Regentrude - question about string theory

[lewelma]

There was a question on the Chat board that I am not in a position to answer, as theoretical physics is certainly not my forte.
 
There have been a few discussions about what exactly a scientific theory is.  As defined by wikipedia "A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on knowledge that has been repeatedly confirmed through observation and experimentation."
 
My understanding is that theoretical physics theories, like string theory and loop quantum gravity, have not been proven.  That they have been described mathematically but not yet tested experimentally, and that they are still competing with each other and other theories for acceptance.  If my understanding is correct, are physicists using the word ' theory' in a different way than the definition above? And secondly, do theoretical physics theories need to be experimentally proven to be accepted?
 
Thanks,
 
Ruth in NZ

[Gwen in VA]

If folks are going to discuss string theory, my only contribution can be the greatest a capella spoof on advanced physics (a Queen takeoff) by a seriously inspired physics grad student.

 

Enjoy!

 

[HSinNH]

DD12 just came down from her bedroom while I was watching this video and here was our conversation:

 

DD: Oh, I have seen this video before.

Me: (puzzled at why my 12-year-old is watching videos about advanced physics) Oh, you have?

DD: Ya, I watched it at Joy's house.

Me: Oh, you did? Do you know what it is about?

DD: The String Theory.

Me: (shocked) Right. Do you know what the String Theory is?

DD: It has something to do with space.

Me: Right.

 

Huh. This is from the girl who just last week asked me to get her some books that explain Einstein's Theories in terms she could understand. I guess I will be watching this post!!

[regentrude]

I have to admit that I do not know very much about string theory. I will have to consult a colleague.

 

I do know, however, that this is precisely one of the controversies about string theory: does it make falsifiable predictions? Some critics say the predictions are outside the realm of what is experimentally testable, which would render String theory NOT scientific. Proponents of string theory are pointing out possible experiments that could serve as a test; while some predictions can not be tested, certain predictions about supersymmetry can. Whether the experiment can be conducted with today's technology is irrelevant for this; it just has to be possible in principle.

At present, it seems that certain predictions could be checked by means of particle accelerators, but no conclusive evidence has been found yet.

 

Here is  a nice article I found:

http://www.dispatch.com/content/stories/science/2013/08/18/1-string-theory-takes-a-hit-in-latest-experiments.html

[Arcadia]

Ruth,

 

My boys idea of theory is closer to Merriam Webster's dictionary's definition.  Probably a layman's way of seeing. Is there an industrial accepted standard of definition for "scientific theory"?

 

": an idea that is suggested or presented as possibly true but that is not known or proven to be true

5 : a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena <the wave theory of light>

6a :  a hypothesis assumed for the sake of argument or investigation "

 

 

 

Huh. This is from the girl who just last week asked me to get her some books that explain Einstein's Theories in terms she could understand. I guess I will be watching this post!!

 My boys love the NOVA videos on string theory.  They also have a fascination for black holes.

http://www.pbs.org/wgbh/nova/physics/elegant-universe.html

 

[regentrude]

Ruth,

 

My boys idea of theory is closer to Merriam Webster's dictionary's definition.  Probably a layman's way of seeing. Is there an industrial accepted standard of definition for "scientific theory"?

 

": an idea that is suggested or presented as possibly true but that is not known or proven to be true

5 : a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena <the wave theory of light>

6a :  a hypothesis assumed for the sake of argument or investigation "

 

Yes, in order for a theory to be scientific it must be possible to disprove it through an experiment.

(Note: you can never prove a theory by doing experiments, but you can disprove it by having an observation that does not agree with the predictions made by the theory).

So, a theory that predicts only things that can not, in principle, be tested against an experiment is not scientific.

Note the "in principle": it is irrelevant whether the experiment can be done with today's technology; the only thing that matters is that such an experiment exists principally.

This qualification is extremely important, because it distinguishes science from any explanation that relies on faith or a higher power outside the realm of the knowable.

 

ETA: I have been trying to construct an example for illustration that avoids any controversial religious subject:

Let's assume we are looking at an explanation for the existence of special energy nodes in the earth that create locations of high spiritual significance (think Sedona, AZ).

Explanation A says: the energy is concentrated there, but the effect can not be measured, because the very spiritual nature of the phenomenon is outside the realm of observable things; we have to be spiritually open and then we will feel the effect. This is NOT science.

Explanation B says: the energy concentration is due to anomalities of the earth's magnetic field at that location and the reaction of magnetite in human's brain to these anomalities; the effect is very small and there is very little magnetite, so we do not have instruments that can measure this effect. This IS science: the effect is open to observation, and the experiment is simply not doable with today's technology, but a refinement of measuring would, in principle, make it possible to check out this theory.

[Arcadia]

Yes, in order for a theory to be scientific it must be possible to disprove it through an experiment.

 

In that case, would it be technically correct to say that string theory is a theory that is proposed but not a scientific theory per se.  I am looking at the point of discussion with friends who are scientists and don't want my terms muddle up while having a fun discussion.

[regentrude]

In that case, would it be technically correct to say that string theory is a theory that is proposed but not a scientific theory per se.

 

I think that point has not been settled yet. If you read the article I linked, it seems as if they do propose experiments that could support or falsify the theory.

It would be correct to say that string theory is not yet a widely accepted scientific theory.

 

[C_l_e_0..Q_c]

The guy who did that A Cappella song is local to me. He was homeschooled - at least for a while, as he did sciences with the elder kids of a friend of mine. (my kids do sciences with her younger kids). 

[FrogMom5]

Yes, in order for a theory to be scientific it must be possible to disprove it through an experiment.

(Note: you can never prove a theory by doing experiments, but you can disprove it by having an observation that does not agree with the predictions made by the theory).

So, a theory that predicts only things that can not, in principle, be tested against an experiment is not scientific.

Note the "in principle": it is irrelevant whether the experiment can be done with today's technology; the only thing that matters is that such an experiment exists principally.

This qualification is extremely important, because it distinguishes science from any explanation that relies on faith or a higher power outside the realm of the knowable.

 

ETA: I have been trying to construct an example for illustration that avoids any controversial religious subject:

Let's assume we are looking at an explanation for the existence of special energy nodes in the earth that create locations of high spiritual significance (think Sedona, AZ).

Explanation A says: the energy is concentrated there, but the effect can not be measured, because the very spiritual nature of the phenomenon is outside the realm of observable things; we have to be spiritually open and then we will feel the effect. This is NOT science.

Explanation B says: the energy concentration is due to anomalities of the earth's magnetic field at that location and the reaction of magnetite in human's brain to these anomalities; the effect is very small and there is very little magnetite, so we do not have instruments that can measure this effect. This IS science: the effect is open to observation, and the experiment is simply not doable with today's technology, but a refinement of measuring would, in principle, make it possible to check out this theory.

 

Regentrude

Ds really likes your definition of a scientific theory.  He says it makes an important distinction. 

I interrupted his studying to watch the video and read this thread.  Now, it back to work for both of us. 

Denise

 

[FrogMom5]

The guy who did that A Cappella song is local to me. He was homeschooled - at least for a while, as he did sciences with the elder kids of a friend of mine. (my kids do sciences with her younger kids). 

 

You are very fortunate.  Your dc and hers together must be a dynamic combination.  How wonderful for all of you!

Denise

 

[8filltheheart]

So will it change your opinion of me if I revealed to you that this song is a perfect example of my current communication level with my ds??  :blushing: I watched the video with him and inside I am singing "momma........any way the wind blows......" ;) Completely clueless. Just nod my head and sing along with my own interpretation. LOL!! :lol:

[ErinE]

Can this be an "ask a physicist" post?

 

Why ten dimensions?

[lewelma]

Thanks Regentrude!

 

I have a follow on question.  For me, a scientific theory is already accepted by the scientific community as the best explanation of a natural phenonema.  It is not a hypothesis that is in the process of being supported or in competition with other hypotheses.  Clearly, that is not how physicists are using the word, 'theory', when refering to string theory.  So I am wondering if physicists simply use the word differently than biologists.

 

Here are two more definitions of scientific theory in the way that I use the term.  To me, string theory does not meet either of these definitions, but yet the word 'theory' is still attached.  So I am a bit confused.

 

 

A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon. One definition of a theory is to say it's an accepted hypothesis.

 

A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. If enough evidence accumulates to support a hypothesis, it moves to the next step—known as a theory—in the scientific method and becomes accepted as a valid explanation of a phenomenon.

 

Thanks,

 

Ruth in NZ

 

[regentrude]

Thanks Regentrude!

 

I have a follow on question.  For me, a scientific theory is already accepted by the scientific community as the best explanation of a natural phenonema.  It is not a hypothesis that is in the process of being supported or in competition with other hypotheses.  Clearly, that is not how physicists are using the word, 'theory', when refering to string theory.  So I am wondering if physicists simply use the word differently than biologists.

 

Here are two more definitions of scientific theory in the way that I use the term.  To me, string theory does not meet either of these definitions, but yet the word 'theory' is still attached.  So I am a bit confused.

 

Editing for clarity after discussion with another theoretical physicist:

 

As I said before, string theory is controversial and not universally accepted.

But this said, there can be no other term for it than "theory", because it is an extremely complex mathematical construction that can not simply be called a "hypothesis", and it is not just an "equation" or set of equations.

A theory is more than a hypothesis: it begins from a hypothesis, links it to other facts and ideas, explores consequences, makes predictions - once you have an internally consistent elaborate description of a phenomenon, you have a theory. It is a theory whether or not it has been tested experimentally - the only provision is that it must be possible to test it experimentally.

Sometimes a theory is developed that turns out to be wrong, disproven by experiment. And sometimes a theory stands the experimental test and will be accepted as valid. But it is already a theory before it comes to that.

 

Come to think of: mathematicians have theories as well. Bifurcation theory, field theory, graph theory, number theory - none of which are scientific and have any experimental validation, because math is not science.

[lewelma]

Fascinating.  So theoretical physicists are not using 'scientific theory' in the same way as the above definitions. I wonder how many other fields of science are using the term in a different way. I might just do some hunting.

 

Thanks!

[serendipitous journey]

Thanks Regentrude!

 

I have a follow on question.  For me, a scientific theory is already accepted by the scientific community as the best explanation of a natural phenonema.  It is not a hypothesis that is in the process of being supported or in competition with other hypotheses.  Clearly, that is not how physicists are using the word, 'theory', when refering to string theory.  So I am wondering if physicists simply use the word differently than biologists.

 

...

 

Ruth, this caught my attention ... I'm more familiar with the field of neuroscience, and in that field there are actively competing theories that coexist.  There is for example a phase-dependent encoding/retrieval theory of memory that is not generally accepted (actually at this point it's pretty much moot but it was much in the air during my grad student years) but is considered a theory.  It was much more complex and filled-out than "hypothesis", as regentrude indicates above in terms of theory versus hypothesis. 

 

Maybe there's a difference between little-t theory (like phasic encoding/retrieval) and big-T theory (like Theory of Evolution).  So string theory gets a bolded little t???? 

 

[nansk]

The guy who did that A Cappella song is local to me. He was homeschooled - at least for a while, as he did sciences with the elder kids of a friend of mine. (my kids do sciences with her younger kids). 

 

He shared his background in this interview.