Many people feel that time starts when our universe was created, a point of infinite density where everything was infinitely small and had a temperature of over a quadrillion degrees, and this beginning is what we call the Big Bang. I believe that anything that exists must have a mechanism to explain it, so this Big Bang theory always makes me think that the Big Bang was sparked by something else which happened before it. There is a theory called Cosmic inflation that sets up this initial state before the Big Bang. Cosmic inflation started out as a theory to explain a period of extremely rapid exponential expansion of the universe during its first few moments, but I think it is possible that this period existed before the Big Bang. If it did, during this Inflation period of time before the Big Bang, our universe was extremely cold, almost at absolute zero, and it was empty of everything but empty space, and that empty space carried energy that stretched the universe out to this enormous size and into the initial state before the Big Bang. If this is what happened, then this pre-bang universe period should be where time began. If time did not begin at the bang, if a long era preceded the onset of the present cosmic expansion, then time would just be an abstract concept that means nothing.
String theory grew out of a model that Gabriele Veneziano wrote down in 1968 to describe the world of nuclear particles (such as protons and neutrons) and their interactions. Despite much initial excitement, the model failed. It was abandoned in favor of quantum chromodynamics, which describes nuclear particles in terms of more elementary constituents, quarks. String theory was revived when it was theorized that quarks were tied together by elastic strings. String theory is built upon Einstein’s notion of space-time, but where Einstein’s theory has three space dimensions and one time dimension, string theory predicts a few more space dimensions, but most of these dimensions are compactified, so they are curled up on themselves on very small scales, leaving us with the three spatial dimensions and time. Some physicists think that after some passage of time, the string interactions caused the symmetry of the universe to spontaneously break, resulting in the three spatial dimensions expanding. The time when the symmetry is broken is thought to be the birth of the universe. The birth of length, width and height gave us size and volume and without that, all we would have is nothing.
String theory also proposes the idea of parallel universes and M-theory proposes a Universe of 11 dimensions. What if our universe is not the only universe, how does that effect time? The multiverse is a hypothetical group of multiple universes. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. It is hard to think about anything that lies beyond our universe, but it is possible that our universe is just one of many in a much larger multiverse.
Written for Fandango’s Provocative Question #178 which asks, “When did time actually begin.”