Astronomers have already found thousands of planets that orbit their own stars. Some are at a distance where it’s neither too hot nor too cold for life to exist. With new, bigger telescopes being built, astronomers will be able to analyze the chemical composition of these planets’ atmospheres to determine whether Earth is the only planet of its kind in the universe. In this interview filmed at the Aspen Ideas Festival, Carl Sagan Institute director and astronomer Lisa Kaltenegger explains this impending scientific breakthrough. “It’s going to change our worldview to know that we are not alone,” she says.