Paul Steinhardt's "cyclic model," a radical alternative to the big bang and inflationary cosmology, proposes that the universe's evolution is periodic and that key events shaping its structure occurred before the bang. Peter Galison studies historic fundamental shifts in physics and what types of evidence count as truth. Having first met during their graduate-school days at Harvard, they were quick to accept Seed's invitation to consider: Where is the line between physics and metaphysics? Is infinity unscientific? What is it, ultimately, that we want from science?
To read the full Salon, order Science is Culture: Conversations at the New Intersection of Science + Society - out October 12.
Video production by Joe Carroll