Space sage

This beautifully illustrated book (20 colour plates, many more in black and white) is a fitting tribute by more than 20 of his friends and colleagues to the best-known astronomer of our time. In one way it makes sad reading, as the essays were addressed to Carl Sagan on his 60th birthday in October 1994, two years before his untimely death. But it is also exhilarating, because it records a veritable explosion in our knowledge of the universe - an explosion in which Sagan often acted as a fuse.

The book is divided into four sections: "Planetary exploration", "Life in the cosmos", "Science education" and "Science, environment and public policy". Its flavour may best be given by some of the titles: "Impacts and life: living in a risky planetary system" (David Morrison); "Do the laws of physics permit wormholes for interstellar travel?" (Kip Thorne); "Science and the press" (Walter Anderson); "Science and religion" (Joan Campbell); "Carl Sagan and nuclear winter" (Richard Turco); "Science and pseudoscience" (James Randi); "Nuclear-free world?" (Georgi Arbatov) and "Highlights of the Russian planetary programme" (Roald Sagdeev).

All the essays are by leading authorities in the field, yet all are accessible to the non-specialist reader. They are full of fascinating and little-known items of information; for example, in this era of mega-budgets, it is encouraging to learn that the most important discovery in radio-astronomy - the 21-centimetre hydrogen line - was a $500 bargain. And if you want to send a telegram 1,000 light-years, it would cost only a dollar a word - even with today's technology. (Of course, you will have to wait 2,000 years for a reply.) So two-way conversations are not likely for quite some time - but look at the impact on our culture of the "monologs" we already have with the Greeks and Romans, and all the great thinkers of the past. The possibility of what might be called "inter-stellar archaeology" is so exciting that one can sympathise with the researchers in this field, who have had their modest budgets cut by Congress. I once gave them the advice: "Despite disappointments and false alarms, continue the search for intelligent life in Washington."

In view of this book's general level of accuracy, I was appalled to find one contributor repeating the hoary old myth that a human body would "literally explode" in a vacuum. Nonsense: as a Nasa physiologist once remarked to me, "The skin is a pretty good spacesuit." Animals have survived in vacuum for several minutes: I do not know the record for humans, and would be most interested to have it.

Carl Sagan's Universe covers such a vast range of topics, from the big bang at the beginning of time, to avoiding unwanted bangs (natural or man-made) in our immediate future, that I cannot imagine any intelligent reader failing to derive both information and entertainment from it.

My only serious criticism is that I never had a chance of contributing a chapter myself. So here it is, for the next edition ...

In 1950 I published a slim volume, Interplanetary Flight, which was the first book to give Anglophone readers the basic principles of astronautics. (There had already been several highly technical works in French, German and Russian.) Carl Sagan was then in high school, and, as he wrote more than 30 years later: "I was interested in the other planets and I knew that rockets had something to do with getting there. But I had not the foggiest notion about how rockets worked or how their trajectories were determined. Then I came upon an advertisement for a book called Interplanetary Flight by one Arthur C. Clarke ... I sent away my money and breathlessly awaited its arrival .... the part about it that was most striking for me was the discussion of the gravitational potential wells of planets and the appendices, which used differential and integral calculus to discuss propulsion mechanisms and staging and interplanetary trajectories. The calculus, it slowly dawned on me, was actually useful for something important and not just to intimidate high-school algebra students ... As I look back upon it, Interplanetary Flight was a turning point in my scientific development."

Though I am certainly proud to have started Carl Sagan on his career, I have little doubt that he would have managed pretty well without my impetus. A later attempt of mine to expand his sphere of activity was not so successful.

I do not recall when we first met, but by the 1960s I must have been well aware of his work at the Smithsonian Astrophysical Observatory. So when, in the summer of 1964, Stanley Kubrick and I started generating ideas for a little home-movie with the working title How the Solar System Was Won, I decided that Sagan might be a useful ally in our brainstorming. Here are his own comments, after the dinner we had in Kubrick's East Side penthouse.

"They had no idea how to end the movie - that's when they called me in to try to resolve a dispute. The key issue was how to portray extraterrestrials ... Kubrick was arguing that extra-terrestrials would look like humans with some slight differences, maybe a la Mr Spock. And Arthur was arguing that they would look nothing like us ... I said it would be a disaster to portray the extraterrestrials .... the number of individually unlikely events in the evolutionary history of man was so great that nothing like us is ever likely to evolve again anywhere else in the universe ... any explicit representation of an advanced extraterrestrial being was bound to have at least an element of falseness about it ... What ought to be done is to suggest them."

After a third of a century, I do not recall Kubrick's immediate reaction to this excellent advice, but following abortive efforts during the next couple of years to design convincing extraterrestrials, Kubrick accepted Sagan's solution in the film 2001. What he did not accept was Sagan himself. After the dinner, we had arranged to meet the very next day for a further discussion, but when I got back to my hideaway at the Hotel Chelsea Stanley called me and said: "Make any excuse, take him anywhere you like, I don't want to see him again."

Fortunately I had an excellent alternative, and mumbling something about Kubrick having an unexpected, urgent engagement (probably with MGM's increasingly hysterical bean-counters), I suggested that we go to the just-opened World's Fair. To my great relief, Carl agreed, and so we set off via subway, to what was the Far East to a temporary Manhattanite like myself - Flushing.

Mingling with the (rather thin) crowds of sightseers, we wandered at random from one exhibit to another. But before we had finished our grand tour it started to rain, so we scurried into a large tent that was featuring a movie on the wonders of the universe. It was very enjoyable and well made but as the exhibit was the showpiece of a well-known religious organisation, it ended with a commercial for God.

On the way out, to my amused embarrassment, Carl buttonholed one of the attendants and started to lecture him on the intellectual dishonesty of the movie's concluding message. As it happened, I largely agreed, but felt constrained to point out that: 1) We had been kept nicely dry, and for free; 2) We had enjoyed an interesting movie; 3) The gentleman who had ushered us to our seats was unlikely to have been the scriptwriter. (Now I have seen Hollywood in action, I am no longer so sure of this.) Although Stanley Kubrick and Ronald Reagan seem to have little in common apart from their Hollywood connections, their reactions to Sagan were remarkably similar. Roald Sagdeev's fascinating autobiography, The Making of a Soviet Scientist (1994), records this encounter during the 1988 Moscow summit meeting: "When it was my turn to be introduced to the guest of honour, Gorbachev seized my arm and said 'Mr President, this is the man who is promoting the flight to Mars.' I had a funny feeling that Gorbachev's words struck some chord of curiosity in Reagan. As if to underscore his apparently successful start to his Mars public relations campaign with the American president, Gorbachev added: 'Academician Sagdeev has friends and colleagues in America who share the same vision of a joint flight.' "Then Gorbachev turned to me, as if looking for help with a few names. But before I could react, he went on: 'Carl Sagan.' "In a fraction of a second I could tell that something had clicked the wrong way. The guest of honour appeared to lose interest in the subject immediately. Gorbachev apparently did not understand that there was not a great deal of political compatibility between Ronald Reagan and Carl Sagan."

Sagan - who wrote the foreword to Sagdeev's book - deserves a great deal of credit for building bridges between American and Russian scientists at the height of the cold war. This effort began in 1966 when he collaborated with the maverick astrophysicist Iosef Shklovsky on the landmark book, Intelligent Life in the Universe. Sagan's greatest achievement, however - and the one by which he is best known - was, of course, the 13-part series Cosmos, undoubtedly one of the most superb feats of education/entertainment that has ever appeared on TV. There cannot be too many programmes of this kind, to counter the mind-rot now being purveyed by press, radio, movies and television - astrology, psychic powers, reincarnation, the paranormal, UFOs, creationism. We lost Sagan at just the time when he was most needed.

However, to give credit where it is due, Cosmos was actually a joint project with Gentry Lee, science director of the 1976 Viking Mars Lander, and chief engineer of the Galileo space probe that is mapping the moons of Jupiter. Lee took time off from the Jet Propulsion Laboratory to produce Cosmos, and later helped Sagan to develop the movie script that was the genesis of Contact, based on Sagan's 1985 novel.

My own last encounters with Sagan were at rather long range. During a brief visit to London in July 1988 I had the privilege of joining him by satellite, in a three-cornered conversation with the only scientist of equal fame, Stephen Hawking. For two hours, moderated by an occasionally baffled Magnus Magnusson, we discussed "God, the universe, and everything else" - but for some unfathomable reason the resulting programme was never broadcast.

And in 1996 Carl and I both set out - digitally - for Mars together, with greetings to future colonists. Alas, the Russian launch vehicle failed to escape from Earth, and our message ended up somewhere in the Pacific. I still hope it will be delivered on some later mission; meanwhile you can see and hear us (and also review the entire history of speculation about this fascinating world) on the CD-Rom Visions of Mars (available from the Planetary Society, which Sagan helped to found, in Pasadena, California).

What a great pity that Sagan just missed two events in 1997 that would have been of special interest to him: the landing of Pathfinder on Mars at what has now been named the Carl Sagan Memorial Site; and the success of the movie Contact, which would have delighted him.

Twelve years ago, Carl sent me a copy of the novel, with this inscription: "For Arthur, whose fiction and non-fiction, and advocacy of the peaceful uses of the space environment, have been a source of inspiration since my boyhood. With every good wish, Carl 9/25/85."

It is indeed a tragedy that Carl Sagan never lived to see this dramatisation of his ideas. Yet however successful Contact may be, on earth's big and little screens, I wonder if it will ever reach as many viewers as Cosmos. For how many alien eyes have already seen Sagan, whose image is now almost 20 light years from earth? It will soon reach Vega -and out round Sirius, at less than half that distance, they are probably watching the reruns.

Arthur C. Clarke celebrates his 80th birthday on December 16. His personal history of 20th-century technology, Many Happy Returns, will be broadcast on December 14 and 31 on the Discovery Channel.