# Hypothetical QM Question

1. Dec 27, 2005

Suppose an experiment was published next week in Science that conclusively falsified quantum mechanics, how would the science of physics change ? Here I assume that QM is a true scientific theory and via Popper must be open to falsification (that is, if QM cannot ever be falsified it is not science). Perhaps a bit too much toward philosophy, so move it to that area of the forum if need be.

2. Dec 27, 2005

Staff Emeritus
It would depend on just what feature of QM was falsified. For example if the experiement showed that realism was true - that particles have properties independent of observation, the results would be different than if it were shown that evolution is something nonlinear instead of unitary.

What no new experiment could disprove is all the prior experiments. Any new theory would have to account for them as well as for the ground breaking new one.

3. Dec 27, 2005

Thank you "selfAdjoint". So, it would appear that this Science paper could in theory take three separate forms, and that any of these would falsify quantum mechanic theory:
1. Show that non-realism is false.
2. Show that evolution is nonlinear
3. Show both 1 & 2 above

4. Dec 28, 2005

### kleinwolf

Non-realism is "particle don't have properties (because in superposition ?)before a measurement (?)"...and the measurement disturbs the system collapsing into a measured state...but what if the system itself distubrbs the observer or measurement apparatus...is this non-realism (hwo do you read the result of observation if the measurement apparatus does not change it's state during the measurement process ?)

5. Dec 28, 2005

Staff Emeritus

There is at least one other property, localism (I am following Dr. Chinese here). So you have three independent (well....) properties, call them R, U, and L, and QM is ~R/U/L, and your conjectured experiment could show that reality is R, ~U, or ~L, in any combination.

6. Dec 28, 2005

Excellent, so many ways to falsify QM using the scientific method--so, when can I realistically expect to see this Science paper in print ? Next I would like to have a discussion on the following, which would also help with the question by "kleinwolf":
1. Type of experimental design required to show that reality is R, which would then falsify QM
2. Type of experimental design required to show that reality is ~U....
3. Type of experimental design required to show that reality is ~L....
That is, I would like to better understand the format required for the experimental designs that would conclusively falsify QM based on your ~ R/U/L criteria.

7. Dec 28, 2005

Staff Emeritus
Well I don't have any idea how such an experiment would work. And I more than half suspect no such experiment is possible; that is I believe that quantum mechanics captures some essential features of reality. It doesn't have to be a perfect theory to do that.

8. Dec 28, 2005

Well then, all that I can conclude up to this point in the thread discussion is that this hypothetical paper in Science will never appear because QM theory is not a scientific theory that can be falsified via experimentation. Is this the majority view of this physics forum, that QM is not a theory that can be falsified via experimentation ? If not, would someone please provide me the required experiments that would conclusively falsify QM as identified by "selfAdjoint" and given in post #6.

9. Dec 29, 2005

### Staff: Mentor

On the face of it, this seems a silly statement. QM has made countless specific, surprising (compared to classical physics) predictions which--so far--have all been verified. Had these predictions failed to be verified, then QM would easily be falsified. Just because a theory is successful (so far) hardly makes it unscientific or unfalsifiable! A theory that makes specific, unexpected predictions--like QM--is eminently falsifiable.

And when future experiments push the envelope so far that even QM fails, then it too will need to be replaced by a better theory.

It seems to me that what you are really asking is "What one experiment will, now and forever, conclusively show that QM is correct?" Such an experiment is impossible. But any of the many experiments done to date could have shown QM to be wrong.

10. Dec 29, 2005

Staff Emeritus
And in addition to what Doc Al said, which is absolutely true, the fact that there is no experiment we can imagine now doesn't mean there can never be one. QM is a powerful theory that makes new predictions as we investigate it more. It is logically possible that some future experiment dealing with some future prediction will falsify it.

I will note that QM workers nearly all believe that the Aspect and other experiments testing the Bell inequalities have confirmed ~R, so based on what we know today it's only U and L that are up for grabs. And indeed you see papers suggesting non-linear replacements for QM and nonlocal replacements for relativity - all conformed to agree with the theories they replace at the scales we have been able to investigate so far.

11. Dec 30, 2005

[To Doc Al and selfAdjoint] I appreciate your comments, but can you see how they may lead to confusion ? First, selfAdjoint indicates that "no experiment can be imagined that would falsify QM", then Doc Al informs that in fact many such experiments have already been published and QM has never been falsified. Then selfAdjoint states that R (Realism as defined above) most likely has been falsified via experiments, but were not these experiments designed to falsify R and not QM ? Finally, selfAdjoint informs that U and L are still fair game, that is, someday an experimental design may be thought of that will falsify the predictions of QM concerning U and L--thus my quantum mental state.
And, to Doc Al, no, I really am not looking for a way to show that QM is correct, such is not the way of science, we do not set out to prove a theory true, we design an experiment to falsify the theory (more often a hypothesis in the null form). And thus the reason for my thread, I would like to understand the details of the experimental designs that would be required to "falsify" QM as it predicts ~ R, ~ U, ~ L as presented above by selfAdjoint.
Finally, I still have no answer to my post # 1 question, e.g., how would science of physics change if next week the paper in Science appeared that "falsified" QM ?---it is a hypothetical question, thus hypothetical answers are allowed I would think.

12. Dec 31, 2005

### inha

Physicists are mostly very practical people so we would keep on using QM within it's domain of appliacability and work on it's successor. There really isn't anything more to it.

Last edited: Dec 31, 2005
13. Dec 31, 2005

### cartuz

14. Dec 31, 2005

### inha

There is no article. This was a hypothetical question.

15. Jan 1, 2006

### Sherlock

What is unique to QM? What is QM's fundamental hypothesis? That there is a fundamental quantum of action?

Last edited: Jan 1, 2006
16. Jan 1, 2006

### DrChinese

QM is falsifiable per Popper. However, it was not falsified, it was supported. So it is no longer possible to publish such a paper as you describe. The only thing that could be published is a paper that is in contradiction with some secondary area of QM - i.e. a prediction which is a consequence of QM. (This would not actually be a falsification of QM, it would merely be setting limits on its domain of applicability.)

HOWEVER... none of that really matters. Every theory has a domain over which it may be useful. Outside of such domain, it ceases to be useful. That does not change it from being a "true" theory to a "false" theory. Popper's ideas about theory evaluation are themselves useful tools, but they are not absolute in any sense.

Theories compete - may the best theory win! Perhaps someday, someone will publish a BETTER theory than QM.

17. Jan 11, 2006

### RandallB

I think I can give an answer to your question, as long as you allow for some range of results based on “how wrong” QM is found to be.

Example: Ptolemy and Tyco theories are considered completely wrong in their geocentric orbital theories. BUT if the deferent and epicycle paths are made ecliptics the results would not just be close but identical to Copernicus with Kepler.
But Newton’s Theories are considered ‘wrong’ or incomplete in fine detail and stand as corrected by relativity. But still considered correct with appropriate limitations. EX: Newton could never explain the source for the additional energy required to account for the Precession of Mercury, where GR accounts for the precession without any added energy though curved space-time. But short of things like that Newton’s is considered OK.

So what will it mean to physics if QM is Proven to be wrong. Well it depends on how wrong, it will not be able to be shown as in accurate, that much seems to be sure.

So worst case; It would be an accurate and highly successful, useful, and productive analogy. Much as you have to admit both Ptolemy and Tyco theories could have been if they’d cracked the ellipse problem first.

Best case; It in could be ‘wrong’ but able to be ‘completed’ (like Newton’s) with the addition of something currently unknown.

I cannot imagine that the formulas that have been generated by QM based on the real success they have given in practical science would not survive. Either in a new and replacing theory, or as part of the ‘completed’ from of some combined theory(ies).

Now as to what hypothetical proof could show QM wrong, “or falsified”.
I think Dr C would agree, it would take something like Einstein’s “unknown variables” being discovered in a manner that allows them to SUCCESSFULLY make some sort of prediction, that QM is unable to predict or predicts incorrectly based on experimental results. ( I consider Dr C the expert here on the various arguments between entanglement and local variables. Plus any replacing theory would certainly IMO need to explain entanglement.)

Is this a little more on target to your OP hypothetical?

18. Jan 15, 2006

Yes, thank you for taking the time. You seem to take the position that you believe it unlikely that QM, if ever falsified, will not be completely replaced by a deeper theory. I have seen nothing added to this thread to indicate that you are incorrect.
I also found the comments of "selfAdjoint" very useful for they showed exactly the type of experiments that would need to be conducted, which I repeat below:
1. Experimental design to show that reality of wavefunction is R, which would then falsify QM
2. Experimental design to show that reality of wavefunction is ~U, which would falsify QM
3. Experimental design to show that reality of wavefunction is ~L, which would falsify QM
where, R = real, ~U = not unitary (linear), ~L = not local
So, clearly, your comments are well taken, the "answer" to my OP must depend on which of the above experiments first falsify QM, and to what degree and under what conditions (context dependent) they falsify QM. Now, numerous comments have been given that the experiment # 1 above will "never" be found, valid experiments have been conducted, it can be falsified, but never has been falsified. Thus, it would appear that the hypothetical paper in Science will have to address experiments # 2 & 3, or ideally both at the same time.

19. Jan 16, 2006

### reilly

Rade -- Perhaps i'm a bit naive, but I do not understand what the "reality" means in the phrase "reality of the wave function". And, I don't have a clue about how to design the experiments you discuss.

There's virtually no chance that QM will be falsified in the realms in which the theory has been spectacularly successful. But, it's not out of the question that QM could have problems at very, very high energy; there are certainly issues surrounding QM and gravity, Generally, the new stuff tends to come from folks who push the boundaries, go over the top into new areas, and so forth.

Regards,
Reilly Atkinson

20. Jan 16, 2006

### JesseM

What do you mean by "completely replaced" though? Would you say that General Relativity completely replaces Newtonian Gravity, despite the fact that its predictions can be shown to come arbitrarily close to Newtonian predictions in certain well-defined limits? As long as you assume that all the existing experiments which have confirmed QM's predictions will continue to do so when repeatedly performed in the future, and that the only way QM could be shown wrong would be in making wrong predictions about new experiments that no one has performed yet, it seems that any new theory that replaces QM will have to reproduce quite a lot of the predictions of QM in a variety of circumstances.
If R is just supposed to represent "realism", the idea that particles have well-defined properties at all times, doesn't Bohm's interpretation show that it's possible to have a realistic nonlocal theory that reproduces all the same empirical predictions as ordinary QM? Maybe what you mean is that existing evidence shows it's impossible for R to be true and for L to be true.

Last edited: Jan 16, 2006