From the time the Universe was just four-hundred thousand years old to when it was one-billion years old, most of its hydrogen was neutral. Neutral hydrogen produces 21cm radiation, and the amount of information in this signal dwarfs that of all other cosmological probes. TA scientists are part of the team which is operating the Mileura Widefield Array (MWA), a large radio interferometer being built in Western Australia to observe this signal. On the theoretical front, TA scientists are attempting to understand the details of the 21cm signal and how this signal can be used as a probe of the reionization process, of the cosmological Dark Ages, and of the Cosmology.
Lars Hernquist, Abraham Loeb, George B. Rybicki, Matias Zaldarriaga