Among scientists involved in the Search for Extraterrestrial Intelligence (SETI), its quite common to be focused on the future, ever mindful that it could take years, or even decades, to find a signal from otherworldly intelligence. But if historian Steve Dick has his way, astronomers will also turn their attention toward the past as they search for life beyond Earth.

"I am a firm believer that history should inform our present actions, that we should learn from our past to help us make good decisions for the future," says Dick, author of Life on Other Worlds: The 20th Century Extraterrestrial Life Debate. "Youve heard the saying that those ignorant of history are condemned to repeat it; without prior preparation based in part on history, we could make big mistakes with big consequences."

Dick cautions against using examples like this to predict reactions to a real SETI detection. Most egregiously, Dick argues, such comparisons use hypothetical face-to-face encounters to predict responses to a SETI detection involving signals sent across interstellar distances. "The Orson Welles War of the Worlds broadcast is the ultimate example of what radio listeners thought was physical culture contact," which Dick argues "is very different from the impact if the extraterrestrials are light years away."

As an alternative, Dick proposes a fundamental principle that should guide "the broader idea that history can and should inform SETI impact studies." According to Dick, we should focus on "analogues based on the transmission of ideas between cultures, rather than on physical culture contact."

"The analogue most often cited is contact between cultures on Earth, which usually led to disaster: Cortez and the Aztecs, Pizarro and the Incas, the Europeans and the American Indians, and many others." For predicting responses to a SETI detection, however, Dick maintains, "these are not good analogues because they involve physical culture contact."

Instead, he proposes analogues based on the dispersion of ideas between cultures. "If a SETI signal is deciphered," Dick suggests, "a tantalizing terrestrial analogue is the transmission of Greek science via the Arabs to the Latin West in the 12^th and 13^th centuries." In this analogy, "the Greeks are the extraterrestrials," the Islamic scholars serve as the bearers of the message from one culture to another, and "the medieval translators and commentators in Spain and elsewhere are those who bring the new knowledge to the masses."

Following standard research practices, the first steps that astronomers will take after detecting a signal reflect the normal process of science. After confirming the validity of their discovery, they will share their findings with the world. Even if the research team detecting a signal attempted to keep the discovery quiet, in the process of confirming with astronomers at other observatories, it seems unlikely they would be able to conceal the news for long. In Dicks view, "human nature will not allow that to be kept a secret."

Though there may be frustratingly little to report in the days following signal detection, Dick emphasizes the importance of being as complete as possible from the beginning: "In general people are eager and willing to believe in ETs on the slightest evidence. So, wed better get the announcement right the first time, as well as any further details. In the absence of information, rumor will fill the void."

There should be no great uncertainty in determining that we have detected intelligence beyond Earth, in Dicks view, because the signals themselves would be unlike anything found in nature: "We are looking for very narrow band signals of the kind that nature does not generate, so the fact that a signal is artificial should be obvious." Instead, Dick expects the ambiguity would come later: "It will be much harder to decipher any message, a problem that I think SETI scientists underestimate. We know from cosmic evolution that civilizations could be billions of years old. Whether we could communicate with such entities is doubtful."

Given the potential value of analogies in SETI, how can we be sure we are making appropriate comparisons? "In order to have a good analogy to contact," says Dick, "one needs very much to specify the scenario." As we have already seen, it is vital to distinguish between scenarios where evidence is transmitted across interstellar distances and scenarios where contact is up close and personal. But even within SETI scenarios involving contact at a distance, we need to consider several other factors.

"Is there just a dial tone signal that indicates general intelligence, or is there a flow of information? Fast flow after immediate translation, or slow flow after perhaps generations of decipherment?" As Dick emphasizes, "These are all very different cases of contact."

In spite of his enthusiasm for using historical analogues, Dick urges vigilance: "I have always been careful to emphasize that historical analogues cannot be used to make predictions. They can only serve as guides to our thinking, as tools that tell us that not all things are possible, nor is just one thing possible." Though analogies can play an important role in preparing for the detection of life beyond Earth, as Dick reminds us, "they are guidelines that must be used with caution."