The Universe

Evidence of the Big Bang

What follow-up study of the cosmic microwave background solidly confirmed the Big Bang theory?

In 1992 NASA launched the Cosmic Background Explorer (COBE) satellite. Its purpose was to study the nature of the cosmic microwave background radiation. Instruments on COBE confirmed that the radiation detected by Penzias and Wilson in 1964 was a nearly perfect profile of the temperature of the universe, and that the cosmic microwave background temperature was almost exactly 2.73 degrees Kelvin (about 454.7 degrees below zero Fahrenheit). Furthermore, careful analysis showed that there are tiny variations of temperature in the background radiation: These variations were barely a few ten-thousandths of a degree Kelvin and are the fossilized signature of the original miniscule fluctuations of the matter and energy density in the early universe from nearly 13.7 billion years ago. Those fluctuations seeded the changes that have since caused the universe to age and evolve from what it once was—a kernel of space-time nearly uniformly filled with energy—into what it is today: a vastly variegated tapestry of dense and sparse regions, sprinkled with galaxies, stars, planets, and more.


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