STRING THEORY’S WEIRDEST IDEAS FINALLY MAKE SENSE—THANKS TO VR
Extra dimensions are a critical part of Greene's field of study. String theory posits that the universe is built not just from three spatial dimensions (up/down, side/side, forward/backward) and the single dimension of time, but at least six other dimensions. These extra dimensions would be too small for humans to detect—about 10-33 centimeters. But, according to the theory, the six, curled up dimensions play a major role in controlling how subatomic strings vibrate, and those vibrations determine how quarks, electrons, and other fundamental particles behave. Ultimately, these phenomenon scale up to explain modern how gravity and quantum mechanics fit together: Otherwise known as The Biggest Question in Physics. "String theory," says Greene, "is speculative and hypothetical, but mathematically quite compelling."
It's also quite confusing. Those six extra dimensions some string theorists predict come wrapped together in what are known as Calabi-Yau manifolds. Greene is a great writer—bestselling, even—but even he can't perfectly explain what these things look like. VR helps him make the shapes make sense. Sort of. Greene brings up a video of a wire in the virtual reality space. To a human, he says, this is a two dimensional object: a line. The video zooms in, and something new appears: an ant, walking in a circle around the wire's girth. The lesson here is that extra dimensions are invisible unless you are the right size to see them.