  The development of the atmospheric Cherenkov imaging technique has led to
significant advances in gamma-ray detection sensitivity in the energy range
from 200 GeV to 50 TeV. The Whipple Observatory 10m reflector has detected the
first galactic and extragalactic sources in the Northern Hemisphere; the Crab
Nebula has been established as the standard candle for ground-based gamma-ray
astronomy. The highly variable Active Galactic Nuclei, Markarian 421 and
Markarian 501, have proved to be particularly interesting. A new generation of
telescopes with improved sensitivity has the promise of interesting
measurements of fundamental phenomena in physics and astrophysics. VERITAS (the
Very Energetic Radiation Imaging Telescope Array System) is one such next
generation system; it is an array of seven large atmospheric Cherenkov
telescopes planned for a site in southern Arizona.
