[bhaak]

This is a plausible hypothesis. I don't know if somebody else has already proposed this as a solution to the Fermi paradox.

But it doesn't even need to be encrypted communication. Highly compressed communication is also indistinguishable from random noise.

Of course, only under the assumption, that aliens are using the same technology as we are.

[VLM]

Hollywood IT proposes that people who know nothing about computers all "know" that every computer thing that has ever been invented is trivially interoperable with every other computer thing that has ever been invented on a fast hollywood movie timescale given a sufficiently advanced computer mage to recite some incantations and be treated as socially inferior if its a plot requirement. I think everyone here is experienced enough to laugh at that.

There is an EXTREMELY close analogy in EE / telecom land where people with no domain specific knowledge think all radio hardware, modulation methods, protocols, are all trivially interoperable with each other. Sure... go ahead and try to listen to trunked public service comms using a spark gap era coherer detector, good luck with that. Or try to listen to 60s era SSB voice using 30s era AM receiver. Higher order PSK/QAM is indistinguishable from white noise on a non-phase oriented receiver. This is all before we get into weirdness like trivial line coding, think of old T-1 circuits and B8ZS "scrambling" to get around the clock sync limitations of AMI line coding. Try to use an aircraft NDB receiver on GPS satellites or vice versa in order to navigate. Or connect an accurate clock built to sync to WWVB to the GPS constellation instead, or again vice versa. Telecom, being usually run at the limit of hardware when it was new, is even less interoperable than "computers in general". Given poor interoperation pragmatic results on our own planet, the odds of communicating with space aliens is basically zero, even the odds of detecting are almost zero.

[JupiterMoon]

> every computer thing that has ever been invented is trivially interoperable with every other computer thing that has ever been invented

Isn't this what Perl is for? To my eyes it fits the incantations part of the description as well.

[bhaak]

> Hollywood IT proposes that people who know nothing about computers all "know" that every computer thing that has ever been invented is trivially interoperable with every other computer thing that has ever been invented on a fast hollywood movie timescale given a sufficiently advanced computer mage to recite some incantations and be treated as socially inferior if its a plot requirement. I think everyone here is experienced enough to laugh at that.

Yes, although the details are important.

On a theoretical scale without any time limits and any space limits, anything every invented is interoperable with every other computer every invented. Hollywood is not really wrong there but just tosses out the practical issues because of the rule of cool. And "no time and space limits" is just wishful thinking as every computer has those constraints.

Of course, trying to hook up a Mac to a alien computer for transferring a computer virus is not impossible. It's just highly unlikely to succeed within a few hours of preparation. But it would have made a less entertaining movie. ;-)

[tomphoolery]

I'll just take it in my ready room.

[blacksmith_tb]

I am far from a HAM or radio pro, but doesn't SDR actually make some of this possible? Not using ancient sets to listen to modern signals, but using one set of kit to rule them all, as it were?

[VLM]

Only kind of. If someone hasn't seen fit to write the code for a 240 hz morse code filter, you don't get one. Or a very advanced AGC filter. Those are "easy" because you could modify an existing set of code, assuming open source application. GNUradio has a compile/run architecture although you can build rather highly configurable real time systems so it's "close" to programming in real time.

Harder is something like "digital radio monodiale" which aside from having an unfortunate acronym is a digital shortwave voice modulation scheme... without having the specs in front it would be very hard to decide where to start. There are military intelligence people who do exactly this stuff with captured enemy signals, given an enormous head start of knowing the rough technology level of the other side and maybe some stolen documents. Still its not easy for them. A good analogy would be imagine a radio intelligence officer in WWII heard some 8VSB over the air broadcast TV from 2015... honestly I think you'd end up with question marks for at least 50 years trying to figure that signal out in 1940.

Right now, perhaps we are getting a 40 dB below the noise digital data signal from space aliens. Without any idea how to build the specific demod, we're going to get nowhere, and a level that low below the noise floor will not show up on any normal waterfall so we'd likely miss it.

Existing modes tend to reflect hardware ability. So some gear some of the time is stable enough to use WSPR modulation which is an ultra low bandwidth digital mode for HF (shortwave)... some gear drifts in frequency too much to use it, today. Oscillator stability can be improved to make it work, but replacing the IF stages with A/D converters won't do it, takes more than just doing demodulation in software with SDR instead of in hardware to fix the root frequency stability problem. Its possible space aliens modulation method would assume close in phase noise or IMD performance beyond 2015 capabilities, because for them its trivial star trek dilithium crystal stuff or whatever, but we're not going to invent the noise free monochromatic oscillator for another 150 years or whatever, so the front end performance of our radios wouldn't be good enough even with a preprogrammed SDR on the back end to demodulate. Another example, we don't have the technology today or the legal framework to do "real" beyond ultra wide band RF work, but there's no reason to think space aliens wouldn't.

[jahnu]

What if they just use a very focused transmission technique instead of blasting a signal in every direction?

[bhaak]

Then we have almost no chance to detect it anyway unless we almost spot on between sender and receiver. But this is a similar constraint to detecting exoplanets with the transit method. Star, planet and Earth have to be in one line for this method to work.

We are detecting lots of potential planets with this method, so if technical alien civilizations were as abundant as planet we should have detected a few already. ;-)

BTW, we ourselves stopped to do the "blasting a signal in every direction" like we used to 50 years ago. With fiber optics, satellites, and other modern technology, we are leaking much less electromagnetic radiation. The chance of another civilization picking up us is shrinking.