What do you think is the most likely explanation for the Fermi paradox?

[Noclevername]

Our communications with dolphins are rudimentary. Their communications with each other may be far from rudimentary, as we're only beginning to understand how they communicate. It's fairly well established that individual dolphins have "signature whistles" comparable to names, but what else they do with their whistling is still an open question.

I'd also make the point that when studying dolphins and other Earth animals, including birds, we know a lot of things that we wouldn't necessarily know about an ET species that we got some sort of message from. For instance we know what shape a dolphin is, how it moves around, what it feeds on, how it reproduces, the size of its social groups... and all these things are potentially clues to what dolphins might communicate about...

If ETI is truly I, that is, if they're smart enough to send a signal, there must be certain principles that they have mastered in physics of radio transmission. That gives us a starting point to at least try from, though success is of course not guaranteed.

[Colin Robinson]

If ETI is truly I, that is, if they're smart enough to send a signal, there must be certain principles that they have mastered in physics of radio transmission. That gives us a starting point to at least try from, though success is of course not guaranteed.

Isn't that like saying: "If dolphins make sounds we can hear, they must have mastered the physics of acoustic transmission in the same way we have" ?

[Noclevername]

Isn't that like saying: "If dolphins make sounds we can hear, they must have mastered the physics of acoustic transmission in the same way we have" ?

No, because dolphins make sounds naturally and without developing any technology to do so. A species that sends powerful, clearly non-natural interstellar transmissions (the only kind we'd recognize as ETI contact) would have to work at it.

[Colin Robinson]

No, because dolphins make sounds naturally and without developing any technology to do so. A species that sends powerful, clearly non-natural interstellar transmissions (the only kind we'd recognize as ETI contact) would have to work at it.

What would make a powerful transmission "clearly non-natural"? Natural radio emissions from astronomical objects can be powerful too, after all.

If you're thinking of something like a sequence of prime numbers or digits of pi, then yes... If we ever receive something like that, we'd recognise it as ETI contact...

The thing is, we won't receive anything like that unless:

1. There are ETIs who do maths the same way that we do, plus
2. Unlike most humans, they think it is worthwhile to use up energy sending out free information via powerful transmissions into interstellar space.

In short, this form of SETI will only detect the subset of possible extraterrestrial species who are very very like us humans, except that they're nicer.

[Roger E. Moore]

What would make a powerful transmission "clearly non-natural"?

I have heard that a purely random signal would attract great attention.

[Noclevername]

What would make a powerful transmission "clearly non-natural"? Natural radio emissions from astronomical objects can be powerful too, after all.

If you're thinking of something like a sequence of prime numbers or digits of pi, then yes... If we ever receive something like that, we'd recognise it as ETI contact...

The thing is, we won't receive anything like that unless:

1. There are ETIs who do maths the same way that we do, plus
2. Unlike most humans, they think it is worthwhile to use up energy sending out free information via powerful transmissions into interstellar space.

In short, this form of SETI will only detect the subset of possible extraterrestrial species who are very very like us humans, except that they're nicer.

No, we've sent transmissions ourselves, and as our technological capacity, resources and energy budget increase as we move out into the Solar System, we're likely to try again. So "niceness" does not enter into it. Just opportunity.

For determining what is not natural, that's kind of the point; we might not know. That's why I specified a "clearly" artificial one. As with finding life directly, it's the same conundrum; what is life, what is intelligence, and how would we recognize them? Perhaps, by their knowledge of the Universe's physical properties. That could (not will, could) serve as a basis for meaningful interaction.

[Colin Robinson]

No, we've sent transmissions ourselves,

Up till now, we've put a lot more effort and resources into SETI than into METI.

and as our technological capacity, resources and energy budget increase as we move out into the Solar System, we're likely to try again.

Maybe we will and maybe we won't.

Conceivably future human societies will husband their energy resources more strictly than we do today, and will be more averse to possible dangers of METI.

For determining what is not natural, that's kind of the point; we might not know.

Very true... And yet there are quite a few writers on this topic who think the universe "looks dead" just because we haven't observed anything recognisably artificial that isn't our own work.

That's why I specified a "clearly" artificial one. As with finding life directly, it's the same conundrum; what is life, what is intelligence, and how would we recognize them?

As David Grinspoon argues in his book Living Worlds, if we are looking for life (rather than intelligence), we should look first for planetary environment where there are energy sources that could be used by things that grow and reproduce. Worlds which are active, in terms of atmospheric chemistry, meteorology, geothermal activity.

Perhaps, by their knowledge of the Universe's physical properties. That could (not will, could) serve as a basis for meaningful interaction.

I agree that it could, depending on whether they express their knowledge in terms we can understand...

[Noclevername]

Up till now, we've put a lot more effort and resources into SETI than into METI.

Both your statement and mine are true. We have in fact tried METI. It wasn't a comparison to any other activity.

Maybe we will and maybe we won't.

Conceivably future human societies will husband their energy resources more strictly than we do today, and will be more averse to possible dangers of METI.

A lot of things are conceivable. We've still tried METI already even with limited budgets. But I see growth as more likely than contraction.

Very true... And yet there are quite a few writers on this topic who think the universe "looks dead" just because we haven't observed anything recognisably artificial that isn't our own work.

As David Grinspoon argues in his book Living Worlds, if we are looking for life (rather than intelligence), we should look first for planetary environment where there are energy sources that could be used by things that grow and reproduce. Worlds which are active, in terms of atmospheric chemistry, meteorology, geothermal activity.

OK.

The Fermi problem asks why they aren't here, and the conversation we were having is about why we haven't heard from them.

I agree that it could, depending on whether they express their knowledge in terms we can understand...

Well yes, that's my point. Whether we have a basis for understanding. If they understand radio well enough to use it on a large scale that's already a point of similarity. If their communication is recognizable as communication (if!) then that's another. (If it's not it won't matter to us anyway because we'd miss it.)

[Colin Robinson]

The Fermi problem asks why they aren't here, and the conversation we were having is about why we haven't heard from them.

Well yes, that's my point. Whether we have a basis for understanding. If they understand radio well enough to use it on a large scale that's already a point of similarity. If their communication is recognizable as communication (if!) then that's another. (If it's not it won't matter to us anyway because we'd miss it.)

When we're considering the question of why we haven't heard from them, the possibility that we might not recognise their signal does matter. Because that's a possible answer to the question we're considering.

[Noclevername]

When we're considering the question of why we haven't heard from them, the possibility that we might not recognise their signal does matter. Because that's a possible answer to the question we're considering.

Yes. That was my point.

[Bearded One]

I have heard that a purely random signal would attract great attention.

Data compression is darn useful and we can assume ET would use it. Unfortunately it also turns the data stream into random noise. The better the compression algorithm the more noise-like the final output.

I wonder if a very advanced and old technological civilization would even recognize an analog signal? Would the thought even occur to them? They might find an AM signal interesting but trying to turn it into sound might never occur to them.

[7cscb]

Hi Colin Robinson,

You wrote: "Conceivably future human societies will husband their energy resources more strictly than we do today, and will be more averse to possible dangers of METI."

Going back millennia, one of our distinguishing traits is an increasing per capita usage of ever cheaper energy, of which the universe is full. I don't see how or why some future successful society would husband energy more strictly.

Radio emissions are only one sign of our technological presence. We have broadcast to the universe for centuries at least. Any sufficiently advanced ETI would have detected changes in our atmosphere as our effluence increased. We are on the verge of such observations ourselves. ETI is better equipped.

cheers,

[Noclevername]

Hi Colin Robinson,

You wrote: "Conceivably future human societies will husband their energy resources more strictly than we do today, and will be more averse to possible dangers of METI."

Going back millennia, one of our distinguishing traits is an increasing per capita usage of ever cheaper energy, of which the universe is full. I don't see how or why some future successful society would husband energy more strictly.

Agreed. Human nature is that as the supply of something increases, we become more profligate with it. Wasteful, even. As we expand into space resources of the Solar system, both material and energy, will also become (after getting over the hump of the huge initial investments in exponential bootstrapping) more available. Stingy energy use will almost certainly not be a problem in the long term.

[Colin Robinson]

Hi Colin Robinson,

You wrote: "Conceivably future human societies will husband their energy resources more strictly than we do today, and will be more averse to possible dangers of METI."

Going back millennia, one of our distinguishing traits is an increasing per capita usage of ever cheaper energy, of which the universe is full. I don't see how or why some future successful society would husband energy more strictly.

Radio emissions are only one sign of our technological presence. We have broadcast to the universe for centuries at least. Any sufficiently advanced ETI would have detected changes in our atmosphere as our effluence increased. We are on the verge of such observations ourselves. ETI is better equipped.

cheers,

Your word "effluence" points to the downside of how we've been behaving. What you call "ever cheaper energy" appears to have long-term costs, such as climate change, which may be extremely expensive.

We may be on the verge of detecting ETIs via their effluence, but I'm not convinced.

Considering what makes Earth's atmosphere different from the atmospheres of other rocky planets, the really large differences (e.g. level of atmospheric O₂) are the work of non-technological life (photosynthesising microbes, algae and plants). Effects due to technology would be much less easily detected by remote astronomers.

For this reason, I think it's likely we'll find good evidence of non-technological ET life long before we find evidence of technological life (if we ever do).

[Noclevername]

Your word "effluence" points to the downside of how we've been behaving. What you call "ever cheaper energy" appears to have long-term costs, such as climate change, which may be extremely expensive.

If you assume a one-world economy will always be our limitation, yes. We have limited resources on Earth.

[Jens]

If you assume a one-world economy will always be our limitation, yes. We have limited resources on Earth.

I think that this question can actually be split into three possibilities:
(1) A one-world economy
(2) A multi-world economy with very little trade between worlds
(3) A multi-world economy with significant trading between worlds

I would not choose (1) in the long-run. But I'm not sure between (2) and (3). If you have (2), then for practical purposes it isn't different from (1).

[Noclevername]

I think that this question can actually be split into three possibilities:
(1) A one-world economy
(2) A multi-world economy with very little trade between worlds
(3) A multi-world economy with significant trading between worlds

I would not choose (1) in the long-run. But I'm not sure between (2) and (3). If you have (2), then for practical purposes it isn't different from (1).

In the long run 2 leads to 3, as the off-Earth population and industry grows. Eventually, we would end up with more happening off-planet than on.

[7cscb]

Your word "effluence" points to the downside of how we've been behaving. What you call "ever cheaper energy" appears to have long-term costs, such as climate change, which may be extremely expensive.

We may be on the verge of detecting ETIs via their effluence, but I'm not convinced.

Considering what makes Earth's atmosphere different from the atmospheres of other rocky planets, the really large differences (e.g. level of atmospheric O₂) are the work of non-technological life (photosynthesising microbes, algae and plants). Effects due to technology would be much less easily detected by remote astronomers.

For this reason, I think it's likely we'll find good evidence of non-technological ET life long before we find evidence of technological life (if we ever do).

Indubitably, Climate Change will be extremely expensive. It will require huge and likely unheard of quantities of energy resources to have a chance of taking control of our predicament. No matter how clean new energy sources become, total power dissipated will gradually increase global temperature and we'll have to deal with that within 100 years or so. ETI behaviour may sidestep greenhouse gases but will still have to face the same existential planetary thermodynamics issues facing all technological civilizations. So when the galactic tribunal judges us, we can say: "Oh yeah? Youse too!".

Earth has been emitting signs of life, in the visible spectrum, for aeons. Astronomy is increasing by leaps and bounds. An alien civilization would have been studying Earth for millennia, noticing recent changes, all from farther and with better science than we could imagine. I think the concern about METI is overblown. We likely can't hide.

Cheers,

[Noclevername]

An alien civilization would have been studying Earth for millennia, noticing recent changes, all from farther and with better science than we could imagine.

An interesting idea, but only if they have both the inclination and the proximity to examine us in detail.

[Colin Robinson]

Earth has been emitting signs of life, in the visible spectrum, for aeons. Astronomy is increasing by leaps and bounds. An alien civilization would have been studying Earth for millennia, noticing recent changes, all from farther and with better science than we could imagine. I think the concern about METI is overblown. We likely can't hide.

If you're right — if they have been getting extensive information about Earth for millenia — then yes, that means that sending them METI would be unlikely to cause harm to us.

But what good would our METI do, either for them or for us?

I mean, we could send them a message saying "Earth is inhabited, and we'd love to exchange scientific information with you."

They pick it up, and laugh at it, thinking: "Well, yes, we knew Earth is inhabited. And we have more advanced and efficient ways of getting scientific information, even about Earth, than exchanging radio messages with primitive beings like you."

[Noclevername]

If you're right — if they have been getting extensive information about Earth for millenia — then yes, that means that sending them METI would be unlikely to cause harm to us.

But what good would our METI do, either for them or for us?

I mean, we could send them a message saying "Earth is inhabited, and we'd love to exchange scientific information with you."

They pick it up, and laugh at it, thinking: "Well, yes, we knew Earth is inhabited. And we have more advanced and efficient ways of getting scientific information, even about Earth, than exchanging radio messages with primitive beings like you."

They might not have picked up signals not specifically designed to be coherently received. Our local TV and radio blend into background noise after a couple of light-years. So our intelligence could still be a noteworthy surprise.

[Jens]

In the long run 2 leads to 3, as the off-Earth population and industry grows.

Does it? I posed it as a question that I'm not certain of, because I'm not sure I understand how that would happen. But if you say that it does lead to (3), you must know more than I about it. How does that happen? Normally on earth, trade has grown due to things such as economies of scale and availability of resources (this is what I studied in college, actually). What is going to lead this expansion of trading? Lower costs? Will economies of scale really be that important? Or just things like helium 3? I'd like to understand the scenario.

[Noclevername]

Does it? I posed it as a question that I'm not certain of, because I'm not sure I understand how that would happen. But if you say that it does lead to (3), you must know more than I about it. How does that happen? Normally on earth, trade has grown due to things such as economies of scale and availability of resources (this is what I studied in college, actually). What is going to lead this expansion of trading? Lower costs? Will economies of scale really be that important? Or just things like helium 3? I'd like to understand the scenario.

So you think a space-based economy and population would remain static? Forever? Hard to picture.

Based on the amounts of material resources and energy available in the Solar system, once off-Earth industry is established to the point of independence it would be capable of massive expansion beyond anything currently foreseeable. But to get to that point would require technology that can utilize in-situ resources from dust to done, that is, processing regolith and ice into working industrial grade machines.

[Jens]

So you think a space-based economy and population would remain static? Forever? Hard to picture.

I didn't say I think that.

I was wondering about it. There's a big difference between the two. And despite the argument from incredulity, I think that it's still an issue that's interesting to discuss.

Based on the amounts of material resources and energy available in the Solar system, once off-Earth industry is established to the point of independence it would be capable of massive expansion beyond anything currently foreseeable. But to get to that point would require technology that can utilize in-situ resources from dust to done, that is, processing regolith and ice into working industrial grade machines.

I completely agree with that second part. I'm not thinking at all at whether there will be a massive expansion (I think there will) but what I'm wondering is how much trade there will be between the earth and other places, given the cost of the exports. And just to be clear again, I'm not saying that there won't. I'm saying I'm not convinced there necessarily will. I realize it's a subtle difference, but I think it's an important one.

[Noclevername]

I didn't say I think that.

I was wondering about it. There's a big difference between the two. And despite the argument from incredulity, I think that it's still an issue that's interesting to discuss.

I made an argument from "I didn't understand". What do you actually think, then?

[Jens]

I made an argument from "I didn't understand". What do you actually think, then?

I don't think I've been particularly unclear about that.

In the long run 2 leads to 3, as the off-Earth population and industry grows.

I'm unclear about whether that is necessarily true. I don't think it's wrong, but I'm not sure it is right as well. I am uncertain about whether inhabitation of multiple worlds would inevitably lead to a large amount of trading between them. That's what I wanted to ask you to explain (why you think it is inevitable). And I guess that it just comes from incredulity (in other words, you can't imagine that it wouldn't happen).

[Noclevername]

I don't think I've been particularly unclear about that.

Think what you like, but it wasn't clear to me.

I'm unclear about whether that is necessarily true. I don't think it's wrong, but I'm not sure it is right as well. I am uncertain about whether inhabitation of multiple worlds would inevitably lead to a large amount of trading between them. That's what I wanted to ask you to explain (why you think it is inevitable). And I guess that it just comes from incredulity (in other words, you can't imagine that it wouldn't happen).

Maybe the confusion comes because you equate growth of "trade" with growth of "population and industry" which is what I said would expand. And "worlds" in this context does not just mean planets, space habitats and asteroid resources are also likely to be in play. An economy based on non-scarcity would be very different than today's exchange-based systems.

[Jens]

Maybe the confusion comes because you equate growth of "trade" with growth of "population and industry" which is what I said would expand.

Then I'm really confused. Because I said.

(2) A multi-world economy with very little trade between worlds
(3) A multi-world economy with significant trading between worlds

Where the difference is clearly about trading. And you said:

In the long run 2 leads to 3, as the off-Earth population and industry grows.

So you are talking about 2 leading to 3, but not talking about trade? But my issue between 2 and 3 was precisely about trade.

Why did you say that "a multi-world economy with little trade" would lead to "a multi-world economy with significant trade" if you weren't talking about trading... I'm sorry, but I am finding it hard to understand...

[Noclevername]

OK now I am totally confused. I think we're just miscommunicating, talking about two different ideas.

I'll stop for a while before I get into a tailspin here.

[Colin Robinson]

They might not have picked up signals not specifically designed to be coherently received. Our local TV and radio blend into background noise after a couple of light-years. So our intelligence could still be a noteworthy surprise.

I'd agree it's plausible that ETIs might know a lot about Earth, including that there is life on Earth, without knowing that Earth has intelligent life.

In that case, yes, METI from Earth could provide them with new information which they may consider noteworthy.

The question then is whether we humans want to provide free information about ourselves to ETIs whose character and motives we don't know?

I'm thinking of David Brin's argument that natural selection seldom produces inter-species altruism, i.e. altruistic behaviour by one species towards another.

Moreover, if Brin's point is accepted, is it not a simple and plausible explanation for the so-called "eerie silence" — the fact that we haven't detected ETIs altruistically beaconing out free information to us humans?