Have we reached the point when it is kooky to not believe in massive amounts of intelligent life having evolved throughout the universe?

Great Debates
321

It sounds to me like the debate is coming down to whether or not self-replicating probes are possible and something that might be done by an advanced civilization. No SRs, no Fermi Paradox. Is that about it?

In that case, we should just discuss self-replicating probes and,whether or not they are possible.

If they are flying to other stars in decades, then they are traveling at significant percentages of the speed of light. That brings back the energy problem.

Accelerating 1 kg to 1/3 C with perfect efficiency would require 1,205,451 MWh. Double it to slow down at the destination. How many millions of kilograms would a self-replicating probe have to be? And due to the rocket equation, the probe will have to be overwhelmingly fuel by weight, so however large the probe is, it will be a tiny fraction of the weight of the entire system.

If you have the ability to create and manipulate matter and energy like that, why colonize other stars?

And why do you think it can replicate itself with an asteroid? Something as complex as a self-replicating probe probably needs a huge amount of different elements, all of which are unlikely to be found on a single asteroid, or perhaps on any asteroids.

How does the probe know where to go next? Does it have to build its own telescope and search for its next destination? And survey its new system to find resources?

It seems far more likely to me that a civilization that had the ability to send complex probes to other star systems would simply set up a probe factory and send them all out from the home system. Then you don’t get exponential expansion, but you maximize the speed at which star systems could be probed in the short term, which seems more important.

How much failure rate can you withstand? If every probe fails 50% of the time or more, you get probes that maybe make it to a couple of star systems before failing, and you never get geometreic expansion.

It seems to me that we are doing a lot of assuming that somewhere, somehow a civilization would build self-replicating probes that work and colonize the galaxy. I don’t think our understanding of everything from life to information theory is strong enough to make that claim. And the evidence we have so far is that it didn’t happen.

My priors are such that if we can’t see alien self-replicating probes everywhere, it’s more likely that they were never developed for whatever reason than that we are alone in the universe. The latter seems far less likely to me, and it violates the Copernican principle. So the null hypothesis should be that there are likely alien civilizations out there, and they never developed self-replicating probes and deployed them. Or, they tried and the failure rate was such that the expansion collapsed after a time.

322

That’s more than the dimming we use to detect exoplanets. Not noticable by eye, but by instruments, absolutley.

Infrared. It’s still going to be emanating all the heat from the host star.

Also, why would you build just one? We should detect them by seeing pretty much all the stars be covered.

So, we are just fine tuning the goalposts slightly then. It’s not before they leave their solar system, but it is before they get here.

It’s also not at all inevitable that they all die out leaving no trace, nor any descendants.

I also don’t see why you would. What is causing this decline? What is causing every single alien civ out there to decline?

What makes it so that every single civilization that develops it loses it?

But there is no reason to think that that would be necessary. They would take what they can get. There is no reason to think that there is a lower limit to what is needed. And there is plenty of stuff here.

323

No, not at all. SR-probes were just one example among many. I also mentioned things like megastructures or beacons as things that would be detectable and not require breaking FTL. Then you have generation starships, and more targeted communications etc.
And of course we cannot rule out “something we haven’t thought of yet”. All we can do is list examples of things which seem feasible to an advanced ETI.

Though k9bfriender said “decades”, it’s not necessary for SR-probes to be an issue for the Fermi paradox. They can travel much more slowly than that.

A kg of mass perfectly converted to energy is 25 million MWh. I can’t see energy being the issue for a project like this for an advanced ETI.

This assumes that it is a rocket, which is not a good assumption to make.

  1. We don’t know how complex a mix of elements a probe would require.
  2. Asteroids are very rich in many elements. That’s the whole point of mining them; the vast cocktail of elements which largely sunk to earth’s core are far more accessible in an asteroid.

I disagree for the various reasons given above.
And again, I am not assuming any given species will make probes. We are just taking the data point that we see no evidence of probes, or anything else, seriously.
It should make us pessimistic about how common ETIs are and constraint some speculation…it stretches credulity to imagine a galaxy with millions of ETIs and none of them ever tried or succeeded in launching an SR-probe.

324

No, that is absolutely not what the debate is, or ever has been about. It was one example of one way that alien civs may have left evidence. It is not the only way, nor the more, IMHO, likely way.

Well, we can discuss them, but since your initial premise is flawed, I disagree that we should in any way limit it to that.

How does this follow? How far is our Oort Cloud from Alpha Centauri’s?

You don’t have to go clear across the galaxy when you have neighbors next door.

Because you are not creating matter and energy. They are the resources you are going to other starts to get.

I suppose one possible answer to the Fermi Paradox is that we do discover how to create energy and matter out of nothing, and therefore never have any reason to get any other resources, but I limit my personal discussions on the topic to the laws of physics as we know them, as if we start coming up with new laws of physics, then anything goes.

Why not? What element is on the Earth that doesn’t exist in any asteroids?

Sure, one of many ways it could go about its task. It’s not that hard to do, comparatively.

Have you seen the state of AI right now? It’s pretty impressive, and so I don’t see why no AI can ever be developed that can’t look through some sensors and plot a course to an asteroid a couple million miles away.

Yes, that, too has been mentioned. The self replicating probes was just one way of exponential expansion.

I think the real assumption is that no where, no when, no one will ever build any form of replicating system, whether it be a probe or a habitat.

I think that it’s becuas they were never developed becuase we are alone in the univserce.

The Copernican principle states that we should be existing somewhere in the void between galaxies a hundred trillion years in the future. Being on a planet around a star in a galaxy while the universe is a mere dozen billion years is already a massive enough violation that it shouldn’t be thought of as any sort of predictor of what is out there.

What do you think the chances are that there is a first civilization?

I disagree that that’s a reasonable null hypothesis, as it makes far too many assumptions and assertions.

325

As for detecting other civilizations, maybe we’re just not reading the data correctly, or our instruments are still not good enough to see what’s right in front of us.

For example, in 1980 this paper was written:

The paper speculates that the best way to spot ET would be to look at the spectra of stars for evidence of radioactive byproducts that are not made in stars, but could be ‘seeded’ into the star either as a form of communication or as a means to dispose of nuclear waste. The star would be an ‘A’ type star because they rotate slowly and their spectra are more precise. An ‘A’ star that has short-lived actinides in it would be a strong indicator of manipulation by a civilization. Carl Sagan even wrote in 1966 that such a star would be a strong candidate for ‘technosignature’ SETI.

Enter Przybylski’s star, type Ap (the ‘p’ stands for ‘peculiar’). In the latest GAIA DR3 data dump there is a complete spectrum for this star. And guess what? It contains all kinds of short-lived radioactives not associated with ‘A’ stars, and no one knows why. In fact, it seems to contain ALL the elements, including ones that are exotic, have short half-lives and are only created on Earth artificially. There are theories, but they are all just tentative attempts to explain the star without resorting to ALIENS.

The fact is, before we discovered the star we thought that such a discovery would be hard evidence for aliens, but once we did discover it we did flips and twists to explain it by any means other than aliens (as we should). But this means we could actually be missing alien signals or technosignatures because of our strong anti-alien bias towards new information.

A good writeup on Przybylski’s star:

Then there was Tabby’s star, which turned out to be dust clouds but had all the earmarks of a Dyson swarm under construction - a century of constant dimming coupled with periodic short term dimming and brightening. Exactly what you would expect to see with a dyson swarm, and yet we just detected this recently. It is totally plausible that there are other stars out there with similar patterns that aren’t dust, which we have yet to discover. Maybe thousands of them. Or millions.

Here’s Astrowright on another interesting star, KIC 12557548. This star has a very strange light curve with a relatively poor exolanation:

Both of these stars could be examples of a communication system. In the first case, the ratio of actinides and their types could encode information. In the aecond, giant louvres or satellites in orbit could be used to modulate starlight.

Modulated starlight strikes me as a very plausible means for aliens to communicate. It’s similar to a transistor amolifier in which a small current is used to modulate a large one. No need to build a giant transmitter of massive power - you already have one. You just need to modulate it, which takes a fraction of the effort,

And long before aliens could build self-replicating probes they’d have the ability to assemble huge structures in orbit around a star. So modulating starlight seems like a no-brainer.

The good news is that we are rapidly cataloguing the sky with GAIA, the upcoming Nancy Roman Grace telescooe and others. Our anility to discover such anomolies has gone up by orders of magnitude since Kepler, and we are just starting to go through the data. It should be an exciting decade.

326

To directly address the OP-

“Have we reached the point when it is kooky to not believe in massive amounts of intelligent life having evolved throughout the universe?”-

I would say no, we have not reached the point where it is kooky, at least to have plenty of healthy skepticism about intelligent life being common. Fermi’s Paradox illustrates that the null hypothesis is still that there are no aliens until proven otherwise.

The most we can now say from direct observation that we couldn’t before is that planets are now known to be common. We’d presumed as much but we only recently have proven it.

Barring the direct detection of techno-signatures, the next step in observational evidence would be to confirm, or rule out, earthlike biomes within several score light years. This would place bounds on the prevalence of Earthlike life in our galaxy.

327

It’s more that everything needs to be ruled out first. It could be aliens, but it could also be some thermonuclear chemistry that we didn’t know about before. Either way, the star is interesting and bears further study, but unless we find more evidence, we should assume it’s not aliens. My guess is that we will figure out how this happens naturally.

(Side note, a few years back, I met someone with that last name, and they were impressed that I could pronounce it properly, as I’ve seen a number of videos about the star.)

I was a bit excited when I heard about that, and I’m still excited for two reasons. The first is that we learned something new about the universe. The second is that it proved that we can detect a Dyson Sphere under construction or falling apart within 1200 light years.

Tabby’s star was not discovered by professional astronomers, it’s data was filtered out as not looking like a transiting planet. It was a citizen scientist (Tabby) who noticed its oddities. Since then, we’ve run that filter on the TESS data, and found others like it.

Could be. Worth a look, as either we answer one of the most fundamental questions we have asked since the first human looked up, or we answer some other questions.

Probably a lot better than lasers or radio waves, sure. But, in order to build something like that, we’d have to be well on our way to being a K-2 civ, and I don’t see any reason why a K-2 would limit their expansion.

You are going to need pretty much all the technology of self replicating probes in order to assemble such space megastructures.

And how far and hard will we look without finding any evidence of alien civilization before it seems reasonable to you to assume that they are not out there?

Don’t get me wrong, I’m skeptical about aliens, but I’m a very hopeful skeptic. Being alone in this universe is a bit terrifying, to be honest. But, even coming on this journey starting from the position of believing they were out there somewhere, the data just doesn’t support it, and I believe in data more than I believe that the universe conforms to my desires.

One of the reasons that I really want to see the Europa and Enceladus missions is that they are some of the most likely places to find life in our solar system. What we find there will give us a whole lot more data to consider when we think about what is out there.

My guess is that we find some sort of primitive bacteria or other single cell organism that shares some similarities to Earth life, but not so much that it implies panspermia. If we find nothing at all, that is data that life itself is rare. If we find more complex organisms, then that implies that some of the early filters or steps were not as steep as we thought.

If we find whales composing poetry, then I will assume that the universe is absolutely brimming with intelligent life.

328

I’m all for expanding the criteria and remit for the definition of ‘intelligent life’, here: it doesn’t have to mean little green men in space-ships. I’d posit that sentience is the single pre-requisite trait for a being to be both intelligent and alive; said entity only needs to know of itself and interact with the universe consciously, with free will and some form of critical judgement. It certainly doesn’t have to be carbon-based, or breathe oxygen (or, indeed, breathe anything at all).

For all we know, such entities might already exist on a teeny-tiny quantum level, or in stars (or could a star itself be sentient?), or any other corner of the universe which we would not normally equate to being habitable (because it is hostile to us).

Secondly, and I’m borrowing ideas from Iain M Banks here, it is also myopic to presume that aliens will be at a similar stage of technological progress to us - inasmuch as they have ‘home planets’ and travel around in purpose-built vessels, and presumably require resources for energy, consumption, etc… Surely a civilisation which has had 1 billion years or so more than us to get going will have made advancements in technology which we could not even dream of. For our intents and purposes, such beings would be god-like, having solved the faster-than-light-speed issue millennia ago, and living in a kind of post-scarcity utopia. Such beings would be omnipresent, so - if they do exist - they’re probably here right now.

329

We don’t know that FTL is solvable…from our current understanding of physics, it looks either outright impossible or, at the least, causality-breaking.

Apart from that though, I agree with you.

I think people seem to not appreciate how much difference mere millions of years of equivalent technological progress means.
Maybe because the earth is billions of years old? So it’s easy to say a species is billions of years ahead, without quite appreciating how big a deal it would be to have a sentient, technological species around for deep time.

(And yes, I know some here will argue that perhaps all civilizations fall before that point. But, in the context of the Fermi paradox, we would need to posit that civilizations always fall before even getting centuries ahead of current humans. Because humans are not far off being potentially “noisy”.
So look around you…this needs to be the pinnacle of achievement, this needs to represent as far as any species gets).

330

This is not, and has never been, the idea behind a Dyson Sphere. Freeman Dyson imagined this construct to be a swarm of energy-collecting satellites in non-intersecting orbits. Some, many or most of these satellites might be habitable, but that is not the important part of the concept. Collecting the energy, the luminosity, of the star, is the objective. Dyson swarm is a better descriptive term for this idea.

Dyson wasn’t a science fiction author, and neither was von Neumann, who first examined the concept of self-reproducing automata in depth. These are projects that could be conceived by any sufficiently advanced civilisation, but if there were Dyson swarms or self-replicating automata in our galaxy we might expect to detect them. Rather than science fiction fantasies, these are thought experiments which need to be considered when considering the Fermi question.

331

There’s also the issue of whether or not we’d know if such probes have visited the Solar System in the past, or even whether any are the Solar System now.

332

I don’t even know if I’d say it’s the objective, but rather the result. We (future we) aren’t saying, “Hey, let’s collect all the light from the star and find something to do with it.” What we would be saying is, “Let’s keep building these habitats and power collectors that are useful to us, until we have to stop because we’ve blocked out the whole sun.”

333

You would first have to convince me that there is intelligent life here on Earth. Good luck on that!

335

The Proxima Centauri signal seemed to be an interesting shred of a speck of evidence of extra-terrestrial technology. Interestingly, the possibility of it being alien technology is debunked because “The chances against this being an artificial signal from Proxima Centauri seem staggering,” said Lewis Dartnell, an astrobiologist and professor of science communication at the University of Westminster. “We’ve been looking for alien life for so long now and the idea that it could turn out to be on our front doorstep, in the very next star system, is piling improbabilities upon improbabilities.
“If there is intelligent life there, it would almost certainly have spread much more widely across the galaxy. The chances of the only two civilisations in the entire galaxy happening to be neighbours, among 400bn stars, absolutely stretches the bounds of rationality.” Cite.

I think it’s interesting that even we, with the JWST, can detect conditions likely to indicate life, so a signal near our solar system shouldn’t “stretch the bounds of rationality”, because it might be here because of us. BTW this is one of the most interesting threads I’ve ever read on the possibility of alien technology.

336

There have been a handful of interesting anomalies–another one being the Wow! signal–but I demand a little more than that to really move into the “evidence” category. It’s a speck of something, and worth investigating, but just being unexplained isn’t enough. There are lots of unexplained things out there, and while some of them might be from unknown phenomena, as a general rule we should assume they have mundane causes.

I mostly agree, though it raises the question of how said aliens know about us. Maybe they sent out zillions of tiny probes to figure out if any planets had life, and they’re too small for us to see. Our radio emissions are too weak and too recent to attract any interest, I think.

337

My guess

1
The universe is teeming with life.
We will find microbial life within the solar system, perhaps even some multicelled creatures in the seas of a moon

2
Intelligent life is rare and takes billions of years of evolution

3
Faster than light travel is impossible

4
So we will never meet intelligent aliens
We will find some weird lumps of metal on a dead planet, some odd signals from far away in space and time… and we will conclude these are probably evidence of alien civilisation

But We will probably destroy ourselves before rhis

338

I’m afraid even “lumps of metal” is too close.

If humans are any indication (and we’re the only example we have), there are merely thousands of years in-between being able to refine metals from ores, and being noisy on an interstellar level. The blink of an eye.

339

That sums up my feelings fairly well.

340

All likely correct. But I would clarify it by saying, “The time it takes to evolve intelligence is likely orders of magnitude longer than the time it takes for a technological species to destroy itself.”

If it takes a billion years to evolve intelligence but only 1,000 years for a technological civilization to destroy itself, then technological civilizations only exist for a millionth of the time it took to develop the species. Therefore, there could constantly be millions of intelligent species in various stages of development but the odds are still that no more than a couple of spacefaring civilizations ever existed at the same time.

The conclusion of this is that our galaxy may be a graveyard of dead civilizations - perhaps millions of them. But we might be the only technological civilization currently in existence.

341

“By lumps of metal “ i mean the wreck of an alien space probe fhat crashed millions of years ago.
Or some other artefact.