String theory

[kalexia]

Why is the number of dimensions in string theory so specific? Does it not seem like scientists are 'making up' the theory of extra dimensions because they cannot explain why the force of gravity is so weak compared to the other fundamental forces. The idea of miniscule undetectable universes present in our own seems to have derived from nowhere.

[Jay-qu]

Hi Kalexia, where have you been reading about string theory? it seems you have heard some little facts about it without understanding the reason behind them.

 

String Theory works by representing all the fundamental particles with strings instead of being point like. There are many versions of String Theory, some have closed stings - loops, some open, and some include more exotic forms such as branes. Im not sure if its always the case but these strings are only 2-dimensional, in order for all the particles to be described by the theory they are proposed to 'vibrate'. Different vibrational patterns give rise to different properties of the particles. It turns out that string theory requires 10 dimensions (bosonic actually needs 26..) to have solutions that result in flat spacetime like we observe.

[kalexia]

Hi. I do know these facts about string theory but I can't get my head around the compactification of several of the dimensions to make our currently existing four and that there may exist microscopic universes with more dimensions within our own.

[Qfwfq]

It is a mathematical model. It predicts nothing other than what can be evinced by other means except that it constitutes a single, self-consistent framework instead of a set of them which however get into difficulties with each other. There is nothing wrong with it, but to ask whether it is "true" is a metaphysical question as far as we currently know.

[HydrogenBond]

I don't know too much about string theory, but from a conceptual level it doesn't make sense. If we model particles in terms of 2-D strings, why does matter act in 3-D? A point mass, will exhibit gravity coming out as a sphere, with any point on that 3-D sphere the same as any other point. To compensate for using 2-D to explain 3-D, one has to add more dimensions. The 2-D approach makes sense for energy, since it moves as a particle-wave, sort of in a thin cylinder. This could be modeled with strings. If they could make the strings more 3-D, the number of dimensions should fall.

 

Let me give an example. All the colors can be made with combinations of red, yellow and blue. If we plot this as 3-D we can get all the colors on one graph. If we only use two colors at a time, to keep it 2-D, then we need 3 graphs to get just the all the two color combinations. To approximate three color combinations we need to add at least one more graph based on intermediate color combinations. For example, we can't get white or gray using only 2-D. What we need to do is make even another graph, where we takes points off the first three graphs so we can blend these for white and gray. If we make the strings more 3-D at the start, these four graphs become only one graph, lowering the number of dimensions. Those extra dimensions are a mathematical necessity, not reality.

[snoopy]

Hi. I do know these facts about string theory but I can't get my head around the compactification of several of the dimensions to make our currently existing four and that there may exist microscopic universes with more dimensions within our own.

 

 

As far as I know string theory does not allude to 'microscopic' universes within our own,

 

It alludes to other universes out there but those are full blown versions,

 

The other dimensions when curled up produce gravity as we percieve it in string theory.

 

This is actually the best reason to believe in string theory imo, it turns out that gravity is just as strong a force as the other fundamental forces but we percieve it to be so weak because of this curling up of dimensions.

 

This is a neat explanation as you start out with all the forces with more or less the same value.

 

And then you account for the weakness of the gravitational force 'exactly' by one mathematical operation.

 

Seems to good to be true....

But when things are right they feel right and this feels right to me....

even if the theory fails this part of it will survive in some form as its too good an explanation of why gravity is so much weaker than the other forces

 

Peace

:shrug:

[Little Bang]

Jay, maybe something like f=MC^2/h ?

[Jay-qu]

Jay, maybe something like f=MC^2/h ?

Whats that sorry, I dont understand your point..

[Little Bang]

You plug the mass of a particle into this equation and get it's string theory frequency.

[Jay-qu]

You plug the mass of a particle into this equation and get it's string theory frequency.

cool, I admit I am not savvy with any string theory math. I can only guess that to include all the particles into the theory it is required that more dimensions be included to describe all the vibrations fully.. :naughty:

 

im not swimming here..

[Little Bang]

It is actually derived from Planck's energy equation and Einstein's. I don't have a clue wither string theorist use it or not. But like string theory it implies that all particles are a form of electromagnetic radiation and not a particle.

[Jay-qu]

Im not saying I didnt undrstand your equation, it was the frequency of a de broglie wave -and no it doesnt imply that all particles are a form of electromagnetic radiation, its a quantum mechanical wave representation.

[Little Bang]

Yeah, your obviously right what a dumb thing for me to suggest that particles don't exist. Heresy against the standard model.

[Qfwfq]

Because, of course, only the standard model claims that particles exist. :)

[Little Bang]

I suppose the experiment at the Standford linear accelerator which produced an electron and positron by colliding two beams of EMR doesn't suggest that matter is made of electromagnetic radiation? Also, did you guys get a chance to read this? Flipping particle could explain missing antimatter - fundamentals - 18 March 2008 - New Scientist

[Qfwfq]

Pair production is not extraneous to the standard model.

[Jay-qu]

And anti-matter/matter anihilation doesnt prove that the photons created are made from particles either. Mass and energy are intertwined, but that doesnt mean that one is made out of the other.