The Hidden Reality_ Parallel Universes and the Deep Laws of the Cosmos - Brian Greene [154]
*This loose definition will suffice for now; in a moment, I’ll be more precise.
*In Chapter 3, we discussed how the energy embodied by a gravitational field can be negative; this energy, however, is potential energy. The energy we’re discussing here, kinetic energy, comes from the electron’s mass and its motion. In classical physics this has to be positive.
*Besides flipping the coins, you could also swap around their locations, but for the purpose of illustrating the main ideas, we can safely ignore this complication.
*If you’re interested in the full story, I highly recommend Leonard Susskind’s excellent book The Black Hole Wars.
*The reader familiar with black holes will note that even without the quantum considerations that lead to Hawking radiation, the two perspectives would differ with regards to the rate of time’s passage. Hawking radiation makes the perspectives yet more distinct.
*There is a related story that I’ve not told in this chapter, to do with a long-standing debate regarding whether black holes require a modification of quantum mechanics—whether, by swallowing information, they upend the ability to fully evolve probability waves forward in time. A one-sentence summary is that Witten’s result, by establishing an equivalence between a black hole and a physical situation that does not destroy information (a hot quantum field theory), supplied conclusive evidence that all information that falls into a black hole is ultimately available to the outside world. Quantum mechanics needs no modification. This application of Maldacena’s discovery also establishes that the boundary theory provides a full description of the information (entropy) stored on a black hole’s surface.
CHAPTER 10
Universes, Computers, and Mathematical Reality
The Simulated and the Ultimate Multiverses
The parallel universe theories we considered in previous chapters emerged from mathematical laws developed by physicists in their pursuit of nature’s deepest workings. The credence accorded one set of laws or another varies widely—quantum mechanics is viewed as established fact; inflationary cosmology has observational support; string theory is thoroughly speculative—as does the type and logical necessity of the parallel worlds associated with each. But the pattern is clear. When we hand over the steering wheel to the mathematical underpinnings of the major proposed physical laws, we’re driven time and again to some version of parallel worlds.
Let’s now change tack. What happens if we seize the wheel? Can we humans manipulate the cosmic unfolding to volitionally create universes parallel to our own? If you believe, as I do, that the behavior of living beings is dictated by nature’s laws, then you may see this as no change of tack at all but simply as a narrowing of perspective, to the impact of physical law when funneled through human activity. This line of thought quickly engages thorny issues such as the age-old debate about determinism and free will, but that’s not a direction in which I want to head. Rather, my question is this: With the same sense of intent and control you feel when you choose a movie or a meal, might you create a universe?
The question sounds outlandish. And it is. I’ll tip you off now that in addressing it we will find ourselves in territory even more speculative than what we’ve already covered, and considering where we’ve been, that says a lot. But let’s have a little fun and see where it takes us. Let me lay out the perspective I’ll take. In contemplating universe creation, I’m less interested in practical constraints than in the possibilities made available by the laws of physics. So, when I speak of “you” creating a universe, what