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NASA launched its Cosmic Background Explorer (COBE) satellite on 18 November 1989 to 鈥渢est ideas about the big bang theory of the creation of the Universe鈥�, we reported on 25 November that year. 鈥淎ccording to the theory,鈥� we wrote, 鈥渢he Universe began with a cataclysmic explosion 15 billion years ago.鈥� The idea was that COBE鈥檚 three instruments, each detecting radiation in a different part of the spectrum, would reveal the early universe in unprecedented detail.
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The satellite sought that detail in the cosmic microwave background (CMB), the first light emitted in the universe, just 380,000 years after the big bang. The mission was the brainchild of John Mather, who dreamed it up as a 28-year-old graduate student. Mather鈥檚 team, which included collaborators such as George Smoot, wanted to launch its satellite on an expendable rocket. NASA insisted on a shuttle launch. Then, on 28 January 1986, the Challenger space shuttle disaster resulted in the deaths of seven crew members. COBE seemed as good as finished. Still, NASA desperately needed something to restore its image, and picked COBE 鈥� on the condition it was launched within two years.
Nobody thought that was possible. But COBE met its launch window, and it worked like a dream. By early 1990, it had precisely measured the CMB鈥檚 spectrum, confirming that it fit perfectly with the big bang theory. It also revealed that the CMB is almost completely uniform, with a constant temperature across nearly the whole sky 鈥� but not quite. Two years later, NASA announced that its satellite had discovered tiny fluctuations, or 鈥渞ipples鈥�, in the CMB. Thought to be the primordial 鈥渟eeds鈥� of the galaxy clusters strung across the universe today, the identification of these fluctuations was deemed by Stephen Hawking to be 鈥渢he discovery of the century, if not of all time鈥�.
The CMB has since been measured with greater precision, revealing key details about the size, matter content, age, geometry and fate of our universe. There was a hiccup in 2014, when claims we had discovered proof of the breakneck expansion of the early universe turned to dust. But cosmologists are getting closer to revealing the last secrets of the 鈥渁fterglow of creation鈥�. No wonder, then, that Mather and Smoot jointly won the 2006 Nobel prize in physics.
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