So is the cat dead or alive?

I know you people will flame me for this, but I cannot get a handle on this dead and living cat thing. I don’t even know what it is called, but I know that it is someone’s cat and it is supposed to be alive and dead at the same time. Oh yeah…the cat’s in a box too. I would really appreciate any help you can provide.



It’s Schroedengers cat. I know I mispelled it,I’m pretty sure Cecil wrote about it. Someone will follow this post with more info.

The poster beneath me is really smart!

Oh, Lord, the cat’s out of the box again!

Erwin Schrodinger (umlaut ad lib) was a theoretical physicist in the earlier part of this century who came up with the interesting concept of explaining quantum indeterminacy at the macro, observable level, like this:

Imagine a cat in a sealed box, complete with oxygen, CO2 scrubber, cat food, kitty litter, catnip mouse, and all that makes for feline contentment. You cannot observe the inside of the box, or detect the cat hanging out in it. Attached to this box is a tank of poison gas with a closed valve. The valve is governed by a relay which is hooked to a photocell. The photocell is set to “observe” a radioisotope with a given half-life. When the photocell picks up enough scintillations from atoms breaking down, it will trigger the relay to open the valve. Now, leave the cat in the box for exactly one half-life of the radioisotope.

Answer the following question: is the cat alive or dead? Since the radioisotope has gone through one half-life, the odds are 50:50.

According to Schrodinger, the cat is both alive and dead, in 50% probability of being either, until the box is opened and you can determine which happened.

Probably UndeadDude can amplify this or make it clearer, but that contrary-to-common-sense result is what the laws of physics say happens.

BTW, thanks, Orangecakes! :slight_smile:

Here’s Cecils (quite literary) replay about Schroedinger’s cat.

Reply, that is.



Schroedinger’s Cat is a pretty complicated problem to understand.

First, the setup:

You take a kitty and put in a box. The box has a glass flask of poisonous gas (or something fatal). There is a hammer in the box which is set to break the flask if a geieger counter detects and radiation.

Okay, so you take a radioactive atom. If/when the atom decays it will trigger the geiger counter which will trigger the hammer which will trigger the gas which will kill the cat.


the state of the cat
= the state of the glass flask
= the state of the hammer
= the state of the geiger counter
= the state of the atom
= a wave function

Quantum physics states that the state of the atom is the superposition of the wave functions of decayed and non-decayed states of the atom until an observation is made. Once an observation is made (hearing the geiger counter click, hearing the hammer fall, hearing the glass break, or opening the box to check on poor kitty) the wave functions collapse into either the decayed or non-decayed state; however, until the observation is made the cat is both dead and alive.

What more could you expect from somebody who lets people kick him to the head?

So basically, you aren’t actually supposed to believe that the cat is alive AND dead, it is just a way of saying that you don’t know if the cat is alive or dead…right?

The way I understood this was that Shroedinger proposed this thought experiment to show how silly much of the talk about the Uncertainty Principal is. The wave expression is only used to represent the possible states a particle/cat could be in - it is not meant to be definitive. Obviously a particle has a single velocity and location etc. but it cannot be known.

To answer the real question: the cat is EITHER alive OR dead, it is just not known which until the box is opened. If you had to do mathematical equations that involved the livlihood of the cat you would have to use an average of dead and not dead.

Sorry, Greathouse, you’ve got it precisely backwards. I don’t know if Schroedinger actually meant it sarcastically as Cooper claims, but modern physicists take it very seriously.

The idea is that until we open the box, the question “Is the cat dead?” cannot be answered. But this is not because we have insufficient information. Rather, it is because the question is meaningless. One cannot talk about the cat being alive or dead, only about the possiblity that it’s alive, or the possiblility that it’s dead. Only after we look inside does the possibility become a reality.

I do not really understand the underlying principles as well as I’d like, but it is very clear that the very concept of reality is what is being discussed here.

I beleive that origins of this concept are related to experiments which conclusively prove light to be made of particles, while other experiments - made by the same people! - conclusively prove light to be made of waves, while those same people agree that it is impossible for light to be both waves and particles. In other words, the reality is affected by the mere observing of the event.

Here is a totally unrelated idea which might help a little: Take this statement: “It will rain tomorrow in location ABC at time XYZ.” Is this statement true or not? Well, it could be argued that right now, the statement is both true and false, and we won’t know till tomorrow. Alternatively, we could say that the statement is meaningless, being neither true nor false, until tomorrow. So too, Schroedinger’s cat is both alive and dead, and neither alive nor dead, until we look in the box.

This problem is very much largely oddball, but I disagree that the cat is “either alive or dead”, the cat is very much like the atom. It’s state is the superposition of the decayed wave equation and the non-decayed wave equation.

This must be so, because it is similar to the photons through the slits problem. The passage of the photons through slit A is an equation, the passage of the photons through slit B is another equation, and the photons true passage is the superposition of those equations, which results in the unmistakable pattern (the alternating light and dark patterns were the waves are in phase or not). This pattern exists even if the rate of photons (or electrons) is low, meaning that the photons do pass through both slits.

Similarly, the cat is both alive and dead.

Either that or I don’t understand this either, which I confess is a real possibility.

Brain . . . frying . . . must . . . go . . . watch . . . Simpsons . . . .

Okay, let me try this again. The can can be alive AND dead because we don’t have enough information to form a conclusive answer one way or the other…right?

This drives me crazy because we all know it is impossible for the cat to be alive and dead at the same time. It’s not logical.



Exactly, Greathouse. But that’s the result. In fact, IIRC, there was an experiment where a single photon was released in the photons-through-slits experiment, and it passed through both slits. Or at least the moire pattern resulting said it did.

It is very confusing. But there is another facet to this not yet covered and that is the probability wave. If you take these wave equations as a kind of probability wave and start solving them out what you do get is a probability that the cat is dead or alive which approaches 100% as more time goes by (higher chance that the atom is in the decayed state), which now that I think about it might be what Cooler (I think it was him) was getting at.

Personally, the cat is a pretty cool paradox, but difficult to really grasp. To really understand this mumbo jumbo look into the twin slits problem. It makes things much clearer. has an .ra file of a lecture on the twin slits. I am sure you can find other sites with info on the twin slits.

The thing I don’t understand about the Schrodinger’s cat problem is how quantum physics is involved per se. It seems like we could forget radioisotopes and have pretty much the same thing.

Here’s the accountant’s version of the same problem, which we’ll call Badenov’s cat (I’m not an accountant or a physicist, but we’ll pretend).

So there’s this cat, certified by the Cat Fanciers’ Association to be worth $1000. It goes messing around a vault with a time-lock. The vault is filled with enough food to keep a cat alive for an average of three days. Some busybody shuts the door on the vault, which locks for three days. What is the estimated value of the vault’s contents (assuming there’s nothing else in there)?


Is this because a half-dead cat is worth half the money? No, if the cat’s alive it’s worth all the money; if the cat dies, even two seconds before the vault opens, it’s worth zilch.

So, take out all the physics, and the Schrodinger’s cat problem is pretty much the same. It seems much more like a statement about probability and information. If you don’t have the facts (and we don’t, in observations of subatomic particles, or in economic forecasts), you at least need to be sure of your estimates of various likelihoods. Saying, “the vault’s contents are worth $500” might not be very informative in a single case, but in a bunch of cases combined, it works just fine.

So, that’s why I don’t know why physics per se are involved in the problem.

Nothing I write about any person or group should be applied to a larger group.

  • Boris Badenov

Off-topic, but one of my favorite absolutely true stories:

My friend Bruce lives in LA and used to work at the Court House. During the last solar eclipse, he made a pin hole camera out of a cardboard box and went out to project the eclipse on the front steps. A typically unaware Angelino (hey, I love the city, but the people sometimes blow my mind!) sees Bruce with box, staring at the steps, and asks “What’s in the box?”

Bruce: “It’s a pin hole camera.”

Stranger #1: “What are you taking a picture of?”

Bruce: “The eclipse.”

Stranger #1: (Looking at the sun) “I thought it was in the sky?”


Stranger #1: “Oh.” (walks away)

Stranger #2: “What’s in the box?”

Bruce: (getting annoyed) “It’s a pin hole camera.”

Stranger #2: “What are you taking a picture of?”

Bruce: “The eclipse.”

Stranger #2: (Looking at the sun) “I thought it was in the sky?”


Stranger #2: “Oh.” (walks away)

Stranger #3: “What’s in the box?”


Stranger #3: “Oh.” (walks away)

One of my favorite Bruce-isms.

See, I still don’t get this, and I assure you all I’m trying my best to follow along. I’m not grasping why it’s not an either/or proposition, and I’ll frankly admit that chances are good that I’ll never grasp that. But even the accounting example doesn’t make any sense. The contents of the vault are NEVER worth $500. Ever. So why would that be an estimated value under any circumstances? The contents are worth either 0 or $1,000, no matter how many vaults and how many cats (assuming each if valued separately). The only justification I can see for valuing them at $500 is to minimize loss potential (i.e., the hit you take if you’re wrong), which makes sense in terms of accounting but not in terms of Schroedinger’s cat. Help me out here.

The trick is that you always change to the third door. That way, regardless of whether the cat is alive or dead, you will win the prize.

The question of money in envelope was discussed here, ad infinitam, as a probability/statistics problem.