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Author Topic: Is There any Evidence for String Theory?  (Read 4258 times)

Heronumber0

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Is There any Evidence for String Theory?
« on: 08/07/2007 00:26:30 »
This one puzzles me. There is so much information about this topic that I feel a bit nervous.  However, is there a shred of scientific evidence to back up the theory that the fundamentals of the Universe are made of energy strings?

Would love to hear otherwise. [?]


 

Offline tony6789

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Is There any Evidence for String Theory?
« Reply #1 on: 08/07/2007 17:18:37 »
string theroy?
 

Offline DoctorBeaver

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Is There any Evidence for String Theory?
« Reply #2 on: 08/07/2007 19:50:41 »
There is no current evidence. However, when the LHC (Large Hadron Collider)at CERNE comes online it may detect particles that are predicted by some theories.

Present colliders only work at a few hundred GeV whereas the LHC will operate at 1TeV (1000GeV). Some particles predicted by string theory should then become detectable. If they do, it won't necessarily prove that string theory is correct; but it will certainly give strong indication that the theory is on the right lines. Conversely, if those predicted particles are not detected, that will not necessarily mean that string theory is wrong; merely that certain aspects will need looking at again.

Strings themselves, if they exist, are far too small (10-33cm) for us ever to measure or even detect directly as the energy required to probe such minute distances would be such that the energy itself may well be enough to collapse into a micro-blackhole. It is certainly way beyond any energy level we could ever hope to create.
« Last Edit: 08/07/2007 19:56:29 by DoctorBeaver »
 

Offline DoctorBeaver

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Is There any Evidence for String Theory?
« Reply #3 on: 08/07/2007 19:54:51 »
string theroy?

String theory states that particles are the result of oscillations of incredibly small open or closed strings (closed strings are loops).

For string theory to work there must be 10 dimensions (Ed Witten proposed that 10-dimensional string theory is actually the same thing as 11-dimensional supergravity), rather than the 3 spatial and 1 temporal dimensions that we are aware of.

You may find this link informative...
[url]http://www.damtp.cam.ac.uk/user/gr/public/qg_ss.html[url]
« Last Edit: 08/07/2007 21:39:05 by DoctorBeaver »
 

Offline Soul Surfer

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Is There any Evidence for String Theory?
« Reply #4 on: 08/07/2007 23:52:34 »
The simplest models of particles as points fail at the highest energies because they involve all sorts of awkward infinities in the mathematics.  like saying one divided by zero. 

A good example of this is the inverse square law of gravity and electric charge as you get closer to an infinitely small point particle the field increases without limit and theory becomes meaningless.

Having your particles described in terms of finite and irreducible sized elements can get round this.  In the simplest form these are one dimensional strings but other versions use two or more dimensional membranes "branes".  This could of course include simple spherical surfaces like balloons.  Various numbers of "dimensions" up to around 32 have been proposed but around 10 to 11 are currently preferred.  These dimensions could be  like having more dimensions in space but they could be like the the real and imaginary numbers commonly used in wave analysis  just a mathematical artifice that allows the sums to work.  They could also be simple descriptors that create a property like electrical charge.

As has already been said to resolve these properties using "microscopes" (particle accelerators) is very likely to be far beyond human resources but there may be extreme conditions in collapsing stars and or the early universe where confirmation may be observed.  However this will require a very careful analysis of predictions of very many alternative models.
 

Heronumber0

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Is There any Evidence for String Theory?
« Reply #5 on: 09/07/2007 20:14:50 »
Quote
The simplest models of particles as points fail at the highest energies because they involve all sorts of awkward infinities in the mathematics.  like saying one divided by zero. 

Thanks for this. Is this the classical model of particles we are talking about?

Quote
A good example of this is the inverse square law of gravity and electric charge as you get closer to an infinitely small point particle the field increases without limit and theory becomes meaningless.

Having your particles described in terms of finite and irreducible sized elements can get round this.  In the simplest form these are one dimensional strings but other versions use two or more dimensional membranes "branes".  This could of course include simple spherical surfaces like balloons.  Various numbers of "dimensions" up to around 32 have been proposed but around 10 to 11 are currently preferred.  These dimensions could be  like having more dimensions in space but they could be like the the real and imaginary numbers commonly used in wave analysis  just a mathematical artifice that allows the sums to work.  They could also be simple descriptors that create a property like electrical charge.

This is what I wondered, are 11 dimensions real or just brought out of the blue like Penn and Teller to fit the figures?

Quote
As has already been said to resolve these properties using "microscopes" (particle accelerators) is very likely to be far beyond human resources but there may be extreme conditions in collapsing stars and or the early universe where confirmation may be observed.  However this will require a very careful analysis of predictions of very many alternative models.

Is this what the search for the elusive Higgs Boson is all about? Would that prove that particles exist as one dimensional strings?
Thanks for the response.  I can't stop thinking now...
 

Heronumber0

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Is There any Evidence for String Theory?
« Reply #6 on: 09/07/2007 20:19:09 »


Present colliders only work at a few hundred GeV whereas the LHC will operate at 1TeV (1000GeV). Some particles predicted by string theory should then become detectable. If they do, it won't necessarily prove that string theory is correct; but it will certainly give strong indication that the theory is on the right lines. Conversely, if those predicted particles are not detected, that will not necessarily mean that string theory is wrong; merely that certain aspects will need looking at again.

Strings themselves, if they exist, are far too small (10-33cm) for us ever to measure or even detect directly as the energy required to probe such minute distances would be such that the energy itself may well be enough to collapse into a micro-blackhole. It is certainly way beyond any energy level we could ever hope to create.

Thanks for the response.  Doesn't scientific method fall apart if something can be neither proved nor disproved?
 

Offline DoctorBeaver

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Is There any Evidence for String Theory?
« Reply #7 on: 09/07/2007 20:22:45 »
If string theory turns out to be correct, then the extra dimensions are real. They could be curled up so small (compactification) that they are invisible, or they could be infinite but still invisible to us (the reasons for that are a bit complex and would need a separate thread).

The Higgs boson is supposedly the particle that gives certain gauge bosons (force-carrying bosons) their mass. Check out the Wiki article http://en.wikipedia.org/wiki/Higgs_boson. That explains it pretty well.
« Last Edit: 09/07/2007 20:26:52 by DoctorBeaver »
 

Offline DoctorBeaver

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Is There any Evidence for String Theory?
« Reply #8 on: 09/07/2007 20:23:30 »


Present colliders only work at a few hundred GeV whereas the LHC will operate at 1TeV (1000GeV). Some particles predicted by string theory should then become detectable. If they do, it won't necessarily prove that string theory is correct; but it will certainly give strong indication that the theory is on the right lines. Conversely, if those predicted particles are not detected, that will not necessarily mean that string theory is wrong; merely that certain aspects will need looking at again.

Strings themselves, if they exist, are far too small (10-33cm) for us ever to measure or even detect directly as the energy required to probe such minute distances would be such that the energy itself may well be enough to collapse into a micro-blackhole. It is certainly way beyond any energy level we could ever hope to create.

Thanks for the response.  Doesn't scientific method fall apart if something can be neither proved nor disproved?

Absence of evidence is not evidence of absence. There are theoretical considerations that indicate string theory is a good candidate for the way things really are. Yes, there are holes in it; but as the theory is further developed and, possibly, indirect evidence is found, the stronger its claim to validity becomes.
« Last Edit: 09/07/2007 20:26:01 by DoctorBeaver »
 

Heronumber0

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Is There any Evidence for String Theory?
« Reply #9 on: 09/07/2007 20:31:54 »
If string theory turns out to be correct, then the extra dimensions are real. They could be curled up so small (compactification) that they are invisible, or they could be infinite but still invisible to us (the reasons for that are a bit complex and would need a separate thread).

The Higgs boson is supposedly the particle that gives certain gauge bosons (force-carrying bosons) their mass. Check out the Wiki article http://en.wikipedia.org/wiki/Higgs_boson. That explains it pretty well.
Thanks Doc, I will check out the article.  Does it mean that when I raise an arm, I could be passing through the start and end of these extra dimensions? 
 

Offline DoctorBeaver

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Is There any Evidence for String Theory?
« Reply #10 on: 09/07/2007 23:26:12 »
If string theory turns out to be correct, then the extra dimensions are real. They could be curled up so small (compactification) that they are invisible, or they could be infinite but still invisible to us (the reasons for that are a bit complex and would need a separate thread).

The Higgs boson is supposedly the particle that gives certain gauge bosons (force-carrying bosons) their mass. Check out the Wiki article http://en.wikipedia.org/wiki/Higgs_boson. That explains it pretty well.
Thanks Doc, I will check out the article.  Does it mean that when I raise an arm, I could be passing through the start and end of these extra dimensions? 

That's a tricky 1. Compactified dimensions are trillions of times smaller than a hydrogen atom (the smallest atom there is) so there is no way any atom could pass through 1. However, the particles comprising those atoms would be made of strings which are of a similar, if not smaller, size then the compactified dimensions so they could pass through.

Just as at any point in space the "normal" 3 dimensions are all around you, so are the extra dimensions; it's just that we can't perceive them due to their size.

I mentioned in my previous reply that dimensions of infinite size could also be invisible. The thinking behind that is that there could be what are known as branes on which particles and forces are confined. So, our 4-dimensional (3 spatial, 1 temporal) universe could be situated on 1 of these branes. All the particles and forces in our universe would be trapped on the brane (with the exception of gravity, which is free to move in the bulk and on other branes). The brane could be situated in a higher-dimensional universe, known as the bulk, which would contain more branes than just ours. For reasons I won't go into here, if the bulk is warped it could be infinite but not visible to us. The branes may, or may not, be the boundaries of the higher dimensions of the bulk.

This theory (conceived by Randall & Sundrum) does not involve strings, just particles & forces. The particles that comprise our bodies are fundamental and confined to our brane. As such, there is no way that waving your arms would mean that any particles in your body would pass through an extra dimension.

Just to add an interesting thought here; there is another theory (by, I believe, Steven Hawking among others) involving what are known as baby universes. These are universes that could spring from our own into other dimensions and so be invisible to us. You could have 1 of these expanding from a point in your underpants right now and you would never know it!

By the way, I'm not a physicist, I just take an amateur interest in the subject. People such as SoulSurfer, another_someone and chrisdsn could explain these theories better & in more detail than I can.
« Last Edit: 09/07/2007 23:35:01 by DoctorBeaver »
 

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Is There any Evidence for String Theory?
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