Some quantum mechanics experiments seem to suggest that our current understanding of reality is flawed.

  • Entanglement experiments show us that particles separated in space, can still somehow communicate - and they interact instantaneously (faster than the speed of light).
  • Some "which way"/"cosmic eraser" variations of the double slit experiment suggest that this communication might actually be "faster" than instantaneous.

If the effect in some experiments can precede their cause, does that mean our basic scientific method is flawed?

  • 2
    A quick comment: "which way" and "cosmic eraser" experiments can be coherently understood without invoking faster-than-light influences. Doing so, however, might end up committing you to the many-worlds hypothesis, or a similar interpretation of quantum mechanics, depending on what constraints you would like to impose upon your ontology. Oct 7, 2011 at 19:38
  • I'm confused by the last sentence. Are you suggesting that the scientific method relies on cause and effect (in that order)?
    – stoicfury
    Oct 7, 2011 at 22:53

3 Answers 3


The question contains an interesting slippage, between the idea that "our current understanding of reality is flawed" and "our basic scientific method is flawed." Clearly, we need to be careful here to separate the substantive from the methodological. It goes without saying that all of the findings of quantum physics mentioned in the question were discovered and documented by the scientific method.

That being said, there are some points where quantum physics may run into methodological difficulties in terms of the scientific method. Since the scientific method depends upon the notion of "controlled observation", quantum effects that are themselves dependent upon the process of observation cannot, by definition, shed any light on the unobserved behavior. Put in simple terms, if observing a particle necessarily has an effect on that particle, there is (necessarily) no way for us to know what the particle is like in its unobserved state.

On the other hand, this is of very little concern in the bigger picture of things, because these quantum effects are only relevant at absurdly microscopic levels. If you are dealing with anything the size of an atom (or, better yet, everyday phenomenal objects), this stuff just doesn't matter.

So, the end result is not that the scientific method is flawed; rather, that it has limits, and that it is possible for us, at times, to brush up against those limits.

  • It is good, but I would hesitate to say that "this stuff just doesn't matter." Clearly it doesn't for most people's daily work or practices, but there are certainly aspects of their daily lives that depend on such effects. The size their electronic gadgets, for example, is in some ways limited by quantum mechanical considerations. Oct 24, 2011 at 19:55

I'd say no. Running the risk of committing a circular reasoning fallacy, quantum mechanics is part of science, and we use the scientific method to verify the results we discover. Even though quantum mechanics is pretty mind-boggling, we wouldn't be able to increase our knowledge in the field if we're not able to

  • Observe the factual nature of reality
  • Create a hypothesis about why things are as they are, and hopefully be able to expand it to a proper theory
  • Peer review after disclosing the results where everyone tries to expose weaknesses in the hypothesis
  • Be able to repeat and (dis)confirm the experiments made by others

As of today, the scientific method is the best way we have to gain knowledge about reality, and even if we found another way, it still would have to pass the scientific method. :)


Let me rephrase the question: people using the scientific method have found various pieces of evidence that makes one particular theory seem to not be entirely consistent; does this mean the scientific method is flawed?

Phrased this more general way, isn't it quite clear that the answer is: no, it's working just fine!

The validity of the scientific method depends only upon reproducibility (including reproducibility of reproducibility). If everyone measures an interference pattern instead of all photons arriving at a spot, this doesn't matter to the logic of the scientific method. All you need is if you set things up this way, you'll get a result that looks like that. So far, all QM experiments have been replicable in this way. (And there is nothing about the scientific method that even requires the cause to come before the effect; that's the way it's always happened so far, but if we found a peculiar situation where it worked the other way around it would still be easy to tell the direction: futzing with the cause would destroy the effect, but futzing with the effect wouldn't alter the cause.)

Anyway, superluminal communication has not been definitively ruled out; the most simpleminded way to communicate is ruled out by the mathematics of the entangled systems (the no-communication theorem), but this doesn't cover more complex schemes that detect not the state but the status of having-been-measured-or-not. Nonetheless, this isn't some shocking new defect in physics theories (much less in the scientific method), since we already know that we don't have a good theory for combining relativity and quantum mechanics. Superluminal communication doesn't lead to any e.g. time-travel paradoxes in the absence of relativity; I am unaware of any experiment that shows any paradox (post a link if you know otherwise). So there's really nothing wrong: we already know theory doesn't cover these cases all that well, and we have an example of something that could potentially be weird. Hopefully we'll eventually get data on the issue and revise theories accordingly.


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