String Theory

[TobiasTheViking]

It is important to note that string theory is a popular hypothesis but has not been "officially" accepted because it is impossible to directly or indirectly observe a string. At least for right now.

The calculations involved describe the universe very well but will remain nothing but interesting mathmatical constructs until someone can figure out a way to detect a string.

I remember that at the end of "The Elegant Universe", the author suggests possible observations that would lend credibility to the idea. Unfortunately, all are technologically impossible.

I actually wrote this in my first post in this thread.

M-Theory can't make any prediction at all so far, thus it is a philosophy, not a theory.

but, KingMerv00, in "The Elegant Universe" they did talk of a few possible observations, as you mentioned, and some of them should be testable within the next 10 years or so.

Specificly Supersymmetry, and the finding of the gravitron would prove M-Theory, if i remember correctly, i may be wrong on supersymmetry.

With the new accelerators currently being build, they might be able to find the gravitron.

As far as i know the gravitron is a lot smaller than the messenger particles currently found(and predicted in Quantum Physics), which is one of the reasons it haven't been observed yet.

With the new accelerators we may be able to get enough speed, and big enough resolution, to observe the gravitron.


Again, i am fairly certain that either supersymmetry or the gravitron will prove M-Theory. But i may be wrong, and both can also validate other theories. Thus we end up with more than one theory they fit, and we are no closer to a real M-Theory.

Sincerely
Tobias

As always, i may be incorrect.

 

[Bronze Dog]

I'm no expert on all the tiny particles out there, but I like to try to keep up:

By "messenger particles", I take it you're talking about strong gluons, weak bosons, electromagnetic photons, and the hypothetical gravitons/gravitrons? Do they have antiparticle counterparts like their bigger cousins?

 

[TobiasTheViking]

I'm no expert on all the tiny particles out there, but I like to try to keep up:

By "messenger particles", I take it you're talking about strong gluons, weak bosons, electromagnetic photons, and the hypothetical gravitons/gravitrons? Do they have antiparticle counterparts like their bigger cousins?

Messenger particles are particles for the 4 forces.

Electro magnetic
Strong force
Weak force

Those three have been found.

The fourth one
gravity
is in M-Theory, but it is, to my knowledge much much smaller than the other forces messenger particles.

It also have no weight.. at all, not sure if the other messenger particles have weight.

As for antiparticles... i believe that is "Supersymmetry"

 

[TobiasTheViking]

One of the predictions of string theory is that at higher energy scales we should start to see evidence of a symmetry that gives every particle that transmits a force (a boson) a partner particle that makes up matter ( a fermion), and vice versa.

http://www.superstringtheory.com/experm/exper4.html


Which i believe is what we can prove with the next generation accelerators.

But yes... as yet, it is still a philosophy, not a theory.

 

[Dorman]

As for antiparticles... i believe that is "Supersymmetry"

No. Antiparticles of the force-carrying particles are other force-carrying particles. Some force-carrying particles, like photons, are antiparticles of themselves. These antiparticles have been found already.

Supersymmetry, that's a whole another ballgame and new undiscovered particles.

 

[TobiasTheViking]

No. Antiparticles of the force-carrying particles are other force-carrying particles. Some force-carrying particles, like photons, are antiparticles of themselves. These antiparticles have been found already.

Supersymmetry, that's a whole another ballgame and new undiscovered particles.

that is what i tried to say in the message just above yours.. i realized i was wrong when i looked at the page in the link.

Sorry i didn't make myself clearer

 

[CurtC]

It is important to note that string theory is a popular hypothesis but has not been "officially" accepted because it is impossible to directly or indirectly observe a string. At least for right now.

The calculations involved describe the universe very well but will remain nothing but interesting mathmatical constructs until someone can figure out a way to detect a string.

It shouldn't be required that they detect a string, which I think is pretty much impossible with the energies that we're limited to, but if string theory could actually be used to make a prediction, we could see if that prediction came true. The problem as I understand it is that string (and M) theory is a big squishy ball at this point that can, with great effort and lots of simplifying assumptions, be made to predict just about anything. We can't nail it down to figure out something specific that it would predict at the exclusion of other possible results. This seems to me to be its potential downfall. I'm glad all these really bright people are at least trying, but it doesn't seem like a very useful discipline if it's just a philosophy and can't be used to predict something that we can possibly measure.

 

[Soapy Sam]

I can't get my head around the "tiny" dimensions.

In my view, dimensions are a property of the universe, not of objects within the universe.
A brick does not "have " three spatial dimensions; It simply exists in a universe which has three spatial dimensions.
The dimensions are not properties of the brick and do not stop at the surfaces of the brick. They are continuous.

The Elegant Universe (book) seems to imply that these dimensions are properties of the strings, rather than the universe in which the strings exist.

What I would like to understand is where those tiny dimensions are between the strings. Does every point in spacetime have 7 extra tiny dimensions? But points, surely are dimensionless. Isn't that the point of points?

Space (spacetime) appears to be continuous. For tiny dimensions to exist within the spacetime universe, it seems they must be discontinuous. We therefore do not need just 7 tiny dimensions. We need trillions of them. Or, if we have 7 infinitesimally small dimensions, they must be outside space time, possibly in a coffee jar on the garage wall of the gods?

 

[Tony]

Its been five years and I am still fascinated by this idea. In that time I've done a bit more reading and viewing. More questions remain though.

Why does the idea of strings necessitate the existence of more dimensions?

What about branes? If strings make up quarks and gluons? How are they attached to branes? What are these branes and where are they?

Where do gravitons come from?

If string theory is correct, does this mean that we can (theoretically) change they way strings vibrate and design new sub atomic particles?

 

[Modified]

I can't get my head around the "tiny" dimensions.

In my view, dimensions are a property of the universe, not of objects within the universe.
A brick does not "have " three spatial dimensions; It simply exists in a universe which has three spatial dimensions.
The dimensions are not properties of the brick and do not stop at the surfaces of the brick. They are continuous.

The Elegant Universe (book) seems to imply that these dimensions are properties of the strings, rather than the universe in which the strings exist.

What I would like to understand is where those tiny dimensions are between the strings. Does every point in spacetime have 7 extra tiny dimensions? But points, surely are dimensionless. Isn't that the point of points?

Space (spacetime) appears to be continuous. For tiny dimensions to exist within the spacetime universe, it seems they must be discontinuous. We therefore do not need just 7 tiny dimensions. We need trillions of them. Or, if we have 7 infinitesimally small dimensions, they must be outside space time, possibly in a coffee jar on the garage wall of the gods?

I know nothing about string theory, but I've always assumed the extra dimensions were properties of the universe, and that the universe was closed (and very small) in those dimensions.

 

[Skwinty]

I remember that at the end of "The Elegant Universe", the author suggests possible observations that would lend credibility to the idea. Unfortunately, all are technologically impossible.

There was, if i recall correctly, that we may see superstrings with more advanced telescopes.

I think Witten made this fanciful remark.

 

[Beerina]

Nope.. nothing to do with traveling at the speed of light/time slowing down.

String theory have 10 dimensions.

M-Theory have 11 dimensions.

In M-Theory we have 3 (x,y,z) +1(time) = 4.

Thus 7 left we can't see.

Imagine looking at a power line from far far away. it only have one dimension(left, right).

Imagine you are an ant on the power line, now you have another dimension(clockwise counterclockwise).

From a distance you can't see the "around" dimension... because it is too small.


Imagine blowing an atom up to the size of the solar system.. Then those 7 dimensions left, would be about the size of a car.. or a tree. That is how small they are.

The strings move within those 7 dimensions, and acording to the form of those dimensions they have a specific frequency.
That frequency makes it into.. an electron, a photon, a gravitron.

Everything is made up of those strings.... everthing...

Their frequency desides what they do/are.

Their frequency is dictacted by the 7 dimensions(how they are formed).


Of course... i may remember something incorrectly. But.. That is how i remember it.


Sincerely
Tobias

Sounds almost like a programming language. Do the particles fall out naturally from it?

 

[arthwollipot]

I can't call myself an expert, but string theory is something I've looked into a fair bit, and I'll try to answer your questions.

Why does the idea of strings necessitate the existence of more dimensions?

Because the mathematics doesn't work any other way. That's pretty much it.

What about branes? If strings make up quarks and gluons? How are they attached to branes? What are these branes and where are they?

A brane is a string with an additional dimension. If you think about an ordinary piece of string, then think about one of those wide rubber bands, you're kinda getting the idea. A brane is like a ribbon, but it works in basically the same way as a string.

Where do gravitons come from?

Good question. A graviton is a fundamental particle, like a quark or a neutrino. One reason that string theory is very attractive to physicists is that although there are many different formulations of string theory (which are all different ways of expressing M-theory), all of them include the graviton. You can't have a string theory without the graviton being predicted by it.

If string theory is correct, does this mean that we can (theoretically) change they way strings vibrate and design new sub atomic particles?

Yep. Although how we might attempt to do such a thing is, as yet, unexplained.

 

[alfa1]

The energy of the string is huge: minimum energies of strings are actually couple times of the Planck energy(more than billion x billion time of a proton energy).
The question is how such strings with such huge energy generate 'small energy' particles like electrons, protons...?
It's like using mountains to build small rocks!

 

[arthwollipot]

Not really. The strings are under extreme tension. The kind of tension that makes a piano string look slack. Also, the "energy" of the particle (exactly what do you mean by that?) is not directly correlated to the "energy" of the string.

 

[alfa1]

"energy" of the particle. energy of a rock - Einstein formula

 

[alfa1]

If you know the answer you know string theory!

 

[Ririon]

I prefer this explanation.

 

[sol invictus]

I can't get my head around the "tiny" dimensions.

In my view, dimensions are a property of the universe, not of objects within the universe.
A brick does not "have " three spatial dimensions; It simply exists in a universe which has three spatial dimensions.
The dimensions are not properties of the brick and do not stop at the surfaces of the brick. They are continuous.

The Elegant Universe (book) seems to imply that these dimensions are properties of the strings, rather than the universe in which the strings exist.

What I would like to understand is where those tiny dimensions are between the strings. Does every point in spacetime have 7 extra tiny dimensions? But points, surely are dimensionless. Isn't that the point of points?

Space (spacetime) appears to be continuous. For tiny dimensions to exist within the spacetime universe, it seems they must be discontinuous. We therefore do not need just 7 tiny dimensions. We need trillions of them. Or, if we have 7 infinitesimally small dimensions, they must be outside space time, possibly in a coffee jar on the garage wall of the gods?

There are (at least) two distinct questions in there:

1) can there be tiny dimensions?

2) are dimensions made of strings?

To understand 1) (the answer is yes), forget about strings. As you said, such dimensions would be everywhere - a property of the universe, not the objects within it. The tiny dimensions in string theory can be thought of that way too.

As for 2), if string theory is correct, spacetime is in a sense made of strings, but those strings are smeared everywhere in a quantum superposition. It analogous to the way a constant electric field is made of photons. So all dimensions - not just the tiny ones - are made of strings, but not in the way you had in mind. Then on top of that there can be individual strings flying around (just as there can be individual photons passing through an electric field), but they only slightly alter the geometry created by the others (just as the photon only slightly alters the electric field in its vicinity).

 

[arthwollipot]

Remember, even in the Standard Model, we are constantly bathed in a soup of photons, neutrinos and potentially gravitons. This has something to do with something called "quantum field theory" that someone much smarter than me will have to explain.