Published in Physics Today, June 1992

Abstract. Most of the matter in the cosmos can't be seen directly at any wavelength. But we can map and weigh great clumps of this dark matter as they bend the light shining through them from distant background galaxies.

Table of Contents

• INTRODUCTION
• GRAVITATIONAL LENSING
• DARK MATTER AND EVOLUTION
• THE BACKGROUND GALAXIES
• THE FIRST LENSES
• GALAXY CLUSTERS AS LENSES
• SIMULATIONS
• THE INVERSE PROBLEM
• ABELL 1689 EXPOSED
• REFERENCES