by Carl Sagan
The only problem is that the threat of nuclear war has to be dealt with swiftly, because the stakes are too high. The clock is ticking. We cannot permit a leisurely pace.
Suppose you are a linguist. You are interested in the nature and evolution of language. But unfortunately you know only one language. No matter how clever you are, no matter how complete your dictionary of whatever the language is-say, Nahuatl-you will be fundamentally limited in your ability to generate a broad, interdisciplinary, predictive theory of language. How could you be expected to do very well if you knew only one language? If Newton were restricted, in working through the theory of gravitation, to apples and forbidden to look at the motion of the Moon or the Earth, it is clear he would not have made much progress. It is precisely being able to look at the effects down here, look at the effects up there, comparing the two, which permits, encourages, the development of a broad and general theory. If we are stuck on one planet, if we know only this planet, then we are extremely limited in our understanding even of this planet. If we know only one kind of life, we are extremely limited in our understanding even of that kind of life. If we know only one kind of intelligence, we are extremely limited in knowing even that kind of intelligence. But seeking out our counterparts elsewhere, broadening our perspective, even if we do not find what we are looking for, gives us a framework in which to understand ourselves far better.
I think if we ever reach the point where we think we thoroughly understand who we are and where we came from, we will have failed. I think this search does not lead to a complacent satisfaction that we know the answer, not an arrogant sense that the answer is before us and we need do only one more experiment to find it out. It goes with a courageous intent to greet the universe as it really is, not to foist our emotional predispositions on it but to courageously accept what our explorations tell us.
SELECTED Q &A
After each lecture there was a lively question-and-answer period. Unfortunately, the transcripts report that in some cases the audience was not provided with working microphones. These are the fragments of the sessions that survive.
CHAPTER ONE
Questioner; When will we be likely to make contact with another intelligence?
CS: Prophecy is a lost art. But what I would say is that it's clear that if we don't try to seek such intelligence, it will be more difficult to find it. And it is remarkable that we live in a time when the technology permits us, at least in a halting way, to seek such intelligences, mainly by constructing large radio telescopes to listen for signals being sent to us-radio signals- by civilizations on planets of other stars.
Questioner: Considering the accomplishments of scientists like Newton and Kepler, is it likely that science will one day come upon a demonstration of the existence of God?
CS: The answer depends very much on what we mean by God. The word "god" is used to cover a vast multitude of mutually exclusive ideas. And the distinctions are, I believe in some cases, intentionally fuzzed so that no one will be offended that people are not talking about their god.
But let me give a sense of two poles of the definition of God. One is the view of, say, Spinoza or Einstein, which is more or less God as the sum total of the laws of physics. Now, it would be foolish to deny that there are laws of physics. If that's what we mean by God, then surely God exists. All we have to do is watch the apples drop.
Newtonian gravitation works throughout the entire universe. We could have imagined a universe in which the laws of nature were restricted to only a small portion of space or time. That does not seem to be the case. And Newtonian gravitation is one example, but quantum mechanics is another. We can look at the spectra of distant galaxies and see that the same laws of quantum mechanics apply there as here. So that is itself a deep and extraordinary fact: that the laws of nature exist and that they are the same everywhere. So if that is what you mean by God, then I would say that we already have excellent evidence that God exists.
But now take the opposite pole: the concept of God as an outsize male with a long white beard, sitting in a throne in the sky and tallying the fall of every sparrow. Now, for that kind of god I maintain there is no evidence. And while I'm open to suggestions of evidence for that kind of god, I personally am dubious that there will be powerful evidence for such a god not only in the near future but even in the distant future. And the two examples I've given you are hardly the full range of ideas that people mean when they use the word "god."
CS: The questioner asked whether I was familiar with Democritus, bearing in mind my suggestion that we now know things that were not known in the past. Democritus is one of my heroes. I think I know more than Democritus. Now, I don't claim to be smarter than Democritus, but I have the advantage that Democritus did not of having twenty-five hundred years of scientists between him and me. So, for example, I'll give you a few things that I know and that Democritus did not know. Democritus proposed that the Milky Way Galaxy was composed of stars. Far ahead of his time. He did not know that there were other galaxies. We know that.
We know of the existence of many more planets than he did. We have examined them close up. We know what their physical natures are. He did not, although he speculated that they were at least made of matter. We have an idea of how many stars there are in the Milky Way Galaxy.
Democritus was an atomist. You will not exceed me in your admiration for Democritus. And were the vision of Democritus to have been adopted by Western civilization, instead of being cast aside for the pale views of Plato and Aristotle, we would be vastly further ahead today, in my personal view.
CS: The questioner asks have I not perhaps been looking through the wrong end of the telescope; that is, is not the proper province of religion the human heart and mind and ethical questions and so on, and not the universe?
Well, I couldn't agree with you more, except that it is striking how many religions have felt that astronomy is their province and have made confident statements about matters astronomical. It is possible to design religions that are incapable of disproof. All they have to do is to make statements that cannot be validated or falsified. And some religions have very neatly positioned themselves in that respect. Now, that means that you cannot make any statements on how old the world is; you cannot make any statements about evolution; you cannot make any statements about the shape of the Earth (the Bible is quite clear about the Earth being flat, for example), and so on. And then you have religions that are making statements on human behavior, where religions have, in my view, made significant contributions. But it is a very rare religion that avoids the temptation to make pronouncements on matters astronomical and physical and biological.
Questioner: Do you think humans at this time could cope with us finding extraterrestrial intelligence?
CS: Sure. Why not? Well, there's no question that the discovery of something very different will worry people precisely because it's different. Look at the degree of xenophobia in human cultures in which it is other humans, trivially different from us, who are the object of great fear and concern and violence and aggression and murder and terrible crimes. So there's no question that were we to receive a signal, much less come face-to-face, or whatever the appropriate bodily part is, with another intelligent being, there would be a sense of fear, horror, loathing, avoidance, and so on.
But the receipt of a message is a very different story. You are not even obligated to decode. If you find it offensive, you can ignore it. And there is a kind of providential quarantine between the stars, with very long transit times even at the speed of light, that I think obviates, if not altogether eliminates, this difficulty.
CS: The questioner asks that is not one central goal of religions the idea of a personal god, of a purpose for individuals and for the species as a whole, and is that not one of the reasons for the success on an emotional level (I'm paraphrasing) of many religions? And he then goes on to say that he, himself, does not see much evidence in the astronomical universe for a purpose.
I tend very much to agree with you, but I would say that purpose is not imposed from the outside; it is generated from the inside. We make our purpose. And there is a kind of dereliction of duty of us humans when we say that the purpose is to be imposed on the outside or found in some book written thousands of years ago. We live in a very different world than we lived in thousands of years ago. There is no question that we have many obligations to guarantee our purposes, one of which is to survive. And that we have to work out for ourselves.
CHAPTER TWO
Questioner: What is your opinion on the nature of the origins of intelligent life in the universe? CS: I'm for it!
CHAPTER FOUR
Questioner: I'm a wee bit skeptical at Drake's equation. It doesn't really indicate how much extraterrestrial life there is. All it indicates is whether the user of it is a pessimist or an optimist. And given this, why do you bother to use it at all?
CS: That's a perfectly good question. And it has a perfectly good answer. And that is, it might have turned out before you went through this exercise that even in the optimistic case the number of civilizations was so low that it didn't make sense to search. But it doesn't turn out that way. There's a sequence of perfectly plausible numbers that lead to a large number of civilizations. It doesn't say it's guaranteed, but it survives the initial test. That's the only function that this has, apart from the very nice fact that there is a single equation that connects stellar astrophysics, solar-system cosmogony, ecology, biochemistry, anthropology, archaeology, history, politics, and abnormal psychology.
Questioner: Oh, this scares the hell out of me. But there's one fact that I think Professor Sagan hasn't brought into account in Drake's formulation. The point is that he's only taken this galaxy into account and not all the other-I don't know- thousands or millions of other galaxies, way back to the big bang 15,000 million years ago. So, I mean, if you're going to take that particular formula, why don't you multiply it by that particular factor?
CS: Again, a good question, and I was merely talking about the justification for the search for signals from advanced civilizations in our galaxy. Clearly you can imagine them in some other galaxy. For their signals to reach us here, they have to have a technology far in advance of ours, but that's perfectly possible. And in fact Frank Drake and I have made a search of just a few nearby galaxies with exactly that idea in mind. We found nothing at the few frequencies we looked at. But, you see, once you start imagining signals coming from another galaxy, then you are into significant power levels and therefore significant dedication by some other civilization to try to make contact with what for them would be a distant galaxy. If you imagine civilizations in our own galaxy, you can at least contemplate that they know that this solar system is a plausible abode for life, even if they haven't visited here to check it out, that there's some way that they could target our particular region of the galaxy for a specific message. There's no way that this could be the case from a distant galaxy, as far as I can see.
This does remind me, though, that I forgot to say something. Very nearby civilizations can detect our presence, and that is because television gets out. Not just television but radar. Radar and television get out. Most of AM radio, for example, doesn't. So let's just look at the television for a moment. Large-scale commercial television broadcasting on Earth begins when? In the late 1940s, mainly in the United States.
So forty years ago there's a spherical wave of radio signals that spreads out at the speed of light, getting bigger and bigger as time goes on. Every year later it's an additional light-year away from the Earth. Now, let's say it's forty years later, so that expanding spherical wave front is forty light-years from the Earth, containing the harbingers of a civilization newly arrived in the galaxy. And I don't know if you know about 1940s television in the United States, but it would contain Howdy Doody and Milton Berle and the Army-McCarthy Hearings and other signs of high intelligence on the planet Earth. So I'm sometimes asked, if there are so many intelligent beings in space, why haven't they come here? Now you know. It's a sign of their intelligence that they haven't come. (I'm just joking.) But it's a sobering fact that our mainly mindless television transmissions are our principal emissaries to the stars. There is an aspect of self-knowledge that this implies that I think would be very good for us to come to grips with.
CHAPTER FIVE
Questioner: How do you recognize the truth when it is upon us?
CS: A simple question: How can we recognize the truth? It is, of course, difficult. But there are a few simple rules. The truth ought to be logically consistent. It should not contradict itself; that is, there are some logical criteria. It ought to be consistent with what else we know. That is an additional way in which miracles run into trouble. We know a great many things-a tiny fraction, to be sure, of the universe, a pitifully tiny fraction. But nevertheless some things we know with quite high reliability. So where we are asking about the truth, we ought to be sure that it's not inconsistent with what else we know. We should also pay attention to how badly we want to believe a given contention. The more badly we want to believe it, the more skeptical we have to be. It involves a kind of courageous self-discipline. Nobody says it's easy. I think those three principles at least will winnow out a fair amount of chaff. It doesn't guarantee that what remains will be true, but at least it will significantly diminish the field of discourse.
Questioner: Have you any comments to make on the Shroud of Turin?
CS: The Shroud of Turin is almost certainly a pious hoax; that is, not a contemporary hoax but a hoax from the fourteenth century, when there was significant traffic in pious hoaxes. And my technical knowledge of the Shroud of Turin comes from Dr. [Walter] McCrone of Chicago, who has worked on it for some years. He found the "blood" to be iron oxide pigments, and there is nothing that cannot be explained by the technology available in the fourteenth century. By the way, there is no provenance of the Shroud of Turin earlier than the fourteenth century [8] So I'm sorry that my knowledge is secondhand on this issue, and I know that there are people who believe, for reasons that are apparent. No, I'm sorry. I haven't said that fairly. There are people who believe that it is the authentic death shroud of Jesus on the cross. But the evidence is very meager.
Questioner: The religionists proffer ghosts and miracles. The physicists propose equations. What is the fundamental difference between them?
CS: A very good question. How can we tell what's what? One thing we can do is we can check out the explanation in terms of repeatability. Verifiability So, for example, if physicists after Isaac Newton say that the distance that a falling object falls in time t is a constant times t2, and if you are skeptical or dubious about that, you can perform the experiment, and you will find that if it takes twice as long to fall, it goes four times farther, and so on. They will also say that the velocity increases proportionately to the time. You can check that. You can drop boulders off bridges, if it's permitted by the local police, and check out these contentions. After a while you get a sense that, at least in this limited realm, the physicists know what they're talking about. What is more, it is remarkable that Buddhist physicists find just the same regularity. And Hindu physicists, and atheist physicists, and Christian physicists, and so on. All find the same laws of nature. Somehow it doesn't depend on the local culture, on the local training. What the physicists say seems to be true all over the Earth. And then you look at other planets. Other stars. Other galaxies. And the same laws apply everywhere.
Now, this doesn't say that every contention of every physicist has this wonderful degree of regularity. Physicists make mistakes just like anyone else. But the way in which physicists have an advantage is that there is a tradition of skepticism and a tradition of mutually checking out each other's contentions. Whereas in religion there is a practice of great reluctance to challenge what any other member of the professional caste says. That is not true in physics. A physicist is almost as delighted in disproving another physicist's contention as in demonstrating
some new principle of physics. And you know Newton's famous remark that if he had seen further it was by standing on the shoulders of giants. What he meant was that there is a continuous progress in science. And through this progression of insights, through this mutual checking, the subject advances mightily. Whereas if you take supposed religious proofs of the existence of God, it is really quite remarkable that no new proof has been offered-never mind the validity-no fundamentally new proof has been offered in centuries. The anthropic principle that I talked about in an earlier lecture is as close as you can come, but it is merely a variant on the argument from design.
So I see methodologically a significant difference between how science proceeds and how religion proceeds. Now, an earlier questioner gave a very good example. He said, "Scientists talk about the expanding universe. What began the expansion?" Now, many astrophysicists would say that's not their problem. Their problem is to tell you what the universe is doing but not to tell you why it's doing it. They avoid that "why" question- and it's not due to modesty, although it's sometimes phrased in a way to suggest that we don't want to mess around with the really big questions. But physicists love to mess around with the big questions. The reason that questions such as "Why did the universe expand?" are considered off-limits is that there's no experiment you can do to check it out.
CS: The question has to do with the Bermuda Triangle. This is certainly not significantly different from UFOs and ancient astronauts. It is as good an example. Here is a case where if you track the mysterious disappearances or sinkings of airplanes and ships, you find, it is alleged, a concentration of these disappearances in a triangular region off Bermuda. And the explanations that have been proposed are many, one of which is that there is a UFO on the Atlantic floor that eats airplanes and boats.