Fast Radio Bursts are Helping to Locate the Universe’s Missing Matter

You’re probably aware that most of the matter of the Universe is “dark matter,” and astronomers still don’t know what it is. But 75% of the regular matter in the Universe is also hidden, located in the thin gas between galaxies. Probing this gas is difficult, but astronomers have used a new technique, analyzing the light from fast radio bursts as they pass through billions of light-years of gas. Longer, redder wavelengths are slowed down compared to shorter, bluer wavelengths, allowing the hidden material to be weighed.