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What did the COBE satellite discover about cosmic microwave background fluctuations?

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Examine the observable universe's place within the whole universe — Cosmology Learn about defining and measuring the observable universe within the “whole” universe.

The Cosmic Background Explorer (COBE) satellite, launched in 1989, provided critical evidence for the big bang theory by measuring the cosmic microwave background (CMB) with unprecedented precision.1

Using its Differential Microwave Radiometer (DMR), COBE discovered "wrinkles" in the CMB, revealing that the radiation field was isotropic to 1 part in 100,000. These temperature fluctuations, which appeared as patches of light and dark, represented the first evidence of a departure from exact isotropy.12

These findings were significant because they indicated that the early universe was slightly denser in some regions than in others. This spatial variation provided the necessary conditions for gravitational separation, which ultimately allowed galaxies and clusters of galaxies to condense from an otherwise structureless universe. For this discovery, COBE project scientists John Mather and George Smoot were awarded the Nobel Prize for Physics in 2006.12