Pale Blue Dot - Carl Sagan [130]
If, on the other hand, none of our candidate signals is an authentic alien radio beacon, then we’re forced to the conclusion that very few civilizations are broadcasting, maybe none, at least at our magic frequencies and strongly enough for us to hear:
Consider a civilization like our own, but which dedicated all its available power (about 10 trillion watts) to broadcasting a beacon signal at one of our magic frequencies and to all directions in space. The META results would then imply that there are no such civilizations out to 25 light-years—a volume that encompasses perhaps a dozen Sun-like stars. This is not a very stringent limit. If, in contrast, that civilization were broadcasting directly at our position in space, using an antenna no more advanced than the Arecibo Observatory, then if META has found nothing, it follows that there are no such civilizations anywhere in the Milky Way Galaxy—out of 400 billion stars, not one. But even assuming they would want to, how would they know to transmit in our direction?
Now consider, at the opposite technological extreme, a very advanced civilization omnidirectionally and extravagantly broadcasting at a power level 10 trillion times greater (1026 watts, the entire energy output of a star like the Sun). Then, if the META results are negative, we can conclude not only that there are no such civilizations in the Milky Way, but none out to 70 million light-years—none in M31, the nearest galaxy like our own, none in M33, or the Fornax system, or M81, or the Whirlpool Nebula, or Centaurus A, or the Virgo cluster of galaxies, or the nearest Seyfert galaxies; none among any of the hundred trillion stars in thousands of nearby galaxies. Stake through its heart or not, the geocentric conceit stirs again.
Of course, it might be a token not of intelligence but of stupidity to pour so much energy into interstellar (and intergalactic) communication. Perhaps they have good reasons not to hail all comers. Or perhaps they don’t care about civilizations as backward as we are. But still—not one civilization in a hundred trillion stars broadcasting with such power on such a frequency? If the META results are negative, we have set an instructive limit—but whether on the abundance of very advanced civilizations or their communications strategy we have no way of knowing. Even if META has found nothing, a broad middle range remains open—of abundant civilizations, more advanced than we and broadcasting omnidirectionally at magic frequencies. We would not have heard from them yet.
ON OCTOBER 12, 1992—auspiciously or otherwise the 500th anniversary of the “discovery” of America by Christopher Columbus—NASA turned on its new SETI program. At a radio telescope in the Mojave Desert, a search was initiated intended to cover the entire sky systematically—like META, making no guesses about which stars are more likely, but greatly expanding the frequency coverage. At the Arecibo Observatory, an even more sensitive NASA study began that concentrated on promising nearby star systems. When fully operational, the NASA searches would have been able to detect much fainter signals than META, and look for kinds of signals that META could not.
The META experience reveals a thicket of background static and radio interference. Quick reobservation and confirmation of the signal—especially at other, independent radio telescopes—is the key to being sure. Horowitz and I gave NASA scientists the coordinates of our fleeting and enigmatic events. Perhaps they would be able to confirm and clarify our results. The NASA program was also developing new technology, stimulating ideas, and exciting schoolchildren. In the eyes of many it was well worth the $10 million a year being spent on it. But almost exactly a year after authorizing it, Congress pulled the plug on NASA’s SETI program. It cost too much, they said. The post—Cold War U.S. defense budget is some 30,000 times larger.
The chief argument of the principal opponent of the NASA SETI program