Cillian Murphy’s chiselled features, his gaunt face, mysterious and half-shaded by tilted trilby, adorns billboards all over the world. Robert Oppenheimer is back and the feature film’s first weekend suggests this could be the biggest movie of the year. Murphy’s brilliant, compromised, chain-smoking Oppenheimer rekindles our fascination not just with the man but the era, capturing the paranoid mood that bedevilled America as it emerged, omnipotent, after the second World War. Nuclear was the ultimate victory of physics and the 20th century became the physics century, with celebrities such as Albert Einstein, the most famous man in the world. The…