Knowing the Universe: Revealing & Replicating

Thirty years ago, our knowledge about the state of the universe was highly uncertain.  Although theorists had identified the some of the key physical processes at play as cosmic structure formed, our understanding of how these various processes interacted with each other to sculpt the large- and small-scale (ie galaxy-scale) diversity that the universe manifests was rather rudimentary.    In the late 80s, the situation started to change dramatically, propelled by the commissioning of powerful new telescopes probing the cosmos across the entire EM spectrum, the development of new technologies like “digital film” (CCDs), and the emergence of powerful new supercomputers.   Extragalactic astronomy has gone from being data starved to immensely data rich, to even data overwhelmed.  Focusing on cosmic structure, I will highlight the key findings of the past 30 years and then discuss how astrophysicists, like myself, go about building a comprehensive model for the formation and evolution of structure in the universe.   I will discuss how astrophysicists  address the fundamental challenge: the fact that we have but one experiment - our observable universe - and no chance of tinkering with the conditions and repeating the experiment.  I will show that contemporary models are remarkably successful at explaining the origin and evolution of the large-scale structure of the cosmic web and at explaining the nature of the small and medium-sized galaxies.   I will also discuss the regime where the model strains and fails, and discuss what is required to make further progress.