Time runs in one direction, but new research indicates the Big Bang might’ve created a mirror universe where time runs backward. We have yet to confirm if that universe’s Spock has a goatee.
Back in 2004, a theory proposed by Cal Tech professor Sean Carroll and his grad student Jennifer Chen posited that time moves forward because the movement toward high entropy gives it direction. As PBS notes, the theory says that time advances because of “the contrast in entropy between then and now, with an emphasis on the fact that the future universe will so much more disordered than the past.”
But a new theory is a whole lot more intriguing. Julian Barbour, at the University of Oxford, has proposed a theory that says a low-entropy early universe is inevitable because of gravity, and ultimately that’s what gives time its arrow. They tested the idea with a basic model with 1,000 particles and the physics of Newtonian gravity, to see how it worked. Here’s Scientific American’s take on the findings:
The system’s complexity is at its lowest when all the particles come together in a densely packed cloud, a state of minimum size and maximum uniformity roughly analogous to the big bang. The team’s analysis showed that essentially every configuration of particles, regardless of their number and scale, would evolve into this low-complexity state. Thus, the sheer force of gravity sets the stage for the system’s expansion and the origin of time’s arrow, all without any delicate fine-tuning to first establish a low-entropy initial condition.
To take that a step further, the study also shows the “simulated Big Bang” actually happened in two directions — meaning if the real Big Bang followed the same rules, it would’ve created a mirror universe where time essentially runs in reverse from our universe. Basically, time would run backward there.
Here’s how Barbour described the potential findings, in what almost sounds like the pitch for a high-concept sci-fi flick:
“If they were complicated enough, both sides could sustain observers who would perceive time going in opposite directions. Any intelligent beings there would define their arrow of time as moving away from this central state. They would think we now live in their deepest past.”
Whoa. Mind. Blown.