Early Universe
6 questions tagged Early Universe — spanning every one of the seven Ws.
Why is the cosmic microwave background so important?
The cosmic microwave background is the leftover glow from when the universe first became transparent about 380,000 years after the Big Bang. It gives us a snapshot of the infant universe and helps measure its age, composition, and shape.
Why did the early universe become transparent only after 380,000 years?
Before that, the universe was a hot plasma that scattered light constantly. Once it cooled enough for electrons to bind with protons, photons could travel freely through space.
What is cosmic inflation?
Cosmic inflation is the idea that the early Universe underwent a brief period of extremely rapid expansion. It was proposed in the early 1980s to explain several features of the cosmos.
What is reionization in cosmology?
Reionization was the era when the first stars and galaxies ionized the hydrogen gas in the Universe again. It ended the cosmic dark ages and began the transparent Universe we see today.
Why did the early universe become transparent only after hundreds of thousands of years?
Before neutral atoms formed, free electrons scattered light constantly, making the universe opaque. Once atoms formed, light could travel much more freely.
What is the cosmic microwave background?
The cosmic microwave background is faint radiation left over from the early universe, about 380,000 years after the Big Bang. It is now observed as microwaves filling all of space.