An artist rendering of the “bubbles” of ionized atoms theorized to have surrounded the earliest stars. As Parsons explained: “The first galaxies lit up and started ionizing bubbles of gas around them, and soon these bubbles started percolating and intersecting and making bigger and bigger bubbles. Eventually, they all intersected and you got this über bubble, leaving the universe as we observe it today.” Illustration from Scientific AmericanAn artist rendering of the “bubbles” of ionized atoms that surrounded the earliest stars. As Parsons explained: “The first galaxies lit up and started ionizing bubbles of gas around them, and soon these bubbles started percolating and intersecting and making bigger and bigger bubbles. Eventually, they all intersected and you got this über bubble, leaving the universe as we observe it today.” Illustration from Scientific American