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

by Brian Greene

Copyright © 2020 by Brian Greene

(ebook) | ISBN 9781524731670

Ebook ISBN 9781524731687

Preface

Yes, I thought. That is the romance of mathematics. Creativity constrained by logic and a set of axioms dictates how ideas can be manipulated and combined to reveal unshakable truths.

1

THE LURE OF ETERNITY

Beginnings, Endings, ...

To work and play, to yearn and strive, to long and love, all of it stitching us ever more tightly into the tapestry of the lives we share, and for it all then to be gone—well, to paraphrase Steven Wright, it’s enough to scare you half to death. Twice.

Still, here on earth we have punctuated our moment with astonishing feats of insight, creativity, and ingenuity as each generation has built on the achievements of those who have gone before, seeking clarity on how it all came to be, pursuing coherence in where it is all going, and longing for an answer to why it all matters. Such is the story of this book.

Stories of Nearly Everything

Maybe we will fully grasp how the seemingly mundane, a glint of light reflecting from a spinning dinner plate, can churn through the powerful mind of a Richard Feynman and compel him to rewrite the fundamental laws of physics. More ambitious still, perhaps one day we will understand the workings of mind and matter so completely that all will be laid bare, from black holes to Beethoven, from quantum weirdness to Walt Whitman. But even without having anything remotely near that capacity, there is much to be gained by immersion in these stories—scientific, creative, imaginative—appreciating when and how they emerged from earlier ones playing out on the cosmic timeline and tracing the developments, both controversial and conclusive, that elevated each to their place of explanatory prominence.4

The ability to manipulate the environment thoughtfully provides the capacity to shift our vantage point, to hover above the timeline and contemplate what was and imagine what will be. However much we’d prefer it otherwise, to achieve “I think, therefore I am” is to run headlong into the rejoinder “I am, therefore I will die.”

Information, Consciousness, and Eternity

Reflections on the Future

We are the product of a long lineage that has soothed its existential discomfort by envisioning that we leave a mark. And the more lasting the mark, the more indelible its imprint, the more a life seems to be a life that mattered. In the words of philosopher Robert Nozick—but they could just as easily have come from George Bailey—“Death wipes you out…To be wiped out completely, traces and all, goes a long way toward destroying the meaning of one’s life.”7

We will journey across time, from our most refined understanding of the beginning to the closest science can take us to the very end. We will explore how life and mind emerge from the initial chaos, and we will dwell on what a collection of curious, passionate, anxious, self-reflective, inventive, and skeptical minds do, especially when they notice their own mortality. We will examine the rise of religion, the urge for creative expression, the ascent of science, the quest for truth, and the longing for the timeless. The deep-seated affinity for something permanent, for what Franz Kafka identified as our need for “something indestructible,”10 will then propel our continued march toward the distant future, allowing us to assess the prospects for everything we hold dear, everything constituting reality as we know it, from planets and stars, galaxies and black holes, to life and mind.

As our trek across time will make clear, life is likely transient, and all understanding that arose with its emergence will almost certainly dissolve with its conclusion. Nothing is permanent. Nothing is absolute. And so, in the search for value and purpose, the only insights of relevance, the only answers of significance, are those of our own making.

2

THE LANGUAGE OF TIME

Steam Engines

A Statistical Perspective

From This to That

With irreversibility being so central to how things evolve, you would think we could easily identify its mathematical origin within the laws of physics. Surely, we should be able to point to something specific in the equations that ensures that although things can transform from this to that, the math forbids them from transforming from that to this. But for hundreds of years the equations we’ve developed have failed to offer us anything of the sort. Instead, as the laws of physics have been continually refined, passing through the hands of Newton (classical mechanics), Maxwell (electromagnetism), Einstein (relativistic physics), and the dozens of scientists responsible for quantum physics, one feature has remained stable: the laws have steadfastly adhered to a complete insensitivity to what we humans call future and what we call past.

sequence of events to occur, then the laws necessarily permit the reverse sequence too.

Why then is our experience so lopsided? Why do we only ever see events unfold in one temporal orientation and never the reverse?

Entropy: A First Pass

Entropy: The Real Deal

But what does “pretty much look the same” mean for a large collection of gas molecules?

Accordingly, for a large collection of molecules in a container, we say that different configurations “pretty much look the same” if they fill out the same volume, have the same temperature, and exert the same pressure.

The entropy of the macrostate is the number of such look-alikes.

Volume first.

The conclusion, then, is that smaller and tightly clustered configurations of molecules have lower entropy, while larger and evenly spread configurations have higher entropy.

Temperature next.

If the temperature of the steam is low, the allowed rearrangements of the molecular speeds will be comparatively few in number: to keep the temperature fixed—and thus ensure that the configurations all pretty much look the same—you have to offset any increase in the speeds of some molecules by a suitable decrease in the speeds of others. But the burden of having low temperature (low average molecular speed) is that you don’t have a lot of room to decrease the speeds before hitting rock bottom, zero. The available range of possible molecular speeds is thus narrow, and so your freedom to rearrange the speeds is limited.

By comparison, if the temperature is high, your game of musical chairs once again revs up: with a higher average, the range of molecular speeds—some larger than the average and some smaller—is much wider, providing greater latitude for mixing up the speeds while preserving the average. More rearrangements of the molecular speeds that all pretty much look the same means that higher temperature generally entails higher entropy.

Finally, pressure.

The pressure of the steam on your skin or on the bathroom walls is due to the impact of streaming H2O molecules that slam into these surfaces: each molecular impact exerts a tiny push, and so the greater the number of molecules the higher the pressure.

Fewer H2O molecules in your bathroom (you took a shorter shower) means fewer rearrangements are possible, and so entropy is lower; more H2O molecules (you took a longer shower) means more rearrangements are possible, and so entropy is higher.

To summarize: Having fewer molecules, or having lower temperature, or filling a smaller volume results in lower entropy. Having more molecules, or having higher temperature, or filling a larger volume results in higher entropy.

How life is able to produce such exquisite order is a theme we will address in later chapters. For now, the lesson is simply that low-entropy configurations should be viewed as a diagnostic, a clue that powerful organizing influences may be responsible for the order we’ve encountered.

Laws of Thermodynamics

Saying it yet more generally, if a physical system is not already in the highest-entropy state available, it is overwhelmingly likely that it will evolve toward it.

Energy and Entropy

Before the explosion, we say that the dynamite’s energy is high quality: it’s concentrated and easy to access. After the explosion, we say that the energy is low quality: it’s spread out and difficult to utilize. And since the exploding dynamite fully abides by the second law, going from order to disorder—from low entropy to high entropy—we associate low entropy with high-quality energy and high entropy with low-quality energy. Yes, I know. It’s a lot of highs and lows to keep track of. But the conclusion is pithy: whereas the first law of thermodynamics declares that the quantity of energy is conserved over time, the second law declares that the quality of that energy deteriorates over time.

Why then is the future different from the past? The answer, apparent from what we’ve now developed, is that the energy powering the future is of lower quality than that powering the past. The future has higher entropy than the past.

Boltzmann and the Big Bang

The second law is not a law in the traditional sense. The second law does not absolutely preclude entropy from decreasing. It declares only that such a decrease is unlikely.

I explained earlier that the laws of physics put future and past on equal footing. The laws thus ensure that physical processes that unfold in one temporal sequence can unfold in reverse. And since those very same laws govern everything, including the physical processes responsible for how entropy changes over time, it would indeed be curious, erroneous really, to find that those laws only allow entropy to increase. They don’t. All the entropically increasing processes you’ve experienced day in and day out during your entire life—from the mundane of a shattering glass to the profound of bodily aging—can happen in reverse. Entropy can decrease. It’s just ridiculously unlikely.

And so we are led to ask: How did today’s less-than-maximum entropy state come to be?