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.

Science uncovers the origin of the first light in the Universe

‘Let there be light’ isn’t just biblical. It’s science.

“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

When we look out at the Universe today, highlighted against the vast, empty blackness of the sky are points of light: stars, galaxies, nebulae and more. Yet there was a time in the distant past before any of those things had formed, just after the Big Bang, where the Universe was still filled with light. If we look in the microwave part of the spectrum, we can find the remnants of this light today in the form of the Cosmic Microwave Background (CMB). But even the CMB is relatively late: we’re seeing its light from 380,000 years after the Big Bang. Light, as far as we know it, existed even before that. After centuries of investigating the origins of the Universe, science has finally uncovered what physically happened to “let there be light” in space.

Arno Penzias and Bob Wilson at the location of the antenna in Holmdel, New Jersey, where the cosmic microwave background was first identified. Image credit: Physics Today Collection/AIP/SPL.

Let’s take a look at the CMB, first, and where it comes from going way, way…