Question

why were conditions right for the production of helium from hydrogen only between 100 and 300 seconds after the universe began?

Answer 1

here is the answer

Step-by-step explanation:

At the beginning of the universe, the temperature was extremely hot (over 10 billion Kelvin). This allowed hydrogen to fuse into helium, releasing energy in the form of light and heat. As the universe aged and cooled, however, the temperatures dropped too low for hydrogen fusion to take place. The 100 to 300 second window after the universe began was the only time when the temperature was high enough for the production of helium from hydrogen.