In the program, leading physicists delve into the mystery of whether time travel is possible, and if so, how one might go about building a time machine.

Part 1, "Einstein's Dream," introduces string theory and shows how modern physics—composed of two theories that are ferociously incompatible—reached its schizophrenic impasse: One theory, general relativity, successfully describes big things like stars and galaxies, while another, quantum mechanics, is equally successful at explaining small things like atoms and subatomic particles. Albert Einstein, the inventor of general relativity, dreamed of finding a single theory that would embrace all of nature's laws. But in this quest for the so-called unified theory, Einstein came up empty-handed, and the conflict between general relativity and quantum mechanics has stymied all who've followed. That is, until the discovery of string theory.

Part 2, "String's the Thing," opens with a whimsical scene in a movie theater in which the history of the universe runs backwards to the Big Bang, the moment at which general relativity and quantum mechanics both came into play, and therefore the point at which our conventional model of reality breaks down.

Then it's string theory to the rescue as Greene describes the steps that led from a forgotten 200-year-old mathematical formula to the first glimmerings of strings—quivering strands of energy whose different vibrations give rise to quarks, electrons, photons, and all other elementary particles. Strings are truly tiny, being smaller than an atom by the same factor that a tree is smaller than the solar system. But, as Greene explains, they are able to combine the laws of the large and the laws of the small into a proposal for a single, harmonious theory of everything.

Part 3 of "The Elegant Universe” with host Brian Greene shows how Edward Witten of Princeton's Institute for Advanced Study, aided by others, revolutionized string theory by successfully uniting the five different versions into a single theory that is cryptically named "M-theory," a development that requires a total of eleven dimensions.

Ten...eleven...who's counting? But the new 11th dimension implies that strings can come in shapes called membranes, or "branes" for short. These have truly science fiction-like qualities, since in principle they can be as large as the universe. A brane can even be a universe—a parallel universe—and we may be living on one right now.

Using courtroom reenactments based on transcripts and interviews with those present, NOVA looks at the events of the federal case of Kitzmiller v. Dover School District.