Abstract:

Roughly 90% of the matter in the universe is dark, which presents a problem for those who would like to study its structure. Astronomers have traditionally studied the small fraction which emits light, but gravitational lensing can in principle reveal any foreground mass concentration given background sources of light. Initially applied only to the densest regions of the universe, gravitational lensing has matured enough to reveal the subtle net effect of the many overdensities between us and a typical background galaxy. Measurements of this "cosmic shear" effect are beginning to complement other methods in constraining the density of matter in the universe and other cosmological parameters. Although the agreement among different methods is encouraging, the errorbars are still large. I will talk about our detection of this effect, compare the other detections which have appeared in the literature, and show the vast potential for improvement over the next few years.