Illustration of the effect of matter on the cosmic microwave background (CMB). On the right, the CMB is released shortly after the Big Bang, with tiny ripples in temperature due to fluctuations in the early universe. As the radiation traverses the universe, it experiences slight perturbations. In the direction of the giant newly-discovered void, the WMAP satellite (top left) sees a cold spot, while the VLA (bottom left) sees fewer radio-emitting galaxies. CREDIT: Bill Saxton, NRAO/AUI/NSF, NASA