Science Uncovers the Origin of the First Light in the Universe
As the Universe continues to expand and cool, we create nuclei, neutral atoms, and eventually stars, galaxies, clusters, heavy elements, planets, organic molecules, and life. And through it all, those photons, left over from the Big Bang and a relic of the end of inflation that started it all, stream through the Universe, continuing to cool but never disappearing. When the last star in the Universe flickers out, those photons — long since shifted into the radio and having diluted to be less than one-per-cubic-kilometer — will still be there in numbers just as great as they were trillions and quadrillions of years prior.
Before there were stars, there was matter and radiation. Before there were neutral atoms, there was an ionized plasma, and when that plasma forms neutral atoms, those allow the Universe to deliver the earliest light we see today. Even before that light, there was a soup of matter and antimatter, which annihilated to produce the majority of today’s photons, but even that wasn’t the very beginning. In the beginning, there was exponentially expanding space, and it was the end of that epoch — the end of cosmic inflation — that gave rise to the matter, antimatter, and radiation that would give rise to the first light we can see in the Universe. After billions of years of cosmic evolution, here we are, able to piece together the puzzle. For the first time, the origin of just how the Universe “let there be light” is now known!