Reionization and the Cosmic Dawn with the Square Kilometre Array
  The Square Kilometre Array (SKA) will have a low frequency component
(SKA-low) which has as one of its main science goals the study of the
redshifted 21cm line from the earliest phases of star and galaxy formation in
the Universe. This 21cm signal provides a new and unique window on both the
formation of the first stars and accreting black holes and the later period of
substantial ionization of the intergalactic medium. The signal will teach us
fundamental new things about the earliest phases of structure formation,
cosmology and even has the potential to lead to the discovery of new physical
phenomena. Here we present a white paper with an overview of the science
questions that SKA-low can address, how we plan to tackle these questions and
what this implies for the basic design of the telescope.
