“We are told to let our light shine, and if it does, we won’t need to tell anybody it does. Lighthouses don’t fire cannons to call attention to their shining- they just shine.” -Dwight L. Moody
The farther away in space we look, the farther back in time we’re seeing. Light arriving from a star ten light years away is ten years old; light that took a billion-year journey from a distant galaxy is a billion years old. If we look out today at the most distant light we can see, we discover that it originates from the Big Bang itself: the Cosmic Microwave Background, or CMB.
But this doesn’t mean the light has never interacted with anything since the birth of the observable Universe. In fact, many arose from matter/antimatter annihilations, all of them have scattered off of charged particles, and the CMB photons we detect today were all released when the Universe was a few hundred thousand years old. Because of the way the Big Bang works, the particles are literally everywhere, all at once, including right here.