Let's imagine aliens exist. You have the extraordinary task of crafting a message that they might conceivably understand. How would you do it? And what would you say?

These are daunting questions yet humans throughout history have tried to answer them. Fascinating approaches, ranging from brilliant to absurd, are detailed by science journalist Daniel Oberhaus in his new book Extraterrestrial Languages.

Designing an interstellar message forces us to think about what makes us human and recognize this humanity in others. Daniel Oberhaus, Science Journalist

With clarity and wit, Oberhaus offers readers a historical view of humankind's efforts to develop communications with extraterrestrial life, from 19th century mirrors to entire mathematical languages to modern radio telescopes. Freethink spoke to Oberhaus about the technological and philosophical challenges of conversing with alien life, and what this whole endeavor can teach us about ourselves.

The interview has been lightly edited for clarity and length.

Freethink: It feels like there's kind of a lot going on on Earth right now. Why is figuring out how to have an interstellar conversation important?

Daniel Oberhaus: Two reasons. One, it forces us to think in terms of generations, which is especially important now as we face existential crises like climate changes. If we do establish contact with an extraterrestrial intelligence, it will likely be located well over 100 light years from Earth. That means at least 200 years, but likely much longer, will elapse for a two-way conversation to occur. Humans aren't used to thinking on such long time scales, but interstellar messaging helps us wrap our heads around it.

The other reason, and the most important in my opinion, is that crafting an interstellar message forces us to think about what connects us as humans. The U.S. and many other countries around the world are seeing a trend toward political nationalism, which focuses on differences and separations between nations.

But if we want to engage with our extraterrestrial neighbors, it won't just be a conversation between one individual or even one nation and the ETI. We'll be responding as a planet and as a species, and we really need to think about how we want to represent ourselves. Designing an interstellar message forces us to think about what makes us human and recognize this humanity in others.

Freethink: What inspired you to write a book on this subject?

Daniel: I've always been interested in the question of extraterrestrial life in the universe, but a few years ago, I started reading about the life of Hans Freudenthal, a prominent Dutch mathematician in the mid-20th century. Freudenthal led a remarkable life. He escaped from a Nazi workcamp during the Holocaust — and even managed to win a literary prize for fiction while hiding in Amsterdam — and was instrumental in reforming how mathematics was taught in the Netherlands in the postwar years.

Freudenthal was also interested in the extraterrestrial question, and in 1960, he applied his views on mathematics to create a language specifically designed for transmission to extraterrestrials. It was called Lingua Cosmica ("Lincos" for short), and it was the first major linguistic contribution to the study of interstellar communication.

I ended up writing an article for The Atlantic about Freudenthal and Lincos, and that ended up getting spun into a full-length book.

Freethink: The book opens with a really intriguing story about astronomer Frank Drake sending an encoded letter to nine of the brightest minds in the United States in 1961. Can you tell us about that experiment?

Daniel: Frank Drake is really the father of the modern search for extraterrestrial intelligence or SETI. In 1960, he spent a few months using the radio telescope at Green Bank, West Virginia, to scan two nearby stars for signs of an intelligent signal. Drake came up empty handed, and shortly after the conclusion of the experiment, he invited some of the brightest scientific minds to Green Bank to discuss the future of SETI — or whether SETI should have a future at all.

If we receive an intelligent message from space, how would we design a response? Daniel Oberhaus, Science Journalist

The Green Bank conference was a milestone in the history of SETI and determined the course of the search for the better part of the next half century. One of its most memorable products was the Drake Equation, which can be used to estimate the probability of intelligent life in the universe.

But when the conference was finished, Drake realized they had neglected a very important issue: if we receive an intelligent message from space, how would we design a response? So in 1961, Drake created a prototype interstellar message and sent it to the Green Bank conference attendees to see if anyone could decipher it. That message actually served as the blueprint for the first interstellar message sent into space from the Arecibo telescope, 13 years later.

Freethink: What are the fundamental requirements for designing a message for extraterrestrials?

Daniel: I'm not sure if there are any hard and fast rules for designing a message to extraterrestrial intelligence. If you look at the history of the messages we've sent, they've been incredibly diverse in their design. There have been bitmaps, theremin concerts, Beatles songs, vaginal contractions, electronic music, and custom languages broadcast to the stars.

Some of these designs are more likely to be understood than others, but you could fill a book explaining why — in fact, I have!

"If you look at the history of the (extraterrestrial) messages we’ve sent, they’ve been incredibly diverse in their design. There have been bitmaps, theremin concerts, Beatles songs, vaginal contractions, electronic music, and custom languages broadcast to the stars." Daniel Oberhaus, Science Journalist

Freethink: I was surprised to learn that dolphins played a major role in shaping how people think about interstellar communication. How did that happen?

Daniel: You can thank John C. Lilly for that. He was a neuroscientist who ran a controversial lab down on St. Thomas, where he had assistants live in flooded houses with his dolphins and even injected them with LSD. Lilly's life goal was to establish communication with dolphins, which he thought were likely as intelligent as humans.

Both Lilly and other scientists recognized that interspecies communication shares many of the same problems with interstellar communication, so Lilly was invited to participate at Drake's Green Bank conference. He must have made quite an impression on the group, because after the conference, they started referring to themselves as the Order of the Dolphin. They even had little dolphin pins made to distribute to the attendees!

Freethink: The book details two whole languages invented specifically for communicating to extraterrestrials. Can you talk about how they were developed and evolved?

Daniel: The first language is called Lingua Cosmica or Lincos, which as I mentioned above was developed by the Dutch mathematician in the mid-'60s. It's a combination of symbolic logic, basic arithmetic, and natural language. Basically, Freudenthal begins with self-evident information, like counting, and builds up the language to the point that it can be used to convey facts about life on Earth and human society.

The second generation of Lincos was also developed by a Dutch mathematician named Alexander Ollengren. He was an expert in computer science, and so he applied this to the problem of interstellar communication. Lincos 2.0 draws upon two technical fields of logic — the lambda calculus and the calculus of (inductive constructions) — to create a logical meta-language that can be used to describe the relationship between words in a natural language text.

It sounds complicated, but it's actually a very elegant solution to the problems of interstellar communication and should be recognizable to an extraterrestrial that is familiar with digital computation.

Freethink: You describe some pretty wild ideas for communicating with aliens — including one astronomer's proposal to set off all our nukes at once above Earth. Do you have a favorite among any of these out-of-the-box schemes?

Daniel: My favorite is probably Marvin Minsky's suggestion that we ought to send a cat across the universe. He was using this as an example to talk about why computers make a good choice for interstellar communication, but as a cat owner myself it's funny to imagine shipping a cat to ET as our extraterrestrial diplomat. They probably wouldn't want to talk to us after that!

"My favorite (idea for communicating with aliens) is probably Marvin Minsky’s suggestion that we ought to send a cat across the universe." Daniel Oberhaus, Science Journalist

Freethink: You also talk about messages sent to space on physical objects, such as the famous designs on the Golden Record, conceived by Carl Sagan and others. Which aspects of the record do you find most ingenious or limiting?

Daniel: I really like how Carl Sagan and his collaborators thought to use the spin-flip transition of a neutral hydrogen atom as the key to understanding the rest of the contents on the record. This is the most abundant element in the universe and is presumably familiar to ET. They labeled this transition on the record in binary, which can then be used to understand the rotational speed of the record itself, the trajectory of the Voyager spacecraft, and so on. It's really clever.

Freethink: What was the coolest thing you learned while researching the book?

Daniel: That is a tough one. I personally loved learning about schemes that mathematicians devised 150 years ago for contacting aliens. At that point, most people still thought there could be aliens on Mars or even the moon, so people had some pretty far out ideas for how to get their attention.

I don't want to give too much away, but a representative idea of that time comes from the Austrian astronomer Joseph von Littrow. He wanted to dig massive trenches in the Sahara Desert, fill them with water, top them with kerosene, and then set them on fire to send math equations to the Martians. Thankfully, this never came to fruition, but it sure would be a hell of a way to say hello!

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