The Elusiveness of Dark Matter: A Theorist's Apology

A preponderance of astronomical evidence suggests that the galaxy is filled with dark matter. Despite knowing remarkably little about what this dark matter is, we expect that it is not composed of ordinary matter. Though we have spent 30 years expecting that it may be related to pressing open problems in fundamental physics, a heroic experimental program has shown that dark matter is even more elusive than we had initially imagined.