  We discuss low frequency radio astronomy from the moon, predominantly in the
context of studying the neutral intergalactic medium during cosmic reionization
using the HI 21cm line of neutral hydrogen. The epoch of reionization is the
next frontier in observational cosmology, and HI 21cm studies are recognized as
the most direct probe of this key epoch in cosmic structure formation. Current
constraints on reionization indicate that the redshifted HI 21cm signals will
likely be in the range of 100 MHz to 180 MHz, with the pre-reionization signal
going to as low as 10 MHz. The primary observational challenges to these
studies are: (1) ionospheric phase fluctuations, (ii) terrestrial radio
frequency interference, and (iii) Galactic and extragalactic foreground
radiation. Going to the far side of the moon removes the first two of these
challenges. Moreover, a low frequency telescope will be relatively easy to
deploy and maintain on the moon, at least compared to other, higher frequency
telescopes. We discuss the potential 21cm signals from reionization, and
beyond, and the telescope specifications needed to measure these signals. The
near-term ground-based projects will act as path-finders for a potential future
low frequency radio telescope on the moon. If it is found that the terrestrial
interference environment, or ionospheric phase fluctuations, preclude
ground-based studies of reionization, then it becomes imperative to locate
future telescopes on the far side of the moon. Besides pursuing these
path-finder reionization telescopes, we recommend a number of near-term studies
that could help pave the way for low frequency astronomy on the moon.
