# Quantum Physics and What Our Animals See When We're Not There.

**URL:** <https://boards.straightdope.com/t/quantum-physics-and-what-our-animals-see-when-were-not-there/673807>\
**Category:** Factual Questions\
**Created:** [November 13, 2013, 9:22am UTC](https://boards.straightdope.com/t/quantum-physics-and-what-our-animals-see-when-were-not-there/673807 "2013-11-13T09:22:57Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\
**Post date:** [November 14, 2013, 10:21pm UTC](https://boards.straightdope.com/t/quantum-physics-and-what-our-animals-see-when-were-not-there/673807/21 "2013-11-14T22:21:29Z")

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> [@Indistinguishable](#):
>
> Here, let me fix that for you:
> 
> “The observer doesn’t have to be aware at all - a simple particle detector is an observer that’s sufficient to turn the wave function into a particle.”
> 
> This whole thread is based on a popular misunderstanding of quantum physics as ascribing a special role to conscious observers in its laws, such that it is necessary to understand whether a cat has the same kind of consciousness as a human in order to answer the OP. But that is not the case, at all.
> 
> (Which is not to deny that there are perplexing questions as to how to interpret collapse/measurement/observation/…; they just don’t have to do with answering the question “What counts as conscious?”)

But even this idea isn’t really right as in quantum mechanics wave functions don’t turn into particles, rather particles are described by wave functions. For example even a particle you’ve just measured can be assigned a wave function and there’s a postulate of QM which tells you what it is.

It also equates measurement with the physical act of detection, but this would seem to fly in the face of the delayed-choice quantum eraser experiment for example where the observer can choose to perform whether or not a certain is performed measurement on a particle after the actual act of detection has taken place. Or interaction-free measurement where a measurement is performed on a particle despite the fact the particle is not detected.

The laws of quantum mechanics are essentially independent of what constitutes a measurement. Even if quantum measurement required that you make a blood sacrifice and utter the magick words it wouldn’t change the fundamental theory behind quantum mechanics. We can say that quantum decoherence seems to be an essential element of quantum measurement, but at the same time, for fairly basic mathematical reasons (i.e. the unitary nature of decoherence vs the non-unitary nature of collapse) we know they can’t be the same thing without a very radical and not unproblematic interpretation (i.e. doing away with collapse completely as in the many-worlds interpretation), but what actually constitutes a quantum measurement is still a very open problem.

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**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\
**Post date:** [November 14, 2013, 10:34pm UTC](https://boards.straightdope.com/t/quantum-physics-and-what-our-animals-see-when-were-not-there/673807/22 "2013-11-14T22:34:22Z")

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Right, absolutely (“what actually constitutes a quantum measurement is still a very open problem” was what my last, parenthetical line was addressing). My intention in that post was just to emphasize that “conscious observer” has nothing to do with it, which seems to be the OP’s (common) confusion.

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