Kai Zhou

In collisions of heavy nuclei at colliders, quark-gluon plasma is born — a state of matter where quarks and gluons are as free as water in steam. Heavy quarks, such as b-quarks, entering this plasma lose energy, and their bound states, bottomonia, are destroyed.

The world's most precise stopwatch still runs with one eye on an old pendulum. Hydrogen masers — the best radio-frequency flywheels (devices that keep the rhythm between comparisons with a reference)—accumulate error because noise between ticks leaks into the final signal.