Even when physical geographers have developed a theory about how reality operates they still need to determine if this theory ‘works’ in the ‘fi eld’. The ‘fi eld’ refers to the arena within which the theory is assessed to see whether it operates as expected. This could be the fi eld as understood as the natural environment, it could be the fi eld as understood as a controlled subsection of the environment as in fi eld trials. Laboratory-based and computer model simulations would also count as the ‘fi eld’ in this context. ‘Work’ in this context is assessing whether the results of probing reality, its measurement, matches the expectations that have been derived from the theory.