Suppose, during a routine observing session on the 305 metre
radio telescope at Arecibo
Observatory in Puerto Rico, a faint, narrow band
signal were
detected at a frequency of 2388 MHz (12.6 centimetre wavelength)
and that after a variety of tests ruled out
interference from terrestrial sources, Earth satellites or
planetary probes, artifacts due to equipment failure or
miscalibration, or even a prank on the part of a member of
the observing team, astronomers began to suspect they
had just made one of the most profound discoveries in the
history of science--a beacon transmitted by intelligent
extraterrestrials.
Theorists would certainly rush to propose models of natural physical processes capable of producing such a signal, and further observations would be required to put those theories to the test. After all, when the fast, extraordinarily precise signals from pulsars were first detected, they too appeared so unlike other astronomical sources that some suspected they were interstellar beacons and referred to them as "LGM sources" (for "Little Green Men"). In the case of the pulsars, theorists suggested that quickly rotating neutron stars with intense magnetic fields could produce signals like those observed, and subsequent observations confirmed that theory beyond a shadow of a doubt.
But, suppose this time that doesn't happen. Rather, optical telescopes find a star, somewhat dimmer than the Sun and about two billion years older, along the line of sight. Further, intense scrutiny of the signal reveals a Doppler shift consistent with its source being in a 230 day orbit around the star. Finally, after round-the-clock observations of the signal by observatories all over the globe and reduction of the observations with supercomputers, it is found to be modulated, repeating the same sequence of 1679 on-and-off pulses over and over.
At this point few, if any, other hypotheses would remain viable. The signal would be acknowledged by virtually all observers to be a message transmitted by intelligent extraterrestrials. The relentless Copernican demotion of Homo sapiens from the centre of the universe would be complete; we would know we were not alone in a dead and meaningless universe, but rather an outpost of life and consciousness, in all probability one among a multitude, just having received our invitation to connect to the galactic Internet.
Once the signal was accepted as being a modulated transmission from an extraterrestrial species, the question would immediately be, what does it say? At first glance, this might appear to be an unsolvable puzzle: not only do we share no common language with the beings who sent the message, we can't even be sure they have the same sense organs--perhaps the creatures who sent the message are gasbags who live in the eternal night deep in the atmosphere of a Jupiter-like gas giant planet and communicate chemically--by emitting and sensing odours. Consider two human beings, one knowing only Japanese, another only Portugese, trying to establish communication by sending telegrams to one another. Hopeless!--yet Japanese and Portugese are members of the same species who, other than the language they learned as children, are for all intents and purposes identical. How can we possibly hope to comprehend a message from a species with no common lineage whatsoever?
We could send a picture! In the early 1960's astronomer Frank Drake suggested that even the crudest image could convey information comprehensible to any being with a visual sense remotely similar to ours. An interstellar message received in the electromagnetic spectrum must have been sent by a species which understands electrodynamics. From first principles, one can determine the frequency bands in which the universe is largely transparent; if the transmitting species lacked senses capable of revealing the existence of other stars, for what conceivable reason would they be motivated to squander energy beaming a transmission into the murky dark? No--it's a safe bet any being which sends an electromagnetic message will have senses which respond to electromagnetic radiation. But in what wavelength band? After all, prior to the 20th century, our own species was unaware of all but the tiny optical octave of the electromagnetic spectrum. Again, there is an obvious answer. A life form which evolves on an Earthlike planet circling a star is almost certain to have a visual sense with maximum acuity in the predominant wavelengths which reach the surface. Vision is of such value that an enormous variety of terrestrial species possess it.
Now suppose our Japanese and Portugese interlocutors were no longer limited to sending telegrams to one another but could, instead, communicate by FAX. Now progress would be possible, albeit slowly at first. Each could send the other freehand drawings of various things, with the words for them written alongside. For those objects recognisable to both, this would allow compiling a vocabulary of each other's languages. With a little more artistic creativity, verbs, adjectives, and other parts of speech could be exchanged. Eventually, effective communication could be established. Might it not be the same between humans and extraterrestrials? If we received an image, we might be able to make enough sense of it to learn something about the senders and, perhaps, how to obtain more detailed messages.
Assume the message is the following pattern of 1679 binary bits, sent over and over. What might we deduce from this sequence?
0000001010101000000000000101000001010000000100100010001000100101 1001010101010101010100100100000000000000000000000000000000000001 1000000000000000000011010000000000000000000110100000000000000000 0101010000000000000000001111100000000000000000000000000000000110 0001110001100001100010000000000000110010000110100011000110000110 1011111011111011111011111000000000000000000000000001000000000000 0000010000000000000000000000000000100000000000000000111111000000 0000000111110000000000000000000000011000011000011100011000100000 0010000000001000011010000110001110011010111110111110111110111110 0000000000000000000000000100000011000000000100000000000110000000 0000000010000011000000000011111100000110000001111100000000001100 0000000000010000000010000000010000010000001100000001000000011000 0110000001000000000011000100001100000000000000011001100000000000 0011000100001100000000011000011000000100000001000000100000000100 0001000000011000000001000100000000110000000010001000000000100000 0010000010000000100000001000000010000000000001100000000011000000 0011000000000100011101011000000000001000000010000000000000010000 0111110000000000001000010111010010110110000001001110010011111110 1110000111000001101110000000001010000011101100100000010100000111 1110010000001010000011000000100000110110000000000000000000000000 0000000000111000001000000000000001110101000101010101010011100000 0000101010100000000000000001010000000000000011111000000000000000 0111111111000000000000111000000011100000000011000000000001100000 0011010000000001011000001100110000000110011000010001010000010100 0100001000100100010010001000000001000101000100000000000010000100 0010000000000001000000000100000000000000100101000000000001111001 111101001111000
Well, the first thing a mathematician would observe is that 1679 is the product of two prime numbers: 23 and 73. This suggests that the bits might be arranged in rectangular array with those dimensions. Well, there's two ways to do it; first we try 23 rows of 73 columns: gibberish. Then we try the other, 73 rows of 23 columns and...Eureka! Here is the rearranged message with the ones written in darker type so they stand out more clearly.
00000010101010000000000 00101000001010000000100 10001000100010010110010 10101010101010100100100 00000000000000000000000 00000000000011000000000 00000000001101000000000 00000000001101000000000 00000000010101000000000 00000000011111000000000 00000000000000000000000 11000011100011000011000 10000000000000110010000 11010001100011000011010 11111011111011111011111 00000000000000000000000 00010000000000000000010 00000000000000000000000 00001000000000000000001 11111000000000000011111 00000000000000000000000 11000011000011100011000 10000000100000000010000 11010000110001110011010 11111011111011111011111 00000000000000000000000 00010000001100000000010 00000000001100000000000 00001000001100000000001 11111000001100000011111 00000000001100000000000 00100000000100000000100 00010000001100000001000 00001100001100000010000 00000011000100001100000 00000000001100110000000 00000011000100001100000 00001100001100000010000 00010000001000000001000 00100000001100000000100 01000000001100000000100 01000000000100000001000 00100000001000000010000 00010000000000001100000 00001100000000110000000 00100011101011000000000 00100000001000000000000 00100000111110000000000 00100001011101001011011 00000010011100100111111 10111000011100000110111 00000000010100000111011 00100000010100000111111 00100000010100000110000 00100000110110000000000 00000000000000000000000 00111000001000000000000 00111010100010101010101 00111000000000101010100 00000000000000101000000 00000000111110000000000 00000011111111100000000 00001110000000111000000 00011000000000001100000 00110100000000010110000 01100110000000110011000 01000101000001010001000 01000100100010010001000 00000100010100010000000 00000100001000010000000 00000100000000010000000 00000001001010000000000 01111001111101001111000 |
Since this is an image, let's look at it as one, at the right. The
first thing that jumps out at us is the humanoid figure in the middle
of the image toward the bottom. Imagining a natural process which
could cause a binary message containing such an image over and over
would be a daunting task for even the most sceptical theorist. The
image as a whole would be irrefutable evidence of an intelligent
sender. Dissecting the image piece by piece, we may discover a multitude
of information about whoever sent it.
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| M13 in Hercules |
You probably won't get it all--certainly I didn't--but how much you can discover, and your own ideas on how such a small message can be made more free of anthropocentric assumptions and easier to interpret may, in the fullness of time, contribute to the decoding of our own species' galactic CQ DX.
Please try to work it out from the raw message and its image representation at the right. I guarantee you'll learn a lot about how hard it is to communicate even relatively simple concepts across the gulf of space and time to beings who may have less in common with us than bacteria living at the vents along the mid-Atlantic ridge. Good luck, and happy hunting!
Okay, now that you've worked out as much as you can of
the meaning of the message, you can compare your results
with the answers in the document...
Click on title to order on-line from
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