Things get weird--spectacularly so--at the borderlands of physics. The rarefied realms described mathematically and sometimes glimpsed in experiments are all the more extraordinary for not being the mere products of someone's hyperactive imagination.
For instance, string theory's equations imply that the universe contains six extra dimensions, which are too tiny to have yet been detected. Some physicists also see innumerable theoretical universes in their equations. And although we perceive space and time as being continuous, quantum principles imply that, in fact, at the very smallest scales they actually come in pieces. The effects of this discrete structure could be revealed in experiments in the near future.
Intellectual enrichment aside, it might be tempting to think that none of what scientists are learning by probing the frontiers of physics truly matters in our everyday lives. Not so. As just one example, consider general relativity, which explains how gravity results from bends in the fabric of spacetime itself. To be accurate, commonplace GPS receivers--which calculate location using a constellation of orbiting satellites--must take the effects of general relativity into account.
In the pages of this special edition, we invite you to take an armchair journey through our curious universe, with our scientist authors as tour guides. You're in for a mind-boggling treat.