The use of computer simulations is changing the nature of scientific investigation and providing us unique insights into the way that the world works. As simulation moves from the desktop to more ubiquitous portable devices (such as PDAs), we can draw upon the unique affordances of these devices - portability, social interactivity, context sensitivity, connectivity, and individuality. The purpose of this research project is to develop and examine a new simulation platform that is designed from the ground up for handheld to create augmented reality simulations (i.e. simulations that bridge virtual and real worlds). This paper describes Environmental Detectives, one such augmented reality simulation that is currently being developed at MIT. In the upcoming months, we will develop and test this concept as well as produce a suite of authoring tools that students and teachers can use to design their own augmented reality simulations.