Broca's Brain - Carl Sagan [41]
White dwarfs such as Sirius B evolve from stars called red giants, which are very luminous and, it will be no surprise to hear, red. Ancient writers of the first few centuries A.D. actually described Sirius as red—certainly not its color today. In a conversation piece by Horace called “Hoc Quoque Tiresia” (How to Get Rich Quickly) there is a quotation from an unspecified earlier work that says: “The red dog star’s heat split the speechless statues.” As a result of these less than compelling ancient sources there has been a slight temptation among astrophysicists to consider the possibility that the white dwarf Sirius B was a red giant in historical times and visible with the naked eye, completely swamping the light of Sirius A. In that case perhaps there was a slightly later time in the evolution of Sirius B when its brightness was comparable to that of Sirius A, and the relative motion of the two stars about each other could be discerned with the unaided eye. But the best recent information from the theory of stellar evolution suggests that there simply is not enough time for Sirius B to have reached its present white dwarf state if it had been a red giant a few centuries before Horace. What is more, it would seem extraordinary that no one except the Dogon noticed these two stars circling each other every fifty years, each alone being one of the brightest stars in the sky. There was an extremely competent school of observational astronomers in Mesopotamia and in Alexandria in the preceding centuries—to say nothing of the Chinese and Korean astronomical schools—and it would be astonishing if they had noticed nothing.* Is our only alternative, then, to believe that representatives of an extraterrestrial civilization have visited the Dogon or their ancestors?
The Dogon have knowledge impossible to acquire without the telescope. The straightforward conclusion is that they had contact with an advanced technical civilization. The only question is, which civilization—extraterrestrial or European? Far more credible than an ancient extraterrestrial educational foray among the Dogon might be a comparatively recent contact with scientifically literate Europeans who conveyed to the Dogon the remarkable European myth of Sirius and its white dwarf companion, a myth that has all the superficial earmarks of a splendidly inventive tall story. Perhaps the Western contact came from a European visitor to Africa, or from the local French schools, or perhaps from contacts in Europe by West Africans inducted to fight for the French in World War I.
The likelihood that these stories arise from contact with Europeans rather than extraterrestrials has been increased by a recent astronomical finding: a Cornell University research team led by James Elliot, employing a high-altitude airborne observatory over the Indian Ocean, discovered in 1977 that the planet Uranus is surrounded by rings—a finding never hinted at by ground-based observations. Advanced extraterrestrial beings viewing our solar system upon approach to Earth would have little difficulty discovering the rings of Uranus. But European astronomers in the nineteenth and early twentieth centuries would have had nothing to say in this regard. The fact that the Dogon do not talk of another planet beyond Saturn with rings suggests to me that their informants were European, not extraterrestrial.
In 1844 the German astronomer F. W. Bessel discovered that the long-term motion of Sirius itself (Sirius A) was not straight but, rather, wavy against the background of more distant stars. Bessel proposed that there was a dark companion to Sirius whose