How did the Cosmic Background Explorer support the big bang theory?

The Cosmic Background Explorer (COBE) satellite, launched in 1989, provided critical empirical evidence for the big bang theory by analyzing the cosmic microwave background (CMB) radiation.1

COBE supported the theory through two primary findings:

• Spectral Accuracy: Using its Far Infrared Absolute Spectrophotometer (FIRAS), COBE measured the spectrum of the cosmic background radiation with unprecedented precision. It confirmed that the radiation perfectly matched the blackbody spectrum predicted by the big bang model, which posits that the early universe was a hot, dense state that cooled as it expanded.12
• Detection of Anisotropy: COBE’s Differential Microwave Radiometer (DMR) mapped the sky and identified minute temperature fluctuations, or "wrinkles," of about one part in 100,000. These variations were essential to the theory, as they provided the necessary evidence that the early universe was not perfectly uniform. These slight density differences allowed for gravitational separation, which eventually led to the formation of galaxies and large-scale structures.12

These results were foundational to modern cosmology, earning project scientists John Mather and George Smoot the Nobel Prize for Physics in 2006.1