Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe

by Brian Greene

First, in this chapter we are not taking into consideration the role of gravity. In chapter 3, we will. And as we will see, gravity has a profound impact on the nature of high-entropy particle configurations. In fact, while it won’t be our focus, in a given finite volume of space the maximum entropy configuration is a black hole—an object deeply dependent on gravity—that completely fills the spatial volume (for details, see, for example, my book The Fabric of the Cosmos, chapter 6 and chapter 16). Second, if we consider arbitrarily large regions of space—even infinitely large—the highest entropy configurations of a given amount of matter and energy are those in which the constituent particles (matter and/or radiation) are uniformly distributed over an ever-larger volume. Indeed, black holes, as we will discuss in chapter 10, ultimately evaporate (through a process discovered by Stephen Hawking), yielding higher-entropy configurations in which particles are increasingly spread out. Third, for the purpose of this section, the only fact we need is that the entropy currently present in any given volume of space is not at its maximum value. If that volume contained, say, the room you are now inhabiting, entropy would increase if all the particles making up you, your furniture, and any other of the room’s material structures were to collapse into a small black hole, which would subsequently evaporate yielding particles that would spread through an even larger volume of space.