Here's a breakdown:
* Big Bang: The prevailing scientific theory about the origin of the universe, suggesting it began in a hot, dense state and has been expanding and cooling ever since.
* Early Universe: In the very early universe, the extreme heat and density meant photons (light particles) were constantly interacting with matter. This resulted in a very hot, opaque state.
* Cooling and Expansion: As the universe expanded and cooled, the photons eventually decoupled from matter, meaning they stopped interacting as frequently.
* Cosmic Microwave Background: This leftover radiation from the decoupling event is the CMB. It's a faint glow of microwaves that fills the entire universe.
The discovery of the CMB was a major confirmation of the Big Bang theory and provided crucial evidence for the age, size, and evolution of the universe.
