Julia Margaret Cameron, “Sir John Herschel”, 1867. Credit: V&A PICTURE LIBRARY

What a scientist (or artist, author, composer⃛) looks like should not matter to us. It would make no difference to the theories of relativity if Albert Einstein was clean-shaven, or even if he had a retroussé nose. Yet we harbour an apparently irresistible urge to scrutinize the appearance of famous and infamous persons — above all their faces — as if we might use outer signs to understand exceptional inner attributes.

A select body of images of famous persons have come to serve as more than physiognomic records. They have assumed iconic status, standing for something more archetypal than the traces of individual appearance.

The fame of the subject is crucial, but the nature of the portrayal must exhibit the potential to work with popular archetypes. Good examples are Yousef Karsh's photograph of Winston Churchill as British ‘bulldog’, and Andy Warhol's schematic Marilyn Monroes as the all-American blonde bombshell.

Orren Turner, “Albert Einstein”, c. 1947, Library of Congress. Credit: US LIBRARY OF CONGRESS /SPL

Sometimes the image can be of an assumed persona, like Charlie Chaplin's tramp, accompanied by the attributes of hat and stick. Once established, the person can be pictured through minimal cues of caricatured resemblance, particularly if reinforced with simple symbols, like Churchill's cigar.

Few images of scientists have achieved this status. Leonardo is familiar enough, but he stands for universal genius rather than professional scientist. No face of Sir Isaac Newton readily looms into public view when his name is mentioned. Yet Einstein has come to be instantly recognizable in caricatured form — wild halo of white hair, hooded eyes, characterful nose, bushy moustache and exaggeratedly large ‘brain-box’ — as seen on T-shirts and orchestrating word-processing ‘help’ programmes. The theatrically lit image by Orren Turner, photographed at Princeton around 1947, plays as potently on the notion of the venerable sage as any of the photographic studies of the older Einstein.

The general ancestry of Einstein as magus is clear, and more specifically it stands in line of descent from Julia Margaret Cameron's Victorian photographs of the great astronomer and pioneer of photographic processes, Sir John Herschel. So concerned was she to capture the qualities she recognized in the friend whom she called her ‘teacher and High Priest’, that she cajoled him into washing his hair so that it would encircle his head like an aura of cerebral light.

James King-Holmes, “Stephen Hawking”, 1997. Credit: JAMES KING-HOLMES/SPL

Such images, once they have assumed canonical status, serve to anchor our mental picture of the celebrity at a particular point in their lives. Although Herschel and Einstein were unquestionably once young, as was Leonardo, it is very difficult to invisage them other than as venerable, wise men, as those who are old enough to ‘know the secrets’. There are photographs of Einstein as an excise clerk, dark haired and photographically naive, but they somehow seem unformed and do not do the iconic job at all.

It would be difficult today to invisage the lighting of a portrait of a great scientist in the same overtly stagy way as those of Herschel and Einstein, but this does not exclude the possibility of new icons. The most likely candidate is Stephen Hawking, Newton's latest successor at Cambridge as Lucasian Professor of Mathematics. His prominence as a public persona, through his authorship of the improbable best-seller, A Brief History of Time, and his unembarrassed willingness to disclose the effects of his motor neurone disease, has meant that his appearance has become widely familiar. The contrast between the clear signs of Hawking's physical infirmity, and the public perception of him as a genius of modern science, points up the traditional mind-body duality.

Whereas the portraits of Herschel and Einstein radiated deep wisdom through their external aura, Hawking is, by implication, pure mind trapped in a physical integument whose incapacity mocks the capacity and reach of his intellect. James King-Holmes's 1997 photograph shows how a portrait of Hawking may possess potential not just to portray individual appearance but to embody the kind of general concepts that are necessary for an image to achieve iconic status.