forms. They are extremely small (sub-Planck length in fact) and as such it will never be possible to confirm or deny their existence (convinient, isn't it) as we cannot conceivably probe anything smaller than the Planck length. I am not sure whether they are considered massless or not, but I think that they are, seeing as some strings can represent massless particles (like the graviton).

quote Rome

but I'll probably need to understand physics a little better before I can really grasp this that well.

This is again where I recommend Greene's book. The first few chapters completely explain modern physics (quantum mechanices/relativity) and their history to provide the required background knowledge before diving into the intricacies of string theory.

quote luffyluffy

and it turns out the doctor had a theory that time was like a string and if you loop it you could travel within your own lifetime

One thing I thought of when I read this was that it could be a possibility, but only if one of the tiny, curled dimensions I refered to before was another time dimension rather than a spacial one. As it stand, we live in a world with four dimensions; three spacial and one time. We assume these are all linear rather than curled simply because it is unlikely that if we head in one direction through the universe and do not deviate from that direction we will not end up back where we started (however, they could be curled but have such an infinitely large radius that they appear linear to us). Getting back to the time travel thing, if this tiny, curled time dimension were for some reason to expand to such a size that we could travel through it, then technically in that time dimension we could travel in a loop and return to a previous instance in time; however, such a concept is almost incomprehensible as it implies us living in two separate time dimensions.

However, that is merely an interesting, if highly inlikely, possibility that may very well be, and probably is, incorrect. In the terms of string theory itself however, as both Koloth and Fatal Error have said, it has no real roots in time travel; it is an attempt at creating the TOE, which is like the Holy Grail of physics.