When we look at the night sky, we can see the moon, stars, planets and sometimes even faraway clouds of gas and dust. All that visible matter — the stuff we can see — has a gravitational force, the same way the moon pulls on our oceans and creates the tides. But for decades, physicists have noticed something weird: There’s more gravity in the universe than we should expect. Why?

Physicists think the answer lies with dark matter, an invisible form of matter that accounts for that extra gravity they're observing. University of Washington physicist Alvaro Chavarria helped build a dark matter detector deep below the French Alps. Chavarria joins us to help demystify dark matter, how the detector works and its potential applications.