Cosmic Connection (29 page)

There are many phenomena in contemporary astronomy that are not understood. Quasars, for example, are one. The reported very high-intensity gravitational waves coming from the center of our galaxy are another. The list can be extended considerably. As long as we do not understand these phenomena, we cannot exclude the possibility that they are manifestations of extraterrestrial intelligence. This hardly demonstrates the likelihood of extraterrestrial intelligence, any more than our inability to understand seasonal changes on Mars (Chapter 19) provided strong evidence for vegetation on that planet. As the Soviet astrophysicist I. S. Shklovskii says, “Following the principles of law, we should assume all astronomical phenomena natural until proven otherwise.”

Some scientists have asked, in the reformulation of Fermi’s question, why it is that advanced civilizations are not much more obvious. Why have stars not been rearranged into entirely artificial patterns in the sky–perhaps blinking advertising lights, detectable over intergalactic distances, for some cosmic soft drink? This particular example is, of course, not very tenable–one society’s soft drink may be another society’s poison. More seriously, the manifestations of very advanced civilizations may not be in the least apparent to a society as backward as we, any more than an ant performing his anty labors by the side of a suburban swimming pool has a profound sense of the presence of a superior technical civilization all around him.

T
o deal with the possibility of enormously advanced extraterrestrial civilizations, the Soviet astrophysicist N. S. Kardashev has proposed a distinction in terms of the energy available to a civilization for communications purposes.

A Type I civilization is able to muster for communications purposes the equivalent of the entire present power output of the planet Earth–which is now used for heating, electricity, transportation, and so on; a large variety of purposes other than communication with extraterrestrial civilizations. By this definition the Earth is not yet a Type I civilization.

The power usage of our civilization is growing at a rapid rate. The present power output of planet Earth is something like 10
¹⁵
or 10
¹⁶
watts; that is, a million billion to ten million billion watts. The standard exponential notation simply indicates the number of zeros following the 1. For example, 10
¹⁵
means fifteen zeros after the 1. The concept of power in physics is that of an energy expenditure per unit time. One watt is ten million ergs of energy expended per second. All of the power used on the Earth is thus equivalent to lighting up, say, one hundred trillion hundred-watt bulbs. Especially if this energy were put out in the radio part of the spectrum, it might be detected over very sizable distances.

A Type II civilization is able to use for communications purposes a power output equivalent to that of a typical star, about 10
²⁶
watts. We already see particularly bright stars at optical frequencies in the nearest galaxies. A Type II civilization, putting out in our direction 10
²⁶
watts in some fairly narrow radio bandpass, could be detectable over vast inter-galactic distances. It would be easily detectable, if we used the right search procedures, were there only one such civilization in the nearest spiral galaxy to our own, M31, the great galaxy in the constellation Andromeda. M31 is by no means the largest galaxy. For example, an elliptical galaxy, M87–also known as Virgo A–contains perhaps 10 trillion stars.

Finally, Kardashev imagines a Type III civilization, which would use for communications purposes the energy output of an entire galaxy, roughly 10
³⁶
watts. A Type III civilization beaming at us could be detected if it were anywhere in the universe. There is no provision for a Type IV civilization, which by definition talks only to itself. There need not be many Type II or Type III civilizations for their presence to be felt once a search for extraterrestrial civilizations is organized in earnest. It may well be that a few Type II or Type III civilizations would be far more readily detectable than a large number of Type I civilizations–if they choose to signal us (see Chapter 31).

The energy gap between a Type I and a Type II civilization or between a Type II and a Type III civilization is enormous–a factor of about ten billion in each instance. It seems useful, if the matter is to be considered seriously, to have a finer degree of discrimination. I would suggest Type 1.0 as a civilization using 10
¹⁶
watts for interstellar communication; Type 1.1, 10
¹⁷
watts; Type 1.2, 10
¹⁸
watts, and so on. Our present civilization would be classed as something like Type 0.7.

But there may be more significant ways to characterize civilizations than by the energy they use for communications purposes. An important criterion of a civilization is the total amount of information that it stores. This information can be described in terms of bits, the number of yes-no statements concerning itself and the universe that such a civilization knows.

An example of this concept is the popular game of “Twenty Questions,” as played on Earth. One player imagines an object or concept and makes an initial classification of it into animal, vegetable, mineral, or none of these three. To identify the object or concept, the other players then have a total of twenty questions, which can only be answered “Yes” or “No.” How much information can be discriminated in this manner?

The initial characterization can be thought of as three yes-no questions: Conceptual or objective? Biological or nonbiological? Plant or animal? If we agree that a particular game of “Twenty Questions” is in pursuit of something alive, we have, in effect, answered three questions already by the time the game begins. The first question divided the universe into two (unequal) pieces. The second question divided one of those pieces into two more, and the third divided one of those pieces into yet two more. At this stage we have divided the universe crudely into 2×2×2=2
³
=8 pieces. When we have finished with our twenty questions, we have “divided the universe into 2
²⁰
additional (probably unequal) pieces. Now, 2
¹⁰
is 1,024. We can perform such calculations fairly quickly if we approximate 2
¹⁰
by 1,000=10
³
; therefore, 2
²⁰
equals (2
¹⁰
)
²
, which approximately equals (10
³
)
²
=10
⁶
. The total number of effective questions, twenty-three, has divided the universe into about 2
²³
, or approximately 10
⁷
pieces or bits. Thus, it is possible for skillful players to win at “Twenty Questions” only if they live in a civilization that has an information content of about 10
⁷
bits.

But, as I discuss below, our civilization is characterized by perhaps 10
¹⁴
bits. Therefore, skillful players should win at “Twenty Questions” only about 10
⁷
out of 10
¹⁴
times, or one in 10
⁷
, or one in ten million times. That the game is won more often in practice is because there is an additional rule–usually unstated but well understood: Namely, that the object or concept being named should be one in the general cultural heritage of all the players. But this must mean that 10
⁷
bits can convey a great deal of information about a civilization, as indeed it can. Philip Morrison has estimated that the total written contribution to our present civilization from classical Greek civilization is only about 10
⁹
bits. Thus, a one-way message, containing what, by the standards of modern radio astronomy, is a very small number of bits, can contain a very significant amount of new information and can have a powerful influence on a society in the long run.

What is the total number of bits in an English word? In all the books in the world? There are in general English usage twenty-six letters and a sprinkling of punctuation marks. Let us estimate that there are thirty-two such effective “letters.” But 32=2
⁵
; that is, there are something like five bits per letter. If a typical word has four to six letters (for an average of six letters a word, there would have to be a lot of fancy words), there will then be about twenty to thirty bits per word. A typical book–about three hundred words per page and about three hundred pages–would have about a hundred thousand words, or about three million bits. The largest libraries in the world, such as the British Museum, the Bodleian Library at Oxford, the New York Public Library, the Widener Library at Harvard, and the Lenin Library in Moscow, have no more than about ten million volumes. This is about 3×10
¹³
bits.

A poor-quality low-resolution photograph may have a million bits in it. A quite complex caricature or cartoon might have only about a thousand bits. On the other hand, a large, high-quality color photograph or painting might have about a billion bits. Let us make allowances for the amount of fundamental information contained in graphics, photography, and art in our civilization, as well as the recorded oral tradition. Let us also try to estimate–this can be done only very crudely–the information we are born with about how to deal with the world. (Human beings are, relative to other animals, born with very little such information–we deal with the world much more in terms of learned rather than inherited or instinctual information.) I estimate, then, that we and our civilization can be very well characterized by something like 10
¹⁴
or 10
¹⁵
bits.

Parenthetically, the ancient Chinese saying that a single picture is worth ten thousand words (three hundred thousand bits in English; but in Chinese?) is approximately correct–provided that the picture is not too complex.

We can imagine civilizations that have a much greater number of bits characterizing their society than characterizes ours. In general, we would expect a civilization high on the energy scale to be high on the information scale. But this need not necessarily be true. I certainly can imagine societies that are very complex and require many more bits to characterize them than our society requires–but that are not interested in interstellar communication. Characterization of interstellar civilizations requires us to characterize their information content as well.

If we have used numbers to describe energy, we should perhaps use letters to describe information. There are twenty-six letters in the English alphabet. If each corresponds to a factor of ten in the number of bits, there is the possibility of characterizing with the English alphabet a range of information contents over a factor of 10
²⁶
–a very large range, which seems adequate for our purposes. I propose calling a Type A civilization one at the “Twenty Questions” level, characterized by 10
⁶
bits. In practice this is an extremely primitive society–more primitive than any human society that we know well–and a good beginning point. The amount of information we have acquired from Greek civilization would characterize that civilization as Type C, although the actual amount of information that characterized Periclean Athens is probably equivalent to Type E or so. By these standards, our contemporary civilization, if characterized by 10
¹⁴
bits of information, corresponds to a Type H civilization.

A combined energy/information characterization of our present global terrestrial society is Type 0.7H. First contact with an extraterrestrial civilization would be, I would guess, with a type such as 1.5J or 1.8K. If there were a galactic civilization of a million worlds, and if each were characterized by a thousand times the information content of our terrestrial civilization, that galactic civilization would be of Type Q. A billion such federated galaxies, with all the information held collectively, would be characterized as a civilization of Type Z.

But as we argue in the next chapter, there is not enough time in the history of the cosmos for such an intergalactic society to have developed. The run of letters from A to Z appears to run the gamut from societies much more primitive than any of Man’s to societies more advanced than any that could be.