Existential Physics opens with an anecdote about a difficult question a young man posed the author during outreach: because of quantum physics, his deceased grandmother isn’t really dead, is she? “Physicists are really good at answering questions,” author Sabine Hossenfelder quips, “but really bad at explaining why anyone should care about their answers.” And from my own experiences, I do agree. In the biological sciences, it’s really easy for people to care about the science. Or even if it’s a topic that’s dense, we can usually connect it to some disease that terrifies you to attention. The mechanisms of biology are intimately embedded in our own flesh and blood. No matter how you feel about the Krebs Cycle or the structure of insulin receptors, it’s easy to understand why these are crucial to understand. On the other hand, the sweeping conclusions in physics about the universe feel less universal.
If you’re going to read this book, definitely go with an ebook or a physical copy. I listened to the audiobook, and I found myself rewinding a lot to go back to a definition or an explanation that I missed. There’s also a handy dandy PDF of diagrams that goes along with the book, and I think that would be really helpful for anyone really trying to absorb this information.
As expected, this novel covers a ton of topics: gravity, relativity, black holes, time, aging stars, and even the beginning and ending of the world. Along the way, Dr. Hossenfelder debunks various pseudoscientific physics myths (i.e., people can’t use quantum leaps to travel through time and space). It also encourages us to think critically about these theories, which the doctor admits can sound ridiculous. As a neuroscience major, I really liked the explanation of Boltzmann brains, the product of a theoretical thought experiment where the tiniest chance of atoms colliding in space makes a brain form spontaneously from the element soup. That brain has maybe half a thought before its parts collapse back into the mush.
Honestly, as the book gets deeper, I felt like that brain: briefly having a moment of insight before falling into an ocean of mild confusion. Don’t get me wrong, it was incredibly fun, but I feel like I may have only absorbed about 60% of the information. Don’t underestimate the “Existential” half of Existential Physics. This book not only introduces uncertainty, but it revels in it. Why do we do science at all if the laws of science, just like everything else, might stop working tomorrow? Does anything actually exist or is it just our perception as “brains in a vat”? Where did we come from and how will the world end? Does free will exist?
Still, the prose of this title brings things back to a more understandable state. At the end of each chapter, the professor gives the main takeaway in a sentence or two. So even if we don’t completely know what’s going on, we can get the big idea. Even more, she interviews other physicists about their own views on the theoretical physics theories of the day. These sections, written in a more direct and casual way, helped me understand the concepts in context. It also has some entertainment value, the same way someone would watch an Actors on Actors video interview.
This book is quite unique in that it covers very dense, deep content, but it never feels stifling. Dr. Hossenfelder’s tone, aimed at older teenagers and adults, doesn’t talk down to the audience. She doesn’t mistake oversimplification with approachability, which is something I find really refreshing about this book. I’ve noticed that while short form internet content (Instagram Reels, Youtube Shorts, TikToks) can give people bite sized pieces of information, it also dumbs things down to fit the time limit of the posts. Because of the format, this book is able to really delve into different topics, and the result is a complete, enriching experience. If you want to learn more about how the big physics questions can help you recontextualize your own life, give it a chance.
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