Was all the matter of the universe created at the time......

[peter]

The problem re testability is not so great if the theorys are invariable to a high degree. A good scientific explanation has the quality of being very difficult to vary ie to tweak to accomodate new facts as they arise - if these fly in the face of the explanation then good ones rapidly need to be abandoned where poor ones will alow alteration to accomodate the new data.

[Hashi Lebwohl]

No, those extra dimensions are quite "real" even though we probably won't ever be able to detect or interact with them--they are either too close or too small. That is M-Theory's most drastic downfall--it is untestable and thus non-verifiable.

Hahaha, and therefore not readily distinguishable from the imaginary.

--A

That is how things are from time to time. Consider gravity. You can't measure or detect gravity itself, only gravity's effects on things yet we know that it is real.

Mathematically it can be shown that those extra dimensions are real--well, at least until a better theory comes along--but we won't ever be able to test them directly as far as I know.

[Vraith]

The problem re testability is not so great if the theorys are invariable to a high degree. A good scientific explanation has the quality of being very difficult to vary ie to tweak to accomodate new facts as they arise - if these fly in the face of the explanation then good ones rapidly need to be abandoned where poor ones will alow alteration to accomodate the new data.

Yea, if they can both make predictions and account for/explain new data when it comes in, it's a pretty powerful theory.
That's one of the break-throughs/advantages of the M-like theories...
Someone calculated that there could be as many as:
1000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000
DIFFERENT String theories. No possible way to test all of them, even
if one had a fast and simple test available.
M-ish theories collapse them, show they're the same...in a way similar to electricity and magnetism become electromagnetic.
They've only done it for a few so far.

But according to Michio Kaku, it's not the best effort to worry about testing
the theory at this point. Because if we instead completely solve the math first, it will [or will not] accurately predict and describe all the things we CAN test. [at least I think he said that on something I was watching once].

Orlion....Seems to me we test math with math in these areas because it is easier and faster to correct/eliminate than it would be to build physical tests for everything. Particle accelerators are expensive! But they will still have to test against reality at SOME point, or they're useless...we can't do anything with them.

[Avatar]

Mathematically it can be shown that those extra dimensions are real... [/color]

My problem with mathematical proofs is that they're argued from their conclusion as it were.

--A

[Hashi Lebwohl]

That is the nature of theoretical physics at this time. You start with equations which are known to be true or have already been shown to be true, perform a variety of complex functions on them, then obtain a new result. As long as every step is verifiable the results are as valid as the original statements. That doesn't mean that your conclusions can be tested, only the method used to derive the result.

I have to admit that I am not certain how the knowledge that there are 7 more dimensions that the ones we can see and experiment with, presuming that M-Theory is true, is going to help us any. If we cannot detect or test those dimensions then the only positive benefit is to say "we know they are there". Many findings in cosmology seem to be "knowledge for sake of knowledge". That isn't necessarily a bad thing but it won't really help us make any scientific advancements in the near future.

[peter]

Can I change tack a minute (doesn't seem necessary to start a new thread ............actually I think I better had - it's on time travel!

That's a strange place for science to be Hashi. It sounds as though physics at it's far edges is beginning to merge with metaphysics - there was always a possibility that this would happen, it's been on the cards for a long time. Frijof Capra was saying as much in his book 'The Tao of Physics' some thirty years ago.

[Hashi Lebwohl]

I read The Tao of Physics--it was well worth it. Yes, that book probably jump-started the path that cutting-edge physics has taken since its publication.

[Avatar]

That is the nature of theoretical physics at this time. You start with equations which are known to be true or have already been shown to be true, perform a variety of complex functions on them, then obtain a new result.

That's not how I see it...I see it as postulating something, then working backwards in an attempt to get the math to fit your postulation.

M-Theory is a prime example...they couldn't get the result they wanted without postulating an extra dimension from whatever it was...string theory IIRC.

So they sorta said "let's pretend that extra dimension is there, so that the math will work out."

It's all imaginary.

--A

[peter]

That is the nature of theoretical physics at this time. You start with equations which are known to be true or have already been shown to be true, perform a variety of complex functions on them, then obtain a new result.

That's not how I see it...I see it as postulating something, then working backwards in an attempt to get the math to fit your postulation.

M-Theory is a prime example...they couldn't get the result they wanted without postulating an extra dimension from whatever it was...string theory IIRC.

So they sorta said "let's pretend that extra dimension is there, so that the math will work out."

It's all imaginary.

--A

This is the point about variability - if an explanation allows you to vary detail to achieve a 'fit' with new data, then in all likelyhood it is a poor explanation. At it's extreme end it becomes no different to the invention of myth to explain the situation we find ourselves in. [An good example of invariability is the explanation of the seasons resulting from the tilt in the Earths axis. The theory was formulated to explain the different positions of sunrise at different times of year, by extension explained also the occurence of seasons (by utilising the existing knowledge about the heating effects of radient heat on tilted bodies) and the differing day lengths of summer and winter, allowed predictions to be made that could be tested about other parts of the globe never visited (indeed about any tilted planet anywhere in the Universe) ie had reach, and could not be varied in any of it's detail without the whole theory having to be abandoned. This is a good explanation.]

[Hashi Lebwohl]

That's not how I see it...I see it as postulating something, then working backwards in an attempt to get the math to fit your postulation.

Technically yes, math is all imaginary despite the fact that we can verify its results in the real world. The process of working backward--begin with the conclusion and try to trace the path to your original position--is valid for mathematics but not for any other science. If your original position is true and all the subsequent intermediate steps are also true then your conclusion, which began as a guess, must also be true. If you cannot find the logical path or one of your intermediate steps would turn out to be false then your guess was wrong; when this happens you guess again and start over.

[Avatar]

If your original position is true and all the subsequent intermediate steps are also true then your conclusion, which began as a guess, must also be true.

But not necessarily real.

--A

[peter]

I don't know Hashi - I'm not sure that the 'inductivist' (I go out and randomly collect data from which I derive my explanations by induction) or empiracist (because it happened this way yesterday, and the day before, and the day before etc, etc, it will always happen this way) positions cut it any more. The search for 'good explanations' always begins with conjecture, and that conjecture is in itself theory laden. What applies to maths here may apply to the other sciences more than we think.