Introduction

‘The principle of science, the definition almost, is the following: The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth”’.

So wrote Richard Feynman, famous scientist and Nobel Prize winner, noted for his contributions to physics.

It is possible that when Feynman wrote these words he had in mind elaborate experiments devised to reveal the ‘secrets of the Universe’, such as those involving the creation of new particles during high energy collisions in particle accelerators or others to determine the structure of DNA. Experimentation encompasses an enormous range of more humble (but extremely important) activities such as testing the temperature of a baby's bath water by immersing an elbow into the water, or pressing on a bicycle tyre to establish whether it needs inflating. The absence of numerical measures of quantities distinguishes these experiments from those normally performed by scientists.