Computation itself seems immaterial, but whether on your smartphone or in ‘the cloud’, it is very physical: electrons moving on silicon wafer photons streaming along optical fibres.  In this chapter, we explore this physicality of computation.   Physics puts fundamental limitations on computation, and we see how this means that computation and information must come together at the same point in time and space.  Practically, we have not reached these limits, Moore’s Law drives the miniaturisation and commoditisation of computation, which in turn enables radical changes including the Internet of Things and even coating every surface with a computation.  In robots, autonomous vehicles, drones, and Alexa in your living room computation is physically amongst us.  However physical computation has been around for many years: the success of market economies is due to the physical representation of information in money, a role that is now changing with digital currency and online commerce.

Keywords: embodied computation, ubiquitous computing, physical computation