Monthly Archives: April 2025

Existential Physics by Sabine Hossenfelder

blog, , ,

The full title is Existential physics: a scientists guide to life’s biggest questions. This one came out in 2022.

I read this one right after reading Sabine’s previous book entitled Lost in Math. This was a good followup. As an amateur astronomer and a physics major from college a LONG time ago, I often have my head in the clouds and I ask myself some of the same deep questions that are posed in her new book. Some of those questions are:

“Does the past still exist? Do particles think? Was the universe made for us? Has physics ruled out free will? Will we ever have a theory of everything?” and — Does the universe think? Are humans predictable? What’s the purpose of anything anyway?

I did not mark as many pages to comment on as I did with the Lost in Math book, but I found this one just as enjoyable.

Starting on page 95, she interviewed David Deutsch. It was noted that he wrote some books, The Fabric of Reality and the Beginning of Infinity. They sound interesting.

Chapter 6 (page 125-) – Has physics ruled out free will? This depends on what you mean by free will. In short, she thinks that the answer to that is no. She wrote:

“The major problem with discussions about free will is that philosophers have put forward a heap of definitions that have nothing to do with what nonphilosophers think free will means. I am tempted to write “normal people” as opposed to ‘philosophers,’ but maybe that’s a little uncharitable. And I don’t want to be uncharitable. Certainly not.” More of this chapter was transcribed at this blog post.

I liked this line on page 134 — “If you tell someone you think free will is real because the renormalization group equations might run into an essential singularity, you might as well paint GEEK on your forehead.”

Brief answer on this question (page 141) — “According to the currently established laws of nature, the future is determined by the past, except for occasional quantum events that we cannot influence. Whether you take that to mean that free will does not exist depends on your definition of free will.” Not sure I agree with her on this.

Page 191 – Zeeya Merali wrote a book — Big Bang in a little room: the Quest to Create New Universes.

On page 217, she starts an epilogue. She noted that physicists who propose unobservable parallel universe, they are not using science. “It’s religion masquerading as science under the guise of mathematics.”

However, on page 219, she says she agrees with Stephen Jay Gould on how religion and science are two “nonoverlapping magisteria.” I do not agree with her on that point. I think that religions overlap (or try to overlap) into science all the time. It was a mystery how thunder and lightning worked, and it was a mystery how alcohol was made as literal spirits. Over time, science has shown how weather works, and how alcohol can be made. Science continues to explain things that religions do not, but religions never explain things (yet) that science could not. But I do agree that there are some questions that are asked by both religious and scientific people all the same, and we do not have good answers yet, or some questions may not be answerable — ever. Both groups want to make sense of the world, and to make sense of how people and groups of people behave.

She concludes with “So, yes, we are bags of atoms crawling around on a pale blue dot in the outer spiral arm of a remarkably unremarkable galaxy. And yet we are so much more than this.”

Sorry, but I prefer to think of myself as a meat robot with a skeleton and a brain, but anyway, yes, we are more than just those things.

Lost in Math by Sabine Hossenfelder

blog, , , , , , ,

The full title of the book is Lost in Math: How Beauty Leads Physics Astray. She wrote this back in 2016-2017, and it was published in 2018. She interviewed about a dozen researchers to get their takes on the concept of beauty in physics. In 2020, she provided an update to the book as it was going to paperback. She has current blog posts – essentially daily! Peter Woit also wrote a good overview/review of the book.

She feels that physics is losing its way, because it is becoming too dependent upon supposedly beautiful mathematical concepts, and less upon data derived from experiment. Physicists are not following the scientific method. At the small end of the physics spectrum where subatomic particles are being researched, physicists are starting to hit a wall where the energies needed to break apart protons and neutrons are getting to be too high.

There are problems where supersymmetry (SUSY) and string theory just cannot be verified with physical experiments. While the mathematics of the theories may look good, it is extremely difficult to verify with experimental data.

She is also not a fan of the multiverse idea, since that is near-impossible to verify — right now anyway.

I really like the subtitles of each chapter, such as Chapter 2 What a Wonderful World In which I read a lot of books about dead people and find that everyone likes pretty ideas but that pretty ideas sometimes work badly. At a conference I begin to worry that physicists are about to discard the scientific method. Or, Chapter 4 Cracks in the Foundations In which I meet with Nima Arkani-Hamed and do my best to accept that nature isn’t natural, everything we learn is awesome, and that nobody gives a fuck what I think. Other chapter titles can be found here. Most of the chapters had three or four bullet points at the end as nice summaries to tie things up.

In any case, I highly enjoyed the book. I am looking forward to reading her newer book, Existential Physics: A Scientist’s Guide to Life’s Biggest Questions.

Some of my favorite quotes are:

“Theoretical physicists used to explain what was observed. Now they try to explain why they can’t explain what was not observed. And they’re not even good at that. In the Multiverse, you can’t explain the value of parameters; at best you can estimate their likelihood. But there are many ways to not explain something.” (page 108)

“The canary isn’t doing well. You’d think that scientists, with the professional task of being objective, would protect their creative freedom and rebel against the need to please colleagues in order to secure continued funding. They don’t.” (Page 197)

While talking with Katie Mack (future author of The End of Everything: (Astrophysically Speaking)), Sabine said “I think nature has more beauty in store for us. But beauty, like happiness, can’t be found by complaining about its absence.” (Page 209)

“But even with good problems and clearly stated assumptions, there can still be many mathematically possible solutions. In the end the only way to find out which theory is correct is to check whether it describes nature; non-empirical theory assessment will not do. In the search for a theory of quantum gravity and for a better formalism of quantum physics, the only way forward is to derive and test different predictions. And so, my third and final lesson is this: Observational guidance is necessary. Physics isn’t math. It’s choosing the right math.” (Page 234)