• Question: how does shrodingers cat work

    Asked by dyaskelly to Ben, Clare, Ezzy, Mario, Sam on 14 Mar 2012.
    • Photo: Sam Vinko

      Sam Vinko answered on 14 Mar 2012:

      Its a way of illustrating a concept in quantum mechanics of superposition for two states: that you can have two states at the same time.

      The story goes that you have a cat in a closed box, into which you cannot see, nor have any other way of knowing whats going on inside (say, hearing the cat purr). Now in the box with the cat there is also something else, which after a certain period of time, has a certain probability of killing the cat. For example, after 1 hour you could have 50% chance the cat is dead, 50% its alive.

      Now normally you’d think that after 1 hour the cat is effectively either dead, or alive. You might not know which of the two, but you’re sure its only one of the two things. Dead. Or alive.

      In quantum mechanics though thats not the case, and the cat is both dead and alive, in a strange limbo of both of the two. Only when you look in the box does the limbo ‘collapse’ into one of the two possible outcomes (dead or alive) but ONLY then, not before!

      Thats the bizarre world of quantum mechanics.

    • Photo: Clare Burrage

      Clare Burrage answered on 14 Mar 2012:

      One of the big ideas in quantum mechanics is that making observations is important. Until we look at something and make a measurement all things (that are allowed by physics) are possible. The universe doesn’t have to choose between all of these possibilities until we make a measurement, and until then all of the different possibilities are happening at once.

      The idea of Schrodinger’s cat is that we place a cat inside a box with a radioactive element and a bottle of poison that will smash if the radio active element decays (don’t try to do this!). Then we close the box so that we can’t know anything about what’s going on inside. Two things could be happening either the bottle of poison could be smashed, which would kill the cat. Or the bottle of poison could not be smashed, and the cat would be alive.
      What quantum mechanics tells us, is that both of these things are happening at once, and it’s only when we open the box to look inside that the universe chooses which one we will see. How it chooses is described by the equations of quantum mechanics.

      It’s very strange, but our world really does seem to work like this!

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