The End of Everything


Katie Mack




Date Reviewed:

August 27, 2021

he back cover-flap of The End of Everything (Astrophysically Speaking) states that the author, Katie Mack, is an assistant professor at North Carolina State. My first thought was - how is it that someone as obviously bright as her has not been awarded a full professorship yet? My second thought was - how fun would it be to take a class taught by her! Mack has the ability to explain difficult concepts ( at least, I think I understood what she was talking about), and also inject some witty remarks into the descriptions. Of course, a real class of physics would probably contain math beyond my level of comprehension. But there is no math in this book, it is entirely readable by a layman.

The End of Everything discusses five possible scenarios in which our universe may end: Big Crunch, Heat Death, Big Rip, Vacuum Decay and Bounce. But before Mack spends a chapter describing each of these doomsday possibilities, she first devotes a chapter to The Big Bang to Now, describing how astrophysicists currently think the universe formed. After all, if Mack is going to predict where we are going, it helps to know where we all got here in the first place. The Big Bang is described, and then the mysterious concept called inflation - in which the universe expands much much faster than the speed of light, as the pinpoint singularity of the Big Bang swells to the size of a beach ball in an instant. Inflation explains why we can see objects in the sky that are 46 billion light years away, even though the universe is only 13.5 billion years old.

The chapter on the Big Crunch describes what would happen if our expanding universe stopped expanding and reversed itself, and began to contract. After billions of years, the distant stars and galaxies would grow closer and closer. Also, a contracting universe would bring together all the photons and cosmic rays that have dissipated into the expanding universe - all of that energy would now grow more and more concentrated, creating a hellish environment until finally the entire universe potentially is annihilated in another singularity. Not that we have to worry about this possibility, it would be so far in the future that all of humanity will surely have long since perished.

Heat Death describes a universe that goes on expanding forever - the galaxies all recede from each other, the stars of our local galaxy all burnout, and eventually even matter decays until the state of maximum entropy is achieved. Again, this is doomsday is so far into the future that humans will never witness it.

The Big Rip discusses dark energy, which apparently is the unmeasurable force that causes more and more space to be created, which is what drives the expansion of the universe. Something called the equation state can have a negative value, and if the equation state value turns out to be less than -1, then dark energy will overwhelm gravity and everything will fly apart. I confess, I don't really understand what was happening here, but this chapter has interesting stuff about Einstein's cosmological constant, and I think I might understand now what Dark Energy is. Maybe.

Another scary outcome for the fate of the universe is Vacuum Decay. A particle called the Higgs Boson creates a field. This Higgs field is what gives particles their mass, though not to all particles - photons and neutrinos don't have mass. If the Higgs field failed, then matter would disintegrate, everything would vanish. Advanced mathematics apparently shows that the Higgs could exist in a more stable, lower state - if the Higgs rolled into that state, then our universe ends. This could happen at any time, though if it did happen, the effect would be so swift we would never feel a thing. However, the Higgs Boson has obviously remained at its current state for 13+ billion years, so there is no use fretting about Higgs failing in our lifetimes.

The final scenario is the Bounce. This theory postulates that the Big Bang was caused by two parallel universes (called branes) smashing together. The encounter is so violent that the result is an explosion like the Big Bang. Well, if branes could collide once, then they might collide again - and if our brane-universe bounces against another one, then the resulting explosion would pretty much end our current universe.

The book is enjoyable and informative. Did you know that gold is such a heavy element that it is thought that even a super nova explosion is thought to not have enough energy to fuse atoms into gold? Apparently on the collision of neutron stars creates conditions extreme enough to create gold. It makes me wonder just how many neutron stars collision there could possibly be, it seems gold ought to be extremely rare. This book is as good as gold to anyone interested in cosmology.