Perhaps this is the appropriate point to identify another and less well-known name appearing in these pages, that of Hsue-shen Tsien. In 1936, with the great Theodore von Karman and Frank J. Malina, Dr Tsien founded the Guggenheim Aeronautical Laboratory of the California Institute of Technology (GALCIT) – the direct ancestor of Pasadena's famed Jet Propulsion Laboratory. He was also the first Goddard Professor at Caltech, and contributed greatly to American rocket research through the 1940s. Later, in one of the most disgraceful episodes of the McCarthy period, he was arrested on trumped-up security charges when he wished to return to his native country. For the last two decades, he has been one of the leaders of the Chinese rocket programme.

Finally, there is the strange case of the 'Eye of Japetus' – Chapter 35 of 2001. Here I describe astronaut Bowman's discovery on the Saturnian moon of a curious feather 'a brilliant white oval, about four hundred miles long and two hundred wide... perfectly symmetrical... and so sharp-edged that it almost looked... painted on the face of the little moon.' As he came closer, Bowman convinced himself that 'the bright ellipse set against the dark background of the satellite was a huge empty eye staring at him as he approached...' Later, he noticed 'the tiny black dot at the exact centre', which turns out to be the Monolith (or one of its avatars).

Well, when Voyager 1 transmitted the first photographs of Iapetus, they did indeed disclose a large, clear-cut white oval with a tiny black dot at the centre. Carl Sagan promptly sent me a print from the Jet Propulsion Laboratory with the cryptic annotation 'Thinking of you...' I do not know whether to be relieved or disappointed that Voyager 2 has left the matter still open.