Freeman Dyson

Martin Rees's essay, "Living in a Multiverse", is a wonderfully clear and readable summary of what we know and don't know about cosmology. Martin emphasizes two things, the connectedness of everything we know, and the vastness of everything we don't know. He is out there on the frontier, scanning the unknown territory with his over-the-horizon radar. As Hubble said long ago, describing the beginnings of observational cosmology, Martin is "searching among ghostly errors of observation for landmarks that are scarcely more substantial". The most provocative of Martin's speculations is the idea that we and our visible universe may be "in the matrix", computer simulations run by a society of intelligent aliens to explore the consequences of various alternative laws of nature. Here Martin is stepping over the border between science and science-fiction, following in the footsteps of the philosopher and science-fiction writer Olaf Stapledon. As a long-time admirer of Stapledon, I say to Martin: "Welcome to the club".

Yours sincerely,

Freeman Dyson

John Maddox

British Astronomers Royal are no longer the powerful figures they once were, commanding great observatories (and the observers that go with them). Rather, they remain academic astronomers or astrophysicists with an informal license to throw their weight about on matters that affect the research community. The most effective are those who work subtly.

Sir Martin Rees is the most subtle of recent incumbents. He does not make waves, but is, if anything, over-modest. But his opinions, on issues as different as the status of black holes and the need for arms control, are well thought-out and are defended, if they are not instantly accepted, with a steely determination. The palliative for those who lose an argument with him is that his natural charm takes the raw edge off controversy.

One of the hallmarks of his spell as Astronomer Royal is his popularization of astronomy. A year ago, he was the President if the British Association for the Advancement of Science (the British equivalent of the AAAS). He is well on the way to being a one-book-a-year man, read by fellow-astronomers as well as amateurs for their originality. He talks in public to enthralled audiences with what seems to be increasing frequency. He is an asset not only to the international community of astronomers, but to the men and women in the streets worldwide.