The physicist’s final theorem, about why the universe seems fine-tuned for life, contains some provocative predictions. Will they be as fruitful as his insights into black holes?
THERE was no one quite like Stephen Hawking. His work on cosmology dealt with extremely arcane mathematics, yet he was, until his death in 2018, the most recognizable scientist in the world. He explored the deepest mysteries of the universe, but he also appeared on The Simpsons.
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Hawking’s most famous contribution concerns the nature of black holes. In the 1970s, he found a precise way to describe their boundary, or event horizon, in terms of thermodynamics – the theory describing the interplay between temperature, heat and energy transfer – which led him to predict that black holes can emit radiation. This flew in the face of the assumption that nothing could escape a black hole – and thus sparked decades of deep thought and debate, as physicists grappled with the implications. Today, many see this black hole conundrum as the most likely route to a more unified theory of physics.
Has Hawking done it again with his final theorem? It turns out that, later in life, he spent 20 years pondering the question of why, out of all the possibilities, the universe has the particular properties that make it so well suited for life to emerge. In our feature “Stephen Hawking’s final theorem turns time and causality inside out”, we have a wonderfully intimate account of his insights and how he came to them, written by his close collaborator, physicist Thomas Hertog.
The gist of the idea is that the laws of physics, rather than truths that transcend time, were forged in the big bang and “evolved” into their current form, shaped by the environment of the early universe. As Hertog explains, the proposal involves a host of eye-popping predictions, including the idea that causality can run backwards, time disappears at the big bang and the universe is a hologram.
Hawking’s final theorem is difficult to get your head around, and could be harder still to test, but it may yet be a gift to cosmologists. He has once again set the cat among the pigeons with a bevy of ideas that challenge and inspire. And, once again, it is up to physicists to digest them to see if they will be as fruitful as his big breakthrough on black holes.