Physics progresses by breaking our intuitions, but we are now at a point where further progress may require us to do away with the most intuitive and seemingly fundamental concepts of all—space and time themselves. Physics came into its modern form as a description of how objects move through space and time. They are the stage on which physics plays out. But that stage begins to fall apart on the tiniest scales and the largest energies, and physics falls apart with it. Many believe that the only way to make physics whole again is to break what may be our most powerful intuition yet. In our minds, space and time seem pretty fundamental, but that primacy may not extend beyond our minds. In many of the new theories that are pushing the edge of physics, spacetime at its elementary level is not what we think it is. We’re going to explore the “realness” of space and time over a few upcoming episodes. We’ll ask: Do our minds hold a faithful representation of something real out there, an
Here’s the story we like to tell about the beginning of the universe. Space is expanding evenly everywhere, but if you rewind that expansion you find that all of space was once compacted in an infinitesimal point of infinite density—the singularity at the beginning of time. The expansion of the universe from this point is called the Big Bang. We like to tell this story because it's the correct conclusion from the description of an expanding universe that followed Einstein's general theory of relativity back in the 1910's. But since then we've learned so much more. Does our modern understanding of the universe still insist on a point-like Big Bang? Recent work actually gives us a way to avoid the beginning of time. The key to understanding whether the universe had a beginning is to decide whether there exists what we call a past singularity—whether all points in space were at the same point at time t=0. And from the earliest models of the ex