The most detailed snapshots so far of the infant universe are confirming that the cosmos consists mostly of mystery material, called dark energy, that accelerates the universe's expansion.
The new evidence comes from the Arcminute Cosmology Bolometer Array Receiver (ACBAR), a South Pole network of 16 detectors that probes the temperature of the Big Bang's remnant radiation, known as the cosmic microwave background. That radiation provides an image of what the universe looked like about 400,000 years after the Big Bang, when photons first streamed into space.
Although the radiation has cooled to an average temperature of 2.73 kelvins, the remnant light emanating from some patches of sky is slightly cooler or hotter. These tiny hot and cold spots reveal the earliest phases of gravitational clumping of matter and radiation, the seeds of galaxy formation.