The very term ‘experiment’ implies uncertainty, because why would one want to conduct an experiment if the outcome is certain? The goal of experimentation is to learn something new about a system, something that is unknown, or only poorly understood. Experiments are a natural outgrowth of models, because a model, whether conceptual, physical or numerical, will always be a simplified representation of a system, and experiments with this model help us to understand its strengths and weaknesses. In terms of consequences, the simplifications embodied in the model may not matter under many circumstances, but then along comes the special situation when the model becomes vulnerable. In this context, models invite experiments that put them to the test, in a process of validation.

Just as model building begins with a concept, a mental image of how something is constructed or functions, so also does experimentation begin with what are called ‘thought experiments’. These experiments are mental forays that explore the consequences of assumptions or possible paths of action. Albert Einstein was a firm advocate of thought experiments; many of his early concepts about relativity stemmed from his attempts to visualize how the universe would appear if he were to hitch a ride on a beam of light.

Experiments essentially pose questions and seek answers. A good experiment provides an unambiguous answer to a well-posed question.