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The notion in the article is great fodder for a novel, but I think this perspective is sound. You've said almost as much, but I think there's a good argument to be made that societies which undergo an industrial revolution either collapse the ecology that supports them, or survive it by maturing and expending energy on QoL for the whole biosphere. In either case the window of time for making a cosmic racket is fairly small. It could just be that interstellar networking is generally quite rare.

Personally I think the same tendency which makes us so enterprising and leads to thinking up 'paradoxes' like this, is the same thinking that makes us not-so-certain to pass the ecological test.

The argument I've heard most is that a civilization only has a short time where it's blasting broadcasts into space willy-nilly, before improving their tech and making it more efficient, thus dramatically lowering its potential to be discovered by its stray broadcasts.

I wonder if all habitable planets with simple life would have the conditions necessary to create oil and coal. Love them or hate them, they still power most of our civilization. Imagine if we did not have a gas/coal readily available? We refined nuclear as a weapon first. The need for a nuclear bomb might not arise in a power constrained civilization and thus go much long before being discovered (if ever)

I'm sure someone has simulated that but it appears highly likely that a planet with plants (or any carbon based life) will at some point "generate" fossil fuels.

And maybe, if we hadn't found oil, we would've come up with more efficient ways to use electricity generated from renewable sources. Would've taken longer but we could've made up for that later in the process. Batteries were known at the time of the oil revolution and electricity from hydro & wind were also known.

or maybe we wouldn't have bothered with electricity because of a lack of energy reserves.

There's plenty of hydro energy available. Not having fossil fuels would've shifted where we settle. Texas would likely be less economically successful compared to Canada which has plenty of hydro capacity and hydro reserves. Long-distance electricity transportation would've come up later making ACs less popular. In the US, that would've favoured the north heavily over the south. In Asia, Singapore would've never been as successful (they say themselves that success came with the AC). Maybe China would've become dominant much earlier.

That's a nice thought experiment. Our capability of harnessing energy from renewable sources (but not electrical energy) covers 3,000 years already: sailing ships and windmills. By the time magnetism and later electricity were discovered, we already had wind-powered propulsion, milling, and water drainage.

What made them impractical for industrial uses (the first applications for coal power were steam-powered textile mills iirc) was the same issue we have with solar and wind today: output is dependent on external factors that we can't control. Coal became valuable exactly because it was the first controllable energy source.

It's hard to imagine us making the same amount of progress without an ever-present energy source (coal caches, fuel tanks, and the electrical energy grid). And it's hard to imagine why we would construct an energy grid without a prior ever-present energy source. Looking at our current means of energy storage, it seems that only hydro-electric storage is a viable option if you discount fossil fuels.

So without fossil fuels, I think an electrical grid could have originated only in very specific locations: lots of wind power, and a natural basin to be converted into a reservoir with relative ease. We would have seen massively different industrial sprawl in such a scenario, and I wonder if such a situation would ever give rise to a truly continental electrical grid like we have now.

Apart from hydro power as a very steady energy source, we also have thousands of years of history of using another arbitrarily controllable renewable resource: wood. We even processed wood to turn it into coal. And in the absence of trees we could have been burning other plants.

Granted, the amount of wood you can extract within a decade from an area without turning it into a desert or grassland is limited, but in the last 400 years we turned our focus more and more on sustainable forestry and as a result got quite good at using wood in a renewable, carbon-neutral way.

I suspect too that our usage patterns for wood are "subsidized" by the availability of coal. There was just an article here the other day that talked about how deforestation in Ethiopia (for use as fuel) has had dramatic ecological impacts up and down the Nile.

IIRC Coal caught on in England in part because deforestation had gotten so bad that they needed another source of fuel to run industrial engines

The potential for nuclear as a power source was well known.

If you read the Farm Hall transcripts [1] there are several conversations in the vein uranium engine vs uranium bomb; they all knew a uranium engine was possible and was the original research, but the war drove them to a uranium bomb.

From section 5: "History will record that the Americans and the English made a bomb, and that at the same time the Germans, under the HITLER regime, produced a workable engine."

[1] http://germanhistorydocs.ghi-dc.org/pdf/eng/English101.pdf

Or everything they’re broadcasting is encrypted, even the metadata and framing bits. With spread-spectrum, directional and burst patterns to mitigate side channels and jamming.

So the alien communications just look like noise to us here on earth.

We’re nearing the “everything encrypted” point ourselves, and we would certainly be very careful about emissions control if we ever got ourselves out of the solar system.

Presumably any other advanced civilization would have had its own paranoid Sci-Fi literature/film/whatever, and would behave accordingly.

> With spread-spectrum, directional and burst patterns to mitigate side channels and jamming.

without regulatory constraints, our own use of radio would've required that rather quickly.

i think it's entirely possible another civilization simply never would've used radio at beyond a hobbyist level without the use of spread-spectrum heavily-coded techniques.

> Presumably any other advanced civilization would have had its own paranoid Sci-Fi literature/film/whatever

i don't think it's a given that another species would even have fiction. or paranoia.

That's how I have always viewed this. There is no reason why a civilization would blast out EM waves in a 360°*360° sphere at incredibly high energy levels indiscriminately forever and ever. Instead what we have seen right here on Earth over the last 100 years is that technological progress lets us do ever more with ever less energy.

Unless we are talking about detection from a relatively low range, a range where the square-cube law hasn't reduced the energy we would receive by too much, I would not expect us to ever receive random radio transmissions from other civilizations. Which, ultimately, turns the Fermi paradox on its head: it would be incredibly unlikely for another civilization like ours to develop at exactly the same time as us and so close to us.

I suspect that some thermodynamics law says that if you burn an amount of energy, you inevitably emit IR radiation. More energy means more radiation.

Yes, but every star emits IR.

Not many things emit a huge amount of IR and nearly nothing more energetic than it. Anything like that would be easily detected with our current tech.

Good point - even protostars have distinctive spectra, I think.

The Fermi paradox isn't only talking about detecting alien civilizations via radio emissions and the like. More likely would be the detection of a civilization that is harvesting a respectable portion of their star's energy. Energy is power, and stars absolutely dwarf any other accessible source.

Once basic space construction is mastered (which we are very close to), large scale solar collection seems a likely path that many civilizations would take. A Dyson swarm would probably be the first step, which would be detectable from very large distances.

But that’s the thing, if our galaxy had lots of 20-21st century Earth level civilizations, we would be able to detect them with our existing SETI programmes.

Personally I like the hypothesis that states eventually all comms will be encrypted and therefore indistinguishable from white noise.

Or simply using tech we haven't discovered yet (i.e. some faster than light method).

We could not detect civilizations at our level because standard transmissions decay the square of the distance and so such would be quantum noise by the time they got to the nearest start. And less than that by the time they further.

According to the SETI FAQ, it would be possible for alien civilizations to detect our higher powered radar systems with SETI setups similar to our own.

Do you dispute this claim from SETI? Can you provide a citation?

He was approaching this from physics and whatever that inverse distance power propagination law is called for 3d space.

I am not at a PC right now, but I can see your point. To counter, Seti should catch anything really high powered. Whether or not a civilization can operate something at that level of power, is a thought experiment.

But, still, they sift the skies, at least we are trying right ? :D

You can shine a laser at a place where you expect a planet.

There's around 512 G-type stars in 100 light years radius around us. That's not many.

Milky Way radius is 100 000 light years.

If our galaxy had lots of civilizations that just learned radio in last 100 years - odds are quite high that we wouldn't be able to detect them YET, even if we had the technology to do so.

I understand the probabilities involved.

The OP made a rather extreme claim that 'the universe could full of earth-level societies and we wouldn't know'.

If all 512 G-type stars in 100 light years had earth-level societies, we would be able to detect their higher powered radio transmissions. Right?

Only those transmissions that were timed (travelling at the speed of light) to arrive in the small number of decades where we have been listening. Other constraints may also apply

Even Seven light years is a vast, vast distance. The limit isn't 100 light years, it's something like one or less light years.

Any ordinary radio transmission dissipates the square of the distance involved. At a certain level, transmissions become so faint they are indistinguishable from quantum noise.

You can find the math done on Quora (apologies for semi-walled-garden link). Remember, there's difference between getting a signal whose properties one knows and getting arbitrary signal - if there a strong GPS transmitter or something we knew, we could wait long enough and get micro-data. But arbitrary signal, no, information theory says no. (read all the answers together).

https://www.quora.com/How-far-can-radio-transmissions-from-E...

> But that’s the thing, if our galaxy had lots of 20-21st century Earth level civilizations, we would be able to detect them with our existing SETI programmes.

But we couldn't. In general, SETI couldn't even detect such a civilization even if it was in the star system closest to earth:

> If an extraterrestrial civilization has a SETI project similar to our own, could they detect signals from Earth?

> In general, no. Most earthly transmissions are too weak to be found by equipment similar to ours at the distance of even the nearest star. But there are some important exceptions. High-powered radars and the Arecibo broadcast of 1974 (which lasted for only three minutes) could be detected at distances of tens to hundreds of light-years with a setup similar to our best SETI experiments.

The OP is right, in order for their to be a paradox we have to assume that civilizations much more advanced than ours are using a particular type of tech (the kind we're looking for, like radio broadcasts), that their using much stronger signals that we have ever used, and that the time period they used these hypothetical super powerful radio signals happens to be at the right time for us to encounter them. IE, let's say they used them for 2,000 years before moving on to other tech, but the signals only reached earth between 1,548,000-1,546,000 BC, or 450,000-458,000 BC, etc.

People are making a set of very, very specific assumptions based on little evidence. Then they see that the evidence that is available suggests that it's unlikely that every single one of their assumptions is correct, and they respond by calling it a paradox.

[1] https://www.seti.org/faq

OP said: 'the universe could full of earth-level societies and we wouldn't know'. It's a very extreme claim and the SETI FAQ answer directly contradicts it.

The SETI FAQ says that in the right circumstances, we might detect some of the closest ones, so the OP's statement is not contradicted.

> But we couldn't. In general, SETI couldn't even detect such a civilization even if it was in the star system closest to earth.

Your quote relies on us detecting re-runs of "I Love Lzcwwdrrr", but our telescopes can reliably do spectrographic analysis of faraway stars and planets these days. We'd likely be able to detect things like unnaturally high levels of hydrocarbons in otherwise oxygen-full atmospheres, and other industrial by-products.

If Alpha Centauri had a planet with an industrial civilization, we might be able to spot city lights.

>Your quote relies on us detecting re-runs of "I Love Lzcwwdrrr", but our telescopes can reliably do spectrographic analysis of faraway stars and planets these days. We'd likely be able to detect things like unnaturally high levels of hydrocarbons in otherwise oxygen-full atmospheres, and other industrial by-products.

We don't know what "unnatural" levels of CO2 on other planets are.

> If Alpha Centauri had a planet with an industrial civilization, we might be able to spot city lights.

We do not even remotely have that capability.

Hmm, it is reasonable to speculate that once our sensor levels get much more accurate we might be able to sense fuzzy, indirect evidence of earth-level societies on other star systems though aggregates like city-light and pollutants. But that is a long way away from present day detection - we're detecting planets through planet going in front of them and other indirect approaches that don't yield detailed information.

See: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanet...

It's also plausible that such societies are non-physical, meaning the content of the society is less about the physical substrate and more about the properties of the system itself

Care to elaborate please?

Or they might realize the universe is just inherently a dangerous place and design their own little universe to go inhabit. Peacefully exiting the universe.

What I've always thought about is if all life eventually struggles for power and destroys itself? Imaging what would happen if the whole world just worked together!

Is this something that is in our DNA, to be on top of everyone? 1% controlling the whole world, limiting their potential... Can we someday put aside our differences and work towards the same goal? Life on earth (humans and animals) don't really work together on a global scale. Is this only because of our nature, here on earth, that we need to destroy thing to live well (coal, forests, animals as food, ...)

Maybe there there are planets that have excess minerals, resources to build starships without killing their environment, without the need of wars (for oil for example).

Haven't we just had bad luck, being evolved on a planet with limiting resources, or just bad luck that we chose to use limited resources for our civilisation, or just bad luck that we need limited resources to survive? Are there a lot of civilisations struggling with the same problems? Or maybe there are aliens that can just drink water to survive and fly to other suns with just oxygen (just to make a silly example)?

This was kind of a response to "Can a civilisation really peacefully exist without destroying itself or the rest of the universe".

On the other note, imagination is such a big advantage of humans, we can achieve so much just by using our imagination. Also the whole topic of "Are we alone and where is the rest" is so interesting!

Google Murray Bookchin

I'm sure a civilization can exist without destroying the rest of the universe -- but it will rely on the rest of the universe pushing back a bit.

Have you, by chance, read the "Three Body Problem" and its two sequels? I don't want to spoil anything if you haven't, but it addresses these questions and that possibility in particular.

Or civilisations that reach a certain level go into a slow dysgenic decline because civilisation eliminates natural selection.

Oh, yes natural selection, that mechanism that mindlessly produced creatures adapted to the Loopdeformation (Regrow->Overpopulate->War->Regrow) and pushing for expansion of there speciality in the LD.

Totally something we should bring back. If evolution as a process could be stuck in local minima, then we would think otherwise - but that is heresy.

The paradox itself makes no such assumptions or speculation. It simply says that everything we know indicates that life and presumably technologically advanced life should be everywhere, yet we see it nowhere. There's an absolutely phenomenal article on the Fermi Paradox at WaitButWhy [1]. Your objections are mostly just scratching the surface of the wide array of possible explanations for it.

[1] - https://waitbutwhy.com/2014/05/fermi-paradox.html

You are simply mistaken. The article you link to filled with speculation concerning "type II" and "type III" civilizations.

If you assume earth-level civilizations as advanced, "where is everyone?" has a simple answer - "I don't know because we couldn't see them anyway". If you assume some other civilization as advanced, you are speculating. That's what speculation means.

I would upvote you so much more if I could. So many issues I see in reasonings are a direct cause of lack of imagination. What we know is limited. Speculating is interesting. But it's critical to identify it as speculation.

You're also speculating. Your original post is quite literally a list of 'what if' scenarios.

Again the paradox has nothing to do with that. The paradox is simply in the discrepancy in what we see versus what our current state of knowledge leads us to expect we ought see. The article covers a wide array of possible reasons for this, including the possibility of advanced civilizations not existing which seems to be your focus.