An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time


Mapping the Cosmic Background Radiation

This map, made from data gathered by the COBE spacecraft, shows the intensity of the left-over radiation from a period not long after the Big Bang. Tiny variations (shown by the different colors) in the intensity of this radiation show where matter in the early universe was more densely or less densely concentrated. The denser regions most likely gave rise to the concentrations of matter (like great groups of galaxies) that we see in the universe today, over ten billion years later. (Courtesy COBE Science Working Group/NASA Goddard Space Flight Center.)

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Changes in the Universe