# Inside the life and work of Roger Penrose: winner of the 2020 Nobel Prize in Physics

**Joel Penrose** writes about the extraordinary contributions made by this Cambridge alumnus in a huge range of fields.

Roger Penrose is a leading British physicist and Cambridge alumnus with a diverse career spanning over 60 years. His influence pervades the scientific world, from the workings of artificial intelligence to the application of quantum theory; some of his work has even found its way into popular culture, with his impossible triangle adopted as the logo of the clothing brand *Palace* in 2009. He is also known for his collaborations with M.C. Escher and Stephen Hawking, the latter of which earned him a brief appearance in the 2014 film *The Theory of Everything *where he is played by Christian McKay. However, he is most famous for his contribution to the understanding of black holes, and it is for this that he has been awarded the 2020 Nobel prize for physics.

Penrose was born in Colchester in August 1931 into an intensely academic Quaker family. His father, Lionel Penrose, was a pioneering human geneticist. Of his three siblings, two would go on to become prominent academics: his sister, Shirley Hodgeson, is a prominent geneticist at University College London; his brother, Oliver Penrose, a theoretical physicist and fellow of the Royal Society. His other brother, Jonathan Penrose, is a chess grandmaster, famously winning the British Chess Championship ten times between 1958 and 1969.

The Penrose family also have a very strong artistic tradition, perhaps accounting for much of Penrose’s interest in geometry and form. Penrose’s paternal grandfather, James Doyle Penrose, was an Irish painter, well-known for his portraits, landscapes, and religious paintings; his uncle, Roland Penrose, was an important part of the British surrealist movement, co-founding the Institute of Contemporary Arts in London. Roland is also notable for his friendship with other artists, including Picasso, Man Ray, and Max Ernst, as well as his marriage to the celebrated photographer Lee Miller. Much of Roland’s work can be found on display in his former home at Farley Farm in Sussex, now an art gallery run by his son, the photographer Anthony Penrose.

Roger Penrose was educated in Canada during the Second World War, and after the armistice pursued a degree in mathematics at University College London. After graduating with a first-class degree, Penrose went on to do a PhD in algebraic geometry at St John’s College Cambridge. Here he attended lectures by Hermann Bondi, Paul Dirac, and S. W. P. Steen, all three of which had substantial influence on Penrose’s later work.

It was while attending a conference in Amsterdam in 1954 that Penrose (then a student at Cambridge) first encountered the Dutch graphic artist M.C. Escher. He became fascinated by the unconventional use of shape and form, and, working with his father Lionel, soon produced similar works of his own: the Penrose Triangle and the Impossible Stair. These clever illusions provided the inspiration for two of Escher’s most famous masterpieces, *Waterfalls* and *Ascending and Descending*, and are still very present in popular culture today. This kind of experimental geometry became a life-long fascination: in the 1970s, Penrose would once again gain acclaim for his invention of Penrose tiling, a non-repetitive pattern with five-fold rotational symmetry. As of 2013, this unique tiling can be found outside the Mathematical Institute in Oxford.

In 1952 when Penrose returned to St John's Cambridge as a research fellow, his work brought him into close contact with the young Cambridge graduate, Stephen Hawking; the two soon joined forces, working together to devise the Penrose-Hawking singularity theorems in 1969. These proved that when space-time reaches a certain level of distortion (such as in a black hole) it inevitably collapses, tending infinitely steeply towards a singularity where Einstein’s equations break down and a new, quantum theory of gravity is needed. Penrose and Hawking received the 1988 Wolf prize for physics in recognition of their work.

“His work brought him into close contact with the young Cambridge graduate, Stephen Hawking; the two soon joined forces, working together to devise the Penrose-Hawking singularity theorems in 1969.”

Penrose was certainly already accomplished, but it was the 1965 publication of his ground-breaking paper “Gravitational Collapse and Space-Time Singularities” which elevated him to international fame. Penrose became the first person to mathematically prove that Black Holes existed as an inevitable consequence of relativity theory. Though Einstein’s theories had predicted the existence of black holes back in the 1910s, many people (including Einstein himself) remained sceptical. All this was changed by the publication of Penrose's work in the 1960s, after which they became a widely accepted scientific truth rather than an unlikely prediction. It is to him that we owe much of our modern-day fascination with black holes, which are so eminent in our contemporary culture.

“Penrose became the first person to mathematically prove that Black Holes existed as an inevitable consequence of relativity theory.”

Penrose went on to conduct research in a range of mathematical fields, most notably including artificial intelligence. In his book *the Emperor’s New Mind*, Penrose argues that the rational thinking of the human mind cannot be replicated by an artificial intelligence – a polemical view that has yet to gain widespread acceptance in academic circles. In one of his more recent publications, *Cycles of Time: An Extraordinary New View of the Universe, *Penrose proposes that the universe is “cycling repeatedly from one big bang to another” - a controversial theory which brought him into conflict with his friend and long-time collaborator Stephen Hawking.

The invention of twistor theory in 1967 should also be listed among Penrose’s greatest achievements - as a branch of theoretical physics, it has helped shape current thinking about space-time, as well as leading to the development of mathematical tools. Penrose can also be credited with the invention of spin networks, a diagram commonly used to depict interactions between fields and particles in quantum mechanics; he has also attached his name to the Penrose diagram, a useful way to visualise the effect of gravity on an object entering a black hole.

Penrose has received numerous awards for his work, being knighted in 1994 and appointed to the Order of Merit in 2000. Recently he was jointly awarded the 2020 Nobel Prize in Physics “for the discovery that black hole formation is a robust prediction of the general theory of relativity.” The other winners were Reinhard Genzel and Andrea Ghez for their “discovery of a supermassive compact object at the centre of our galaxy.” The prize has therefore been divided in two, with Penrose receiving half of the £800,000 prize money.

Penrose is an exceptional physicist, even amongst Nobel Prize winners, for the fact that he has contributed to such a broad range of scientific fields - and we must bear in mind that even at the age of 89, Penrose is still working on the application of quantum theory to biology. His career is far from over: there is work to be done, and he might be the man to do it.

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