What Is the Cosmic Microwave Background?

Imagine you're in a room full of people who all start shouting at the same time. After a while, it gets too loud to hear anything clearly. Then, everyone stops talking and just sits quietly, but their voices still echo faintly around the room. The cosmic microwave background is like that quiet echo from 13.8 billion years ago. It's radiation left over from when the universe was very young and hot, and it's been traveling through space ever since.

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  1. Imagine you're in a room with people all shouting, and when they stop, you still hear faint echoes, that's like what we see in the cosmic microwave background.

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