  We consider problems in which robots conspire to present a view of the world
that differs from reality. The inquiry is motivated by the problem of
validating robot behavior physically despite there being a discrepancy between
the robots we have at hand and those we wish to study, or the environment for
testing that is available versus that which is desired, or other potential
mismatches in this vein. After formulating the concept of a convincing
illusion, essentially a notion of system simulation that takes place in the
real world, we examine the implications of this type of simulability in terms
of infrastructure requirements. Time is one important resource: some robots may
be able to simulate some others but, perhaps, only at a rate that is slower
than real-time. This difference gives a way of relating the simulating and the
simulated systems in a form that is relative. We establish some theorems,
including one with the flavor of an impossibility result, and providing several
examples throughout. Finally, we present data from a simple multi-robot
experiment based on this theory, with a robot navigating amid an unbounded
field of obstacles.
