Extraterrestrial Civilizations - Isaac Asimov [129]
A deliberately emitted beam of radiation could be designed to contain a great deal of information and could be made strong enough to remove all doubt even if its content could not be interpreted.
The trouble is that we do not at the moment want to dispose of the energy to spray messages out into space, especially since we aren’t sure of any specific target, and cannot honestly have much hope of an answer until, at best, many years have passed.
Is there something we can do that will cost less in terms of energy?
We might send a material message, something we can cast arbitrarily into space at little or no cost. To be sure, a material message would be harder to aim than a beam of radiation, and the material message might take many thousands of times longer to get to any specific destination, but at least it would be well within our present capacities.
And the fact is that we have sent a message.
On March 3, 1972, the Jupiter probe, Pioneer 10, was launched. It passed by Jupiter in December 1973, making its closest approach on December 3, and very successfully sent back photographs and other data that enormously increased our knowledge of that giant planet.
If that were all—if, after having passed Jupiter, Pioneer 10 had vanished, or exploded, or simply gone dead—it would have proved worthy of the time, effort, and money expended on it. Anything it could do beyond the Jupiter mission was, in a way, an added bonus. Adding a message to it, therefore, would cost virtually nothing.
Pioneer 10 does carry a message, one that was added at the last minute as a matter of sheer bravado.
The message is a gold-anodized aluminum plate, 6 inches by 9 inches, which is attached to the antenna support struts of Pioneer 10.
Etched onto the plaque is informational matter that was decided on by the American astronomers Carl Sagan and Frank Donald Drake. Most of the information would be completely over the heads of all but a very few human beings. It involves details concerning the hydrogen atom, and that information is expressed in binary numbers. It locates the Earth relative to nearby pulsars, giving the periods of the pulsars in binary numbers. Since pulsars are in a particular place only at particular times, and since their rate of rotation slows so that they will have the given rate for only a period of time, this information tells exactly where the Earth has been relative to the rest of the Galaxy at a particular time in cosmic history.
There is also a small diagram of the planets of the Solar system and an indication of Pioneer 10 itself and the path it took in going through the Solar system.
The most noticeable item on the plaque, though, is a diagrammatic representation of Pioneer 10 and in front of it, to scale, an unclothed man and woman (drawn by Linda Salzman Sagan, Carl’s wife). The man’s arm is lifted in what (it is hoped) will be interpreted as a gesture of peace.
If an intelligent species should happen to pick up the message, will it be understood? Since it is almost as certain as anything can be that it will be picked up only by some species in a spaceship or a free-world, we can suppose that species will have developed a technology that will possess advanced scientific concepts. They should, therefore, certainly grasp the meaning of the purely scientific symbols. Sagan points out, however, that it is the drawing of the human beings that may puzzle them, since the pictures may be like no form of life they have ever encountered. They may not even interpret the markings as representing a life form.
They will also have Pioneer 10 itself to study and, in some ways, that may tell them more about Earth and its inhabitants than the plaque will.
But where is Pioneer 10 taking the plaque? Pioneer 10, as it skittered around Jupiter, gained energy from Jupiter’s vast gravitational field, and by 1984 it will coast past Pluto’s boundary at a speed of 11 kilometers (7 miles) per second. That will