Travelers’ Tales

Travelers’ Tales

This is the time when humans have begun to sail the sea of space. The modern ships that ply the Keplerain trajectories to the planets are unmanned. They are beautifully constructed, semi-intelligent robots exploring unknown worlds. Voyages to the outer solar system are controlled from a single place on the planet Earth, the Jet Propulsion Laboratory (JPL) of the National Aeronatics and Space Administration in Pasadena, California.

On July 9, 1979, a spacecraft called Voyager 2 encountered the Jupiter system. It had been almost two years sailing through interplanetary space. The ship is made of millions of separate parts assembled redundantly, so that if some component fails, others will take over its responsibilities. The spacecraft weighs 0,9 tons and would fill a large living room. It mission takes it so far from the sun that it cannot be powered by solar energy, as other spacecraft are. Instead, Voyager relies on a small nuclear power plant, drawing hundreds of watts from the radioactive decay of a pellet of plutonium. Its three integrated computers and most of its house-keeping functions – for example, its temperature-control system – are localized in its middle. It receives commands from Earth and radios its findings back to Earth through a large antenna, 3,7 meters in diameter. Most of its scientific instruments are on a scan platform, which tracks Jupiter or one of its moons as the spacecraft hurtles past. There are many scientific instruments – ultraviolet …

Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature (Albertus Magnus, thirteenth century). Image : Elena

Understanding the Interstellar Message

Because we will share scientific and mathematical insights with any other civilization, I believe that understanding the interstellar message will be the easiest part of the problem. Convincing the governments to fund a search for extraterrestrial intelligence is the hard part.

In fact, it may be that civilizations can be divided into two great categories: one in which the scientists are unable to convince non-scientists no authorize a search for extraplanetary intelligence, in which energies are directed exclusively inward, in which conventional perceptions remain unchallenged and society falters and retreats from the stars; and another category in which the grand vision of contact with other civilizations is shared widely, and a major search us undertaken.

This is one of the few human endeavors where even a failure is a success. If we were to carry out a rigorous search for extraterrestrial radio signals encompassing millions of stars and heard nothing, we would conclude that galactic civilizations were at best extremely rare, a calibration of our place in the universe. It would speak eloquently of how rare are the living things of our planet, and would underscore, as nothing else in human history has, the individual worth of every human being. If we were to succeed, the history of our species and our planet would be change forever.

It would be easy for extraterrestrials to make and unambiguously artificial interstellar message. For example, the first ten prime numbers – numbers divisible only by themselves and by one – are 1, 2, 3, 5, 7, 11, 19, 23. It is extremely unlikely that any natural physical process could transmit radio messages containing prime numbers only. If we received such a message we would deduce a civilization out there that was at least fond of prime numbers. But the most likely case is that interstellar communication will be a kind of palimpsest, like the palimpsests of ancient writers short of papyrus or stone who superimposed their messages on top of pre-existing messages.

Another World. Artwork by Elena

Perhaps at an adjacent frequency or a faster timing, there would be another message, which would turn out to be a primer, an introduction to the language of interstellar discourse. The primer would be repeated again and again because the transmitting civilization would have no way to know when we tuned in on the message. And then, deeper in the palimpsest, underneath the announcement signal and the primer, would be the real message. Radio technology permits that message to be inconceivably rich. Perhaps when we tuned in, we would find ourselves in the midst of Volume 3,267 of the Encyclopaedia Galactica.

Any messages transmitted from outer space are the responsibility of the BBC and the Post office. It is their responsibility to track down illegal broadcasts (pronouncement from a British Defense Department, the London Observer, February 26, 1978).

(Carl Sagan, Cosmos)