In a recent conversation with National Security Agency whistleblower Edward Snowden, astrophysicist Neil deGrasse Tyson asked about communication with alien civilizations, and how such messages might be encoded.
In any advanced civilization, there is only a “small period in the development of their society when all of their communications will be sent via the most primitive and most unprotected means,” Snowden said. And that if we pick up signals emanating from that civilization’s homeworld, such as television shows, phone calls, or satellite communication, it will most likely be encrypted because “all of their communications [would be] encrypted by default.” Because of how encryption works, those encrypted messages would be “indistinguishable to us from cosmic microwave background radiation.”
Snowden was right about encrypted content looking like noise, but he was wrong about what scientists can tell by looking for alien metadata. Whether or not aliens use encryption, we can tell the difference between signals sent through space using transmitters and natural sources of radio signals — such as the radiation left over from when the universe first cooled down enough for photons to decouple themselves from the rest of matter, shortly after the Big Bang.
The media coverage of this conversation has mostly been abysmal nonsense (“Snowden says aliens could be trying to get in touch right now” on CNET, “Edward Snowden Has A Depressing Theory About Aliens” on Huffington Post, “Snowden Re-Emerges from Russian Isolation With Alien Encryption Theories” on Digital Trends) with some sprinkles of evidence-based coverage from Live Science, also carried by Scientific American.
Today I’m going to dive into the science of searching for extraterrestrial life in our galaxy, communicating across interstellar distances, and the role that encryption and information theory play in all of this.
Are aliens real?
“If you want to think the Earth is the only one that has intelligence, there’s no way to prove that that’s wrong,” says Seth Shostak, senior astronomer at the SETI Institute, a scientific and educational nonprofit devoted to the search for extraterrestrial life. “But that’s a really remarkable statement that suggests that there’s something extraordinarily unusual about this world. And that strikes me as maybe not such a reasonable assumption.”
We have never found any direct evidence of alien intelligence, but personally, I’m betting on the aliens. Our home galaxy, the Milky Way, is a big place, and as far as we know, all it takes for life to evolve is the right environment. Exoplanets that could support life are extremely abundant in our galaxy. “We believe that the number of planets out there that could be habitable, just in the Milky Way, is tens of billions,” says Shostak. “It might be as many as a hundred billion.”
In 1952, Stanley Miller, under the supervision of Harold Urey, conducted a groundbreaking experiment that proved that you can take a primordial soup of the basic molecules that made up Earth’s pre-life environment (water vapor, methane, ammonia, and hydrogen), add some electricity — the same stuff that comes from lightning — and you get the amino acids that are a main component of the stuff of life.
Once life exists on a planet, given enough time, it might evolve the kind of intelligence that will let it communicate with radios, like it did on Earth.
Are aliens trying to communicate with us?
You might think browsing the web with the privacy-enhancing Tor Browser is slow, but the latency of bouncing your signals around Earth a few times is nothing at all compared to interstellar communication — sending signals between the stars. If aliens send us a signal, or if we’re sending a signal out to aliens, the signal will only be moving at the speed of light, the fastest speed that nature allows.
Map of the Milky Way.
Image: NASA/JPL-Caltech/ESO/R. Hurt
If aliens in that star system right now are monitoring our star for evidence of intelligence, all of the signals they are receiving from humans left Earth in the year 1015. At that time, the Vikings had recently founded small settlements in North America; the Byzantine Empire was conquering the First Bulgarian Empire; and Iraqi scientist Alhazen, regarded as humanity’s first theoretical physicist, wrote the Book of Optics while under house arrest in Egypt.
Communication with alien civilizations should be possible as long as we can receive their signals and they can receive ours, however it will be very slow. Proxima Centauri, our nearest stellar neighbor, is over 4 light-years away from us. If we’re lucky enough to find an alien civilization there that’s alive and detectable at the same time as our civilization is looking for life — and that’s an enormous, unlikely if — then it may be possible to communicate with them. Sending a message and receiving a response will take over eight years, though, so it might take many human lifetimes’ worth of communication before coming up with a common language that we both understand.
So are aliens trying to communicate with us? If they are, we haven’t noticed yet. Discovering the metadata — the fact that aliens exist and are using radios to send messages — is the first barrier that we must tackle before we even attempt to look at the content — what the aliens are saying.
SETI is monitoring for metadata, not content
Can we tell the difference between messages sent from extraterrestrial civilizations and natural sources of radiation? “Galaxies make a lot of radio noise. Quasars make a lot of radio noise. Black holes makes some radio noise, and centers of galaxies,” Shostak told me. “All these things make radio noise. But it’s different than a transmitter. A transmitter tends to be on one spot on the radio dial. It’s a narrow-band emission.”
The Allen Telescope Array
Photo: SETI
In fact, in the process of looking for evidence of alien metadata, the content itself, whether it’s encrypted or not, gets destroyed. Shostak says that SETI’s radio experiments “average the incoming signals, if there are any, for at least seconds, and usually for minutes,” which will lose any information in the message. We would need much bigger instruments than we’re currently using if we want to record the content of signals from interstellar space.
“It’s like the ‘on the air’ sign you might see in a radio studio doesn’t tell you what the content is,” Shostak explains. “The content might be Top 40, it might be talk radio, who knows what it is? But you at least know they’re on the air.”
Indistinguishable from random
Scientists aren’t going to confuse an encrypted signal from aliens with cosmic microwave background radiation, or other natural sources of radio noise that we understand, because they’re searching for how the signal was transmitted, not what the signals says. But once we start looking at the content of signals from space, Snowden was entirely right when he said, “You can’t distinguish a properly encrypted communication […] from random noise.”
This property of cryptosystems, that encrypted messages are indistinguishable from random data, is known as ciphertext indistinguishability and is necessary to prevent things like the known-plaintext attack from working. The Nazi Enigma machines were vulnerable to known-plaintext attacks, which is how Alan Turing and his team at Bletchly Park defeated their encryption during World War II.
Ciphertext indistinguishability only refers to the scrambled message. In practice, you can often easily tell if a piece of information is encrypted because of its protocol. For example, if you see a block of random-looking characters that begins with “—–BEGIN PGP MESSAGE—–” there’s a good chance that’s an encrypted message. But without having the right key, you can’t actually confirm that the scrambled message part of it isn’t just random noise.
Most everyday encryption loudly proclaims not only that it’s encrypted, but exactly how it’s encrypted. Otherwise, legitimate recipients who hold the decryption keys won’t understand how they’re supposed to decrypt it. This isn’t true of deniable encryption, and it also wouldn’t be true if we recorded a piece of an encrypted message from aliens mid-stream, failing to record any protocol information associated with the message.
Check out this short video from Khan Academy‘s free online cryptography class explaining one-time pads, which Snowden describes to Tyson. One-time pads are the only type of encryption that have been proven to be perfect and uncrackable so long as they’re used correctly and the attacker cannot steal the key.
When we do receive an alien signal, how do we know what it says?
Picture this: You’re at the headquarters of the SETI Institute in Mountain View, California, USA, Earth, Solar System, the Milky Way. It’s the hopefully-not-too-distant future, and for the first time SETI has just recorded the content of a message from an extraterrestrial civilization. We are not alone.
Now that you have an alien message, how are you going to know what it says? Is it encrypted, or is it perhaps an alien Golden Record, full of information about their history, culture, and technology? We don’t speak their language, and we have never communicated before. All we have is a stream of data to work from, but we know that it came from extraterrestrial intelligence.
In order to learn how much information is in the message, you can do “a statistical analysis on the signal and see if it has what’s called low entropy,” Shostak tells me. “If it has patterns in it, if it has repetitions in it at all, even though you don’t understand a single word of what they’re saying, you can determine that there’s information in it.”
This measurement of entropy is similar to how you might measure the strength of a password. Entropy is random noise. Entropy is essential for encryption — for example, if you’re encrypting something with a one-time pad, you want your key to be made of pure entropy, to have zero patterns, to be entirely random and uncertain. Information resolves uncertainly. A message that contains information will be at least somewhat predictable.
If you have 10 minutes to spare, watch this intriguing video from Khan Academy‘s free online information theory class. It describes SETI’s early work in measuring the entropy of signals by recording baby humans in their “babbling phase,” when they’re just learning to speak, and comparing that to the entropy present in adult human speech — and also comparing this to baby and adult dolphin communications. Based on how much entropy is in dolphin communication — that is, how much of it is entirely random versus how much of it is predictable — it appears that dolphins, like humans, communicate in a structured language. Without knowing anything about the aliens who sent us this signal, you can tell if their message, too, is structured.
Of course, if this message is properly encrypted — if it’s an alien television show or phone call from a civilization where everything is encrypted by default — the content will be indistinguishable from random, which means it will appear to be full of entropy. Although we might be confident that the signal was produced by aliens, we wouldn’t be able to glean any information from the content of the message.
“I don’t doubt that they use encryption technology, at least for their internal communications,” Shostak told me. But if aliens were trying to communicate with us, there’s no way that they would encrypt that message. Instead, they would use “anti-encryption,” encoding their message so that it’s as easy as possible for us to understand. “They would try and make it simple,” Shostak says. “They would send you pictures.”
Encryption is only useful if the recipient can decrypt the messages. Earth scientists listening to the stars can’t make sense of a random signal from space any more than they can break the encryption of a one-time pad — they simply can’t, because it’s not possible.
Caption: Radio telescopes of the Allen Telescope Array are seen Tuesday, Oct. 9, 2007, in Hat Creek, Calif.
Update: Changed wording of Live Science / Scientific American article links to point out that they’re the same article.
In some ways, you could say that communication is already encrypted online without seeing or hearing from the person saying it. Then there’s the environment and the moment that something is being said that affects understanding of how something is being said.
Online you’re always taking a message out of context. That’s not to say you cant have some of the most surprising misunderstandings with people you should know the best.
Thinking of this country, there must be a speed of society or something compared to the speed of light idea, where the results or echoes of various group efforts from tens to hundreds of years ago are what we exist in but the core of what created it can either be significantly altered or has been gone for some time. That could either be a positive or negative thing. I suppose.
Alien communication is totally telepathic.
I agree – this is natural, for when a race develops their technology at the same speed as their spirituality, then there’d be no need for telephones. Since not many are there, I’d suggest using scalar-waves for transmission! ;)
They are faster than light – Einstein lied on purpose – and this is still being taught in schools
(rather look at http://levashov.info/English/index-eng.html
– he [Nicolai Levashov] decrypted the whole octave we currently still inhabit))
and don’t have open “force lines” (flux) so they really are hard to detect, let alone decipher… xP
http://www.k-meyl.de/go/Primaerliteratur/Scalar-Waves.pdf
Maybe we’ll get our hands on this technology – before we are able to communicate telepathically – who knows? x)
There’s some recent technical work in the area of interstellar communications that should inform this discussion, although it hasn’t yet. The basic result relevant to this article is that narrow-band communications is not efficient for interstellar communications. (Contrary to the repeated assertions of 24b4Jeff otherwise.)
It’s straightforward to show that with many wide-band modulations the total signal power present in any single narrow bands is beneath its noise floor. Supplementing ciphertext indistinguishability, this is a form of signal indistinguishability. Whether they _want_ to be located is rather another issue, but it seems the case that if “they” don’t want to be seen, they won’t be seen.
End-to-end interstellar communication system design for power efficiency
David G. Messerschmitt
http://arxiv.org/abs/1305.4684
The full paper is here: http://arxiv.org/pdf/1305.4684.pdf.
A result that applies to much more than interstellar communication, as is well known! Indeed, the high signal noise ratio obtained with FM broadcasting that I mention earlier is partly the same thing.
This work was partly supported by the SETI Institute by way of NASA. Among other things, it explores and proves the concepts behind the idea that several have expressed here that aliens are not communicating with narrow band signals that can be detected. It does this on several levels of accessibility
As someone heavily involved in radar work, I like to examine new possibly relevant ideas. The idea of transmitting burst short bursts sparse in time and frequency, but very high in peak power for communication is interesting, but I think he way underestimates the difficulty in transmitting such high power pulses with a well controlled waveform h(t).
Example. From the box on page 74:
Radars do not invariably transmit short bursts of energy. The premier example is the Arecibo S band planetary radar: it is CW (continuous wave). Why? Precisely to avoid having to transmit very high peak power short pulses. The usual signal transmitted is a (repeating) pseudo random code. When received and decoded, this looks as though a sequence of short very high peak power uniformly spaced pulses had been transmitted, as long as the target object rotates slowly enough so that coherent addition takes place. A code might be over 4000 bauds long, meaning that to achieve the same average power P the peak power of the short pulse equivalent radar would need to be over 4000 times greater than the peak power of the current radar. Not only would this be impractical to build, it probably would blow out all the receiving equipment as well as its own control system from signal leakage.
Even pulsed radars use codes in order to appear as if transmitting a shorter higher power pulse. The other high power Arecibo radar, the 430 MHz pulsed radar used for ionospheric incoherent scatter, is used with Barker codes to increase the apparent power by 13 times, and with other types of codes that allow an effective increase of up to hundreds of times.
This short burst of energy with a carefully controlled waveform h(t) is a very difficult problem at our technological level. Maybe it can be solved, but I do not think that the proposed technique is quite so obviously the right one.
Did you hear about the big headed neutrinos? Massive. Very oscillating, Mr Spook. Blow me up, Nobel.
Snowden’s message of hope.
For me, the most important part of this discussion is entirely missing: the Drake Equation. It estimates the number of active, communicative extraterrestrial civilizations in our galaxy. Even before the discovery of a couple of thousands exoplanets, the Drake Equations was extremely troubling. The exoplanet discoveries make it even more so.
The problem is that before Snowden’s idea, the only reasonable explanation for why we hadn’t heard signals from alien civilizations was because all high tech civilizations self-destruct after a few hundred years so there are no active civilizations in our neck of the woods. Even though there are many civilizations throughout the galaxy, the odds of two civilizations being close will be extremely small if all such civilizations are short-lived.
Snowden’s idea is a beautiful and elegant way to get around this discouraging conclusion. Instead of more advanced civilization self-destructing, they merely switch to communication modes that we can’t detect. If you want to argue against Snowden’s idea then I think you should also come up with an explanation for why we have not yet heard signals from other civilizations.
The Drake equation is the product of several probabilities. Modest overestimation in the individual factors results in a large overestimation of the product. Maybe we have not heard from such civilizations because there just are not so many.
There are plenty of scientists who think that the guesses Drake assigned are too high. But who knows? Maybe discovery is just about to happen.
Mike is exactly correct about the Drake equation. If – and only if – we were able to accurately estimate the individual probabilities, we would be able to make a reasonable estimate of the number of evolved civilizations in the observable universe. But virtually all the probabilities in the equation are pure speculation. So the numbers can be wildly different from the prediction.
My view is that the Drake equation is just an attempt to chain all the factors together, rather than a predictive tool in the true scientific sense. But since it captured the public imagination, it has achieved a stature akin to fact.
Incidentally, our view of the universe has changed radically during the past fifty years. All of the discoveries have led to a picture of a much more hostile environment than was previously conceived. And that is part of the reason why many think the Drake numbers are overly optimistic.
All that said, it seems inconceivable that in the vastness of the universe, we alone have evolved to our present state, and that we are the most advanced life form.
Still, Snowden’s idea mixes well with the berserker scenario. Why are alien civilizations sending signals meant to be indistinguishable from noise? Maybe they’re afraid of being detected by the wrong entity…
Encryption has essentially nothing to do with it. All of our radio communications are becoming increasingly broad band and noise like. It’s all about efficient use of transmission power and radio spectrum. Efficient digital encoding and wide-band spread-spectrum signaling are taking over. Narrow band signals are going away. If we want to be heard by aliens we should be sending deliberately design beacons.
Here we go again.
NSA and other Alphabet mafia with black projects and black money claiming they need lawless boundaries into every computer & electronic communication on the entire planet because .. there *might* be an alien in correspondence.
“Because aliens” is an existing obscure citation as reason for all sorts of sordid overreach, including but not limited to, closed door Congress hearings on Intelligence and the secret Kafkan courts. If our clandestine policy is being crafted by Alien cult leaders and Nazi occult leftovers, it’s time for a division of dogma & dark state. It’s going against citizen & human rights.
For sake of argument, if an alien is going to talk to anyone they are going to need to make the law above board if the Alphabet mafia intends to prosecute anyone for the crime of ET correspondences. Whether or not there are actual aliens, unfortunately, is irrelevant. 1st Amendment holds up as freedom of assembly and speech .. with an alien or your teddy bear.
For now, the US government across the board has been throwing people into jail pre-trial detention without a charge. After the first ~72 hours given time to file charges, that’s an abuse of human rights and legal due process. Clandestine agencies have done this to a lot of people who have witnessed the intergalatically-disposed-crimes-against-humanity conducted by contractors. It may be tough to verify but it’s plausible. They can’t silence all of us.
Unfortunately, there’s no aliens around to conveniently blame for US public policy in clandestine detention program. There’s also no alien grievance dept. for you. It’s just black arts policy.
If you don’t like it, BRING THE LIGHT.
First off, you are confused about what entropy is. Whether we are talking about information theory or statistical mechanics (and thus thermodynamics), entropy is a measure of disorder. It is decidedly not random noise. In an ideal cryptological system, the clear text, which has different letters, pairs, triples, and so on occurring with different probabilities, will be transformed into a sequence in which all symbols, pairs, and so on occur with equal probability, denying the interceptor the ability to easily decode the message based on the characteristics of the language.
On to the next thing. A radio communication system starts with a local oscillator (LO) that produces a sinusoidal wave that is then modulated (multiplied) by the information. The resulting signal is then amplified and coupled to the environment via an antenna. The transmitted signal is at a level that is higher than the background, and this enables us to detect it even if we are completely ignorant of the modulation technique or information content. Whether or not we are able to demodulate the signal, we can detect its presence by scanning over frequency; when the frequency to which we tune matches that of the transmitter LO, we will note an increase in the output of our receiver relative to nearby frequencies outside the signal band. (The signal bandwidth is determined by two things: the information rate and the modulation type. Typical signal bandwidths are on the order of a few percent.) Even though the signal itself may be encrypted perfectly, it is still going to be band limited, allowing its detection.
Now, in certain kinds of systems, called Low Probability of Intercept (LPI) an attempt is made to make the very detection outlined above more difficult. This can be attempted by several means, such as frequency hopping, where the LO frequency itself is changed from one value to another at short time intervals. Of course there are more sophisticated ways of doing this, but the key point is that such systems are of limited effectiveness, often entail operational difficulties, and are rarely used.
That is only one way to do it. Think instead of multiplying the signal by a “random” sequence that has a bandwidth much wider than that of the signal. The resulting signal, when transmitted and then received, can be below the noise level and still recovered if the “random” sequence is known at the receiver. That is kind of the essential idea behind spread spectrum.
True, but I was referring to ordinary communications. As I post below, spread spectrum techniques result in expensive systems without other advantages. For that reason, only groups who are able to operate without practical constraints would even consider using those technologies.
Spread spectrum has been around on earth for a couple of generations now, but its use is very restricted. Almost all of our communications use bandwidths per the Nyquist criterion, for the very simple reasons that they are most robust in the information theoretic sense, and optimize the performance to cost ratio.
Even old fashioned FM radio uses a bandwidth that is wider than implied by Nyquist criteria. It is wide band FM band modulation in which the frequency deviation combined with the spectral bandwidth of the source produce a signal that is substantially wider than the source alone.
How do Nyqvist criteria apply to modern digital communication, such as smart phone? Only very indirectly. For one, thing, everything is compressed, so bits rates are much lower than the “naive” rate. But on the other hand, the smart phone does low resolution video, and so it is really pretty fast for such a small low power thing.
But the issue here is this: given all the cell base stations and all the phones running digital communication at once, if you were to receive the sum total of all such signals emitted by earth could you distinguish this from noise from far away? I really doubt it. Yes, there are set frequency bands where this occurs, so you might be able to determine that there is more power coming from some bands than others, but really, the whole spectrum is filling up, and it will not be too long until it is all full with certain excepts granted for radio astronomy, experimentation, etc. Good luck determine what is from afar!
But the way, there are still some moderately powerful signals leaving earth regularly that would be easily identified as unnatural. For example, what happens if you point a high gain antenna at the moon and receive in the neighborhood of 430 MHz? What you receive is a number of pulsed radar signals. Most are probably from ship radars (military, maybe others); they transmit most of the power horizontally, but radars a quarter of the way around the earth from where the moon is overhead would be pointing approximately towards it part of the time as they scan around.
Modern cellular and wifi networks use spread spectrum techniques to allow a lot of devices to share the same chunk of spectrum without too much interference, so I don’t think you’re right about the claim that this is rare.
What I don’t know is whether this would make it inherently harder for radiotelescopes to detect the signals being used. It seems like it would, but I’m not any kind of an expert.
Intelligent life on earth, that would be news. Until now no one has detected that.
Might be that out there in the mighty universe there is an intelligent living being,
poor creature, being utmost alone.
Roger that! Check this out: http://www.studio360.org/story/168264-theyre-made-out-of-meat/
quote”Intelligent life on earth, that would be news.”unquote
Indeed. If there was, it wouldn’t be broadcasting their presence in a universe full of things that might eat it. :)
Conversations with off world intelligences are an everyday occurrence for us, take a look at http://www.elementalbeings.co.uk .
I’d love to read the physics paper on how you manage to get around the light-speed barrier. Einstein-Rosen bridges? Quantum entanglement? You must have an enormous science budget, and quite an impressive lab.
Micah, I was wondering while reading your very interesting article, what if aliens didn’t use single band transmissions? If I were trying to be clever, I would use a randomly shifting sequence of thousands of bands, maybe millions, for each bit of data, and only a recipient that knew the proper band sequence shifting pattern would be able to receive the message. It would seem like background radiation to anyone who did not know the sequence shift. As long as transmitters and receivers could handle the spectrum efficiently, there would be no problem in communicating this way.
I’m not an astronomer nor an expert on radiation. But it appears to me that any artificial signal, whether it’s narrow-band, spread-spectrum, or anything else, won’t look like natural radiation. I could be wrong though. Scientists at SETI would be the ones to ask.
If extraterrestrials want to hide their signals from anyone listening in (like SETI) I imagine they can do this easily enough by using highly directional antennas, or lasers, to communicate, so that the only receiver that the signal ever reaches is the one that it was aimed at. And if it’s a signals from one part of their planet to another, they could use fiberoptic cables like we do on Earth for some of our communications, which don’t broadcast information into space.
Or an electrical engineer who does communication work.
Most electrical engineers don’t study which astronomical bodies naturally generate radiation that can be picked up from Earth using radio telescopes, and how to tell it apart from artificial sources of radiation.
But an electrical engineer who studies communication research knows the properties of signals used in communication. That is essential knowledge in order to understand whether an alien signal can be distinguished from natural emissions.
Micah, you are completely wrong about this. As other people have tried to explain to you, it is now fairly easy to spread a signal out so the signal level is well below the noise level. One example of this is sending acoustic signals thousands of miles under water in the oceans. When the signal level is less than the noise level (natural radiation) then it will look identical to the natural radiation unless you have the key to unlock it. Snowden was right about this. You ASSUMED aliens would be using the same crude narrowband technology we are using now. Scientists at SETI may not be the ones to talk to about this because their continued funding is based on ASSUMING alien signals will be narrowband. The metadata argument makes no sense because it is based on the assumption of narrowband transmission. You are 100% assuming your conclusion and then using that to say Snowden was wrong.
The whole point of spread spectrum is to make the signal appear noiselike. In a narrowband matched filter receiver, a narrowband signal can be integrated up over time (I know of instances where integration times of hours duration were used to track extremely narrowband signals) to achieve very large processing gains. If one spreads the signal sufficiently the signal energy per unit bandwidth becomes comparable to the background noise, and only through coherent integration can it be extracted. That requires prior knowledge of the transmitted signal frequency and phase at every moment, something akin to a cryptographic key.
Also, highly directional antennas provide high gain, and usually sidelobe levels that are above those of an isotropic emitter. So use of directionality can actually enhance detectability under some conditions.
Unless the time space continuum problemo is solved, no one’s going very far past mother’s apron strings, AT&T. I am not going to call back if this is how long it takes to get in touch. Those folks who go fast sure slow down their wastes of dwell time, don’t they? I say get on board the Wells Fargo, folks. That’s the only way to stay connected, Bill and TED. Be there when they get it.
You didn’t get ANY of my musical jokes? Unreliable Musical Service.
I thought the Weather Report decoder ding was worth a few snorts, Oscillators. Sid this only get passed the sensors since I might have misspelled my address? I’m not perfect, that’s for certain, simulators.
I think I’m relegated back to silo service since I refuse to stay seated in this bomb shelter, Titans. But I am truly yours and for always at the same ID, right, GCHQ? I don’t leave home with stupid pwn. But I am going to make a purposeful mistake just this once so I can assume I’ve been sent to my room, and GCHQ isn’t fucking with me. See? If so, you better stop complaining about suppressed signals, patchjobs.
Speaking of random noise..
I would expect SS to claim that alien communications (with each other) would use a transmitter bandwidth sufficiently narrow for it to stand out from the background noise because that is the only way he could detect this kind of communication. (Of course, if aliens are intentionally trying to communicate with a civilization such as ours, they would do this in order to enhance the probability that we would detect it.)
However, there is every reason to expect that aliens would use other techniques, such the so called spread spectrum technique mentioned in an earlier comment. Such communications have a low probability of detection.
Furthermore, even without spread spectrum, digital communication can be much harder to detect that earlier analog communications just because of the efficiency of the modulation (manner in which information is encoded in the transmission). For example, US analog TV transmissions put a significant amount of power into a “carrier”, single tone used by primitive receivers to enhance detection. But now it is mostly digital, and power is much closer to uniformly spread across the allotted bandwidth. This would be much harder to detect from a distance.
In the context of detecting the LGMs, this is bullshit. The non-random part that “explains” the message can be very small compared to the apparently random data. When detecting weak signals from very far away, you would not be able read such explanations. How do we know this? Consider this, from the article:
SS is saying that they cannot read the message that “explains” the message, but only detect certain statistical properties of the whole transmission, the most basic, for example, being its bandwidth.
Thus an advanced form of communication used by the LGMs among themselves, encrypted or not, is not distinguishable from random noise unless close enough so that the signal is strong enough to allow the details in individual segments to be examined closely. Even then we could easily miss “markers” that explain it since we have no idea how the LGMs would accomplish this.
Encryption can be a language unknown to one trying to break encryption, such as Indian code talkers in WWII.
Breaking such a code has, in the past, required a Rosetta Stone.
Speculation about the methods of communication that alien civilizations might employ is intriguing, yet mankind has only been manipulating a small fraction of the electromagnetic frequencies that comprise light for a little more than a century. Because there are star systems far older than our own, it is not unreasonable to surmise that an ancient extraterrestrial civilization could be manipulating nature in a way that allows for the transmission of information across galaxies without significant degradation. Zero point energy research alone may result in methods to manipulate the very fabric of time/space across great distances. So, too, quantum entanglement poses some unique possibilities as well.
“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”
? Isaac Newton
Fascinating article, thanks.
“A transmitter tends to be on one spot on the radio dial. It’s a narrow-band emission.”
That is part of the assumption that Snowden was challenging. By definition, it is not true of spread-spectrum communications.
Here is where Snowden errs. Spread spectrum accounts for a miniscule portion of the communications traffic on earth, and there is no reason whatsoever to use it unless you want to reduce the probability of intercept. The systems offer no performance advantage whatsoever over matched systems (where the signal bandwidth is matched to the information bandwidth), and are more expensive – often by orders of magnitude. Moreover, they are inappropriate for most transmission media, owing to dispersion effects. These fundamental properties are not going to be any different on the other side of our galaxy, and so we can effectively assume that virtually all the RF energy emitted from some alien world will be of a narrowband nature.
I admire and respect Ed Snowden, but he is certainly not an RF engineer.
Snowden was not assuming aliens with more advanced technologies would have our current technology limits. Reducing the probability of detection and interception may well be highly desirably properties in the future. It seems to go hand and hand with the desire for encryption. Sixty years ago many of the forms of communication and encryption we routinely use now would have been completely impractical and orders of magnitude more expensive than state of the art technology back then. You seem to be assuming that aliens with technologies more advanced than ours would not have technologies that are more advanced than ours. An assumption like this on your part is not an error on Snowden’s part.
Over 20 years ago we were transmitting wideband acoustic signals thousands of miles under the oceans. The wide bandwidth helped beat back severe multipath dispersion. The dispersion would have destroyed any narrowband signals. I wrote a paper about this.
Doing things more privately and more discretely than we are now may be impractical today. That doesn’t mean it will always be so. Technology keeps getting cheaper. The needs for privacy and discretion are increasing.
All this discussion mixing the concepts of security and covertness is leading us astray of the central points. If we assume that an alien civilization uses power lines to transport electrical energy, then they will be radiating very large amounts of narrowband RF at the frequency of their AC systems. If they have broadcast communications (e.g., radio and television) they will be radiating prodigious amount of narrowband energy at other frequencies. And if they are actively attempting to elicit communication from life elsewhere in the universe, they will be radiating narrowband signals in the direction of candidate systems. Also, they will be listening.
If on the other hand, they do not want to be detected, then we will not detect them. The space loss term in the link equation is simply too large to be overcome by any conceivable signal processing gains. We are talking about millions of dB here!
Most digital communications today can be described as spread-spectrum; so can FM radio. The reason for using the technology isn’t only LPI but also resistance to noise, jamming, spoofing, multipath and crosstalk. It’s a superior technology and will be used increasingly as signal processing becomes cheaper and older waveform standards are phased out (the main factor holding it back). Early radio didn’t use it because simple circuits can only produce simple, narrowband signals. It is also the RF equivalent of encryption. And it can ultimately make signals look indistinguishable from noise.
So, Snowden is exactly right; there is no reason to expect we would see extraterrestrial signals unless they wanted us to see them. SETI folks are continuing a search founded on the assumption that they are looking for narrowband signals, and they have to stick to that assumption since it’s all they could hope to see.