GENIUS FORUMS

Trevor Salyzyn wrote:Translation for the idiotic (by me, for me, in this case):

Far away events have no instantaneous effects on local ones. No theory that assumes otherwise can make all these predictions.

That's tautologically true. Something that is not present cannot have an effect on the present. Why would anyone think this violates causality?

What you have stated is the principle of locality, or local realism. It's intuitively the way we think the universe works; it''s hard to think of how else it could work.

However, Bell's theorem says that in the quantum realm, either local realism is not true, or some other seemingly obvious thing is not true, such as counterfactual definiteness.

So, different views (interpretations) of QM have arisen. Something we intuitively think about the universe is not the way it actually works. At present, there is no empirical way to say exactly which is correct. No one has devised an experiment that can unequivocably distinguish between them.

The problem with taking a non-empirical (philosophical) approach is that there are pretty good reasons for rejecting each interpretation. So philosophically, it is pretty tempting to just say QM must be wrong. However, QM is backed up by a lot of experimental evidence. The equations work, but no one really knows what they mean.

This is the limit of the knowledge in physics right now. No one knows how to move forward. It's one of the major outstanding problems in physics, and it has been since the days of Einstein and Heisenberg. By default, some physicists have adopted the "null interpretation" of "shut up and compute" - that is, the equations work, so just use them and don't worry about metaphysical issues. The Copenhagen Interpretation is also well known and sometimes considered the standard interpretation.

There are perhaps four or five other problems in physics equally as deep as this one; they may well be related.

David Quinn wrote:I'm not sure what Elizabeth is talking about in regards to metaphysics. Quantum theory makes no reference to a metaphysical world.

I don't know what she is talking about, and as far as I can tell, neither does she.

Sorry, E.

Cory Duchesne wrote:Ok, so does anyone have a good explanation for why Bohm's theory isn't taken seriously?

The work of Bohm and De Broglie should not be dismissed lightly. It's tempting to say De Broglie is under-rated as a physicist, but he did win the Nobel prize, so it's not like he's been ignored.

I think it's not generally considered for historical reasons - when it was introduced, it had some problems that were later patched up - and also probably because it is a non-local theory.

I think that a lot of the ideas of the Bohm-De Broglie theory are also reflected in decoherence models and the Transactional Interpretation; to me it seems like they kind of evolved out of it.

Ok, but what sort of particles comprise these strings?

The strings are supposedly fundamental. (But then, atoms were supposed to be fundamental...)

David Quinn wrote:I'm not sure what Elizabeth is talking about in regards to metaphysics. Quantum theory makes no reference to a metaphysical world.

Huh? Quantum theory is entirely about describing the metaphysical world.

DHodges wrote:By default, some physicists have adopted the "null interpretation" of "shut up and compute" - that is, the equations work, so just use them and don't worry about metaphysical issues.

DHodges wrote:

David Quinn wrote:I'm not sure what Elizabeth is talking about in regards to metaphysics. Quantum theory makes no reference to a metaphysical world.

I don't know what she is talking about, and as far as I can tell, neither does she.

Sorry, E.

If people are going to stick their heads in the sand and adopt an attitude of "shut up and compute" of course it's going to look like I don't know what I'm talking about. I understand this conceptually, but I do not understand what it is that you don't understand of what I'm saying.

David Quinn wrote:It's the other way around. Bell's Theorem "proved" that no physical theory which postulates hidden local causes can reproduce all of the predictions of QM. In other words, the principle of local events producing local causes doesn't seem to apply in much of the quantum realm.

The meat of what David said is the same thing I said (except that rather than "proved" I would have used the word "stated").

Elizabeth Isabelle wrote:No theory based solely on the physical world takes into account all the things in the metaphysical world. The predictions of quantum mechanics takes the variables from the metaphysical world into account.

Maybe if I rephrase it with some GF terms, that will help:

No theory based solely on reality takes into account all the things in Reality. The predictions of quantum mechanics takes the variables from Reality into account.
.

DHodges,

The problem with taking a non-empirical (philosophical) approach is that there are pretty good reasons for rejecting each interpretation. So philosophically, it is pretty tempting to just say QM must be wrong. However, QM is backed up by a lot of experimental evidence. The equations work, but no one really knows what they mean.

There's only two things I can derive from this: 1) each interpretation must be rejected; and, if we have interpretations that cover the entire possible set of interpretations (which is likely), 2) some, if not all, of the empirical data is flatly wrong.

The tools used to measure the "quantum realm" could be wholly inappropriate to the task at hand, which would explain incorrect empirical data. It could be similar to trying to use your hand to tell the colour of an object. Other than through rather arbitrary coincidences (like the fact that the things that are more frequently hot are more likely to be black), this technique will not produce the correct data.

What would be needed are tools adequate to the task of working with complex theories.

Taking more stock in appearances than philosophic soundness can cause many problems.

David Quinn,

In other words, the principle of local events producing local causes doesn't seem to apply in much of the quantum realm.

I was having difficulty with the word "not". I guess I was mistaken in automatically assuming that he couldn't have possibly been saying the opposite. No wonder my brain hurt: it simply could not accept equality between A and not-A, and forced me to interpret Bell's Theorem wrong.

Trevor Salyzyn wrote:DHodges,

The problem with taking a non-empirical (philosophical) approach is that there are pretty good reasons for rejecting each interpretation. So philosophically, it is pretty tempting to just say QM must be wrong. However, QM is backed up by a lot of experimental evidence. The equations work, but no one really knows what they mean.

There's only two things I can derive from this: 1) each interpretation must be rejected; and, if we have interpretations that cover the entire possible set of interpretations (which is likely), 2) some, if not all, of the empirical data is flatly wrong.

2 is closer to correct than 1. It's like A causes B OR A causes C, but A can not cause B AND C. The difference is an additional variable, making A an ingredient rather than a whole cause. So it's more like A causes B but AD causes C. Once you have C, you can not have B because you already used your A in obtaining C.

If you observe a photon, it "disappears" because it was the photon hitting your retina that converted the photon into the electrical impulse that carried the message to your brain in the form of data. It became like gas that your car already used. If you did not use that photon by observing it, that photon would have gone on to a different fate. This is where empirical data can not describe all of Reality, because the observance of the event which is required to make the data empirical changes the nature of the event itself. Although the empirical data itself is not wrong per se, it does not accurately reflect what would have happened had the event been left undisturbed by observation.
.

Elizabeth Isabelle wrote:If you observe a photon, it "disappears" because it was the photon hitting your retina that converted the photon into the electrical impulse that carried the message to your brain in the form of data. It became like gas that your car already used. If you did not use that photon by observing it, that photon would have gone on to a different fate. This is where empirical data can not describe all of Reality, because the observance of the event which is required to make the data empirical changes the nature of the event itself. Although the empirical data itself is not wrong per se, it does not accurately reflect what would have happened had the event been left undisturbed by observation.

Counterfactual definiteness is a property of some interpretations of QM, but not others.