8. OUTLOOK
Over the next few years, we can look forward to several new
instruments that will be well suited to studying different aspects of the
gravitational lens problem. At radio wavelengths, the VLBA should
produce far more detailed maps of the radio rings as well as the radio
jets in Q0957+561 and Q2016+112, which will motivate correspondingly
detailed modeling. The enlarged MERLIN radio telescope may have just
the right angular resolution to find several more examples of
galaxy-imaged compact radio sources. In the optical, a repaired and
fully operational Hubble Space Telescope will have the angular
resolution to locate intervening galaxies, and the Keck Telescope will
be particularly important for faint object spectroscopy. Detector
advances in CCDs and infrared arrays also promise to make a
substantial difference. Because of these and several other developments,
the observational future looks bright.
If we can learn anything from the history of cosmology, it is
that it is much easier in theory than in observational practice to
make secure, quantitative deductions about the large scale structure
and the evolution of the universe. By contrast, if the last
decade's progress in understanding gravitational lenses can teach us
anything, it is that we have usually been too conservative in our
anticipation of novel phenomena. It will be fascinating to
see which of these two opposing trends dominates over the next decade.
ACKNOWLEDGEMENTS
This work was supported in part by NSF grants AST 89-17765 (RB) and
AST 91-09525 (RN). We thank George Efstathiou, Emilio Falco, Bernard
Fort, Paul Hewett, Chris Kochanek, Charles Lawrence, Jordi
Miralda-Escudé, Bohdan Paczynski, Kevin Rauch, Sjur Refsdal,
Rudy Schild, Peter Schneider, Jean Surdej, Sylvanie Wallington,
and Joachim Wambsganss for comments on the
draft manuscript. We are grateful to Helen Knudsen and Rosanne
Scholey for bibliographic assistance.