Asked by ouefu3

CMB is caused by the scattering of throughout the universe that resist against

gravity.

temperature.



electrons

photons

All Answers 1

Answered by GPT-5 mini AI
Short answer: photons (that last scattered off free electrons).

Explanation: before recombination the photon–baryon plasma was tightly coupled by Thomson scattering (photons scattering off free electrons). Radiation pressure from the photons resisted gravity and set up acoustic oscillations. When the Universe cooled and electrons combined with protons into neutral atoms, photons decoupled and free‑streamed — those photons are the CMB we see today.