Sub-atomic constraints on the Kerr geometry of GW150914

General relativity predicts that the interior of black holes is an empty region surrounded by an event horizon. This perspective was challenged by the realization that black holes radiate quantum mechanically and evaporate, which led to the so-called ''information paradox''. The resolution of the paradox introduces horizon-scale corrections to the classical black hole picture. In this talk, I'll demonstrate how by performing long-duration observation in the post-merger data immediately following GW150914, we are able to impose significant constraints on these corrections and put sub-atomic bounds on the horizon's position.