On Monday evening, UCSB Arts & Lectures hosted a lecture in Campbell Hall featuring prominent string theorist Brian Greene called “Explaining the Elegant Universe.”
Greene is known for popularizing theoretical physics in his numerous written works and for his important contributions to the mathematical study of string theory. In the lecture, Greene sought to explain how mathematical calculations and patterns can often provide telling insights into the nature of reality, even in the absence of observational evidence.
String theory, though currently unsupported by experimentation, has been backed up by numerous mathematical explorations and is currently the leading candidate for a “theory of everything” that would unify quantum mechanics and Einstein’s general relativity theory.
Einstein’s theory of general relativity, published in 1916, describes the nature of gravity among other topics of modern physics.
“Einstein came to the conclusions he did by asking questions a 5-year-old might ask — questions like, how does gravity work?” Greene said.
In Einstein’s model, gravity is the result of distortions in the fabric of spacetime caused by anything with mass. Greene illustrated this with the analogy of a bowling ball placed on a taut sheet of rubber. Just as the bowing ball would create a depression in the rubber, causing a curve around the edges of the depression, so would a planet resting in space hold objects in orbit.
Unfortunately, general relativity has not yet been reconciled with quantum mechanics. At the subatomic level, particles often behave in ways unexplained by Einstein or Newton’s laws. A theory of everything would unify the two into one understanding of how the universe works.
String theory assumes that the smallest subatomic particles, such as quarks, are actually made up of tiny filaments that vibrate in a number of different patterns. Each pattern of vibration produces a different subatomic particle. These vibrations do not occur across only the three dimensions we have observed in our universe, but across many more dimensions. According to Greene, these dimensions are so small that we cannot yet observe them.
“On a piece of paper, you have two dimensions: up-down and left-right,” Greene said. “But if you roll the paper into a tube, the up-down dimension now wraps around the tube … if you roll that tube even tighter, from far away you can only see the one dimension, left-right.”
The tube would appear to be a line segment until one looked closely enough to perceive the extra dimension wrapping around, Greene said. The fabric of spacetime is similarly twisted in tiny, imperceptible ways, into a variety of other possible dimensions. Given the behavior of the presumed strings across all these dimensions, general relativity and quantum mechanics could make sense together, according to Greene.
Greene went on to describe the possibility of parallel universes. Given calculations pertaining to the amount of energy in the Big Bang, it has been found that there would have been additional “cosmic fuel” left over at the end, enough to produce many more Big Bangs and many more universes. In each of these universes, the fabric of spacetime would wrinkle into different combinations of the many, many possible extra dimensions, causing the laws of physics to behave differently in each universe.
The existence of multiple universes would allow for every possible dimensional configuration to exist somewhere. The content of the lecture is explained in full in Greene’s bestselling book, The Elegant Universe.