Thought experiments are the best kind of experiment. They take place in the mind where anything is possible. They involve no dangerously combustible chemicals, no finicky data-collection or the wearing of unflattering lab-coats. No animals are harmed in thought experiments – except perhaps in the case of Schrödinger's Cat - and then only very theoretically.
All that is required for a thought experiment is what - if you were telling a joke - would be the set-up, plus some imagination and wild surmising. The set-up can be very simple or mind-bendingly elaborate and aimed at illuminating the farthest shores of philosophical and scientific thought. Apparently Galileo didn’t actually lob tennis balls and refrigerators off the leaning tower of Pisa in order to conclude that that objects fall at the same speed regardless of their weight. He saved himself all the hard yakker by coming to the same conclusion via a thought experiment.
And of course Herr Schrödinger, in his famous thought experiment, only had to lock an imaginary cat in a box with an imaginary Geiger counter, some completely non-existent hydrocyanic acid and a dab of fictitious radioactive material, in order to elucidate his argument about quantum mechanics. Whatever that was.
I’ve devised a few thought experiments of my own – necessarily constrained by the fact that this column is intended for a general readership. So please, come along with me to the Thought Lab and apply your imagination, intuition and reason to the following three thought experiments. The first couple of experiments are pretty straightforward. The last one though … well, let’s just say it allows plenty of room for thought. ...