what is the quantum cat?

Question

I don't really get what it is, so can someone explain it in simple terms please? also, do quantum particles actually exist, because loads of people seem to refer to some of it as theory...

thanks.

Answer 1

Basically it is a cat that will die if an atom decays.
What the theory says is that the cat and the atom are in supersition. They are both dead and alive or decayed and not decayed. It is only when someone observes the cat that it either dies or survives. This is only a theory as we can not test it because we would have to observe it to see what happens.
This is known as Schroedinger's cat

Answer 2

The second part of your question first ...

Like many branches of physics, the science governing quantum physics is called a theory. This does not mean it is not valid - the theory of quantum physics has made some of the most precise experimental predictions of any physics theory & has explained many many observations that no other theory can explain.

So yes - the theory describes reality very effectively. This can be understood to mean that quantum particles 'exist' is the normal use of the language. However, that brings us to the the first part of your question.

The 'reality' predicted by quantum theories is very different from the reality that you and I experience in our day to day lives. In the quantum world, particles can appear and disappear in random seeming ways - the theory only predicts chances of things happening: never exact times or positions.

Even more bizzarely, in the quantum description of things, seemingly unrelated properties of an object or group of objects become connected so that when one aspect 'changes' randomly this alters the other aspects too.

The predictions about the future behaviour of the system that quantum theory makes, involve statements of probability describing the chance of each different aspect taking on certain values. The system is described completely by an equation that mixes the probabilities for all the aspects into one entity called the 'wave function'.

This unexpected 'mix' of different aspects is what the quantum cat story is about. In the 'thought experiment' we imagine a situation where the cat is enclosed in a box with a radioactive material (uranium or something) and a geiger counter. The geiger counter is connected to a gun and the gun will fire and kill the cat when it counts a certain number of decays.

Now the whole system of cat, uranium, geiger counter and gun constitute a quantum system and the theory can make predictions about the chances of what will happen in the future. So, the theory might say that the cat has a 50% chance of being killed after 2 minutes.

But depending on who you talk to, the prediction can be interpreted in two ways. Either it is just a simple probability and all the time the cat is just in one of the two states: dead or alive - the actual state is revealed when the box is opened.

Or, the theory actually can mean that cat is both dead and alive until you look - since the description of the entire system within the box actually consists of a 'mix' of the dead and alive state. In this view, we are forced to think of the cat as not 'existing' in a conventional sense while its inside the box unobserved - it is both dead and alive since that is how the 'wave function' describes the system of box, cat, geiger counter and uranium.

Clearly this is tough stuff ... the quantum world is not 'sensible' in the same way that the normal world is. Luckily, the vast majority of non-intuitive behaviour occurs on the very tiny scale of atoms and particles, so we don't have to worry about it!

Answer 3

Schrodinger's cat is a thought experiment proosed by Erwin Shrödinger to explain the idea that in quantum mechanics a result can only be given in terms of probabilities and never in terms of absolute facts.

In order to get around the problem that it was all so difficult to visualise he came up with the following idea.

A single atom of a material likely undergo nuclear decay, with a probability that it WILL decay of 50%, is put in a sealed box with a cat.

The atom is in some way linked to a machine which will release a deadly cat poison if it decays, but the cat will only die if the atom decays, and if the box is kept closed.

Now the question is simply if the cat is alive or dead.

Without opening the box, we will never know (if we forget the fact that eventually the cat will die of hunger or thirst or possibly boredom), but opening the box will destroy the experiment.

He proposed this experiment to show the way in which a quantum event could never be defined as an absolute event in the way that we normally consider an event as a visible thing.

But who was he trying to convince (and furthermore succeeded)?
Noone special:
Albert Einstein.

Answer 4

Here's an interesting spin on this if you can bare to Watch Deal or No Deal. All of the boxes contain Schrodinger cats, as the game progresses the probability of there actually being a good cat in your box depends on what has gone before - or does it. It certainly does not depend on providence as the games tries to tell us.

Its a rubbish show, but a great case study in decision making