Did light exist at the beginning of the universe?

undefined 24, 2025

Source: mos

At the universe’s start, light existed but couldn’t travel freely because the hot, dense early cosmos was filled with free electrons scattering photons. About 380,000 years after the Big Bang, the universe cooled enough for electrons to bind with nuclei, letting light escape—this is the cosmic microwave background we detect today. Stars formed around 100 million years later, ending the cosmic dark ages and beginning the era of galaxies and starlight about a billion years post-Big Bang.

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