This book provides a pedagogical introduction to the likely sources of
these neutrinos, their propagation and detection mechanisms. Detection
of high energy neutrinos of extragalactic origin has led to an
interdisciplinary field of research, involving astronomy, astrophysics
and particle physics. An extensive review of various detectors and the
observations is provided that consolidates the latest findings. Above a
few tens of TeVs, neutrinos are conceived as more reliable messengers
for astronomy than photons as these photons get absorbed in the
background photon field. Determining the neutrino spectrum not only
helps in exploring astrophysical objects like AGN, GRB, etc. but also
allows us to study particle physics at unprecedented energies. This
introductory book is intended to help advanced undergraduate and
graduate students to get into the subject with ease, and it
simultaneously caters to practicing theoretical or experimental
physicists as a reference book.