Broca's Brain - Carl Sagan [151]
The decoded message says something like this: “Here is how we count from one to ten. Here are the atomic numbers of five chemical elements—hydrogen, carbon, nitrogen, oxygen and phosphorus—that we think are interesting or important. Here are some ways to put these atoms together: the molecules adenine, thymine, guanine and cytosine, and a chain composed of alternating sugars and phosphates. These molecular building blocks are in turn put together to form a long molecule of DNA comprising about four billion links in the chain. The molecule is a double helix. In some way this molecule is important for the clumsy-looking creature at the center of the message. That creature is 14 radio wavelengths, or about 176 centimeters, high. There are about four billion of these creatures on the third planet from our star. There are nine planets altogether—four little ones on the inside, four big ones toward the outside and one little one at the extremity. This message is brought to you courtesy of a radio telescope 2,430 wavelengths, or 306 meters, in diameter. Yours truly.”
With many similar pictorial messages, each consistent with and corroborating the others, it is very likely that almost unambiguous interstellar radio communication could be achieved even between two civilizations that have never met. Our immediate objective is not to send such messages because we are very young and backward; we wish to listen.
The detection of intelligent radio signals from the depths of space would approach in an experimental and scientifically rigorous manner many of the most profound questions that have concerned scientists and philosophers since prehistoric times. Such a signal would indicate that the origin of life is not an extraordinary, difficult or unlikely event. It would imply that, given billions of years for natural selection, simple forms of life evolve generally into complex and intelligent forms, as on Earth; and that such intelligent forms commonly produce an advanced technology, as has also occurred here. But it is not likely that the transmissions we receive will be from a society at our own level of technological advance. A society only a little more backward than ours will not have radio astronomy at all. The most likely case is that the message will be from a civilization far in our technological future. Thus, even before we decode such a message, we will have gained an invaluable piece of knowledge: that it is possible to avoid the dangers of the period through which we are now passing.
There are some who look on our global problems here on Earth—at our vast national antagonisms, our nuclear arsenals, our growing populations, the disparity between the poor and the affluent, shortages of food and resources, and our inadvertent alterations of the natural environment—and conclude that we live in a system that has suddenly become unstable, a system that is destined soon to collapse. There are others who believe that our problems are soluble, that humanity is still in its childhood, that one day soon we will grow up. The receipt of a single message from space would show that it is possible to live through such technological adolescence: the transmitting civilization, after all, has survived. Such knowledge, it seems to me, might be worth a great price.
Another likely consequence of an interstellar message is a strengthening of the bonds that join all human and other beings on our planet. The sure lesson of evolution is that organisms elsewhere must have separate evolutionary pathways; that their chemistry and biology and very likely their social organizations will be profoundly dissimilar to anything on Earth. We may well be able to communicate with them because we share a common universe—because the laws of physics and chemistry and the regularities of astronomy are universal.