Conflicting theories with same predictions?

[dogjones]

In the history of science, have there ever been two radically differing scientific theories - but that make exactly the same predictions, and could be tested with exactly the same experiments? Of course, assuming there is objective truth (a fair assumption I think), then the fact that the theories differ means that one or both will eventually be falsified. But has this situation ever existed in science (NOT philosophy/religion etc)? If so, how long did it go on for?


*Edited for subject/verb agreement

 

[Paul C. Anagnostopoulos]

How about the current versions of quantum mechanics and M-theory?

~~ Paul

 

[TobiasTheViking]

do both predict super symmetry? and the graviton? i didn't know that.

Then again, i don't really know a lot about QG, or rather, i don't really know anything. So, please verbose, i'm very interested.

 

[epepke]

In the history of science, have there ever been two radically differing scientific theories - but that make exactly the same predictions, and could be tested with exactly the same experiments? Of course, assuming there is objective truth (a fair assumption I think), then the fact that the theories differ means that one or both will eventually be falsified. But has this situation ever existed in science (NOT philosophy/religion etc)? If so, how long did it go on for?

If you're talking about actual theories, then I can think of one case: Lorentzian mechanics versus Einsteinian relativity. That one went on for about 20 years. You'll still find some people who insist on local ether theories.

Note that I'm trying to answer your question as accurately as possible. There have been much longer controversies, but those have consisted of controversies over the measurements. There are other ideas that make exactly the same predictions, but they're usually called interpretations. There are also "theories" that really don't make any predictions, such as so-called "string theory."

Then there are theories that are kept around together because each one makes some calculations easier. Old-fashioned QM and QED, for instance. Or Newtonian mechanics versus Lagrangian and Hamiltonian mechanics. But I suspect that's not what you're looking for.

 

[ClusterBoy]

Slightly OT...
Although they didn't have the exactly the same predictions, the theories of William Farr and John Snow on cholera (airborne transmission v water-borne transmission) are intersting. The reason their theories agreed so well, was that Farr predicted foul air or miasma, was the cause. He used the height above sea level of various areas of london to show this, including fancy mathematical formulae that fitted the data really well.
In general, the higher above sea level you are, the further upstream you are on a water course. It follows that you tend to get dirtier (whence more cholera ridden) water further downstream, in lower areas. Incidentally, Snow used sewage data to further his case. Farr (and his therory) was considered the definitive expert in 1848, Snow had won out by 1855, so 7 years. But the whole thing is a really good example of evidence based science at work...

 

[TobiasTheViking]

There are also "theories" that really don't make any predictions, such as so-called "string theory".

Ehm, doesn't String Theory predict both the Gravitron and Super Summetry?

According to "The Elegant Universe" it does. Granted, that may not be the best source, but still.

Btw, that source also states that tests to find Super Summetry and the Gravitron will start in particle accelerators soon(that is, less than 10 years).

Correct me if i'm wrong.

 

[HappyCat]

If two theories make the exact same predictions, then the theories are logically equivalent to one another. In order for a theory to be falsified, a testable prediction has to consistantly fail under controlled conditions. If both theories make the same predictions, then there is no prediction for one that can be falsified while the other theory remains uncontested. As such, if two theories make the same predictions, then they are not conflicting theories.

This might not be what you mean, though. If you are asking if there have ever been two theories which both made predictions that explained all currently observed data, yet conflicted in untested predictions, then I don't know the answer to that.

 

[dogjones]

If you're talking about actual theories, then I can think of one case: Lorentzian mechanics versus Einsteinian relativity. That one went on for about 20 years. You'll still find some people who insist on local ether theories.

Thanks. I didn't know Lorentz was into ether theory - I thought his work laid the foundations of relativity? I am currently reading up on Lorentz v Einstein but struggling to understand, being no physicist or mathematician. Is the difference explainable to a layman?

 

[dogjones]

If you are asking if there have ever been two theories which both made predictions that explained all currently observed data, yet conflicted in untested predictions, then I don't know the answer to that.

Exactly what I was asking - you put it more aptly, thanks!

 

[epepke]

Ehm, doesn't String Theory predict both the Gravitron and Super Summetry?

According to "The Elegant Universe" it does. Granted, that may not be the best source, but still.

Btw, that source also states that tests to find Super Summetry and the Gravitron will start in particle accelerators soon(that is, less than 10 years).

Correct me if i'm wrong.

The problem with String Theory is that it can be tuned to be consistent with just about anything you can imagine. It can be tuned to be consistent with gravitons and supersymmetry, which are older ideas. But if you can tune it to "predict" anything, it winds up really predicting nothing.

 

[TobiasTheViking]

The problem with String Theory is that it can be tuned to be consistent with just about anything you can imagine. It can be tuned to be consistent with gravitons and supersymmetry, which are older ideas. But if you can tune it to "predict" anything, it winds up really predicting nothing.

Agreed, i didn't know that aspect of it.

I currently don't know enough to agree with your claim that it can be tuned like that. But, if you are right, i agree, and i will, atlest for now, bow down to your better judgement

 

[Dr Adequate]

This might not be what you mean, though. If you are asking if there have ever been two theories which both made predictions that explained all currently observed data, yet conflicted in untested predictions, then I don't know the answer to that.

QM and general relativity are known to be inconsistent, but both work in the cases where they can be tested.

 

[epepke]

Thanks. I didn't know Lorentz was into ether theory - I thought his work laid the foundations of relativity? I am currently reading up on Lorentz v Einstein but struggling to understand, being no physicist or mathematician. Is the difference explainable to a layman?

The problem is that Lorentz insisted on an ether-based theory with contraction using ad-hoc principles in competition with Einstein's theory. If he had been able to give up the notion of the aether, then it might be called the Lorentz-Einstein theory today. The transformations are still called Lorentz to honor Lorentz.

 

[HappyCat]

QM and general relativity are known to be inconsistent, but both work in the cases where they can be tested.

If one can be tested where another can not, then their testable predictions are not the same, only a subset of their testable predictions is the same. If all their testable predictions are the same, then it is impossible to find a test that will distinguish the two theories.

 

[Dr Adequate]

True. Sorry, forgot the OP. Mind wandering...

 

[lenny]

In the history of science, have there ever been two radically differing scientific theories - but that make exactly the same predictions, and could be tested with exactly the same experiments?
*Edited for subject/verb agreement

how about those of Ptolomey and Copernicus, for quite some time after the Copernicus entered the field? as long as you allow "same predictions within the observational noise".

 

[sionep]

QM and general relativity are known to be inconsistent

I agree completely here about that the two pillars of Physics are inconsistent, however the emergence of a new branch over the last decade called 'Quantum Gravity' where the two are united into a single theoretical framework. Obiviously , Professor Hawking is the leader in the field followed by Professor Kip Thorne of Caltech whom Hawking lost a bet to.

 

[lenny]

If one can be tested where another can not, then their testable predictions are not the same, only a subset of their testable predictions is the same. If all their testable predictions are the same, then it is impossible to find a test that will distinguish the two theories.

True, but not the difficulty in this case of QM and GR where there are instances in which both are expected to apply and we simply do not know what calculations to do to make predictions. It is not that one is expected to "win" but rather that both are expected to fail!

 

[lenny]

The problem is that Lorentz insisted on an ether-based theory with contraction using ad-hoc principles in competition with Einstein's theory.

"ad-hoc principles"?
If you had not grown up with it, wouldn't you consider the the special properties Einstein assigned to the speed of light both ad hocand counter-intuitive? the point being that the strength of special relativity is its utility, it provides a better description of nature.

 

[epepke]

"ad-hoc principles"?
If you had not grown up with it, wouldn't you consider the the special properties Einstein assigned to the speed of light both ad hocand counter-intuitive?

No, I wouldn't.

One of the things I specialize in is giving talks about Special Relativity to popular audiences. Part 1 describes the evidence for the two postulates that go into SR (which Einstein didn't have anything to do with). These were the postulates available both to Einstein and Lorentz. Part 2 goes through the qualitative derivation of SR, and there's nothing ad hoc about it.

Lorentz even admitted that his theory was ad hoc.