University of Pennsylvania Astrophysics Seminar

21 cm cosmology -- the concept of using radio telescopes to observe the highly redshifted 21 cm line of neutral hydrogen on cosmological scales -- is a field with tremendous scientific potential.   After nearly 20 years of experimental effort, however, a detection of the Epoch of Reionization (EoR) signal remains elusive.  The fundamental challenge is a sea of foreground emission nearly five orders of magnitude stronger than the signal of interest, although the past two decades have revealed just how much the design of the instrument plays a role in compounding this problem.  This talk will review the status of the field, including the lessons learned from a now-concluded first generation of experiments and updates from a second generation of experiments nearing completion.  I will particularly emphasize the work being done with the Murchison Widefield Array (MWA) and our efforts address the worsening challenge of human generated radio-frequency interference (RFI).  Even if successful, however, these second generation experiments will only be the beginning for 21 cm cosmology, and I will conclude by discussing future directions for the field, both on the ground and the lunar far side.