At the moment of writing (May 1973) preparations are almost complete for an attempt at communication with another intelligence. More accurately, it will be a response to the apparent attempt of such intelligence to contact us; and paradoxically, although it may have taken 13,000 years to convey the first information, from here on the exchange of ideas should take only seconds.
The method of interstellar communication involved was first suggested by R. N. Bracewell, Professor of Radio Astronomy at Stanford University.1 In 1960, when Dr. Frank Drake was conducting "Project Ozma" at Green Bank, Professor Bracewell analyzed the most efficient means of contacting other intelligences. If civilizations possessing advanced technology are spread through the galaxy at 10-light-year intervals, Ozma-style communication—radio waves on some obvious wavelength such as the 21-centimeter "Hydrogen Line"—will soon put them in touch with us.
There are only a few likely stars to check within that radius. But precisely for that reason, the chances of such intelligence being so close to us are not good. if high-technology civilizations are on the average 100 light-years apart, the search would involve 1,000 stars out of 10,000 and long waiting periods, eternity in some cases, for such civilizations to appear at each.
And if the average separation is 1,000 light-years . . .
The most effective means of initiating contact, Bracewell suggested, would be to send out unmanned messenger probes to the likely stars. Such a probe would orbit in the destination system, "listening" for intelligent radio signals; the most effective test of any it received would be to "echo" them back to the planet of origin. If an intelligent response came from the planet, the probe would begin an information exchange, leading eventually to direct radio contact between the two civilizations at a high level of understanding. "Should we be surprised," wrote Bracewell, "if the beginning of its message were a TV image of a constellation?"
But the punch line of Bracewell's paper, which thirteen years later still causes it to be recalled whenever contact with another intelligence is discussed, came a few lines earlier. If a probe were trying to contact us, "its signals would have the appearance of echoes having delays of seconds or minutes, such as were reported thirty years ago by Stormer and van der Pol and never explained."
Now, from 1967 to 1972 I was President of the Association in Scotland for Technology and Research in Astronautics, of which I'm currently Vice-President. ASTRA is the Scottish equivalent of the British Interplanetary Society, and while I was President I conceived and chaired a series of discussions on interstellar travel and communication under the heading "Man and the Stars." For the last part of the project, I undertook research into suggested instances of contact, past and present—and as it happened, I began with the story of the 1920's echoes.
It started in 1927, during research into round-the-world radio echoes (delay time about 1/7 of a second). Taylor and Young in the United States reported hearing echoes they couldn't explain, with delays of only hundredths of a second, coming from 2,900 to 10,000 kilometers overhead. That distance range agrees roughly with the dimensions of the inner Van Allen Belt, discovered by Explorer 1 in 1958, but in 1927 the effect was a mystery.
In December 1927, Professor Carl Stormer of Oslo, an expert on the aurora borealis, chanced to meet a telegraphic engineer named Hals, to whom he mentioned the Taylor-Young puzzle.2 Hals, however, had personal experience of a bigger mystery: in April and October he himself had heard echoes, on experimental pulses from the Philips station PCJJ at Eindhoven, three seconds after the original signal—as if the pulses were coming back from the distance of the Moon. Hals believed that the echoes were being reflected naturally from the Moon itself. However, the Moon is a very poor reflector; when the US Army Signal Corps set out to bounce signals off the Moon deliberately, after the war, they found the task far from easy.
Stormer had a theory about electron streams from the Sun. Believing that the space around the Earth was completely electron-free (far too simple a model, as the Van Allen discoveries showed) he surmised that the 3-second echoes might come from curved surfaces formed by electron streams as they were "bent" by the Earth's magnetic field, to impinge on the atmosphere and generate aurorae. He therefore organized a series of Eindhoven-Oslo experiments, in which three dots (the Morse letter "s") were transmitted at 5-second intervals. Echoes were heard in April 1928, but the results weren't conclusive.
On September 25, new experiments began, with the pulses now 20 seconds apart. Nothing happened until October 11, when Hals phoned Stormer to say that Eindhoven had just come on the air, and he could hear 3-second echoes. Stormer went at once to Hals' home (it took about ten minutes), and arrived to hear signals and echoes ringing through the house. Moments later, however, the echo times began to vary between 3 seconds and 15—and indeed regular 3-second echoes were never to be heard again, after that 10-minute "introduction."
Figure 1 First van der Pol sequence, evening of October 11, 1928 (tentatively identified as an incomplete map of Bootes).
This diagram can be interpreted as demanding an intelligent reply. By moving the 5th pulse (delayed 3 secs.) to a position where it is delayed by 13 secs. (marked X) the constellation Boötes is completed.
This is the required answer and if transmitted back the probe should transmit further information. Note the 8-second "barrier" dividing the diagram into 2 parts. The position of a Boötes—"Arcturus"—can be interpreted as tentatively identifying the map as compiled 13,000 years ago.
A tentative conclusion is that the probe arrived here from Epsilon Bobtis 13,000 years ago.
Caught by surprise, Stormer made only a rough record of the new phenomenon (see later). But he sent a telegram to van der Pol at Eindhoven, and the experiment was repeated that evening. Van der Pol increased the separation between pulses to 30 seconds, but the echoes he himself recorded still ranged from 3 to 15 seconds like those of the afternoon.3 He went on sending at 30-second intervals, however, and when echoes reappeared on October 24, they ranged from 3 seconds to 30. Similar patterns were heard in February and April 1929, and a very long and complex series was recorded by French experimenters in May 1929.
There were many odd things about the echoes. Three dots (two in the French experiments) were being sent out over two seconds, and the "echo" was a dash of exactly two seconds' duration—yet all experimenters remarked that the frequency of the echo was always exactly that of the outgoing signal. Since 1970, US experimenters under Professor Crawford at Stanford have detected a number of apparently natural LDE (Long-Delayed Echoes), consistent with Professor Crawford's theory of beam-plasma interactions in the upper atmosphere—but every instance has showed time compression and frequency shift. (Nor have they ever heard more than one echo at a time.)4 On the other hand, the 1920's echoes were repeatedly described as "loud enough to hurt the ears"—up to 1/3 the intensity of the original signal—which seems to rule out all natural reflection hypotheses, inside or outside the atmosphere. Echoes of 30 seconds' delay were just as loud as those of 3 seconds' delay. And there was the way the echoes seemed to respond, after a slight lag, to each change in the format of the Earth signals—including the extended runs of the French transmissions. In the middle of one such run, the operator "forgot" to, send one signal, but echoes came anyway . . .
(The experimenters concluded from that instance that some echoes were longer than 30 seconds. They were using identifying musical tones to prevent just that possibility of confusion, but for some reason the tone of the echoes wasn't noted just when it was needed—just as no one in the 1920's noticed that the intensity of the echoes flatly contradicted, by the inverse square law, the natural reflection hypotheses they were supposedly checking.)
It took a lot of digging to find all these details, however. (I've given only the major references at the end here.) Last year I was researching possible contact instances for a book on the ASTRA discussions ("Man and the Stars," now much enlarged, Souvenir Press 1974), and after checking the Stormer/van der Pol references given by Bracewell, I thought there was nothing significant in them. Not realizing that they were announcing a change in the phenomenon, I took the varying delay times to show that the "echoes" didn't all come from the same object. Then it occurred to me, however, that if they did all come from the same object, assumed for the sake of argument to be a space probe, then the variations in delay time must be meaningful.
Van der Pol's evening sequence of October 11, 1928 goes 8 seconds, 11, 15, 8, 13, 3, 8, 8, 8, 12, 15, 13, 8, 8, which isn't the standard sequence of prime numbers "supposed" to be used in contact between intelligences—but as Bracewell wrote in 1962, prime numbers "only prove that the designers of high-power transmitters can also count . . . not appropriate to signals in the pre-contact phase." The echo pattern seems random, in fact. But Bracewell thought that a space probe might send us a star map, and since the stars are placed at random in the sky the delay times could be graphical coordinates.
When the echoes are graphed with delay time on the y-axis (standard scientific practice, used for most of the 1920's results), nothing interesting appears. With delay time on the x-axis, and the two double echoes noted by van der Pol each shown on the same line, we get the graph in Figure 1. When I first drew it, my reactions went, "That looks more like an intelligent signal—in fact it looks familiar—I know what that is!"
If Figure 1 is an intelligible diagram, it's divided into two parts of equal area by the vertical "barrier" formed of 8-second dots. On the left there is only one dot, at three seconds—a unique' echo, the only time •the three dots of the original signal came back. (Still without time compression or frequency shift.) And on the right (compare Figure 2) there is a figure with a strong resemblance to the constellation BoOtes, the Herdsman. Of the brighter stars, only Epsilon (Izar) is missing; but if the 3-second dot is transplanted across the barrier, to the corresponding position on the right, it fills the position of Izar and completes the constellation figure. Epsilon Boötes, is presumably the star the probe came from. If we had recognized the pattern in 1928 and returned it (completed) to the probe, it would have known that it had made contact with intelligence. In other words, the probe was trying to rule out natural echoes from Earth. Perhaps the seven dots in the "barrier" were meant to tell us that there should be seven dots on the right of it.
The stars shown are all of first, second, and third magnitude, except for Zeta Boötes at bottom left. From the time of Hipparchus to the present day, however, the apparent magnitude of Zeta has usually been given as three.5 There is very good reason to think that the map really is an old one: Arcturus appears about seven degrees from its present position, which is below and right of its apparent position in Figure 1. (See also Figure 2). Arcturus has one of the largest known angular Proper Motions, however: it moves 2.29 seconds of arc southeast each year. That's the apparent diameter of the Full Moon in only 800 years. Arcturus also has a large radial velocity toward the Earth, which confuses the issue; but if we take the motion to average 2" per year over the period, the indicated seven-degree shift would put the map's date at 12,600 years ago. That presumably was about when the probe arrived, compiling its star maps prior to signaling home.
From a graph like this the date can be determined only roughly, but confirmation that the period is about 13,000 years is apparently given by the sequence of October 24, 1928. Unfortunately less than half of the 48-echo sequence was published (Figure 2b); if, however, the rest of the sequence can be traced and the dots fall into the expected star positions, the space probe hypothesis will be in a very healthy state.
The published part of the sequence, graphed as in Figure 3, seems to cover the swath of sky from Vega to Corona Borealis. Once the distinctive "keystone" figure of Hercules is recognized in the 13-to-21-second part of the graph, the rest of the identification is fairly easy.
Figure 2 (a) The constellation Banes from Norton's Atlas; epoch 1950. t marks the position of Arcturus (a Boötes) 13,000 years ago.
Figure 2 (b) A reproduction of the published part of the October 24, 1928 sequence from "Polar Aurora."
Figure 3 The published part of the October 24th sequence with tentative star identification.
In this hypothesis E Boötes "*" should be pulse No. 15 with an echo delay of 30 secs. Star pulses are marked "0" Vector pulses are marked "*"
Point "A" is the North Celestial Pole 13,000 years ago. The line through "A-B" points to E Boötes. The vertical line "B" at 12 secs. and the vector "CD" mark the rotation limits to align the curved celestial area with a straight line map. The unpublished sequences should cover areas of Boötes, Ursa Major, Canes Venatici, Leo, and possibly include further 'reference points and vectors.
We have all the first, second and third magnitude stars again; we also have three fourth-magnitude stars (Xi, Omicron and Omega Herculis) which bring out the distinctive star pattern of the area. If we had the rest of the sequence, it should go on to Boötes, Canes Venatici and Ursa Major (see Figure 5).
In representing any such large area of sky, allowance has to be made for the curvature of the heavens. We normally draw "planispheres" or else segments projected on the celestial pole, but apparently that wasn't the system used by the probe. If a tracing of the Figure 3 graph is laid over a star map, it has to be rotated to get first the Lyra section, then the remainder, to fit the stars. (In trigonometry, I believe the system is called a "satellite grid," perhaps a nice phrase.) Now in Figure 4, there are four dots which do not correspond to any major stars, marked A, B, C and D. If the graph is rotated about A until the vertical line through B falls parallel to CD, the required fit with the stars is obtained. Farfetched? But A is the position of the North Celestial Pole, by Vega, 13,000 years ago, and the line AB points to Epsilon Boötes.
Now, major misconceptions have developed about this work, due partly to the insistence of the press on calling me a scientist or astronomer. Eminent scientists have then been asked to comment on the star map interpretation, and have replied, "Lunan's work is unscientific—he has no evidence that a space probe exists." But I never claimed to have such evidence; my qualifications are in English and philosophy, and I've produced a logical analysis of the echo patterns, asking, "What meaning do they convey, if we assume that they come from a probe?"
Let's take that interpretation one stage further, therefore. (If we don't, we're almost at the end of the data.) Apart from the French records, the only other published LDE patterns are in Stormer's afternoon record of October 11, 1928. We know that record is inaccurate, and moreover that it contains multiple echoes and one or two unusual ones, none of which are distinguished in Stormer's rough list of delay times. So (carefully distinguishing assumption and hypothesis from evidence), how few changes have to be supposed to turn Stormer's record into star maps consistent with the two we already have?
Only two changes have to be supposed, in fact, out of a total of 43 echoes, in order to obtain recognizable star maps. The 43 echoes were in four distinct groups, of which the first appears in Figure 4 with my suggested correction. If we suppose that the delay times of the eighth and eleventh echoes were accidentally transposed, then in Figure 4 we obtain a map of the Big Dipper as it was about 13,000 years ago; the other stars above mag. 3, namely Alpha Draconis (Thuban), Psi Ursae Majoris, and Canes Venatici, are also shown. The apparent displacement of the Pointers, Dubhe and Merak, gives the date of the map. A and B, the first and last dots of the signal, do not correspond to any major stars; they do, however, form a line pointing right through the drawing to Epsilon Boötes.
Turning to Figure 5, which is a map of the whole area discussed, here is the suggested sequence in chronological order. Afternoon 11.10.28, 20-second Eindhoven pulse spacing, first group: Ursa Major, Canes Venatici. Second and third groups (both short): segments of Draco. Fourth group (admittedly the weakest identification, and supposing one timing error): swath of sky from Delta and Epsilon Boötes to Mu Virginis and Beta Librae. Dots not corresponding to stars set limits of rotation, and point to Epsilon Boötes.
Figure 4 The Stormer sequence of October 11, 1928.
This is interpreted as a possible map of Ursa Major by assuming that the delay times for echoes Number 8 and 11 are in reverse order to that reported by Stormer.
A' and 'B' the first and last pulses form a reference vector pointing to epsilon Boötes.
At that point Eindhoven signals stopped. When van der Pol began again in the evening, he received the critical map of Boötes to which we should have made an intelligent reply. The first four maps were leading up to that; remember that the echoes were still 3-15 seconds, although van der Pol had increased the signal spacing to 30 seconds. But the 30 seconds' spacing was maintained, and the probe apparently compiled a new map for October 24-48 units by 30, where the others had been 15 by 15. That map covered the swath from Vega to Alpha and Beta Coronae, as far as we have it; it apparently went on through Bootes; and there would still be enough dots left to cover Ursa Major, Canes Venatici and Draco. In other words, the big map covered most of the area of the previous five; if we had it in full, we could set the dotted boundaries of Figure 5 more accurately. Looking at the rough square we have, however, it seems clear that the orientation of the whole set of maps is related to Epsilon Boötes.
Epsilon Boötes was named Izar by the Arab astronomers. More recently Struve named it Pulcherrima, "The Most Beautiful." In the telescope it's a double star: the major is described as yellow or orange, the minor as blue. Trying to find more definite information has been frustrating. By a slight majority the sources give its distance as 103 light-years, but values ranging from 70 light-years to 230 abound in the literature. Disagreement over the spectral types of the two suns is even worse: many sources call it a K1 giant, which fits the observed magnitude at 103 light-years, but others give AO, G8, et cetera, which don't fit anything, least of all the values given for the minor sun. Most sources call that AO. But for an AO star, like Sirius, to have the observed apparent magnitude of 6.3, it would have to be more than 500 light-years away! Other values given are F2 (better) and G8. If the major really is a K1 giant 103 light-years away, the minor might be expected to be about F6. We have appealed to current research programs to give us definite values.
At least all sources are in agreement that the stars are about 2".8 apart, which at 103 light-years would be a distance of more than 8,000 million miles, and should allow planets to exist there. On the other hand with the major sun already at the K1 giant stage, conditions there must be pretty rough. When a star leaves the stellar "Main Sequence," that is, exhausts the reserves of hydrogen at its core, it first contracts, emitting higher levels of ultraviolet and X-radiation; then as "helium burning" begins at its core the outer layers of its atmosphere expand, forming the tenuous envelope of a giant star. The star becomes an orange giant, then red; but although its surface- temperature drops because of its expansion, the total radiation emitted by the star is growing all the time. Epsilon Boötes A is now generating 100 times the radiation of our Sun.
Figure 5 The approximate area of sky covered by October 11, 1928 and October 24, 1928 sequences. The boundaries are approximate since the sequence of October 24, 1928 is incomplete.
Maybe, then, life was already highly advanced in the Epsilon Boötes system when the major sun's Main Sequence lifetime ended, and intelligence appeared as a mutation during the radiation bombardment. Steadily worsening conditions from then on would make the mutation favorable, and force it on by ruthless natural selection. There would be a race to establish technological civilization and achieve spaceflight before all life was forced up to the poles and finally rendered extinct. If our Sun had been growing in the sky during man's two million years or so on Earth, we'd just about have made it.
As the Epsilon Boötes people sent out space probes, therefore, they weren't conducting a dispassionate search for contact with other intelligence, as advocated by Professor Bracewell. Their space program was a survival effort, probably the total commitment of the race. Didn't somebody ask recently in Analog how any visitors to Earth would finance their space program? Military-style overdesign may also explain the probe's 13,000-year operational life. But the program wasn't a military one in the sense of a campaign: assuming that any intelligence contacted would be more advanced than they were (Dr. Drake has pointed out that we can expect the same experience), the probe makers were appealing for help. If we make contact with the probe, we can expect heartrending appeals for secrets of advanced interstellar flight and/or locations of unoccupied, habitable worlds.
We would expect that anyone in that situation would start telling us about their environment at some early stage. If there's any common ground between one intelligence and another in the galaxy, such data would in itself constitute an appeal for help: a hostile intelligence, hoping to pull off a planetary takeover, would keep quiet about its problems. The most important of the "panels" of echoes recorded on May 9, 1929, sets the key information before us: it's pretty much the kind of "dot-picture" Frank Drake and others have suggested for interstellar communication, except that it doesn't tell us what they looked like. Where one intelligence was appealing to another through logic, physical appearance might seem pretty irrelevant.
The May 1929 records were obtained by Galle and Talon, on the French naval vessel L'Inconstant, during an eclipse of the Sun at Poulo-Condere in Indochina.6 They had orders to study other effects as well as LDE, but the echo effects were so spectacular that they became the chief study of the expedition. On May 8, signals were sent every 30 seconds for the first 10 minutes of every half-hour, from morning to evening. On May 9, the day of the eclipse, signaling went on all day; and on May 10, signals were again sent for the first 10 minutes of each half-hour. Echoes were heard, sometimes in large numbers, on almost every pulse sent out; for the first time they were clearly divided into two groups by amplitude, the weak echoes being about one percent of the outgoing signals' intensity, the strong ones 1/3 to 1/5. Echoes stopped shortly before the eclipse, and began again halfway through it: the pause attracted much attention (it was first reported to have coincided exactly with the eclipse) but in fact there were several such gaps during the day, and they can be interpreted as "natural breaks" between one message pattern and the next.
The May 1929 echo patterns divide up naturally into "panels" of about 40 signals' duration, on average. They are much more complex than star maps, and my suggestion is that the probe was now sending more advanced information, in a "puzzle" form, to try to attract interest and attention from the supposedly advanced intelligence on the planet. May 9, panel 7 (Figure 6) is apparently the starting point: its main figure, the upright rectangle, is really conspicuous in the sequence, especially with the "starting rows" of high-intensity dots in rapid sequence round about it.
Figure 6 One of the several sequences recorded on May 9, 1929. Interpreted as a presentation of data concerning the possible Epsilon Boötes planetary system. Panel 7 in the sequence. For explanation see text.
Panel 7 can be interpreted as a "join up the dots" puzzle. (Try to imagine it without lines to begin with.) The BoOtes figure appears at upper right, and marking it off gets us started on joining up the dots as we're supposed to do. The starting rows at the top of the figure contain 7 dots, 4 dots, 3 dots and 7 dots, so we're looking for sevens—and there are 7 dots on the left-hand side of the big rectangle. Having so much, the sequence then becomes so clear, each line "dictating" the next, that it can be read off in English:
AB—Start here.
BC—Our home is Epsilon Boötes CDE—which is a double star.
FG, GH, CH, GK—We live on the sixth planet of seven
JKL—check that, the sixth of seven (they read from right to left!)
EM—counting outwards from the sun
FEG, GN—which is the larger of the two.
HO, OP—Our sixth planet has one moon, our fourth planet has three, our first and third planets each have one.
GQ, QR—Our probe is in the orbit of your Moon.
ST—This updates the position of Arcturus shown in our maps.
The prevailing orientation of the panel is right to left, as it is in most of the others. There is a vertical line of seven small dots left of the main figure (with only the sixth planet having its moon beside it), but its function is only to lead into the main figure.
On the extreme left we have a distinctive figure (also found in other panels) which gives the scale of the planetary system, by relating the orbits of the sixth and seventh planets to the distance between the two suns. The sixth planet is something over 1,000 million miles from the sun, and therefore can't be the original home of life: if it were, the sun would have had to be AO when on the Main Sequence, and wouldn't have lasted long enough for life to get started, much less evolve to intelligence.7 On the other hand, if the probe makers were a cold planet life-form, their probe wouldn't end up orbiting Earth in this system. But in panel 7 there are two lines, AIC1 and B1CI, leading from second-planet to sixth-planet dots. Later panels state explicitly that the probe makers migrated from the second planet of Epsilon A to the sixth, at who knows what cost in effort and suffering, before mounting their interstellar program.
Later panels also confirm the hint given by the sequence VW, WX, XY, YZ, and reinforced by X1Y1, Y1Z1, that the space probe came from the seventh planet. From that launch point the probe makers could have boosted the probe on its way, using the gravitational fields of the two suns as a slingshot, in a system described by F. J. Dyson back in 1963.8 It all fits together—and that last suggestion takes care of all the dots in panel 7.
How can it all be put to the test? There are internal tests which can be made—for example, are the indicated orbits stable? The best indication I have so far is that if our system had a minor sun at the distance of Uranus, Earth's orbit would still be stable. That's a distance ratio of very roughly 19:1. Is 7:1 stable in the greater scale of the Epsilon Boötes system? Definite values for the spectral types of the two suns will also be a great help. As noted before, if we can trace the remainder of the October 24th sequence that may also verify the star map hypothesis; but the most important test, of course, is to attempt to locate and contact the probe.
One of the biggest surprises in my research was that weird LDE effects continue to the present day. Radio operators find their own voices coming back to them, a most startling experience by all accounts. (NB: no time compression, no frequency shifts.) It is said that Sputnik 1 was heard again on the air, a year after it was first launched, months after it burned up in the atmosphere. We're also investigating stories of long-delayed TV echoes, and echo interference with communications satellites. In other words, the probe may still be trying patiently to make contact with us.
The search for the probe is being organized by Mr. A. T. Lawton, of EMI Limited, who has placed several thousand dollars' worth of equipment at his disposal. Using channels free of man-made and ionospheric interference, we shall send pulses (much stronger than those of the 1920's) to the Moon Equilateral positions, one of which the probe is believed to occupy.10 (The three-second echoes indicate that the probe is at the distance of the Moon, and the two most stable positions would be the Lagrange or "Moon Equilateral" points in the Moon's orbit. In one of those points, equidistant from the Earth and Moon, the probe would not have to allow for lunar perturbation of its orbit when signaling home. The indications are that it chose the leading equilateral, 60 degrees left of the Moon as seen from the Northern Hemisphere.)
The transmitter array, which is eqquatorially mounted, has been set up at Twickenham in southern England; the main receiver, an extremely sensitive and directional satellite tracking antenna on an altazimuth mount, is at Shepperton. With the help of listening posts elsewhere in the United Kingdom and (we hope) abroad, it should be possible to pinpoint the source of any echoes received. If the echoes we hear come from within the atmosphere, then at least the 40 years' mystery may be solved—if we can eliminate time compression and frequency shift; but if they come from the orbit of the Moon, at the intensities noted in the 1920's, it's going to be difficult to claim that they're natural.11 If they begin a sequence of intelligible signals, then we shall really have hit the jackpot.
If the probe is contacted, this is going to be a memorable year. Probably the first priority will be appropriate international supervision of further contact, lest the great powers use nuclear weapons on it, or worse still on each other, out of panic or suspicion. The next will be to shift to some more advanced mode of communication such as television. On the basis of the probe's sophisticated decisions, Mr. Lawton (head of EMI's Computer research) believes that—it may carry more information than the Encyclopaedia Britannica. It would take a million years to get it all using LDE, but only months by television. (Let's hope we don't take a million years to understand it.)
And beyond that, we have to consider contact with the probe makers themselves. Does the updated map of 1929 mean that a signal has been sent, announcing the probe's activation?
If so, it's not likely that anyone will receive it. If Epsilon A is now 100 times as luminous as our Sun, the sixth planet is still not as hot as Earth is now; and since Epsilon Boötes grew significantly brighter during the Nineteenth Century, the planet has presumably been a frozen waste for the last 13,000 years. It would be only a temporary refuge for the Epsilon Boötes people, and there would be nothing to keep them there once new homes were found. Where are they now, and how long will it be—if the probe exists and we can learn from it—before we meet up with them?
ABOUT THE AUTHOR
Duncan Lunan organized and chaired the "Man and the Stars" discussions on interstellar travel and communication which were conducted during his term as president of the Association in Scotland for Technology and Research in Astronautics (ASTRA). He is currently serving as vice-president of ASTRA, as well as pursuing his interests in science fiction, astronomy, and spaceflight.
REFERENCES
1. R. N. Bracewell, "Communications from Superior Galactic Communities," Nature, 186 (1960) p. 670; also in Interstellar Communication (see below).
2 C. Stormer, The Polar Aurora, Oxford University Press, 1955.
3 B. van der Pol, Nature, 122 (1928), p. 878.
4 Crawford, Sears & Bruce, "Possible Observations and Mechanism of Very Long Delayed Radio Echoes," Journal of Geophysical Research, Space Physics, vol. 7, no. 34, 1.12.1970, pp. 7326-7332; and private correspondence, Prof. F. W. Crawford, 1972.
5 C. Flammarion, Les Etoiles, Paris, 1882.
6 J. B. Galle. "Observations relatives a la radio-electricite et a la physique du globe," L'Onde Electrique, 9 (1930) pp. 257-265.
7 S. H. Dole, Habitable Planets for Man, Blaisdell, New York, 1964.
8 F. J. Dyson, "Gravitational Machines," in Interstellar Communication, ed. Cameron, Benjamin, New York, 1963.
9 Villard, Graf and Lomasney, "There is no such thing as a long-delayed echo AR. . . a long-delayed echo AR," QST, February 1970.
10 D. A. Lunan, "Spaceflight," vol. 15, no. 4, April 1973 (British Interplanetary Society, 12 Bessborough Gardens, London SW IV 2JJ).
11 A. T. Lawton, in the work cited above.