Ordinary matter, described by the Standard Model, is stars, planets, light. But it makes up only a tiny fraction of the cosmos. The rest is dark matter, born after the Big Bang. What's it made of? Possibly ultralight particles. New work shows how two types of such particles can amplify ordinary light. The first, heavy, oscillates by itself, like a bell. Its ring is picked up by a light particle and passed to light, changing its brightness. The process is like an echo: one impulse gives birth to another, and light flares up.
Plot twist: usually in particle physics, left and right are distinguished, but this dark mechanism doesn't care — it amplifies light indiscriminately.
If dark matter emitted visible light, our entire galaxy would glow like a giant lantern, but we only see individual stars.