Miscellaneous desk
< November 2	<< Oct \| November \| Dec >>	Current desk >

Welcome to the Wikipedia Miscellaneous Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 3

Understanding string theory

I had tried to know about string theory.since its information was vast i couldn't understand.can you describe about it,its application and many other simply.Thanks..me from Nepal...Diwas Sawid (talk) 15:43, 3 November 2014 (UTC)[reply]

That's because string theory is rather an arcane subject to tackle. The premise is thus: modeling the behavior of fundamental particles is tricky because their behavior follows the laws of quantum mechanics, which means that these particles do NOT behave like objects you've ever had any experience with. They do not behave like hard little balls flying through space. Instead, it turns out the behavior of these particles is better modeled as though they were standing waves; mathematically the behavior of waves is a closer match to things like electrons than the behavior of a flying ball would be. (see wave-particle duality for a bit of an explanation) The question then becomes what is vibrating to produce the wave. String theory says that the behavior is best modeled treating all particles as one-dimensional vibrating strings; where the strings vibrate into additional dimensions kinda like if you shake a rope, it can vibrate into two additional dimensions (up-down and left-right). Sting theory just uses a lot more dimensions to make the models match reality. I hope that helps a bit; the math and physics is VERY arcane, and I don't fully understand it either, but from my lay-person's understanding, that's how string theory works. Someone else may be able to explain it better. --Jayron32 15:52, 3 November 2014 (UTC)[reply]

This is quite inaccurate. In particular, the idea that the strings are "what is vibrating" to produce wave behavior is wrong. Did you see this claim in some popularization? If so, I'm curious to know which one. Strings do have vibrational modes, but that's just another form of wave behavior in physics. It doesn't explain or substitute for any of the wave behavior of quantum field theory. The first excited mode of a string should have energy comparable to the Planck energy, and since that's much larger than the rest mass of any known particle, those particles are not different vibrational modes of strings (contrary to a claim I have seen in many popularizations).

The idea that strings vibrate in additional dimensions seems somewhat misleading. They vibrate in space. If there are more than three spatial dimensions, they can vibrate in any of them, including the usual three. -- BenRG (talk) 04:10, 8 November 2014 (UTC)[reply]

I'll add that there is currently no strong and agreed-upon empirical evidence supporting the string theory or the physical existence of said strings. Some of the challenges are described at String_theory#Testability_and_experimental_predictions. The framework of string theory generally seems to work, but that doesn't mean the model is correct. Several prominent physicists have complained that focus on string theory has been a problem, [1] because it has attracted much of the talent that could have been spent in other areas. SemanticMantis (talk) 16:46, 3 November 2014 (UTC)[reply]

I'll add as well that there is no strong and agreed-upon empirical evidence in support of any explanation of the behavior of elementary particles, except for those theories whose predictions match expected behavior. The mathematics of string theory matches expected behavior, which is as good as any other explanation. We can't actually see these things in a conventional sense, so we're stuck with observing their behavior indirectly, and then finding mathematical models that match the behavior. String theory is as good as (or better than) any other model insofar as it matches observable behavior. --Jayron32 00:25, 4 November 2014 (UTC)[reply]

It's really a stretch to say that string theory matches observable behavior. It doesn't appear to predict any part of the Standard Model, and no one has even managed to show that it's consistent with the Standard Model. It "predicts" a negative or zero cosmological constant in the sense that those values are natural while a small positive cosmological constant requires a ridiculously precise artificial arrangement of branes. It predicts supersymmetry, which is broken if it exists at all in reality, and which has not been found in the energy range where it would solve the hierarchy problem. String theory seems to be flexible enough or confusing enough that it's not obviously inconsistent with any experimental data so far, but the world we observe is at least extremely unnatural from the perspective of string theory. -- BenRG (talk) 04:10, 8 November 2014 (UTC)[reply]

One very important aspect of this is to avoid coming away with the idea that there are really lots of actual strings out there doing the vibrating. That's not the idea at all. All they are saying is that the mathematics of this system of explanations behaves in much the same way as the mathematics of physical vibrating strings behave. What's TRULY going on at those scale is more or less impossible to know. SteveBaker (talk) 21:05, 3 November 2014 (UTC)[reply]

Your last sentence pretty much describes the science of physics, I think. A collection of useful descriptive metaphors (and supporting math(s)). ‑‑Mandruss ☎ 21:57, 4 November 2014 (UTC)[reply]

Your entire life is a collection of useful metaphors. You don't experience anything. You experience your brain's attempt to make sense of it. If science can be anything, it is merely the overt, collective attempt to do what your mind does to allow you to live, which is to construct models of the world that allow you to operate efficiently within it. Your brain constructs models of the world, and the useful ones allow you to work properly within the world. Science constructs models of the world that allows humanity as a whole to work efficiently within it. Science is life writ large. --Jayron32 00:30, 6 November 2014 (UTC)[reply]

Strings may not be the fundamental objects, but they're as real as, say, electrons, as far as string theory is concerned. -- BenRG (talk) 04:10, 8 November 2014 (UTC)[reply]