Starts With A Bang

Science uncovers the origin of the first light in the Universe (Synopsis)

The distant Universe, as viewed here through the plane of the Milky Way, consists of stars and galaxies, as well as opaque gas and dust, going back as far as we can see. But beyond the last star in the Universe, there's still more light. Image credit: 2MASS.

“By its very nature science knows no boundaries. Walling off any group, for any reason, from full participation damages the entire enterprise of science. We must be scientists without borders.” -Rocky Kolb

We normally think of “let there be light” as when the Universe got its start. In a particular sense, this is true, since you can go back to a time before stars and galaxies existed, when the Universe was only a few million years old or less. But even before the first star, there was still light.

According to the original observations of Penzias and Wilson, the galactic plane emitted some astrophysical sources of radiation (center), but above and below, all that remained was a near-perfect, uniform background of radiation. Image credit: NASA / WMAP science team.

And while that light’s origin can be traced back to the cosmic microwave background and the formation of neutral atoms, there was light even earlier than that. In fact, the very first light arose from the annihilation of matter and antimatter, and from the end of cosmic inflation at the very beginning of as far back as we can trace.

The cosmic history of the entire known Universe shows that we owe the origin of all the matter within it, and all the light, ultimately, to the end of inflation and the beginning of the Hot Big Bang. Image credit: ESA and the Planck Collaboration / E. Siegel.

There was no light until the hot Big Bang occurred, and it’s the end of cosmic inflation that triggers this true “first light.”