The End of Everything (Astrophysically Speaking) (2020)
Katie Mack (1981)
226 pages
Katie Mack is like a kid in a candy store … except that as an astrophysicist her candy store is the universe – unimaginably immense and containing an untold variety of goodies. And the seemingly unquenchable curiosity and sense of wonder she experiences as she explores this realm animates every page of her book The End of Everything (Astrophysically Speaking).
Despite the dire title, Mack’s joy for her work shines through as she examines the implications of current theories in astrophysics for how our universe might end. This theme serves Mack as both a dramatic narrative thread, and a vehicle for describing several of the most significant developments in physics of recent decades, from the experimental confirmations of the Higgs field and gravitational waves, to the implied existence of dark matter and dark energy. These discoveries and others have not only deepened physicists’ understanding of how the universe began, but also of how it may eventually end.
Beginning at the beginning, Mack describes current understandings about the Big Bang. Here she introduces one of the key tools for cosmologists – the ability to see into the past. It arises, she notes, from the fact that light takes time to travel, meaning that
to a cosmologist, the past is not some unreachable lost realm [but rather] an observable region of the cosmos [in which they can] watch the progress of astronomical events that happened millions or even billions of years ago. (15-16)
One crucial discovery, in that sense, has been of cosmic background radiation, which is thought to be a signature of the Big Bang, and the investigation of which has led to an improved understanding of the early universe as well as the evolution of the physical laws that governed it.
Tracing forward from the moment of the Big Bang, Mack sketches out the phases physicists theorize the universe has passed through on the way to its current state. These phases – often described in unimaginable quantities in both space and time – include the Planck Time, the first 10-43 seconds before which nothing can apparently be known, and the inflationary period, during which
our entire observable universe increasing in size by a factor of more than 100 trillion trillion … to about the size of a beach ball … over the course of something like 10-34 seconds. (38-39)
Mack goes on to describe how the theories developed to model what occurred during these phases have motivated the design of lab experiments to recreate the conditions then thought to have been present, and have thereby led to a better understanding of the physical laws that reigned during each of these periods. And through these studies, physicists have achieved ever more comprehensive models of the physical laws of our present-day universe.
A transformative understanding of the universe came, Mack notes, with the discovery that distant galaxies are moving away from us – that is, that the universe is expanding, and not static, as previously thought. The dramatic consequence of this realization provides the spark for Mack’s book, “that a universe that is not static, that had a distinct beginning, must also, inevitably, have an end.” (50) And to the ‘ends of everything’ Mack considers, she gives fairly dramatic, if descriptive, names: the Big Crunch, Heat Death, the Big Rip, Vacuum Decay, and Bounce; none a particularly appealing conclusion to our story.
But each of these dramatic possibilities for the end of the universe provides Mack an opportunity to explain and explore the intersection between developing models of the universe and the experimental data being collected to either affirm or challenge their validity. She makes evident in her narrative the intimate relationship between those physicists who do theoretical work, and those pursuing experimental data. Although Mack herself works as a theoretical astrophysicist, her descriptions of the work of experimental physicists as they push forward the boundaries on what can be measured make evident her excitement for this collaborative effort.
And in fact, late in the book she makes the statement that
creative thinking becomes especially important when we’re faced with a conundrum like “how do we improve on [existing theories such as] Concordance Cosmology or the Standard Model?” Everything we’ve tried so far [in terms of experimental data] has been frustratingly consistent with predictions.
I tripped over this line when I first read it: the data being “consistent with predictions” of the models would seem to be a good thing, not a source of frustration. But in the next line she clarifies this sentiment:
where are we supposed to find clues leading us to new models if we can’t get something in the current model to break?” (190)
Here the clear passion of an astrophysicist who through her work – and I nod here to her apparent love for science fiction stories based on her references them – looks to explore new worlds … to go where no one has gone before.
Having read these two books almost back-to-back (with a big dose of Thomas Piketty's Capital in the Twenty-First Century in between to bring me firmly back to present-day Earth), I can highly recommend both to anyone interested in these topics. Mack provides a quicker read, and certainly a more colloquial style, wearing her passion for her work on her sleeve. Greene’s book by comparison comes in at about twice as long, and he takes a more in-depth pass through the material, if still eminently engaging and readable. In particular, he makes a valiant attempt to lay out for readers the timeline over which the details of these potential “ends of the universe” would play out. His narrative approach is more measured, but like Mack, his fascination and love for his field comes through on every page.
An animating theme that runs throughout Greene’s exposition is, to pull from the subtitle of his book, Our Search for Meaning in an Evolving Universe. Mack, too, explores this, in her Epilogue, recognizing that
it’s impossible to seriously contemplate the end of the universe without ultimately coming to terms with what it means for humanity. … Whatever legacy-based rationalize we use to make peace with our own personal deaths, … none of that can survive the ultimate distribution of all things. (206)
Nonetheless, for Mack – like Greene – such considerations cannot dampen her enthusiasm for what we are learning in the here and now, this moment when astrophysicists are exploring the distant reaches of space and time to better understand the history, workings and future of our universe.
Attempts to understand and model the changing structure in a now recognized to be evolving universe led physicists to postulate the existence of dark matter as a necessary presence to explain the complex dance of galaxies. Though dark matter remains undetected, observations have provided firmer estimates of the amount present in the universe, reaching levels thought to be sufficient to overcome the expansion arising from the Big Bang, and eventually initiate a collapse. Mack refers to this as the Big Crunch, in which the matter of the universe comes crashing back together. More critically, she points out, all the energy that has been radiated out into the universe would also become condensed into an ever-smaller region, creating energies intense enough to “begin to ignite the surfaces of stars,” (65) with ultimately nothing able to survive. A hot, fiery end to our universe.
In the 1990’s, however, came the discovery that the expansion of the universe is actually accelerating, not slowing down as was predicted based on the estimates of the amounts of dark matter. To explain this, “astronomers invoked the existence of a vast cosmic energy field that could make the empty vacuum of space itself have an intrinsic outward push in all directions,” (76-77) referred to as dark energy.
Mack notes that dark energy currently appears to have a constant value that leads to the conclusion that the universe, instead of collapsing in a ball of fire, could end in what she refers to as Heat Death: its expansion will continue to accelerate, with everything beyond our local cluster of galaxies eventually disappearing beyond the edge of our observable range. Ultimately stars will die out and everything will slowly disintegrate, even protons decaying as the universe reaches a cold, dark state of maximum entropy.
The Heat Death scenario assumes that dark energy has – and maintains – the specific, constant value of -1. But, Mack writes, a group of cosmologists have realized that if the value “is even infinitesimally lower,” (112) the result will be a Big Rip. In this scenario, the expansion of space overcomes the other forces in the universe, so that even the space within matter expands, leading ultimately to the disassociation of even atoms.
The next, and perhaps scariest, end to the universe that has arisen out of recent theoretical analysis, came out of what was perhaps the most well-publicized experimental discovery in physics in the past decade: the Higgs boson. The discovery of this particle confirmed the presence of the Higgs field, “a kind of energy filed that pervades all of space and has interactions with other particles in a way that allows them to have mass.” (134) Physicists have determined that the Higgs field has just the right value to permit our universe to exist.
Confirmation of the existence of such a field, however, has provided experimental evidence supporting a proposal from decades earlier: that our universe may not be stable. In fact, Mack notes, the data suggest that the Higgs field could decay to a more stable value, and, critically, this value would no longer allow our universe to exist as it has. She refers to this as Vacuum Decay, and notes that it could be initiated at any moment by a sufficiently powerful event. Such an event would initiate a kind of ripple moving outward at near the speed of light in all directions, as the Higgs field in the surrounding space subsequently decays. Unfortunately, this state is one in which matter would completely disassociate: a painless death that could happen at any time, and that we could never see coming.
The last of the fates of the universe that Mack considers arises out of the recent experimental verification of gravitational waves, found as part of the study of gravity, specifically why it’s so weak compared to the other forces in physics. Among the theories being explored, based on the work of cosmologists interpreting the experimental data that’s been collected, is the idea of extra dimensions. In particular, Mack describes a theory that allows for there being two adjacent three-dimensional universes that move apart and collapse – like clapping hands – with each Bounce, as Mack refers to it, ending, and then restarting the universe in a high-energy, Big Bang like event.
Other notes and information:
Have you read this book, others by this author, or even similar ones by other authors? I’d enjoy hearing your thoughts.
Other of my book reviews: FICTION Bookshelf and NON-FICTION Bookshelf
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