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

by Brian Greene

Thought and the Multiverse

The infinite collection of universes thus realizes every possible history, and each such history is realized infinitely often. This entails a peculiar conclusion: the reality that you and I and everyone else experiences is happening out there in other regions—in other universes—over and over again. Modify that reality in any manner that is not strictly forbidden by the laws of physics (you can’t violate the conservation of energy or electric charge, for example) and it is also out there, over and over again.

Indeed, as Garriga and Vilenkin argue, if you select any finite duration, however long, there will be universes among the infinite collection in which unlikely processes swim against the entropic stream to keep life alive for at least that duration. And so, among the infinity of universes, some will host life and mind arbitrarily far into the future.

Life and thought here in our universe, in what we have long considered the universe, will likely draw to a close. Perhaps there is consolation in knowing that somewhere in the vast reaches of infinite space, well beyond the boundary of our realm, life and thought may persist, conceivably indefinitely. Still, even though we can contemplate eternity, and even though we can reach for eternity, apparently we cannot touch eternity.

11

THE NOBILITY OF BEING

Mind, Matter, and...

Order and Significance

Particles and fields. Physical laws and initial conditions. To the depth of reality we have so far plumbed, there is no evidence for anything else. Particles and fields are the elementary ingredients. The physical laws prompted by the initial conditions dictate progression. Because reality is quantum mechanical, the pronouncements of the laws are probabilistic, but even so the probabilities are rigidly determined by mathematics. Particles and fields do what they do without concern for meaning or value or significance. Even when their indifferent mathematical progression yields life, physical laws maintain complete control. Life has no capacity to intercede or overrule or influence the laws.

Mortality and Significance

Yet the fact that we will all die, and the fact that the human species will die, and the fact that life and mind, at least in this universe, are virtually certain to die are expected, run-of-the mill, long-term outcomes of physical law. The only novelty is that we notice.

Descendants

Meaning

By the grace of random chance, funneled through nature’s laws, we are here.

Acknowledgments

Notes

The description I have given is fine as a broad-brush summary, but there are more exotic physical systems in which to ensure that reverse-run sequences are allowed by the laws of physics we must subject the system to two other manipulations beyond the reversal of time: we must also reverse the charges of all particles (so-called charge conjugation) and also reverse the roles of left- and right-handedness (so-called parity reversal). The laws of physics, as currently understood, necessarily respect the conjunction of all three of these reversals, something known as the CPT theorem (with C standing for charge conjugation, P for parity reversal, and T for time reversal).

More precisely, entropy is the logarithm of the number of members in a given group, an essential mathematical distinction ensuring that entropy has sensible physical properties (for example, when two systems are brought together, their entropies add), but one that for our qualitative discussion we can safely ignore. In parts of chapter 10, we will implicitly use the more precise definition, but for now we are fine.

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.

I am not much for jargon, but were I to label my own view, the one that will guide our discussion across this book, I would call it “nested naturalism.” Nested naturalism, as will become clear in this and subsequent chapters, is committed to the value and the universal applicability of reductionism. It takes as a given that there is a fundamental unity in the workings of the world, and posits that such unity will be found by pursuing the reductionist program to whatever depth it leads. Everything that takes place in the world admits a description in terms of nature’s fundamental constituents following the dictates of nature’s fundamental laws. Nested naturalism also emphasizes, though, that such a description has limited explanatory power. There are many other levels of understanding that wrap around the reductionist account much as the outer parts of a nest wrap around its innermost structure.

There is no controversy over whether group selection can happen in principle. The controversy is whether it happens in practice. The issue is one of timescales: The general expectation is that the typical timescale during which an individual will either reproduce or die is far shorter than the corresponding timescales during which a group will either divide or dissolve. And if this is the case, as critics of group selection argue, group selection is too slow to matter.

In response, David Sloan Wilson, a longtime proponent of group selection (in a yet more generalized form known as multilevel selection), has argued that much of the debate comes down to different but ultimately equivalent accounting methods (different ways of partitioning the entire population) and is thus less contentious than the ongoing disagreements have made it appear (see David Sloan Wilson, Does Altruism Exist? Culture, Genes and the Welfare of Others [New Haven: Yale University Press, 2015], 31–46).

The dark energy density is about 5 × 10-10 joules per cubic meter or about 5 × 10-10 watt-seconds per cubic meter. To run a 100-watt bulb for one second requires 2 × 1011 times the dark energy contained in a single cubic centimeter. Such energy can thus run a 100-watt bulb for about 5 × 10-12 seconds, or five trillionths of a second.

Energy within the earth is also a remnant of the heat produced when the pull of gravity crushed a cloud of dust and gas into the nascent planet. Additionally, heat is also generated as the earth spins, because the motion stresses layers of deep rock that need a constant force to keep up with the rotational velocity.

246.22 GeV,

The current general consensus is that tunneling to a negative value yields a terminal state—in that realm, a true end to time.

Adherents to the Many Worlds view of quantum mechanics may cast this description in a different light. If all possible outcomes happen in one world or another, this world was foreordained. But the fact that self-aware collections are among the possible outcomes is rendered no less extraordinary.

Bibliography

A NOTE ABOUT THE AUTHOR