Our universe is filled with light. This image shows the globular star cluster Omega Centauri with about 300 000 stars, about 17 000 light years away. In addition, there are many photons contained in the cosmic microwave background radiation, the afterglow of the Big Bang. From observations scientists know that the number of photons relative to the number of protons and neutrons is about 1 billion to 1. This provides strong evidence that all antimatter annihilated, producing lots of photons, with only a tiny bit of matter surviving.