The quest for Omega

Is the universe finite or infinite? Will the Big Bang end in a Big Crunch? Is space really curved? How much matter is there in the universe? What form is this matter? The answers to all these questions depend critically on the mysterious number known to cosmologists as Omega, Ω. For decades, experimentalists have grappled with the problem of how to measure Ω using observations of the universe around us with only limited success. But dramatic progress in the development and application of astronomical detector technology suggests the possibility that the value of Ω may finally be pinned down within the next few years. The issue of Ω is, however, not entirely an observational one, because the precise value that this quantity takes holds important clues about the very early stages of the Big Bang, and for the structure of our universe on very large scales. In this article I review why Ω is of such importance and its value so elusive.