May 19, 2024

Why a giant ‘cold spot’ in the cosmic microwave background has long perplexed astronomers

Posted by in category: cosmology

Leftover light from the young universe has a major flaw, and we don’t know how to fix it. It’s the cold spot. It’s just way too big and way too cold. Astronomers aren’t sure what it is, but they mostly agree that it’s worth investigating.

The cosmic microwave background (CMB) was generated when our universe was only 380,000 years old. At the time, our cosmos was about a million times smaller than it is today and had a temperature of over 10,000 kelvins (17,500 degrees Fahrenheit, or 9,700 degrees Celsius), meaning all of the gas was plasma. As the universe expanded, it cooled, and the plasma became neutral. In the process, it released a flood of white-hot light. Over the billions of years since, that light has cooled and stretched to a temperature of around 3 kelvins (minus 454 F, or minus 270 C), putting that radiation firmly in the microwave band of the electromagnetic spectrum.

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