What is the dimension of citation space?

We adapt and use methods from the causal set approach to quantum gravity to analyse the structure of citation networks from academic papers on the arXiv, supreme court judgements from the US, and patents. We exploit the causal structure of of citation networks to measure the dimension of the Minkowski space in which these directed acyclic graphs can most easily be embedded explicitly taking time into account as one of the dimensions we are measuring. We show that seemingly similar networks have measurably different dimensions. Our interpretation is that a high dimension corresponds to diverse citation behaviour while a low dimension indicates a narrow range of citations in a field.