Stephen Hawking’s best-seller A Brief History of Time (BHT) was published in 1988 with worldwide sales of over 10 million. It was an exhilarating gallop through current ideas from physics with chapters on the expanding universe, the uncertainty principle, elementary particles, black holes, the origin and fate of the universe, the arrow of time and the unification of physics.
A book about God?
In the book’s introduction, Carl Sagan declares: “This book is about God … or perhaps about the absence of God.” In the book’s final sentence, Hawking – talking about a unified theory of physics – states: “If we find an answer to that, it would be the ultimate triumph of human reason – for then we would know the mind of God.” Many people must have bought the book expecting it to answer their theological questions, only to get stuck in intellectual challenges such as Einstein’s theory of general relativity being mathematically incompatible with quantum theory.
35 years have elapsed since Hawking’s famous book, with plenty more cosmic theories being proposed and explored. Hawking, who was himself a professor at Cambridge, holding the same professorial Chair that Isaac Newton had held, took the lead in much of this research. Since the 1990s, one of his close collaborators, who had started out as a doctoral student under his supervision, was Belgian physicist Thomas Hertog, who has written his book, On the Origin of Time, detailing those two decades of working closely with Hawking.
The public fascination with Stephen Hawking stems from two impulses: firstly how he managed to live such an energetic life with motor neurone disease that started in his early twenties, and secondly his bold presentation of cosmology, so this book appeals to the reader for those two aspects. Even if one cannot always follow the physics, there is a delight in following how closely, and humorously, these two interacted. The author’s note says: “My numerous conversations with Stephen over a span of twenty years are faithfully and truly woven into the narrative.”
Theory of Everything not found
The plot of Hertog’s book is that Hawking essentially changed his mind about the big WHY of cosmology between the time he wrote BHT and the final years before his death in 2018. In the early years, just after he had spent a decade of research on black holes, he had turned his attention to cosmology when the Jesuits had invited him to a conference at the Vatican, where he presented the possibility that space-time was finite but had no boundary, which means no beginning and no Creator.
Hertog’s book gives a diagram of this (p94) which shows how space and time gets smaller the nearer to its origin point but then “quantum mechanical effects” blur the two together so that the end curves round, like a sphere on which the explorer seems to be striding across two dimensions without a boundary.
Hawking staked his career on finding a set of boundary conditions, as he proclaimed in his inaugural lecture: “(many people) … would regard the question of boundary conditions of the universe as belonging to the realm of metaphysics or religion”, but he predicted “a theory of everything” would be found by the end of the century.
This did not happen. Why not? In the chapter on cosmogenesis, Hertog remarks: “Physicists complained that Stephen’s creative use of Euclidean geometries was like magic … the Euclidean framework … is a semiclassical amalgam of classical and quantum elements put together without clear mathematical guidelines. Stephen and his students were inventing the rules as they went along.”
Physicists at work
There are delightful descriptions of how they did this in the old DAMTP (Department of Applied Maths and Theoretical Physics). They – including Stephen in his automated wheelchair – would meet daily for tea in the common room for individual interactions that often involved scribbling equations on the white-top tables. Hawking kept his research students close to the topics that interested him; “From day one (he) expected us to work with him to transform the grand intuitive picture in his head into fully fledged research project.” With new doctoral students, he took alternate years of focus on black holes and cosmogenesis.
The “no boundary” proposal was discredited by further investigation into the first few moments of our universe that can now be perceived by modern instruments. The explosion was too forceful and too rapid for the weak calculation results propounded by the “no boundary” theory.
Even in an earlier generation of astronomers, contemporary with Einstein, the Belgian astronomer Georges Lemaitre had sketched out in 1927 how the universe had expanded, fast initially and then slowing to a wobbly progress as conditions for life developed. Hertog, as a Belgian, was able to give due credit to Lemaitre by sourcing his notebooks (pages reproduced in the plates).
Lemaitre was a fine cosmologist and an ordained Roman Catholic priest, but he kept the two apart, even in his notebooks. Arthur Eddington and Einstein both acknowledged the increasing evidence that the universe is expanding but rejected any ideas about a beginning, such as Lemaitre’s notion of a primaeval “quantum” that divided into quanta at the Big Bang, with irregularities that became more enhanced with the passage of time, the result being that the conditions of the universe became progressively more suitable for life to develop.
Written from the wrong perspective
Other physicists, like Andrei Linde, expounded multiverses. If the Big Bang is a symmetry-breaking event, then there are many possible ways for symmetry to break, just as a pencil poised on its point can topple anywhere in the circle around it. String theorists were propounding extra (unseeable) dimensions, up to 13 dimensions. So, at the Big Bang, any combination of these could, according to the maths, produce any combination of physical states very different from our universe. These would be ‘islands’ unable to communicate with each other. Stephen was outraged by such proposals for multiple GUTS (Grand Unified Theories each based on different unseeable dimensions).
In 2002, Hawking summoned Hertog (who was on holiday in central Asia exploring the Great Silk Road) back to Cambridge to announce through his clicker: “I have changed my mind. BHT is written from the wrong perspective.”
The basic puzzle is why our universe (granted the plethora of possible GUTS) is so biophilic – humankind’s need to interact with and surround themselves with nature and other living things. I like that new concept as it encompasses a greater realisation that it takes a whole environment to produce a life. In BHT, the term “anthropic” was used. The discussion between Hawking and Hertog about this concerns how physics is done.
Observership in a biophilic universe
As a science, it maintains separation between dynamics governed by supposed “laws of nature” and “boundary conditions” – that is the experiment set up by the scientist, which measures the difference between the initial conditions and the resulting state after the experiment. From Euclid with geometric theorems, to Copernicus on revolving planets, to Newton on the absolutes of space and time in which gravity operates, physical science claims to rest on objective “laws”. Hawking was now moving away from this, with the remark: “Our theories are never fully decoupled from us.”
What he (and Hertog) then proposed was a three-point figure (as on p187) for cosmology, with the origin (boundary conditions for the Big Bang); evolution – what we know of subsequent expansion of the universe – and “observership”, the questions we ask. The concept of the biophilic universe is that at every stage, right from the first seconds of inflation, we can measure and observe how the universe seems to have “chosen” the right conditions for human life to eventually come into being.
There is nothing to be said or measured about other possible worlds because there is only one branch that produced us and the realities we know. “Observership in quantum cosmology … is an indispensable part of the continual process through which physical reality – and physical theory, we argue – come about.”
The last two chapters of this book explain in more detail what this “top-down” (from the observer) theory entails. Intriguingly, this is where the new physics of holography (with diagrams) is introduced. The universe emerges not in time but from a hologram of entangled quantum possibilities. During his last conversation with Hertog, Hawking said: “I was never in favour of multiverse … time for a new book … include holography.”
Contingent on the questions we ask
Hertog, now a Professor of Cosmology at the University of Leuven, comments: “If our top-down cosmology does provide a new worldview, then it is a thoroughly pluralistic one. Notions of time and law-like patterns are seen to emerge in a way that is contingent on the questions we ask, and grounded in the complexity of the universe we see around us.”
This book is an intriguing and enjoyable read, not just for the physics, but for the delightful scenes and explanations of the interactions between Hawking and his student, Hertog.
