Swagato Mukherjee

The expansion of the universe is like a dance floor stretching wider. For decades, physicists assumed that more stretching would spawn more particles, like the floor spontaneously generating new dancers. But those models ignored an obvious fact: dancers sometimes link arms. When particles interact, new simulations reveal, they actually suppress creation.

Water freezes at zero and boils at one hundred degrees. Matter made of quarks and gluons also has boundaries between states, but instead of a thermometer, the temperature here is measured in millions of electron-volts.