[nine_k]

Any civilization that realizes that they are not alone quickly stops bleeding RF signals to outer space, or at least learns to mask them as natural.

Chances that two civilizations, if they detect each other, would be on the same level of development are slim. And once a less technologically advanced civilization meets a more technologically advanced one, game is over soon. Ask Aztecs, or Sioux, or pick any other historical example.

[mkr-hn]

You're anthropomorphizing a hypothetical alien civilization. You can only speculate at what ideologies and motivations drive them, and those drives might (for example) involve maintaining military and technological superiority relative to other civilizations so they can make peaceful contact without risk. Imagine a Borg that seeks out and adapts technology and accumulates knowledge quietly while leaving civilizations to continue developing to a point where they're worth talking to.

There's a long history leading up to those events. I find it unlikely another planet will share it.

[nine_k]

There need not be any nefarious intent. Just being around a civilization which is much more advanced is risky: if they operate nearby, they can hit you by mistake or negligence, and whatever consequences are tiny for them may be significant for you. They can just see you as a nuisance and want you to stay sufficiently away, no matter what your opinion is. Think about an anthill near a human settlement. (Don't think about a wasp nest near a human settlement; may be too depressing.)

[mkr-hn]

From Babylon 5, a quote from G'Kar:

>> "There are things in the universe billions of years older than either of our races. They are vast, timeless. And if they are aware of us at all, it is as little more than ants…and we have as much chance of communicating with them as an ant has with us. We know. We've tried. And we've learned we can either stay out from underfoot, or be stepped on."

https://www.youtube.com/watch?v=ZLZW8Deq8vE

[Izkata]

> if they operate nearby

I think my favorite variation on why we seem alone was how Earth exists in a space version of the Bermuda Triangle, called the Veil of Madness, that all spacefaring civilizations avoid: https://creepypasta.fandom.com/wiki/Mankind

[micromacrofoot]

We can’t even go as far to assume that an alien species has anything resembling an ideology! even a brief glimpse of an alien intelligence could be completely incomprehensible to us… we could spend a thousand years trying to decipher a single signal and get nowhere.

People get all worked up about dyson spheres and radio signals, but these are so deeply rooted in the human understanding of things in our tiny tiny slice of the universe.

[Ekaros]

Also even if we got lucky and found AM signal of some alien speech. Would we have any idea how to translate that? My understanding is that we already have human text which we cannot translate. And that has some ties to existing concepts we know of. With truly alien speech we would have zero context or share concepts.

[amelius]

But we could apply GPT-3 and send alien speech back ...

[sph]

Artificial Intelligence is modeled after human intelligence. It's pretty much useless against a true alien mind, unless we imagine aliens as being human-like with a different shaped body.

The beauty of the film Arrival was showing the challenge of interacting with a truly alien language.

[tomcatfish]

Artificial intelligence is modeled after abstractions on the concept of learning, not human thought. We just name things so that they'll be fun and easy to discuss, but (for example) there's no "human neuron" floating around in the matrix math that you see in some popular techniques.

[neuronic]

Can you also apply GPT-3 to understand whales and dolphins?

[CryptoPunk]

The laws of physics impose contraints that will make certain traits common amongst intelligence species and advanced civilizations.

We see a variation of this in convergent evolution across distantly related species (e.g. the evolution of wings).

[trasz]

This is obviously not true. We can’t even define what intelligence means, leave alone somebody’s physical traits.

[CryptoPunk]

It's obviously true that convergent evolution, that produces similar traits across distantly related species, occurs. So your assertion makes no sense to me.

[trasz]

Only when it happens in a similar environment.

[CamperBob2]

The masking is just a natural result of technological development. We can pick up recognizable signals only from civilizations that have worked out electromagnetic theory but have not yet developed information theory.

50-100 years is probably par for that particular course. A very narrow timespan in the grand scheme of things.

[surge]

Even now we've adopted encryption, which appears sufficiently random. How long til all signals are just encrypted by default. Anyone picking up those signals would have a hard time proving they're not noise.

[dotnet00]

Plus our receivers have gotten more sensitive allowing us to reduce transmit power and a lot of systems use much higher frequencies, which are attenuated more strongly in atmosphere. With another 100-200 years of progress it would probably be pretty hard to pick up a radio signal (that isn't intentionally broadcast) at all from the nearest stars.

[bombcar]

Radio signals sent to space unintentionally are waste - so over time you’d expect them to be reduced or eliminated just because you want to use lower power.

[CamperBob2]

Yep, and that's another layer of noise on top of the noise that results from efficient spectrum utilization. Only n00bs transmit carriers or intelligible sidebands.

[lacker]

Even now we've adopted encryption, which appears sufficiently random.

When you pick up an encrypted signal, it's still obvious there's a signal there. Radio telescopes will pick up cell phone signals, for example; that's why there is a radio quiet zone near the Green Bank telescope. You just can't decode the message itself without the encryption keys and algorithm.

[CamperBob2]

As long as it's over the thermal floor within its own bandwidth, yes, it will be obvious that there's still a signal there.

When it comes to interplanetary reception, though, any intelligently-constructed signals will likely be below the noise floor unless deliberately broadcast for our benefit. No coherent carrier or sidebands? No spreading sequence? No chance of detection, whether encrypted or not.

[ithkuil]

Can spread spectrum be easily detected?

[CamperBob2]

Only if it's strong enough to be obvious there's a signal there to begin with. The idea behind SS is to use more bandwidth than necessary, often much more, so that a much-worse SNR can be tolerated.

Many spread-spectrum applications such as GPS use signals that are well below the thermal noise floor by the time they're received. Those signals generally can't be detected without a known sequence to correlate them against.

[lacker]

We can pick up recognizable signals only from civilizations that have worked out electromagnetic theory but have not yet developed information theory.

Really we are more likely to pick up recognizable signals from civilizations that are intentionally trying to contact us. It's possible we could pick up radio leakage, but the signal would be a lot weaker. So there are orders of magnitude more stars that could be intentionally contacting us, vs accidentally leaking a signal. (At least assuming the ratio of the strength of their intentional vs accidental radio emissions is similar to ours.)

[lacker]

And once a less technologically advanced civilization meets a more technologically advanced one, game is over soon.

That is true historically, but historically we weren't at a distance of light years. Given the vastness of the universe, it seems quite possible that by the time we detect another alien civilization via their emissions in the radio spectrum, that civilization has already gone extinct.

[sgt101]

I pick Maori.

https://en.wikipedia.org/wiki/Treaty_of_Waitangi

More controversially I would pick India and China's encounters with Europe. I think it's possible to argue that both India and China were substantially more technologically advanced than the Europeans when significant links were established. India had maths and spinning (also probably better guns), China had silk, porcelain, paper, printing and the compass; also bigger better ships.

[nine_k]

Europeans reached India around 330 BC, in the form of the armies of Alexander the Great. I won't say that India folded in the result; it's rather the Alexander's makeshift empire folded.

There were several meetings of civilizations of comparable level of advancement and strength on Earth. I posit that in space it's significantly less probable, unless we consider these civilizations to also be sisters, all humanoids coming from a common source, like these of Earth.

[tdehnel]

It doesn’t seem likely to me that a civilization with the ability to travel interstellar distances would have any use at all for our planet or resources. I mean, the amount of matter in “empty” space between them and us would be enormous. What would they need our little rock for?

Not to mention the impracticality of communicating with your home planet across several light years.

If you’re basing this off of what’s happened in the past on this planet, without a good explanation as to why that would apply to an alien civilization, I’d suggest that you’re not using a good model. Bayesian epistemology is not a good way to decide what’s true, because new knowledge is created which makes the old models not work anymore.

[GuB-42]

I think that making the signal look natural does not need an intent to hide.

It is simply a result of Shannon's entropy. To be detectable, signals have to be broadcasted and low entropy, the opposite of what we need for efficient communication. A signal that makes best use of its bandwidth would be indistinguishable from noise for someone who doesn't know the protocol, it is also likely to be precisely targeted at the recipient and unwanted emissions kept to a minimum in order to limit interference.

It is already happening on earth as we are replacing loud analog TV emissions with more subtle and better targeted cell phone signals.

[ada1981]

How do you get to speak on behalf of “any civilization”?

[nine_k]

Any civilization that cares to travel to you to make contact is very likely expansionist. Or at least may have some plans on the space where you happen to dwell.

[ithkuil]

It doesn't even have to be likely for it to be a worry.

Imagine there are 1% chances that an encounter with an alien civilization spells the end of humanity.

Or 0.1%, or 0.01%

Now roll that dice for millions and millions of years. It's probably a good idea to switch to communication technologies that don't broadcast your location (and your technological unsophistication). Just in case.