What have you done to the cat, Erwin? He looks half dead."
- Mrs. Schrödinger.
The above quotation is attributed to Erwin Schrödinger's wife – apparently an early animal rights activist. The rest, as they say, is history.
I was reminded of Schrödinger’s Cat after reading this comment and this comment recently. Each of these commenters enlisted Schrödinger’s Cat to prove some facts woo they were promoting. Unfortunately for them it does no such thing.
First, for those unfamiliar with it, a summary of the Schrödinger’s Cat thought experiment:
Schrödinger imagined that a cat is locked in a box, along with a radioactive atom that is connected to a vial containing a deadly poison. If the atom decays, it causes the vial to smash and the cat to be killed. When the box is closed we do not know if the atom has decayed or not, which means that [the cat] can be in both the decayed state and the non-decayed state at the same time. Therefore, the cat is both dead and alive at the same time...
Note: the cat is both dead and alive at the same time. The woo’s argument goes: this is really weird and counterintuitive, therefore __________ (insert preferred brand of woo) is real. There are several flaws in this line of reasoning.
First, from this translation of Schrödinger's original "cat paradox paper", we know that Schrödinger was deliberately presenting this dead and alive scenario as a “quite ridiculous” case. In other words, since a cat obviously cannot be both dead and alive at the same time, the extreme version of the Copenhagen interpretation (the version that says consciousness is necessary), must be wrong. This could be because “observation” really means “measurement” (ie the Geiger counter measuring the atomic decay is the “observer”), or because Copenhagen itself is wrong. Either way, it is amusing when woos throw Schrödinger’s Cat into the debate, quite oblivious to the fact that is was designed to show the exact opposite of what they think it shows.
But there is a more fundamental reason Schrödinger’s Cat doesn’t support the woo position.
I Taught I Taw A Puddy Tat
Schrödinger’s Cat is a thought experiment only. Thought experiments can be useful to explain a complex idea, or to get people to question assumptions, but a thought experiment cannot by itself prove or disprove anything. To prove or disprove something, you have to perform a real experiment. Schrödinger’s Cat has never actually been performed as a real experiment, and in my view could never even in principle be performed as a real experiment. The reason should be obvious. Schrödinger’s Cat says the cat is both dead and alive until we look at it. But we cannot tell if the cat is dead or alive until we look at it. It’s Catch-22: to perform Schrödinger’s Cat we’d have to look at the experiment without looking at it. Clearly impossible. So it proves nothing.
Of course, this also means that Schrödinger’s point wasn’t proven either: since we can’t say for sure that the cat isn’t both dead and alive, we can’t say if Copenhagen is right or wrong. The “consciousness is necessary” interpretation of QM is unfalsifiable.
But even if the experiment could be performed, and the dead and alive at the same time position confirmed, that still wouldn’t support the many woo claims made for quantum mechanics. If you want to demonstrate that something is true, you need to show some actual evidence that the thing actually is true. Just because quantum mechanics is weird and counterintuitive yet true, it doesn’t follow that any weird and counterintuitive woo is also true.
Poor Puddy Tat!
Actually, I did come up with a way to determine whether or not consciousness is necessary through a relatively simple experiment; I just don't have the clout to get it performed. The trick is to run the double-slit experiment, and have a detector on each slit that, when turned on, will tell us which hole the electron (or whatever) passes through. It's known from prior experiments that if we don't use a detector, we'll see the classic interference pattern, but if we do use it, we'll see the sum of two diffraction patterns from the two slits.
Now, here's the trick: What if we turn the detector on, but don't look at what it's telling us? We can stop the flow of information immediately before any conscious observer knows anything about which hole the electron went through. Hell, we could dump the data as soon as it's collected to be on the safe side. This way, we know that if we see an interference pattern, then consciousness (or something else in a step we blocked off) is what causes the collapse. If we don't see an interference pattern, then we can rule out consciousness as causing the collapse.
I tried running this experiment by my Quantum Professor, but he refused to act on it as he was already sure that consciousness was the key ingredient. I have to see if I can find someone who's unsure and who'll listen to me.
Posted by: Infophile | March 18, 2007 at 11:20 PM
Two links I give aspiring Quantum Quakers:
Quantum Quackery
Schrödinger's Zombie
Posted by: Plan 8 | March 18, 2007 at 11:32 PM
a detector on each slit that, when turned on, will tell us which hole the electron (or whatever) passes through.
You can't, I'm afraid, infophile. I believe that when cunning experiments have been performed to constrain an given electron to a single slit, it goes through both of them. I don't pretend to "grok" it, but I guess nobody does.
Posted by: Big Al | March 19, 2007 at 02:39 AM
Actually, when you set up a detector, you do indeed force the wavefunction to collapse at the slits, so if you only shoot out one electron at a time, you'll find it at only one of the slits. And then, after it passes through, you'll see the classical sum of two diffraction patterns.
Posted by: Infophile | March 19, 2007 at 09:09 AM
This is the first stop in YesBut’s tour of blog land. I arrived here by entering the key words “proves nothing” in Google Blog Search.
The blog certainly gave me something to think about, but now I must move on using the keyword chosen at random from your blog: “irrational”. If you want to know where that takes me check my blog http://grumpyandfarting.blogspot.com on Tuesday 2oth March
Posted by: YesBut | March 19, 2007 at 09:25 AM
Infophile,
Would that experiment really do it? People could always argue that whatever means you sued to store the measurement was actually in a supersposition of states and that you need to observe that for one of those states to be "chosen", much like the cat itself.
So, in these terms, at least, the Copenhagen Interpretation is unfalsifiable.
However, I have the feeling that something like what you suggested has been and it gave non-woo results...
Posted by: valhar2000 | March 20, 2007 at 04:16 PM
Wouldn't the cat itself be an observer in this instance? What if it were two cats in the box, or a person and a cat?
Posted by: G. Shelley | March 24, 2007 at 10:51 AM
Well, presumably the person and/or second cat would be equally affected by the poison. But the point is that the system inside the box is closed off from the outside, so there is no transfer of information between them. Until a measurement occurs, in which information (photons, noise, the smell of rotting cat) is transmitted from the system inside the box to a measurement device outside the box (a monitor, an eye, a person's nose), then the system inside the box is in a superposition state, from the point of view of the measure-er.
Posted by: Tom Foss | March 24, 2007 at 11:35 AM
Great post!
Posted by: beajerry | March 26, 2007 at 07:54 AM
it's actually an interesting read to see what theists have to say about quantum mechanics. Take it from me, someone with an obsessive interest - but no formal training - in Quantum mechanics, that all of what Alex is saying is twaddle.
http://www.vision.net.au/~apaterson/esoteric/esoteric_theory.htm
Posted by: Russ Graham | March 26, 2007 at 10:55 PM
Why wouldn't a recording device in the box with the cat replayed at a later time be sufficient to prove or disprove the indeterminacy of its state?
Moreover, why isn't this the cat thought experiment obviously understood as a reductio? What exists that is not specifically what it is, e.g. either dead or alive? Why conflate lack of measurement with metaphysical indeterminacy?
Posted by: Kevin | March 31, 2007 at 07:38 AM
I think a lot of people get hung up on the cat in this experiment; all the cat is is a recording device, a tool for measurement. The activating of the poison and the death of the cat are both just ways to measure whether or not the isotope has decayed. It makes no difference if you have this Rube Goldbergian cat-killing device or just a simple sensor to tell whether or not the isotope has decayed. It's the system which is in a superposition state, and any such system would remain in that state until there were a net information transfer between it and its surroundings.
I think.
And this is where some of the quantum weirdness comes in, specifically with regard to wavefunction collapse and superposition states. It's not metaphysical in the least, it's simply counterintuitive. Before we make a measurement (a transfer of info from system to surroundings), the system could be in two states, for which there is equal probability. While we have this uncertainty (not Heisenbergian uncertainty, mind you), the system is in a superposition of two states, simultaneously occupying both and neither. When the measurement is made, the wavefunction of the system collapses randomly into one of the possible states (or eigenstates).This may sound utterly useless and metaphysical, but it can be observed and has practical implications, particularly when we talk about double-slit experiments and wave/particle duality. I could go in-depth, but the Wiki entry on superposition is pretty decent as far as summarizing it.
I think the biggest problem with QM and woos is that so much of QM is counterintuitive and just-plain-weird that the woos think it justifies anything counterintuitive and weird.
Because the state is only indeterminate as long as there is no net transfer of information from the system to its surroundings (i.e., from the box to the outside world). Once you pull the recording device out, there has been a transfer of information, and the system collapses. As long as the recording device is inside the box, it is part of the system; it is the system which is in a superposition state.Posted by: Tom Foss | March 31, 2007 at 10:23 AM
I seem to recall discussion of this "large superposition" issue in the pages of Scientific American. (They used balanced playing-cards for their examples and images, if that helps locate the article.) The upshot was that in practice, a superposition that large (or anything like "human scale") is hopelessly unstable, even without an explicit information transfer. The system collapses into a single result within some unimaginably tiny speck of a finely-ground second.
Posted by: David Harmon | April 01, 2007 at 03:54 PM
I am a student at All Saints Catholic school who is currently doing a GCSE course in I.C.T. As part of my course, I have to collect images due to my course relating to a younger audience about eating heathlily. I am asking for your permission if I could use some of the cartoon images to include into my documents.
Thank you for your time
Miss F.O
Posted by: Miss F.O | October 19, 2007 at 02:17 AM