We’ve been listening to the skies with privately and publicly funded radio telescope projects for more than 30 years now. These have included the early, 100-channel Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP), the Megachannel Extra-Terrestrial Assay (META), the Billion-channel Extra-Terrestrial Assay (BETA), the Microwave Observing Program (MOP), and generations of successors. I’ve been following this all with some interest and, for a time during the early 2000s, even joined SETI@Home. This project set up people’s home computers to use spare processing power, sent them packets of radio recordings from the Arecibo Observatory for analysis, and then gathered up the results. I thought (secretly, hopefully, naïvely) that my little Pentium PC might be the first to interpret ET’s messages, but no such luck. Not for me or anyone else.
In all this time, with all this effort, we haven’t heard anything meaningful. No pi in the sky, no thundering prime numbers, no coded instructions for building transdimensional machinery. Nothing but static and the monotonous pulses from radio stars. So, with a universe that must be crawling with life—unless this whole glorious shebang of a hundred billion galaxies, each filled with a hundred billion stars, is wasted on our puny intelligence—why haven’t we heard from ET?
My bet is that, for all of our intelligence and imagination, we may be listening with too narrow a mindset.
Inverse Square Law and Powerful Star Voices
Many people involved in the search have reasoned that we are due to receive a signal because we’ve been manipulating and broadcasting radio waves for about 100 years. That would put us at the center of an ever-expanding sphere—now about 200 light years across—in which alien intelligences and their listening devices can hear and pinpoint us. We’ve been calling out, so ET should be calling back soon.1
The trouble with this line of thinking is the inverse square law. The law, based on simple geometry, describes the way that electromagnetic radiations like light and radio waves grow weaker as they radiate outward from a central point.2 All of the radio and television signals we’ve sent—with the exception of microwave transmissions narrow-beamed from dish to dish across the Earth’s surface—have been broadcast in all directions. So a 50,000-watt television station broadcasting outside Topeka might be received just fine, signal strength S, just a couple of dozen miles away or even a thousand miles above the Earth’s surface (where line of sight issues and the horizon don’t interfere with reception). But at 2,000 miles, that same signal is going to be one-quarter as strong. And at 3,000 miles, one-ninth. What about a million miles away? Or a light year?
Broadcasts of I Love Lucy might theoretically make it out to 100 lightyears from the Sol system, but at that distance they will be so weakened that the clanging of two atoms in interstellar space will drown them out. And those broadcasts have much more than atomic collisions to contend with, because just 93 million miles from Topeka is the Sun, whose own atmosphere is putting up a banshee wail of electromagnetic noise. At interstellar distances, the signal carrying I Love Lucy becomes a mouse fart in a hurricane—easily overlooked by ET’s antennas.
The only way to make yourself heard in this situation is to beam your radio waves rather than broadcast them. Think of those microwave dishes on masts and mountaintops sending signals to each other across the Earth. Of course, to beam a signal, you have to know in which direction to point the dish. We haven’t picked a likely star yet and beamed our messages. No star out there knows where to beam back a reply. And we’ve only been in the radio business for about 100 years. Before that, it was dinosaurs, great apes, and Victorian gentlemen with steam locomotives and telegraph wires. Ours has for too long been the Mute Planet, as far as potential ETs are concerned.
Listening on the Wrong Frequency
We assume that, because radio waves and their near neighbors on the electromagnetic spectrum have been so useful in sending messages through our atmosphere and out to our extraplanetary space missions, that ET will use this part of the spectrum for his/her/their/its communications. Well, you have to start someplace.
For reasons given above related to the inverse square law, an interstellar civilization will probably use beamed communications rather than broadcast to link their colonies and talk to their ships in transit.3 Why waste energy polluting the neighborhood with excess radio waves.
Of course, there’s nothing that says you can’t modulate and send messages by x-rays or gamma rays, either. We find these frequencies difficult and dangerous to work with, because they too easily penetrate the light metals used to make our sensing equipment, and they damage the tissues in our own fragile bodies. But advanced civilizations may be old hands with higher frequencies, just as the old German dirigible crews knew how to handle their potentially explosive hydrogen. Other civilizations might use lead and uranium for their sending devices, which would be designed to handle these intense frequencies. The creatures themselves might not be made of delicate, protein-based membranes or not carry their genetic information on fragile strands of DNA, and so they might not be concerned about the effects of ionizing radiation.
Perhaps those mysterious gamma ray bursts that frequently pass through the Sol System—and which astronomers link to the deaths of massive stars in other galaxies—are coded messages from one civilization to another. Perhaps, considering the distances that separate such civilizations, they need to sacrifice a local star or two in order to make their messages carry across barren space and empty star systems.
The problem of dealing with unknown intelligences is that we cannot know what needs they might have, what powers they might have developed, or what priorities they might place on the intactness of the space around them. Remember that up until the last century, humans hunted whales for lighting and lubricating oil, and some still hunt them today for meat and sometimes even for pet food.
Living on the Wrong Time Scale
We assume that, because our brains developed in a certain way in relation to events on our local planet, that everyone in the universe will live with sixty seconds to the minute, sixty minutes to the hour, or some not-too-detached equivalent in terms of time’s actual passage. We have attention spans measured in seconds or minutes, sometimes hours. We have projects lasting through a year or two of funding, or a lifetime of intellectual pursuit—but again broken up into so many hours per day and days per year. We are closely tied to time in particularly human measurements.
If we were sequoia trees or bristlecone pines, we would have a much longer attention span—two to four thousand years, in fact. Working with such great amounts of time, years would pass like days and days like seconds. Such civilizations might use extremely long waves of electromagnetic energy to send messages that become intelligible only by listening over a span of years.4 Humans just don’t have the patience for this kind of communication. And if such aliens could intercept our broadcasts of I Love Lucy, a whole episode would pass by their brains in a squealing blur.5
Conversely, intelligent mayflies who passed their entire lives in a matter of hours would have immensely compressed attention spans. They might lose interest and move on before a human could rumble out a simple “Hello, how are you, fine thanks, and you?” For them, a single episode of I Love Lucy would be as tedious as the Thirty Years War.
Consider also that the messages passed among interstellar civilizations may not even be in the form of single messages. There was a time on Earth, not so long ago, when if you wanted to make a telephone call from San Francisco to New York, the phone system had to switch long-distance circuits into a single connected wire from one place to the other, which would then carry your conversation as a continuous stream of electronic pulses out and pulses back. That was one reason why “long-distance calls” were so expensive: they tied up the circuits that other people were waiting to use.
No phone system anymore deals in analog pulses that replicate the timing of a human voice. With digital systems—where the voice is reinterpreted from amplitude modulations into a series of zeroes and ones—the conversation is chopped into packets with special coding that heads up the encapsulated information. The packets are sent off over the network in bursts timed to fill available bandwidth in the system. Routers and the receiving station on the other end of the conversation catch those packets with a certain header and assemble them into the original communication stream. It all happens so fast that it sounds like you’re holding an actual conversation in real time. But your voice is being shunted all over the place in disconnected grunts, squeals, and hisses.
If ET is in the communications business, his civilization may be using such a system or something even more complicated. Pity the poor humans, listening on a certain frequency, trying to catch a whole conversation, when it may indeed be flying by our heads in a series of squeaks and barks.
Using the Wrong Language
Even if we detected regular signals—but not too regular, or else they could be the content-free pulses of spinning radio stars—we might not be able to interpret their modulations into meanings. We would lack knowledge of both the code and the language that lay behind it.
Consider that we share the Earth with at least three species of mammals which we believe to be intelligent. Chimpanzees and the other potentially intelligent great apes lack vocal chords, so we can’t detect and interpret a spoken language that might become radio signals—although we can fairly effectively interpret their body language. Various species of dolphins and whales are presumed to be intelligent and they vocalize all the time with complex vibrations, squeaks, and clicks. No one has ever interpreted these languages, though many have worked a lifetime at it. Certainly, there’s a Nobel prize waiting for whoever is first to communicate verbally with a non-primate species.
Some people believe that dolphins and whales might not be speaking in a language of symbols, where sounds equate to concepts, but in a language of mimicry, where sounds reconstruct the sonar image of the referenced object. An alien intelligence might also follow this pattern, with suitable paraphrasing to cover theoretical concepts and emotional states. In trying to think like a dolphin, once we guess that a certain sonar-equivalent pattern means “ball” or “shark,” we can begin to test our hypothesis immediately. But with sonar-mimicking aliens it would be impossible to interpret meaning from an isolated radio wave, because we would not have the referents from their planet and culture with which to compare the sounds.
The language of an alien species will not only be more complicated and bizarre than we have experienced here on Earth—it will be more bizarre that we can imagine.
To work around the language problem, we assume that mathematics will be the universal language and that ET will try to get our attention by reciting sequences of Fibonacci numbers6 or primes. Of course, if we’re just eavesdropping on a galaxy full of conversations back and forth, the speakers will probably not be spending much time trading around prime numbers on the off-chance that newcomers, who only learned to send radio signals in the last hundred years or so, might be listening in and trying to interpret. If you listened in on our telephone network, how many of the conversations would consist of teaching primes to retarded apes?
Further, while we assume mathematics is universal, we forget that it has taken human civilization a couple of thousand years to assemble our particular view of mathematics from the earlier work of the Sumerians, Greeks, Arabs, Italians, and other cultures. We assume that the function of addition (and therefore the existence of the Fibonacci sequence) or multiplication (and therefore prime numbers) is universal. But these relationships depend on the existence in our mathematics of what we call “whole numbers” or “integers” and their having some importance apart from fractions. Aliens might have an entirely different view of numbers and relationships. They might easily put emphasis in different areas of what we probably should call the “mathematical enterprise,” and that might lead them to discoveries and concepts we humans have not yet learned—or even suspect they exist.7
ET Might Not Be Talking
The galaxy may indeed be full of ETs, but many of them might simply have little interest or ability to communicate across the vastness of space. Up until 100 years ago, we humans barely understood that our galaxy of full stars was not the entire universe, and we understood even less about its size and complexity. Other cultures might be sea-based, like the dolphins and whales, and so physically unable to work with electricity and other forces we consider essential to modern physics. Or they might be hive-based or intensely internally competitive, so that they don’t have the time or energy to look up at the sky and wonder what’s out there.
But all of this reasoning is, again, based on human concepts and referents from the planet Earth. When we finally do make contact, or go and visit, we’re going to discover how truly bizarre and wonderful existence can be.
1. Or—worse, to my way of thinking—coming for a visit. They just might be gentle explorers, intent merely on gathering knowledge. But if they are anything as benign as missionaries, bent solely on improving our lives and our catechism, we’re in a heap of trouble. Rome intended to civilize the neighboring cultures they visited. The Spanish missionaries intended to bring the New World natives closer to God. Bad for the neighbors, bad for the natives.
2. Think of the inside surface of a globe with a light bulb or other source at the center. Given the radius of the globe, r, a patch on its surface with a certain area, a, receives a certain amount of light intensity, i. If you double the size of the sphere, you double the radius or distance to the patch but you increase the patch area by the square of the radius. So on a sphere with radius 2r, the patch size is 4a, and on a sphere with a radius 3r, the patch size is 9a. The same amount of light is still shining outward from the center, so on the 4a patch, the intensity i is cut to one-quarter of what it was on the original a patch, and on a 9a patch, the light i is only one-ninth as bright. This is why you can’t turn on a light across the room and use it for reading in the same way as when you’re sitting next to it.
3. If you know where a ship’s going and how fast it’s moving, you can track it and lead it, the same way a duck hunter leads his bird with a shotgun blast.
4. I’m reminded of a musical composition—for which I now can’t find an internet reference—that was intended to be played over several decades on a church organ in a remote village. The opening notes were going to be sustained for a year or more. Sequoia music.
5. Which, of course, for many people here on Earth, the episodes actually do.
6. The Fibonacci sequence is a string of numbers where any two consecutive numbers are followed immediately by their sum. So: 1, 1, 2, 3, 5, 8, 13 … and on to infinity.
7. For comparison, consider the Romans, who used a cumbersome system of the letters I, V, X, L, C, D, and M for numbers. Their counting system was simply stringing these letters together in complex ways in, roughly, base 10. They had a system of fractions, but in base 12 and using another set of letters (or sometimes arrangements of dots, like the pips on the face of a die). They had no concept of zero and little use for negative numbers except in the immediate operation of subtraction. Western civilization didn’t get the zero—which came from the Arabs—until the late Middle Ages, and only then did our mathematics really take off.