Gerard 't Hooft, one of the world's great physicists by any measure, and his collaborator Stefan Vandoren (also a physicist at Utrecht University) have written an ambitious and charming book that will be warmly received by any fans of popular-level science. Their work is highly constrained by challenges inherent in the subject matter, but it is nevertheless well worth reading.
The title, Time in Powers of Ten, reveals immediately that the book follows in the footsteps of Powers of Ten, the iconic short film from 1977 by Charles and Ray Eames, which itself was based on the 1957 book Cosmic View by Dutchman Kees Boeke. Those works explored how the physical world looks different on different length scales, starting from human-sized and working up to the cosmos and down to the subatomic realm.
For physicists, once you have that idea it seems very natural to do the same exercise with timescales. Our universe is structured in interesting ways at every distance and at every interval of time; exploring each level and the connections between them offers a good way of introducing a wide audience to how physicists think about the world.
't Hooft and Vandoren take up the challenge with aplomb. Starting with one second, in the first half of the book they look at processes that take longer and longer times, up to the age of the universe and beyond; in the second half, they start with yoctoseconds (10−24 s) and shorter, working their way back up to the human realm.
The result is a rich and multi-layered look at an enormous variety of physical phenomena. Each chapter examines a decade's worth of timescales, e.g., from 100 s to 101 s, and at each stop the authors choose a number of illustrative examples, color-coded to add some structure to the proceedings: decay times and half-lives, orbital and rotation times, periodic and vibrational periods, the history of the universe, and light-travel times.
Many of the discussions—especially at the very long and very short ends of the spectrum—are from physics and astronomy, but attention is given to human and biological processes where appropriate. Between from 109 s and 1010 s, for example, we learn about the orbital periods of Saturn and the comet Tempel-Tuttle, the half-life of Cesium-137, and the light-travel time to the star Pollux; but we are also reminded of the Thirty-Years War and the tenure of Pope Pius IX (the longest-reigning pope in the history of the Catholic Church). These choices help to ground the reader, drawing connections between familiar experiences and the broader physical world.
Overall, the various examples are very well-chosen. At the shorter timescales, it is difficult to distribute the discussion evenly over many fields, and particle physics begins to take over, but that is fairly inevitable given a project like this. More importantly, the powers-of-ten motif helps the reader appreciate the considerable hierarchy between times that we might casually lump together as “really long” or “really short.” A nanosecond, which sounds small, is a full twelve orders of magnitude longer than a zeptosecond, which represents the lifetime of isotopes such as helium-5 and lithium-4. That is the same relative difference as there is between the lifetime of the universe and a day here on Earth.
But there are also limitations to an endeavor such as this. One of the reasons why the original Powers of Ten resonated so strongly with the audience is that we can see lengths directly; the process of zooming-in or zooming-out is something we can witness with our own eyes as we read a book or watch a film. When it comes to time, the connection is a bit more abstract. The authors can tell us that one process takes ten times as long as another, but we do not experience the difference in quite as visceral a fashion. It would be interesting to see whether a movie version of this book would be able to play with the time intervals in an evocative way.
Structuring a book around the notion of timescales necessarily leads to some abrupt transitions in subject matter. 't Hooft and Vandoren rightfully embrace this feature of their work, encouraging the reader to “hop and skip through the various pages, from one segment that piques your curiosity to the next.” This is not a textbook, or even a systematic introduction to any particular area of science. It is an invitation to think about our world in a certain way—as an interconnected network of vibrations and evolutions at every level.
Sean Carroll is a Senior Research Associate in the Physics Department at the California Institute of Technology. His most recent books are From Eternity to Here: The Quest for the Ultimate Theory of Time and The Particle at the End of the Universe: How the Hunt For the Higgs Boson Leads Us to the Edge of a New World.
