When the Cosmic Microwave Background Was Produced,it Was a Blackbody

question 35

Multiple Choice

When the cosmic microwave background was produced,it was a blackbody with a temperature of 4,000 K.Today,we observe it to have a temperature of 2.7 K.By approximately what factor has the Universe expanded between those two time periods?

• A) 300
• B) 1,000
• C) 3,000
• D) 7,000

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