Here’s another entry in the Codex Futurius project, this blog’s never-ending quest to explore the timeless scientific ideas raised by science fiction. This question about communicating with aliens goes to Jill Tarter of SETI. Thanks again to Jennifer Ouellette, the director the NAS’ Science and Entertainment Exchange (SEEx) program, for connecting us with Tarter.
Would/will we recognize an alien transmission right away? Is there a chance we could miss such a transmission, or they ours?
We will recognize the sorts of electromagnetic signals for which we have built good matched filters: nanosecond optical laser pulses, narrowband radio continuous wave or pulsed signals. If signals are of some other type (e.g., a modulation scheme with higher dimensionality, or something other than electromagnetic waves) then we will not detect them, except by serendipity as we build new instruments to study our universe in different ways, or by using increasing computational power to look for more complex types of electromagnetic signals.
If signals are transmitted via a technology that we haven’t yet invented, we will miss them until we manage to invent the appropriate technology (remember that we are a very young technology (~100 years) in a very old galaxy (~10 billion years). I suspect we have a lot more to learn.
We could also miss signals in time. If technological civilizations and their signals are short lived, we might be searching for exactly the right thing, but long after the signals have come and gone. Likewise, if we do not manage to continue as a technological civilization for a very long time, then any transmission project that we might decide to embark on would have little likelihood of being detected by anyone else.
I continually tell groups containing grad students and post-docs (who touch more data than the rest of us) to resist the temptation to edit out anomalies until they have first satisfied themselves that it isn’t a real effect, perhaps the artifact of someone else’s astroengineering or signaling project—but in truth, it’s very hard to train someone to be a Jocelyn Bell [who discovered pulsars as a post-doc].
There’s no way to estimate what we might be missing.
Will we understand alien communication, and vice versa?
People argue that mathematics is essential for a technology that can create and operate some sort of transmitter. Therefore a language based on mathematics should be mutually understandable, and in 1960 Hans Feudenthal created such a language he called Lincos (for “lingua cosmica”). Another suggestion is a language based on the period table of elements that are (we think) the same throughout the universe; this idea has been pursued by Carl L. Devito. If the signal is electromagnetic, the wavelength of the transmitted signal serves as a common unit of measurement between sender and receiver; you might describe yourself as being N wavelengths tall. Of course it is hard for us to think in any way except the way we do—it might be that another intelligent species with the capability of manipulating its environment to create a transmitter that we can detect could still perceive their environment in such a different way that it might be impossible to find a common ground for describing the same thing. But all of this is a problem that I’d like to have, and I don’t doubt that there would be many other individuals around the globe just as eager to help unravel any information from a detected signal. An old Southern cookbook starts a recipe by saying, “To cook a possum, you must first catch a possum.”
That’s my personal approach to SETI—it’s the detection of a signal that we must work on first. Even if there were no information encoded within a detected signal, or even if we can never decode it, the detection of a signal answers the old important question “Are we alone?” Even a cosmic dial tone tells us something else implicitly: It tells us that there’s a high probability that we can have a long technological future, because technologies must, on average, be long lived. Otherwise we would never overlap in time with another technological civilization, and the detection would not have occurred.
Philip Morrison used to put this most poetically—he called SETI “the archaeology of the future.” Because of the finite speed of light, a detected electromagnetic signal will give us information about their past, but it will tell us about our future.