Dennis Sciama’s Astonishing Cosmological Conversion
From Steady-State Devotee to Leading Advocate for the Big Bang
A Brief Dialogue with 2020 Physics Nobel Laureate Sir Roger Penrose
In the 1950s and early 1950s, Cambridge physicist Dennis Sciama was one of the world’s leading advocates for the steady-state model of cosmology: the idea that the universe, while expanding, continuously fills in the gaps with newly created matter. Then. in 1965, after Arno Penzias and Robert Wilson’s unexpected discovery of the relic microwave background radiation leftover from the hot early universe, Sciama made an astonishing turnabout and fully embraced the Big Bang. He encouraged his own student Stephen Hawking and another Cambridge student, future Nobel Laureate Roger Penrose to pursue the implications of a universe that emerged from a pointlike state. Meanwhile, an increasingly isolated Fred Hoyle, one of the steady-state theory’s proposers, clung to aspects of his hard-fought idea — eventually turning to a modification called the quasi-state-state universe, all in an effort to find a way of avoiding a Big Bang.
At the annual April Meeting of the American Physical Society, in April 2021, during a question and answer session after his talk, I asked Sir Roger Penrose about his recollections of that pivotal era:
Paul Halpern: “Do you recall Dennis Sciama and Fred Hoyle’s reactions to the singularity theorems given their support of the steady-state theory?”
Roger Penrose: “Yes, indeed. That was very interesting.
Well, Dennis was my main source of physics. I went to Cambridge as a graduate student in pure mathematics, but then Dennis took me under his wing and decided I was someday he should involve in cosmology, and so on. And while he wanted me to change to cosmology, I didn’t do that, but I learned a lot from him.
And, at that time, yes, the steady-state model was the great thing at Cambridge. And I knew Bondi, and I knew Gold, and I knew Hoyle, and I knew Dennis Sciama.
And when the Penzias and Wilson observations came about, and became clearer and clearer that the steady-state model had to be wrong, Dennis struggled a bit and he thought he’d produce some explanation of it.
And then when he was convinced that it was wrong, I had an enormous respect for him.
Then he went around giving lectures saying , ‘I was wrong. The steady-state model is wrong. The Big Bang was there and we have to change our minds.”
I thought that was amazing.
Fred Hoyle didn’t. He sort of vacillated for a long time, and stuck to steady-state and various versions of it.
But Dennis was absolutely direct and honest, as a scientist should be, and I had tremendous respect for that.”
I am deeply grateful to Sir Roger Penrose for sharing his fascinating recollections.
Paul Halpern is a University of the Sciences physics professor and the author of seventeen popular science books, including Flashes of Creation: George Gamow, Fred Hoyle, and the Great Big Bang Debate.