* Fourier is now famous for his study of the propagation of heat in solids, used today to understand the surface properties of the planets, and for his investigation of waves and other periodic motion – a branch of mathematics known as Fourier analysis.
On the walls and columns of Karnak, at Dendera, everywhere in Egypt, Champollion delighted to find that he could read the inscriptions almost effortlessly. Many before him had tried and failed to decipher the lovely hieroglyphics, a word that means ‘sacred carvings.’ Some scholars had believed them to be a kind of picture code, rich in murky metaphor, mostly about eyeballs and wavy lines, beetles, bumblebees and birds – especially birds. Confusion was rampant. There were those who deduced that the Egyptians were colonists from ancient China. There were those who concluded the opposite. Enormous folio volumes of spurious translations were published. One interpreter glanced at the Rosetta stone, whose hieroglyphic inscription was then still undeciphered, and instantly announced its meaning. He said that the quick decipherment enabled him ‘to avoid the systematic errors which invariably arise from prolonged reflection.’ You get better results, he argued, by not thinking too much. As with the search for extraterrestrial life today, the unbridled speculation of amateurs had frightened many professionals out of the field.
Champollion resisted the idea of hieroglyphs as pictorial metaphors. Instead, with the aid of a brilliant insight by the English physicist Thomas Young, he proceeded something like this: The Rosetta stone had been uncovered in 1799 by a French soldier working on the fortifications of the Nile Delta town of Rashid, which the Europeans, largely ignorant of Arabic, called Rosetta. It was a slab from an ancient temple, displaying what seemed clearly to be the same message in three different writings: in hieroglyphics at top, in a kind of cursive hieroglyphic called demotic in the middle, and, the key to the enterprise, in Greek at the bottom. Champollion, who was fluent in ancient Greek, read that the stone had been inscribed to commemorate the coronation of Ptolemy V Epiphanes, in the spring of the year 196 B.C. On this occasion the king released political prisoners, remitted taxes, endowed temples, forgave rebels, increased military preparedness and, in short, did all the things that modern rulers do when they wish to stay in office.
The Greek text mentions Ptolemy many times. In roughly the same positions in the hieroglyphic text is a set of symbols surrounded by an oval or cartouche. This, Champollion reasoned, very probably also denotes Ptolemy. If so, the writing could not be fundamentally pictographic or metaphorical; rather, most of the symbols must stand for letters or syllables. Champollion also had the presence of mind to count up the number of Greek words and the number of individual hieroglyphs in what were presumably equivalent texts. There were many fewer of the former, again suggesting that the hieroglyphs were mainly letters and syllables. But which hieroglyphs correspond to which letters? Fortunately, Champollion had available to him an obelisk, which had been excavated at Philae, that included the hieroglyphic equivalent of the Greek name Cleopatra. Ptolemy begins with P; the first symbol in the cartouche is a square. Cleopatra has for its fifth letter a P, and in the Cleopatra cartouche in the fifth position is the same square. P it is. The fourth letter in Ptolemy is an L. It is represented by the lion. The second letter of Cleopatra is an L and, in hieroglyphics, here is a lion again. The eagle is an A, appearing twice in Cleopatra, as it should. A clear pattern is emerging. Egyptian hieroglyphics are, in significant part, a simple substitution cipher. But not every hieroglyph is a letter or syllable. Some are pictographs. The end of the Ptolemy cartouche means ‘Ever-living, beloved of the god Ptah.’ The semicircle and egg at the end of Cleopatra are a conventional ideogram for ‘daughter of Isis.’ This mix of letters and pictographs caused some grief for earlier interpreters.
In retrospect it sounds almost easy. But it had taken many centuries to figure out, and there was a great deal more to do, especially in the decipherment of the hieroglyphs of much earlier times. The cartouches were the key within the key, almost as if the pharaohs of Egypt had circled their own names to make the going easier for the Egyptologists two thousand years in the future. Champollion walked the Great Hypostyle Hall at Karnak and casually read the inscriptions, which had mystified everyone else, answering the question he had posed as a child to Fourier. What a joy it must have been to open this one-way communication channel with another civilization, to permit a culture that had been mute for millennia to speak of its history, magic, medicine, religion, politics and philosophy.
Today we are again seeking messages from an ancient and exotic civilization, this time hidden from us not only in time but also in space. If we should receive a radio message from an extraterrestrial civilization, how could it possibly be understood? Extraterrestrial intelligence will be elegant, complex, internally consistent and utterly alien. Extraterrestrials would, of course, wish to make a message sent to us as comprehensible as possible. But how could they? Is there in any sense an interstellar Rosetta stone? We believe there is. We believe there is a common language that all technical civilizations, no matter how different, must have. That common language is science and mathematics. The laws of Nature are the same everywhere. The patterns in the spectra of distant stars and galaxies are the same as those for the Sun or for appropriate laboratory experiments: not only do the same chemical elements exist everywhere in the universe, but also the same laws of quantum mechanics that govern the absorption and emission of radiation by atoms apply everywhere as well. Distant galaxies revolving about one another follow the same laws of gravitational physics as govern the motion of an apple falling to Earth, or Voyager on its way to the stars. The patterns of Nature are everywhere the same. An interstellar message, intended to be understood by an emerging civilization; should be easy to decode.
We do not expect an advanced technical civilization on any other planet in our solar system. If one were only a little behind us – 10,000 years, say – it would have no advanced technology at all. If it were only a little ahead of us – we who are already exploring the solar system – its representatives should by now be here. To communicate with other civilizations, we require a method adequate not merely for interplanetary distances but for interstellar distances. Ideally, the method should be inexpensive, so that a huge amount of information could be sent and received at very little cost; fast, so an interstellar dialogue is rendered possible; and obvious, so any technological civilization, no matter what its evolutionary path, will discover it early. Surprisingly, there is such a method. It is called radio astronomy.
The largest semi-steerable radio/radar observatory on the planet Earth is the Arecibo facility, which Cornell University operates for the National Science Foundation. In the remote hinterland of the island of Puerto Rico, it is 305 meters (a thousand feet) across, its reflecting surface a section of a sphere laid down in a pre-existing bowl-shaped valley. It receives radio waves from the depths of space, focusing them onto the feed arm antenna high above the dish, which is in turn electronically connected to the control room, where the signal is analyzed. Alternatively, when the telescope is used as a radar transmitter, the feed arm can broadcast a signal into the dish, which reflects it into space. The Arecibo Observatory has been used both to search for intelligent signals from civilizations in space and, just once, to broadcast a message – to M13, a distant globular cluster of stars, so that our technical capability to engage in both sides of an interstellar dialogue would be clear, at least to us.
In a period of a few weeks, the Arecibo Observatory could transmit to a comparable observatory on a planet of a nearby star all of the Encyclopaedia Britannica. Radio waves travel at the speed of light, 10,000 times faster than a message attached to our fastest interstellar spaceship. Radio telescopes generate, in narrow frequency ranges, signals so intense they can be detected over immense interstellar distances. The Arecibo Observatory could communicate with an identical radio telescope on a planet 15,000 light-years away, halfway to the center of the Milky Way Galaxy, if we knew precisely where to point it. And radio astronomy is a natural technology. Virtually any planetary atmosphere, no matter what its composition, should be partially transparent to radio waves. Radio messages are not much absorbed or scattered by the gas between the stars, just as a San Francisco radio station can be heard easily in Los Angeles even when smog there has reduced the visibility at optical wavelengths to a few kilometers. There are many natural cosmic radio sources having nothing to do with intelligent life – pulsars and quasars, the radiation belts of planets and the outer atmospheres of stars; from almost any planet there are bright radio sources to discover early in the local development of radio astronomy. Moreover, radio represents a large fraction of the electromagnetic spectrum. Any technology able to detect radiation of any wavelength would fairly soon stumble on the radio part of the spectrum.