# Schroedinger's Cat and Clocks. **URL:** \ **Category:** Factual Questions\ **Created:** [November 4, 2010, 2:05am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401 "2010-11-04T02:05:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\ **Post date:** [November 4, 2010, 2:05am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/1 "2010-11-04T02:05:44Z")
I think we all know the story of the Schroedinger’s Cat experiment ([here](http://www.straightdope.com/columns/read/113/the-story-of-schroedingers-cat-an-epic-poem) is Cecil’s take on it). IANAQuatum physicist. So my explanation and take on it might not be that good. But basically (as I understand it in my _“limited”_ way) it says that reality only collapses into _one_ form when we perceive it. Schroedinger’s experiment gives the example of a cat, and a device that kills it at random in a closed box (why the cat’s perception is not relevant also puzzles me–but I digress). Anyways, forgive me, but I don’t believe this assertion at all. It goes totally against common sense, I think. For example, now I am at my computer in one room in my house. Just because I am not in another room, for example, doesn’t mean there is anything unusual happening in the other room/s. Anyways, I have an example which I believe demonstrates what I am talking about: clocks. The clocks in my house continue telling time, even when I am not directly perceiving them. Now, it is claimed the cat isn’t dead until perceived by a human. But if this was true of clocks, wouldn’t they show a different time or stop(-?) completely if I exited a room? Then when I come back to the room, I would notice this had happened–no? Anyways, as I’ve said, IANAScientist. So please someone tell me what I am missing here (including as I said above, why the cat’s perception isn’t important BTW). 🙂 ---
**Author:** ![Cheshire\_Human](https://avatars.discourse-cdn.com/v4/letter/c/5f8ce5/32.png) [@Cheshire\_Human](https://boards.straightdope.com/u/Cheshire_Human)\ **Post date:** [November 4, 2010, 3:07am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/2 "2010-11-04T03:07:23Z")
Actually, this is based on a misunderstanding of the Schroedinger’s Cat thought-experiment. His idea was actually to show why certain interpretations of quantum mechanics were ridiculous. He never believed that’s what actually happened. He agreed with you. ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [November 4, 2010, 3:10am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/3 "2010-11-04T03:10:50Z")
These same questions puzzle me too. > [@Jim\_B](#): > > why the cat’s perception is not relevant also puzzles me–but I digress. Rather than being a digression, I have long suspected that the answer to this one is the key to understanding all the others. ---
**Author:** ![Inner\_Stickler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inner_stickler/32/318_2.png) [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)\ **Post date:** [November 4, 2010, 3:11am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/4 "2010-11-04T03:11:14Z")
Right, Schroedinger’s intent was for you to get to the end of the thought experiment and say, “Wait, the cat is both dead and alive?! BULLSHIT.” ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [November 4, 2010, 3:14am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/5 "2010-11-04T03:14:37Z")
> [@Cheshire\_Human](#): > > Actually, this is based on a misunderstanding of the Schroedinger’s Cat thought-experiment. His idea was actually to show why certain interpretations of quantum mechanics were ridiculous. He never believed that’s what actually happened. He agreed with you. My understanding was that although Schroedinger himself proposed it as you say, it was nevertheless accepted by other quantum scientists then and now, with the reaction of “Yes, you’ve illustrated it quite well. And it does seem ridiculous. But it is nevertheless true and accurate. If only we could understand it!” Am I mistaken? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [November 4, 2010, 3:27am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/6 "2010-11-04T03:27:27Z")
As soon as anyone says “It goes totally against common sense” about any aspect of QM, the battle is already lost. Nothing about QM has any relation to common sense. In the first place, there’s not the slightest reason to think that the behavior of atoms at the most basic level of existence should have any relationship to what we see in the everyday world. Common sense tells us an amazing series of wrong things, like the obvious common sense fact that the world must be flat because people on the other side would fall off. QM works as math. When people try to express it in words they need to use analogies, which are more or less bad but never can express things that otherwise have no correspondence to anything in the macro world. (Understanding exactly why there is a macro world is a great question, but not the one asked by people wanting common sense answers.) But of course we continue to insist on “common sense” because that’s the human way. And we continue to insist on words because few of us want to study for the years needed to understand the math. I just wish that people would stop blaming the analogies for not making sense. It’s very much like zen. You comprehend the answer by letting the truth emerge. It’s very much not like a textbook in which the answers are in back. Still, the physics pedants on the Board are often fairly adequate at giving the subject some slight comprehensibility. Which in QM terms is high praise. 🙂 ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [November 4, 2010, 3:29am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/7 "2010-11-04T03:29:35Z")
Of course, Schrodinger’s own _opinion_ isn’t determinative. The illustration may be useful even if he was wrong. > [@Jim\_B](#): > > Anyways, I have an example which I believe demonstrates what I am talking about: clocks. The clocks in my house continue telling time, even when I am not directly perceiving them. Now, it is claimed the cat isn’t dead until perceived by a human. But if this was true of clocks, wouldn’t they show a different time or stop(-?) completely if I exited a room? Then when I come back to the room, I would notice this had happened–no? There’s nothing special about clocks. The walls in your house continue being the same color in the same sense (whatever that may, in fact, be) that the clocks continue telling time. You’d notice if the wall was suddenly a different color when you came back, too–but there’s no reason for such an inexplicable reality to collapse out of the quantum possibilities. > [@Jim\_B](#): > > (why the cat’s perception is not relevant also puzzles me–but I digress). Think of it this way. _If_ there is an observer effect, there must be some characteristic or quality which separates _observers_ from mere objects in the universe. What is that characteristic? Does it imply or require consciousness? _How much consciousness?_ Do all humans do it all the time, necessarily? (While asleep?) Conceiving of this characteristic as a functional boundary, actual cats might or might not be on the same side of it as we are. (If they are, substitute something else for the cat to keep using the illustration.) ---
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [November 4, 2010, 3:44am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/8 "2010-11-04T03:44:55Z")
As usual _[the Family Circus](http://img196.imageshack.us/img196/2743/179qm.jpg)_ has already covered this ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [November 4, 2010, 3:56am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/9 "2010-11-04T03:56:59Z")
There is a pretty accessible explanation of at least part of this issue in _From Eternity to Here_ by Sean Carroll. (The book has received generally positive reviews though is not without its critics.) It is primarily about the nature of time, but does have a few things to say about QM. Most interestingly, Carroll explains one model used to describe this type of phenomenon, the “many worlds” interpretation. > [@Sean Carroll on p. 249](#): > > “Many worlds” is a scary and misleading term for what is really a very straightforward idea. That idea is this: There is no such thing as “collapse of the wave function.”…The response of the many-worlds advocate is simply that your are thinking about it wrong. In particular, you have misidentified yourself in the wave function of the universe…It’s not right to set yourself off as some objective classical observing apparatus; we need to take your own state into account in the wave function. He goes on to say that, in the many worlds model, after you observe an outcome, your consciousness splits off into two branches of the wave function; one, for example, who saw a dead cat and one who saw a live one. But that’s not how the experience seems to us, so it’s difficult to accept. Further, to clarify that “many worlds” is really a misnomer: > [@](#): > > …the universe is described by a single wave function, which assigns a particular amplitude to every possible observational outcome. Before or after, the wave function of the universe is just particular point in the space of states describing the universe, and that space of states didn’t get any bigger or smaller. No new “worlds” have really been created. He also describes the Copenhagen interpretation that describes wave function collapse. He seems partial to “many worlds.” ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [November 4, 2010, 4:02am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/10 "2010-11-04T04:02:12Z")
> [@CookingWithGas](#): > > He also describes the Copenhagen interpretation that describes wave function collapse. He seems partial to “many worlds.” It’s important to remember that both interpretations of QM are mathematically equivalent, even though the way the math is interpreted seems contradictory. Again, set “common sense” aside. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [November 4, 2010, 4:06am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/11 "2010-11-04T04:06:48Z")
The point of the _Schroedinger’s Cat_ thought experiment is that the situation is set up in such a way that a macroscopic event (the killing or otherwise, of the cat) is dependent on the occurrence of events (radioactive decay of atoms) that occur at the quantum level. This is a very special and unusual circumstance. Very few macroscopic events are subject to quantum indeterminacy of this sort. Although everything is technically subject to _some_ quantum indeterminacy, for most ordinary sized things, things observable at the human scale, it is vanishingly small, and can be ignored for all practical (and most impractical) purposes. Unless your clocks are somehow set up to be under the control of radioactive decays or some similar quantum level process, there is no reason to expect them to behave in an indeterministic manner, and whether you observe them or not will have no impact on how they do behave (just as common sense tells us). **Cheshire Human** (who should know, if anyone does), is, of course, right to point out that the cat thought experiment was intended to show that something is wrong, or incomplete, about quantum mechanics (as interpreted by Bohr and Heisenberg). The story is meant to be absurd, but most physicists seem to have preferred to embrace the absurdity rather than reject the theory (because it works so well in so many other respects). However, be that as it may, quantum mechanics does not, in any meaningful way, predict anything absurd about your unobserved clocks. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 4, 2010, 4:40am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/12 "2010-11-04T04:40:54Z")
I don’t know what Scroedinger intended, but it’s not absurd to have a mathematical model that defines multiple possibilities when there is an a unknown factor. **njtt** points out that the absurdity comes from the way the situation is posed. The system inside the box can’t have the cat alternate between life and death as random events occur, the first random event kills the cat. The model can’t determine whether the event occur or not at any specific time, and neither can you unless you open the box. I don’t understand what happens in quantum mechanics, but if it exhibits the behavior of a mathematical model like that, there’s nothing absurd about it. **Exapno** , people can’t fall off the other side of the world because no one could be there in the first place. If you make it past the monsters, mountains, and waterfalls that encircle the world, you’d just fall off and land on the back of a turtle. ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [November 4, 2010, 4:41am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/13 "2010-11-04T04:41:34Z")
> [@Sean Carroll](#): > > No new “worlds” have really been created. By which he means that the possibilities–the “paths,” if you will, of the split consciousness in that interpretation–_continue to coexist_, right? No “worlds” have been added or removed; they’re all “there” all along, threads unwinding out of the same skein of possibility. But any one observer’s perception will seem, internally, to just follow one thread. (Correct me if I have misstated Carroll.) This interpretation lends itself to many kinds of further speculation, [like this](http://en.wikipedia.org/wiki/Quantum_suicide_and_immortality). > [@Wikipedia](#): > > In quantum mechanics, quantum suicide is a thought experiment. > … > It attempts to distinguish between the Copenhagen interpretation of quantum mechanics and the Everett many-worlds interpretation by means of a variation of the Schrödinger’s cat thought experiment, from the cat’s point of view. And finally, if you like what reading _this_ stuff does to your brain, be sure to check out the writings of Greg Egan, particularly the novel _Quarantine_ (Copenhagen wavefunction collapse) and the story “The Infinite Assassin” (Everett-DeWitt many-worlds). These are fun fiction based on ideas about quantum physics, not actual physics: see [Egan’s essay on the distinctions](http://www.gregegan.net/QUARANTINE/QM/QM.html). > [@Greg Egan](#): > > So, what happened to the other possibilities — the other “versions” of the particle? How does the co-existence of many different values for a particle’s location get to be replaced by a state with a single location? When, how, and why does the wave function collapse? Here are some of the answers that have been given to this question: > > 1. Don’t ask stupid questions. Quantum mechanics lets you calculate the probabilities for the various outcomes of any experiment you can describe. What more do you want from a scientific theory? Just shut up and calculate! > 2. The wave function is not a real thing, the way an ocean wave or a wave on a string is a thing. Rather, it describes what we know about a quantum system. When we make a measurement, we get to know something new, so the wave function has to be changed to reflect that. But there is no “objective collapse” — any more than a pea beneath one of three thimbles undergoes some kind of physical change when we see where it is, and we change our probability for its presence there from one in three to 100%. > 3. When the particle interacts with the measuring device (or any other macroscopic object on which it has a significant effect) there is an objective collapse of the particle’s wave function. > 4. When the measuring device interacts with an observer, there is an objective collapse of the combined wave function of the particle and the measuring device. > 5. The wave function doesn’t collapse, and all its possibilities continue to exist; we are simply unable to detect them because of the effects of decoherence. > 6. Conventional quantum mechanics is incomplete. We need a better theory to truly understand what’s going on. > > As readers of Quarantine will know, the novel posits a variation on position 4: human beings alone have a special structure in their brains that actively causes the collapse of the wave function. Only once a human has interacted with the quantum system and perceived a definite outcome are all the other possibilities obliterated. > > As I’ve already said, though this hypothesis leads to some entertaining consequences, I don’t actually believe it for a moment. ---
**Author:** ![Cheshire\_Human](https://avatars.discourse-cdn.com/v4/letter/c/5f8ce5/32.png) [@Cheshire\_Human](https://boards.straightdope.com/u/Cheshire_Human)\ **Post date:** [November 4, 2010, 4:49am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/14 "2010-11-04T04:49:49Z")
> [@Keeve](#): > > My understanding was that although Schroedinger himself proposed it as you say, it was nevertheless accepted by other quantum scientists then and now, with the reaction of “Yes, you’ve illustrated it quite well. And it does seem ridiculous. But it is nevertheless true and accurate. If only we could understand it!” > > Am I mistaken? Nope. He thought “Bullshit”, others though “How Profound”. I’m not a physicist, so I can’t say with any authority, but I agree with “Bullshit”. ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [November 4, 2010, 10:31am UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/15 "2010-11-04T10:31:03Z")
> [@spark240](#): > > You’d notice if the wall was suddenly a different color when you came back, too–but there’s no reason for such an inexplicable reality to collapse out of the quantum possibilities. On the contrary, the whole point is that this could indeed happen. The probability is absurdly small, but that’s not the same as impossible. All of the subatomic particles in that wall are very busy doing whatever it is that subatomic particles do, and one of the great things about being a subatomic particle is that you don’t have to do anything in particular. Of course, you’ll probably do this, and probably not do that, and the probabilities are such that on a macro level, the local humans will never notice the occasional particles that did the unexpected. But the fact is that the laws of probabilities do allow the unexpected to occur, provided that it doesn’t happen too often. But once in a very great while – and for our purposes, this could take a googolplex years or more – all the subatomic particles in that wall could transmute their atoms into pure gold. I will concede that for practical purposes this will never actually happen, but for theoretical purposes it certainly can. ---
**Author:** ![Reno\_Nevada](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@Reno\_Nevada](https://boards.straightdope.com/u/Reno_Nevada)\ **Post date:** [November 5, 2010, 5:00pm UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/16 "2010-11-05T17:00:51Z")
No discussion of Schroedinger’s Cat is complete without a link to [my personal favorite Cecil column.](http://www.straightdope.com/columns/read/113/the-story-of-schroedingers-cat-an-epic-poem) ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [November 5, 2010, 5:12pm UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/17 "2010-11-05T17:12:56Z")
> [@Cheshire\_Human](#): > > Nope. He thought “Bullshit”, others though “How Profound”. I’m not a physicist, so I can’t say with any authority, but I agree with “Bullshit”. Maybe it’s both profound and bullshit at the same time, and we don’t know which until we’ve opened Schrödinger. ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [November 5, 2010, 5:36pm UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/18 "2010-11-05T17:36:36Z")
> [@Keeve](#): > > On the contrary, the whole point is that this could indeed happen. The probability is absurdly small, but that’s not the same as impossible. > … > I will concede that for practical purposes this will never actually happen, but for theoretical purposes it certainly can. You’re right. At least to the limits of my understanding. I think the illustration still correctly suggests why the evidence of clocks seeming to keep time in accord with a pre-quantum understanding of reality is no more meaningful than the evidence of other parts of our physical surroundings seeming to keep existing as they are. ---
**Author:** ![Cayuga](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Cayuga](https://boards.straightdope.com/u/Cayuga)\ **Post date:** [November 5, 2010, 5:54pm UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/19 "2010-11-05T17:54:58Z")
Hey, all you experts: Is this a valid interpretation? Schroedinger made up the story of the cat to say, “If what you’re saying about quantum mechanics is true, then the cat is both dead and alive. That’s obviously ridiculous, so what you’re saying about quantum mechanics must not be true.” And the quantum greasemonkeys (what do you call comeone who works with quantum mechanics, anyway?) replied. “You’re right. In the large-scale, everyday world it would be ridiculous. But it’s a fact of life in the sub-atomic quantum world. Which is why quantum mechanics is such a bear to understand.” Or have all of you said this already? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [November 5, 2010, 6:15pm UTC](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401/20 "2010-11-05T18:15:37Z")
> [@Reno\_Nevada](#): > > No discussion of Schroedinger’s Cat is complete without a link to [my personal favorite Cecil column.](http://www.straightdope.com/columns/read/113/the-story-of-schroedingers-cat-an-epic-poem) You mean the one linked to in the first sentence of the OP? [Next page](https://boards.straightdope.com/t/schroedingers-cat-and-clocks/559401.md?page=2)