WHY SCHRÖDINGER'S CAT IS STILL THE MOST CONTROVERSIAL THOUGHT EXPERIMENT IN SCIENCE

Nearly a century after its formulation, the paradox remains hotly debated among researchers

- DR KATIE MACK

One of the most important tools in the theoretical physicist's kit is the thought experiment. If you study relativity, quantum mechanics or any area of physics applying to environments or situations in which you cannot (or should not) place yourself, you'll find that you spend a lot more time working through imaginary scenarios than setting up instruments and taking measurements.

Thought experiments pose an imaginary question and work through a logical, 'if/then' sequence to explore what the theory really means. Asking "what has to happen if the theory is true?" is vital for developing intuition and anticipating new applications. In some cases, a thought experiment can reveal the deep philosophical implications of a theory or even present what appears to be an unsolvable paradox.

Probably the most famous thought experiment is Schrödinger's Cat - because it involves (purely hypothetical) carnage and its implications for the nature of reality in a quantum world continue to challenge students and theorists everywhere.

The basic (again, purely hypothetical) setup is this. Imagine you have a radioactive atom that has a 50 per cent chance of nuclear decay in a certain time (let's say, an hour). You put this atom in a box along with a vial of poison and a device that will break the vial if the atom decays. Then, you put a live cat in the box, close the lid and wait an hour before opening it again.