Astronomers made first measurements of small-scale ripples in primeval hydrogen gas using rare double quasars

The most barren regions known are the far-flung corners of intergalactic space. In these vast expanses between the galaxies there is just one solitary atom per cubic meter--a diffuse haze of hydrogen gas left over from the Big Bang. On the largest scales, this material is arranged in a vast network of filamentary structures known as the "cosmic web," its tangled strands spanning billions of light years and accounting for the majority of atoms in the universe.