Science with a Giant Segmented Mirror Telescope


The past decade witnessed unprecedented investment (more than
$1.5 B world-wide) in 6-10m class
telescopes (Keck; VLT; Subaru; Gemini; Magellan). The value of this
investment is manifest in the continuous stream of new discoveries from
these facilities --
from the first statistical studies of large scale structure at z > 3 to
analysis of debris disks surrounding nearby stars. While their enormous
potential has yet to be realized fully, they have already pointed the
way toward frontiers of sensitivity and angular resolution that must
be crossed in order to confront fundamental problems.

As a result, a number of groups have begun to explore design concepts
for next generation telescopes ranging in size from 20m to 100m
in diameter. I describe the scientific potential of such telescopes in areas
as diverse as cosmology and large-scale structure; assembly of galaxies;
formation of stars and planetary systems; and discovery and characterization
of exo-planets. Of equal interest are the design challenges that must
be met in order that these telescopes achieve exquisite image quality
in the face of atmospheric turbulence and wind. I describe those 
challenges along with some of the solutions currently under consideration.

Finally, I discuss the status of a number of extremely large telescope
projects, and the prospects both for involving the community during
the design phase of these projects and for providing broad, merit-based
access during once ELTs begin operation.