A timely retrospective

In his new book, Thomas Hertog delves into quantum physics and cosmology while simultaneously giving readers an insider’s view into the cosmological theory he developed in collaboration with Stephen Hawking. In On the Origin of Time: Stephen Hawking’s Final Theory, he interlaces personal stories, historical anecdotes, and other elements to craft a compelling and thought-provoking story.

Hertog eagerly tackles complex physical and cosmological ideas, presenting them in an accessible yet intellectually substantial manner. For example, he employs an endearing analogy involving eggs, chickens, and farms: “How come we have unbroken low-entropy eggs available to make an omelet? Eggs come from chickens, which are low-entropy systems on farms that are themselves part of a low-entropy biosphere.” Similarly, he presents an explanation of cosmic inflation, tailored to a wide readership, that highlights the importance of scalar fields by cleverly describing them as drivers of repulsive “antigravity.”

Throughout the book, Hertog crafts beautiful sentences that captivate the reader’s imagination. One sentence that particularly struck a chord with me describes the Feynman path integral formulation of quantum mechanics: “In Feynman’s view, the world is a bit like a medieval Flemish tapestry—a woven texture of crisscrossing paths that stitch a coherent picture of reality from the threads of a myriad of possibilities.”

The illustrations featured in the book are appropriate and attractive. Some notable examples include Georges Lemaître’s sketch of a hesitating universe born out of a primeval atom and John Wheeler’s depiction of the quantum universe as a self-excited circuit, which add an extra layer of engagement. Hertog also interjects moments of levity into his scientific exploration by including whimsical elements, such as Wheeler’s clever puns. Those lighthearted anecdotes provide a contrast to the weighty scientific discussions and add to the book’s charm.

The question Hertog addresses—namely, what happened at the beginning of time—is deep and fascinating. If time originated with the Big Bang, contemplating what occurred before is meaningless. Even speculating about the cause of the Big Bang seems paradoxical because causality necessitates the existence of time. Among the many who have pondered those questions was Lemaître. Possibly because of Hertog’s background—he is Belgian, as was Lemaître—he provides a comprehensive historical account of Lemaître’s oft-underplayed contributions to the Big Bang theory and the philosophical questions it prompts. As Hertog describes, the Belgian physicist was in dialog with Arthur Eddington and Albert Einstein. But unlike Lemaître, who was deeply religious, Eddington and Einstein cautiously approached the concept of a universe with a starting point because it seemed to imply a supernatural intervention.

In the final chapters, Hertog reveals his theory of cosmology. Although traditional physics works by separating the laws of time evolution, boundary conditions, and observations, Hertog boldly advocates for a cosmology that integrates the three elements. Although I empathize with that perspective, I have some reservations about Hertog’s tendency to overstate the significance of his own idea by likening it to the Copernican revolution. Moreover, it is important to acknowledge that Hertog’s theory, which he credits to himself and Hawking, remains in the realm of speculative debate and contemplation. But even though the final verdict on their cosmology is yet to be issued, Hertog’s description of both the theory and his collaboration with Hawking remains fascinating.

Hertog’s ability to convey profound ideas, such as the enigmatic nature of time and our place in the universe, is on par with that of his mentor Hawking. I had the pleasure of reading most of On the Origin of Time by the shores of Lake Michigan near my home in Hyde Park, Chicago. As I gazed on the vast expanse of the lake, I contemplated the concept of deep time. The ice age that shaped the Great Lakes occurred just 12 000 to 17 000 years ago, which is a flicker compared to the immense stretches of time we physical scientists consider. But there is an undeniable joy in imagining the beginning of all things, especially the beginning of time itself.

Savan Kharel is a theoretical physicist interested in quantum field theory, quantum gravity, and cosmology. He teaches the joy of life in the universe at the University of Chicago.