Recombination (cosmology)

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/recombination-cosmology

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the epoch of recombination?Occurs approximately 380,000 years after the Big Bang
2. What is the temperature at recombination?Around 3,000 Kelvin
3. What happened during recombination in the early universe?During recombination, the hot plasma cooled enough that electrons could stick to nuclei, forming neutral hydrogen and helium atoms. This turned the universe from a fog of charged particles into a gas of neutral atoms. The change made space clear for light to travel.
4. Why did the universe become transparent after recombination?The formation of neutral atoms reduced the number of free electrons that could scatter photons. With fewer scattering events, photons could move freely, so the universe became transparent.

Plasma: An ionized gas consisting of ions and free electrons, exhibiting collective behavior.
Opaque: Not able to be seen through; not transparent.
Cosmic Microwave Background (CMB): Relic radiation from the early universe, a snapshot of the universe at recombination.
Anisotropies: Variations or irregularities in a quantity, such as temperature, across different directions.