Illustration of the Big Bang event 13.8 billion years ago, created on May 11, 2016. (Illustration by … [+]
Stephen Hawking’s wildly popular 1988 book, “A Brief History of Time: The Big Bang to Black Holes,” introduced the world to the late Cambridge University theoretical physicist’s views on cosmology. But what’s less appreciated is that Hawking continued honing his theories on cosmic evolution right up until his 2018 death.
In a compelling new book, “On the Origin of Time: Stephen Hawking’s Final Theory,” written by Hawking’s longtime Cambridge University colleague Thomas Hertog, Hawking’s final thoughts on the origin of our cosmos are re-examined in detail.
By the early 1980s, many cosmologists were enthralled by the idea of a multiverse —- a hypothetical collection of a seemingly infinite number of universes. But Hawking apparently was unsatisfied with such multiverse notions. And towards the end of his life, he sought a theory of cosmogenesis that incorporates some of the deepest philosophical questions about the evolution of a cosmos capable of supporting stars, galaxies, and intelligent life.
The crux of the book deals with Hawking’s interest in reflecting a new cosmic reality in which the laws of physics are mutable enough to change and evolve along with the universe itself.
But Hertog, now a theoretical physicist at Belgium’s University of Leuven, writes that when we trace the universe back to its earliest moments, we encounter a deeper level of evolution, at which the physical laws themselves change. “The rules of physics transmute in the primeval universe, in a process of random variation and selection akin to Darwinian evolution, with particle species, forces, and even time fading away into the big bang,” he notes.
On the Origin of Time
Yet even though the early universe might have been more mutable than previously thought, there are a few immutable truths about the cosmos that Hertog repeats in “On the Origin of Time.”
—- Gravity is an extremely weak fundamental force. If it were stronger, Hertog notes that “stars would shine more brightly and hence die far younger, leaving no time for complex life to evolve on any of the orbiting planets warmed by their heat.”
—- If temperature differences in relic big bang radiation were even one part in ten thousand bigger, “the seeds of cosmic structures would have mostly grown into giant black holes instead of hospitable galaxies with abundant stars,” Hertog writes.
—- Our cosmos happens to have three large dimensions of space, notes Hertog. “Adding just a single space dimension renders atoms and planetary orbits unstable,” Hertog writes. “Earth would spiral into the Sun instead of tracing out a stable orbit around it.”
—- Carbon is essential for life as we know it. And the efficient synthesis of carbon (from atoms of helium) inside stars, rests on a delicate balance between the cosmos’ strong nuclear force (the force that binds all atomic nuclei) and the electromagnetic force. If the strong force were just a fraction stronger or weaker, then the nuclear binding energies would shift, compromising the fusion of carbon and hence the formation of carbon-based life, Hertog writes.
One of the upshots of Hawking and Hertog’s work is that as Hertog notes, our theorizing should “account for our existence within the universe.” In addition, he asserts that “by tracing the universe back in time,” it’s possible to discover “a stage where the rules and principles of physical evolution co-evolve with the universe they govern.”
Even so, in 1981, Hawking proposed a universe that had no boundaries and potentially no beginning. And although he backed off that a bit, he also never fully embraced the idea of a multiverse. Yet he did accept that the universe experienced a rapid expansion which cosmologists term inflation —- the post big bang exponential expansion of spacetime. And to this day, the $64,000 question remains what fueled this massive expansion within the first trillionths of a second after the big bang?
Five years after Hawking’s death, we still have no answers. But there’s hope that within the next decade, ground-based gravity wave astronomers will have detected gravitational radiation from inflation. This might give astrophysicists a new window onto big bang cosmology.
As for the book itself?
By no means is “On the Origin of Time” light reading. But it does offer a comprehensive view of the latest ideas in cosmogenesis.
Ultimately, the book renews debate about whether we are a byproduct of immutable laws of physics or whether the physical axioms that bind us co-evolved with the universe. These aren’t the kind of questions that people normally pose between courses of canapes at standup cocktail parties.
But such conundrums are why theoretical physics continues to be relevant. What could be more philosophically important than the origins of this cosmos we call home and just how we got here?
