Title: Interpreting star formation in galaxies across cosmic time with binary population synthesis models Abstract: The study of distant galaxies is an ever increasing area of astrophysics - piecing together the building blocks that went together to form massive galaxies like our own, and ultimately led to our own existence. The frontier is constantly being pushed back, with new epochs and stellar populations coming within the reach of new facilities. However, the distance to these objects still makes observations and detailed interpretation challenging, even in the era of ALMA and other new instrumentation. Data is inevitably noisy and incomplete, and modelling is required to interpret the detected light in the context of the stellar populations which produced it. In this talk I will discuss a recently developed stellar population synthesis code, BPASS, in which we include binary evolution pathways in modelling the evolution of starbursts. I will describe examples of its application and the scientific insights it has yielded into star forming galaxies in the local Universe, in analysis of the stellar populations giving rise to gamma-ray bursts, and in the analysis of galaxies in the distant Universe.