A hundred years ago, we did not know what atoms were really made of, or why they emitted light only of very specific colors. That puzzle led to the invention of quantum mechanics. The physicists of the 1920s were trying to understand nature, yet from that work came lasers, modern electronics, GPS, and a long list of everyday technologies.

A century later, we have learned to do quantum mechanics in the laboratory. We can cool, trap, and control individual atoms, and use them to build quantum atomic clocks so precise that they would not lose even a fraction of a second over the entire time since the Big Bang. These clocks are so sensitive that lifting one by millimeters measurably changes its tick rate due to changes in in Earth’s gravity.

Meanwhile, we face a new and deeper puzzle: we do not know what most of the universe is made of. Decades of observations point to dark matter and dark energy that dominate the cosmos, yet their nature remains unknown. I will describe how quantum clocks work can act as new observatories for this invisible universe, searching for subtle drifts in their ticking that could signal dark matter, and testing gravity on Earth and, in the future, in space.