Bold Conjectures, Volume II

Dedicated to Lanie Chipkin and Chloe Murray,

the Wolf and the Bee.

Major support for this volume was provided by Naval Ravikant.

Additional support by Daniel Gilbert, Diego Rey, Mike Maples, Jr., Allos AI, and Ben Ferrum.

Conjecture Institute gratefully acknowledges their generosity in advancing this work.

If we really do live in a quantum multiverse, then where does gravity fit into that picture? How does quantum theory solve the problem of time? How can the world be truly local, despite quantum theory’s notoriously bizarre properties? Can we ever settle the debate over whether entropy is subjective or objective? What is the relationship between probability and fundamental reality?

_Bold Conjectures, Volume II: Essays Across Physics_ consists of essays by physicists who explore and answer questions such as these. Drawing from their own careers as researchers, contributors to this entry in our Bold Conjectures series either explain cutting-edge developments in physics that most people are not yet aware of, or they clarify a key idea that popular culture tends to get wrong.

In this compendium, you’ll also read about novel ways by which we may test for quantum effects in biology, the history of string theory, the philosophy of effective realism, a new way to test the nature of gravity, and what constructor theory of information may tell us about how to bring together general relativity and quantum theory.

Each essay may be read independently of the others, though often you will discover that ideas in one essay reinforce those in another. Like the human project that is science itself, _Bold Conjectures, Volume II: Essays Across Physics_ has no singular starting point or end point but rather consists of a collection of explanations, advancements, and open problems that the reader is encouraged to explore as he or she sees fit.

Thanks to all of the physicists who kindly contributed to this compendium: Abdullah Afzal, Julian Barbour, Charles Alexandre Bédard, Giuseppe Di Pietra, Aditya Iyer, Sam Kuypers, Chiara Marletto, Simone Rijavec, Hassaan Saleem, Mia Stamatova, Vlatko Vedral, Maria Violaris, David Wallace, and Antonia Weber.

I thank David Kedmey for his indispensable role in producing the second entry in our Bold Conjectures series, and I thank Aaron Stupple for his countless suggestions during the course of this book’s creation.

Yours,

Logan Chipkin

President & Cofounder, Conjecture Institute