Jie Liu

In the infant universe, right after the Big Bang, space was expanding rapidly, and the vacuum resembled a superheated liquid. When 'boiling' began, bubbles of true vacuum emerged. Expanding at the speed of light, they triggered gravitational waves — tremors of space itself that have reached us.

In cold clouds of interstellar gas, carbon hides inside carbon monoxide (CO) molecules, like sugar dissolved in tea. But near hot, massive stars, this 'tea' boils: harsh radiation tears the molecules apart, and carbon escapes as lone atoms or ions.

A laser strikes a strontium atom, and two electrons fly out at once. Previously, it was thought that in such double ionization each electron acts on its own: one is knocked out first, the second later, randomly.

Imagine a long corridor with an uneven floor: bumps here, pits there. If you roll a toy car along it, it will get stuck in the deepest pit, not where you gave it a push. That's roughly how sound behaves in a phononic crystal — a material made of periodically arranged elements that controls the propagation of elastic waves.