## New Calculations May Lead To a Test For String Theory 284 284

dexmachina writes

*"A team of theoreticians, led by a group from Imperial College London, has released calculations that show string theory makes specific, testable predictions about the behaviour of quantum entangled particles. Professor Mike Duff, lead author of the study from the Department of Theoretical Physics at Imperial College London, commented, 'This will not be proof that string theory is the right "theory of everything" that is being sought by cosmologists and particle physicists. However, it will be very important to theoreticians because it will demonstrate whether or not string theory works, even if its application is in an unexpected and unrelated area of physics.' In other words, string theory may finally have shed its critics' most common complaint: unfalsifiability. However, given the second most common complaint, I can't help but wonder: which string theory?"***Update: 09/03 23:34 GMT**by**S**: Columbia University's Peter Woit, author of the Not Even Wrong blog, says these claims are overblown, and adds that a number of string theorists said as much to Wired.
## Oops (Score:5, Informative)

## Physicist speaking (Score:5, Informative)

As a physicist, I do get a bit annoyed at the constant attacks on string theory in public media.

Let me just state a few points please:

* We have Quantum Mechanics for the realm of the very small

* We have General Relativity for the realm of the very heavy

* Both of these theories fit observational data and work very well

* The two theories contradict each other in the case of very heavy and very small object (e.g. tiny black holes)

So, we need a new theory that gives the same predictions at QM and GR in the realms that we can measure them. This is where string theory etc comes in. But we do not yet have experimental data for very heavy and very small objects. If you want to complain about string theory not being testable, then accept that your same complaint is going to apply to EVERY grand-unified-theory that we know of.

Conclusion

=========

If you complain at string theory, then PLEASE state what you are proposing. What is the use in complaining when you have no alternative? The main scientific proponents against String Theory also just happen to have their own pet theories (e.g Quantum Loop Gravity) which are in an even worse situation.

If you complain about string theory taking so long, then what do you expect? It has taken 16 years just to do a single experiment (The LHC).

The only way we can make String Theory etc testable is by further research. If you dislike, please propose a better solution rather than just complaining.

TL;DR - People complain at string without proposing anything better.

## Re:And when it fails this test too (Score:5, Informative)

Just for the record: Gödel did not proof math to be not consistent. He showed two things:

1. That in every axiomatic system strong enough to capture aithmetic there necessarily are true sentences that can be expressed with the means of the system but cannot be deduced from the axioms (he presented a method to construct such sentences).

2. You cannot deduce a system's consistency from the axioms of such a system. (Which is something completely different from prooving that math is not consistent).

## Re:And when it fails this test too (Score:2, Informative)

## Arxiv version of the original paper (Score:3, Informative)

## Re:Physicist speaking (Score:4, Informative)

We know that very very small objects exists (subatomic particles). We also know that very very massive objects exists (stars).

Usually the two are linear. The smaller an objects, the less mass it has.

Unfortunately there IS a crossover point. There are objects with a density of approximately 370,000,000,000,000,000 kg/m^3. These can be modeled with regular physics for 'large' objects, and they affect things far outside the realm of Quantum Theory (i.e. you can orbit a human around such an object). Get too much above this point though, and you end up with an object that seems to be smaller than the smallest subatomic particles (Quantum Theory) yet affects things that are far outside the realm of Quantum Theory - these items are commonly known as black holes.

How do they work? Well ... they're insanely massive. And they're really tiny. As to what goes on inside them ... we've no clue. We can't use Quantum Theory because it's too massive, and we can't use regular physics, because it's too small.

## Re:And when it fails this test too (Score:1, Informative)

## Re:And when it fails this test too (Score:5, Informative)

To construct arithmetic out of logic, we however need second order predicate logic. Gödel (1930, published 1931 [wikipedia.org]) showed that axiomatic systems in second order logic are either incomplete (true non-provable sentences can be constructed) OR they are inconsistent (containing contradictions).

## Oops; that was a misquote (correction) (Score:3, Informative)

"With all due respect, Dr. Cooper... are you on crack?" -- Dr. George F. Smoot III

## Re:And when it fails this test too (Score:5, Informative)

No, you can NOT say that it is inconsistent, and you can NOT say that it is consistent. The fact that you prove you can't say some A doesn't automaticaly makes NOT A true.

Having a bit of trouble with math, isn't you? What are you proposing to construct the real numbers of? Rational numbers? If so, that is just a tautology. You don't need to construct the real numbers, as you don't need to construct the natural numbers. You don't proff that math exists, that doesn't make sense (well, except if you define "exist" in some mathematical way, but then, you'll be just applying your definition).

## Re:Oops (Score:2, Informative)

Hi. I have a very stupid question for someone working in the field of entanglement.

Spin is measured as up or down, but presumably the spin is actually at some angle in between. So the up or down measurement is rounding the actually spin. Is the resulting rounding error of any significance? Is the accumulation of rounding errors on multiple measurements of any significance? Or, as is most likely, is this a nonsensical question?

Thanks

The measurement is not rounding the real spin value. After the measurement, the spin

isup or down (in the measurement direction), not any angle in between (assuming an ideal measurement, of course). And the direction of the spin before measurement decides the probability of getting up or down (that is, even if your spin is almost up you still have a (low) probability to get "down" (rounding "almost up" would instead always give "up"). Since there's no rounding, there are no rounding errors either (there are, of course, errors due to your necessarily non-perfect measurement equipment, just like in classical physics; unlike in classical physics, this can result in you getting sometimes the opposite result, but only with low probability).## Re:Physicist speaking (Score:3, Informative)

I know you are joking, but I did mean:

"Please state what you are proposing that scientists should do instead of researching such theories"

rather than

"If you can't give an alternative theory then string theory must be true"

## Re:Oops (Score:3, Informative)

## Re:And when it fails this test too (Score:3, Informative)

Hmm, where is the -1 "Woefully misinformed" moderation when you need it.

It's not just that the consistency of Peano arithmetic cannot be proved inside Peano arithmetic, it can't be proved, at all (in any meaningfull way : the only way to "prove" it is to accept it's correctness as axiom).

Well this is just wrong. You can indeed prove the consistency of Peano arithmetic if you're willing to go outside it. Specifically you can use Gentzen's consistency proof [wikipedia.org], which doesn't "accept the correctness of Peano as an axiom" (but has other limitations). To add further weight to this, you may note that the Incompleteness theorems state that the system will either be incomplete (have unprovable truths) or inconsistent; Peano arithmetic is incomplete, for instance Goodstein's theorem [wikipedia.org] is unprovable.

rational numbers and, God help us, real numbers have much, much worse problems than mere doubts. It is known that rational numbers are inconsistent, and real numbers cannot be proven to even exist. There are no known ways to construct real numbers that are not simple extensions of rational numbers.

This is just false as well. Real numbers are on firmer ground than the natural numbers as far as proof theory goes, since there is a complete and consistent axiomitization of the real numbers [wikipedia.org] (in fact several [wikipedia.org]) that aren't "constructed as an extension of the rational numbers". Since the axiomitization is simple enough, it doesn't fall afoul of the incompleteness theorems, and thus can be proved both consistent and complete.