## 0171: "String Theory"

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I admit I know next to nothing about the subject, and thus this isn't a rhetorical question.

If string theory is untestable because different values of its parameter space make lots of things possible, why not test the hypothesis "String theory is true, and these parameters are in the following ranges..."?

FiddleMath

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FiddleMath wrote:If string theory is untestable because different values of its parameter space make lots of things possible, why not test the hypothesis "String theory is true, and these parameters are in the following ranges..."?

It's a subtle problem, and there's value in doing what you suggested, but as far as the big picture, it's the structure of String Theory that's important, and part of the structure of String Theory is the size and character of its parameter space. In the end, you can't really place much credence on String Theory if you cannot verify and to some extent explain that integral part of the structure. Now, you might be able to get sufficiently far by examining the string-fine structure of our universe's specific parameters, but at this point the only conjectured experiments to do this require vast amounts of energy far, far beyond our current capability.
BellPsyc

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### Re:

zombie_monkey wrote:You know those "science" books with ridiculous names that make you cringe when poeple talk about them? I've never managed to make myself consider it seriously, even though it was widely publicised -- the tone was always too similar to that kind of pseudosience. Now it seems my intuition was right, as it's soon to go out of fashion even among the kind of people who buy such books.

I think the "pseudoscience" thing is exactly the problem with string theory.

It's like the old alchemy. Of course there was a philosophic mercury. It was proven...it's just that the other proofs used a bunch of other assumptions that aren't true. Such as "Nothing except the philosophic mercury can be heavier than gold." (If this sounds interesting, read the Baroque Cycle)

This is sort of the same thing. You make assumptions that only work in string theory...then you use them to prove string theory. It's circular.

And then there's things that, as far as I know, they haven't even tried to prove. "The strings are ten dimensional." Why 10? A random number generator said so? It was a nice, round number? You pulled it our of a hat? That just reduces the credibility of the theory.
Don't you hate signatures like this:

If you have no originality, copy this into your signature...and have a signature no different from lots of other people! Kind of defeats the point of sigs.
Tolchok

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### Re: Re:

Tolchok wrote:And then there's things that, as far as I know, they haven't even tried to prove. "The strings are ten dimensional." Why 10? A random number generator said so? It was a nice, round number? You pulled it our of a hat? That just reduces the credibility of the theory.

Because for the math to work, it turns out that the strings have to vibrate in more ways than a 3+1 dimensional universe would allow.

One way to add these extra vibrations would be to place the strings in a higher dimensional space -- and 10 happens to be the lowest one that is consistent with that model. (there are higher dimensional universes which also solve it, but by occam you pick the simplest one)

As a side effect, those extra dimensions provide us with a possible test for string theory. If they are macroscopic and (say) gravity isn't bound to the same brane as the other forces, then we end up with some interesting gravity artifacts at low scales that do things like predict lower energy densities can produce a black hole and the like.

So those are tossed out there as an interesting possibility that, if found, restricts the solution space.

What is also interesting is that the 'shape' of these higher dimensions might produce interesting observable effects on the kinds of string vibrations, and string vibrations are kinds of particle, so ... you can talk about how 'shape' of these higher dimensions might be tied to the particular kinds of particles that can exist (thus predicting the properties of fundamental particles... something that people would love to be able to do ... hopefully using fewer parameters)

Of course, as yet, string theory has not produced a prediction that is inconsistent with the standard model, nor has it produced restrictions on parameters beyond the standard model, at least as far as I know.
One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision - BR

Last edited by JHVH on Fri Oct 23, 4004 BCE 6:17 pm, edited 6 times in total.

Yakk

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### Re: Official "String Theory" Discussion

A bit of a bump (for which I apologise), but UCL's physics faculty apparently agrees with Randall.

Spoiler:

(bad pic quality because of trying to take it surreptitiously on my phone. Also, I suck at photography.)
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Endless Mike wrote:The military wrote custom PS3 software and bought a bunch of them for some very specific application.

A modern warfare lan party, duh.
The1exile

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### Re: "String Theory" Discussion

geoffm

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### Re: "String Theory" Discussion

The String Theory implies that there is hope in explaining the incompatible physics. But it's not testable, and they're still working on discovering it. Yeah, sounds like gold alchemy to me.

I think that this physics problem will persist unless humanity learns to travel 2 lightyears.

tastelikecoke

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### Re: 0171: "String Theory"

buz

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### Re: 0171: "String Theory"

The next time I hear Brian Greene speak, I'm going to be on the edge of my seat waiting for him to use the word "dunno."

rhomboidal

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### Re: 0171: "String Theory"

Thank you. So cute. Thank you for the tip. 49th minute.

Lonely, ignorant but dominant? Really?

Oh. Right? If, there are humans in the distance, then, they will have a different view. We they be able to see us?

http://en.wikipedia.org/wiki/Antoni_Gau ... _his_style

I watched a recorded lecture inside one of these buildings. The lecture stated, "All building become ruins. We are building beautiful ruins."

Those guys studied ruins. Then, they designed buildings that are cool now and will be cool when they fall apart or are bombed. That is a long view.

The view that there will come a day when we can not see stars that are outside the Milky Way, is, a long view, too.
We have lot of stars here in our local galaxy.
Life is, just, an exchange of electrons; It is up to us to give it meaning.