  Parity and time reversal are obvious and plausible candidates for fundamental
symmetries of nature. Hypothesising that these symmetries exist implies the
existence of a new form of matter, called mirror matter. The mirror matter
theory (or exact parity model) makes four main predictions: 1) Dark matter in
the form of mirror matter should exist in the Universe (i.e. mirror galaxies,
stars, planets, meteoroids...), 2) Maximal ordinary neutrino - mirror neutrino
oscillations if neutrinos have mass, 3) Orthopositronium should have a shorter
effective lifetime than predicted by QED (in "vacuum" experiments) because of
the effects of photon-mirror photon mixing and 4) Higgs production and decay
rate should be 50% lower than in the standard model due to Higgs mirror - Higgs
mixing (assuming that the seperation of the Higgs masses is larger than their
decay widths). At the present time there is strong experimental/observational
evidence supporting the first three of these predictions, while the fourth one
is not tested yet because the Higgs boson, predicted in the standard model of
particle physics, is yet to be found. This experimental/observational evidence
is rich and varied ranging from the atmospheric and solar neutrino deficits,
MACHO gravitational microlensing events, strange properties of extra-solar
planets, the existence of "isolated" planets, orthopositronium lifetime
anomaly, Tunguska and other strange "meteor" events including perhaps, the
origin of the moon. The purpose of this article is to provide a not too
technical review of these ideas along with some new results.
