What ended the dark ages of the universe?

New experiments will help astronomers uncover the sources that helped make the universe transparent. When we peer through our telescopes into the cosmos, we can see stars and galaxies reaching back billions of years. This is possible only because the intergalactic medium we're looking through is transparent. This was not always the case. Around 380,000 years after the Big Bang came recombination, when the hot mass of particles that made up the universe cooled enough for electrons to pair with pr...