Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

Abstract: Current pulsar timing array (PTA) projects are galactic-scale gravitational-wave (GW) detectors whose sensitivity is approaching the point at which a signal should become clearly detectable. Despite the strong evidence reported in the literature, I will argue that we do not quite yet have a detection of GWs. Reaching that point requires not merely more data: it involves asking the right statistical questions, ensuring that our analyses respect the underlying physics, and restructuring international workflows so that the sensitivity already present in released datasets becomes available many years earlier.

In this talk, I will give a personal—and at times critical—outlook on the future of data analysis across PTA collaborations worldwide. I will discuss more sensitive detection statistics, the limitations of current methods for reconstructing GW spatial correlations, and how the international PTA community can replace years-long, monolithic data-combination projects with continuously updated analyses of the global dataset. I will also consider how AI-assisted coding can both accelerate methodological progress and fragment shared scientific software. Finally, I will discuss how we can better understand and mitigate one of the principal uncontrolled components of our galactic-scale detector: the interstellar medium. Together, these developments could enable the first robust PTA detection years earlier (possibly with data already already taken!) and determine how much physics we can ultimately extract from the nanohertz GW sky.