What important event happened about 300,000 years after the universe began to expand?
A)Helium was produced
B)The first stars formed
C)The universe became ionized for the first time
D)The universe became transparent

Question

Quizplus · Accepted Answer

Approximately 300,000 years after the Big Bang, the universe cooled enough for electrons to combine with protons, forming neutral hydrogen atoms. This process is known as recombination, and it led to the universe becoming transparent for the first time, as photons could travel freely without being constantly scattered by free electrons.

What Important Event Happened About 300,000 Years After the Universe