Weird Alien Communication: Indistinguishable from Noise
Rock and Roll Ain’t Noise Pollution, but Interstellar Communication Might Be
We must prepare ourselves to be awed by the advanced technology of alien spacecraft
Obviously the holy grail here is direct communication with aliens, but what about a slightly less-ambitious goal? It’d be pretty damn cool even just to eavesdrop on aliens communicating with each other. Maybe if we tune our telescopes just right, we could pick up the sounds of intergalactic warships planning their next move. Or one of the galaxy’s radio stations (“Q-193, the Lunatic Fringe of the Milky Way! We’ve got a block of Zeppelin coming up after the Gamma Burst Report! And the Q-193 van is hanging out at the galactic center all afternoon! Head on down to get your free pulsar!”) Shouldn’t be too hard to do this, right? If there are alien civilizations out there, then the galaxy should be buzzing with broadcasts. So why haven’t we picked up anything yet?
Paul Davies discusses reasons for the radio silence at length in “The Eerie Silence“. For one thing, we have no idea the medium they would use. We humans prefer radio-frequency electromagnetic waves, but who knows what aliens would prefer? We’ve already discussed the advantages that neutrinos would have for intergalactic signaling. But let’s say we’ve guessed right, and aliens are using the plain old EM spectrum like we use. Why haven’t we noticed any suspicious messages so far?
Naively, we might assume that an alien’s galaxy-spanning Morning Zoo broadcast should stand out strongly from the background. We might expect them to use high-energy, obviously artificial signals, pumped through space from their powerful devices. But is this really what we should expect to see from an advanced alien civilization? After all, our own emissions have gotten *fainter* as our technology has increased. For a while, we were getting all of our TV from signals broadcasted by gigantic antennas, which also happen to broadcast straight out into space. Earth is surrounded by a bubble of ever-expanding TV and radio broadcasts, expanding by 1 light year for every year since they were broadcast. (for example, I Love Lucy episodes are now about sixty light years away.) But what has happened in the last few decades? We now send those signals down into cables in the earth, instead of broadcasting to space — that’s more energy efficient. Extrapolate this by millions of years, and we’ll likely be using very energy-efficient means of communication, technologies that might not even be perceptible to the uninitiated. Instead of expecting to see some blatant signature such as giant electromagnetic emissions illuminating the galaxy, perhaps we should expect the aliens to be even more energy-conscious than ourselves.
An image illustrating the JPEG compression algorithm. An image, ironically, in GIF format.
Furthermore, do we really expect to be able to recognize advanced alien communication signals if we capture them? If you extrapolate our progress in communications technology forward millions of years, it seems logical to conclude that interstellar alien communication would be pretty subtle, perhaps nearly impossible to understand. In fact, the ultimate limit of long-distance communication might be completely indistinguishable from noise. We can see that already in efficient communication schemes we’ve developed on Earth that use compression and clever encoding to pack more information into fewer bits. Ever open up a JPEG image file to see the gibberish inside? That gibberish is far more efficient at storing an image, but is far less understandable. Something even more complex than JPEG might look like complete nonsense — you might not even be able to tell it contains any information at all. As Richard Factor (president of the SETI League) says, “Any sufficiently advanced modulation scheme is virtually indistinguishable from noise.” Or as Paul Davies says, “we could be in the midst of a gargantuan alien data exchange, and blissfully unaware of it.” Whatever interstellar communication systems aliens use, it’s probably not very strong in intensity (because, why waste energy, even if you are an ultra-advanced civilization?) — no need to make it stand out more above the ambient noise in the universe than you absolutely have to. In fact, a fully-functional galactic communications system might look not much different than the background static of the universe.
So the fuzz of interstellar noise we see around us might actually contain intentional messages. An important email from Braaaa-AAAK in Zebulon Beta to TCHLET’THCc-9 in Bebulon Zeta might be passing through your living room right now. It is said that when you tune your TV to static, a decent fraction of what you’re seeing is being picked up from space (somewhere between 1% and 30%, depending whom on the internet you believe). Usually this is attributed to the cosmic microwave background, but hell, it could be Q-193 playing a block of Jefferson Starship, too.
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