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
261

That sentient being better aim his radio beacon directly at Earth. If it was an omnidirectional broadcast it would need immense amounts of power to still be above the noise floor by the time it got to us. Omni signal strength drops with the square of the distance.

For example, if you traveled away from Earth carrying our best radio detection gear, you could not detect Earth’s radio emissions after you got out to about a light year. The Voyager probes are already -308 DB down, and we can only communicate with them because they point a directional dish at our huge directional dishes which are pointed straight at them. If we were looking for a random probe in a random direction, we would never hear them.

IMO, we may never hear radio signals from other civilizations, regardless of how many of them are out there. Using stars as amplifiers for light signals seems more likely. Another possibility might be communications through ‘seeding’ stars with rare elements in quantities that encode information to be read through spectroscopy. Low bandwidth, but the signal could be ‘read’ from large portions of the galaxy so long as the light is being blocked in their direction.

Maybe when we build a scope large enough to detect small enough changes in star brightness we’ll find all sorts of communications going on by modulated starlight. We can currently spot ‘transits’ of earth-sized planets around fairly near red dwarfs. How big a telescope would we need to be able to see a giant set of louvers in space opening and closing in front ofma star?

But the fact that we haven’t heard any radio signals yet is not really evidence of anything, given how bloody hard it is to send any kind of EM signal interstellar distances. Laser communications, maybe. Some other form of very tight beam signal, maybe. General broadcasts? Highly unlikely.

262

True, but all we would know is that intelligence existed 1000 years ago.

The Speed of Light.

263

Right, so the Fermi paradox remains.
If every 1000 light years there is a technological civilization, that would give us ~8 million in our galaxy alone (conservatively…I simplified the maths by making the galaxy just one star thick, and a perfect circle of 50k ly radius). We see no signals, megastructures, replicating drones etc from any of them. Why?

Doesn’t make sense as an argument.
You may as well say that it is impossible for you to walk to the next town because it is 5 miles away, and 5 miles is like, really far.
The missing component is how much time there has been, and in the case of the Milky Way, it’s 13.6 billion years. Absolutely ample time to cover 1000 ly.

264

Because there is only a small handful of habitable exo-planets within 1000 ly. Even at 1000 ly such signals would be tenuous and diffuse. Expecting signals from 50,000 ly is wishful thinking.

That means nothing. The civilization would have to pour massive resources into a manned ship that they would never hear back from, nor would they have any idea there is life here.

The number of stars and the age of the galaxy mean nothing here. We know that within 1000 ly there are only a small handful of possible candidates (and note, several of that small list are further than 1000 ly). I think even 1000 ly is too far, myself. That leaves Proxima Centauri b (which is actually not far at all, in the scheme of things) and Gliese 667Cc, which is doubtful and 20ly.

265

What kind of signals? Are you assuming that the kind of signals that humans could transmit circa 2022 represent the maximum power that any species will ever be capable of?
I mean sure…if we assume that humans today have reached the pinnacle of technology, then the Fermi paradox is solved. We can’t make megastructures or self-replicating probes or powerful beacons today, therefore no-one will ever be able to.

It’s…a valid solution to the Fermi paradox I guess, even if not a popular one. Not where I’d put my money, but it’s self-consistent.

A “manned ship” is just one scenario though. Plus, assuming that they would consider it massive resources again comes back to their technological level.
If burning oil and fissioning uranium represent the pinnacle of energy production, then sure, perhaps space travel will always look too costly.
I have no reason to make such an assertion though; we know for a fact that any nucleus lighter than iron can fuse and release huge amounts of energy, and there are additional ways that stars can produce energy beyond that. Maybe no sentient species, even given millions of years, will ever tap those energies (…that humans have already been able to tap, just not in a way that makes an energy profit). Could be, but we have no reason to make such an assertion.

266

Capable of AND having reason to want to do.

What you are doing is adding two additional terms to Drake’s equation: the odds of a civilization hitting the technology level we have not, that you assume is potentially possible, to send an omnidirectional signal of sufficient power to be easily detected by us above background noise from distances that ours are not able to be, AND that they for some reason, have the desire to expend the resources and effort to do so.

What fraction of civilizations that hit our level of technology do you guess will hit that future level of capability and of them, how many will want to send out a signal to possible civilizations thousands of light years away, expecting an answer only from a civilization of the same or greater technology and then no earlier than thousands of years later, otherwise just as shouts of “Kilroy was here.”?

267

Once again (and I’ve had to say this multiple times in this thread) you have this exactly backwards.

I am not claiming any species will do anything for any reason. Maybe the most popular thing for ETIs to do is organize a neverending football game. Or maybe they’ll make a megastructure that’s a big flower just to pretty up the galaxy. Who knows?

What I am saying is this: if someone wishes to posit that the solution to the Fermi paradox is that no species attempts to make noisy beacons, or megastructures, or self-replicating drones, or indeed any “unknown unknown” tech that would nonetheless be visible to us…then they are the ones making a positive claim about all ETIs. Indeed a claim about all significant factions within all civilizations of all ETI planets.
That proposition rests on making a claim about how all ETIs behave, always.

268

I’m trying hard to formulate a way to say this that does not come off just as a pissing match (“No YOU have it backwards” rinse repeat.)

The issue is the Drake Equation and the terms in it, making wild assed guesses about some, and working off the parts we can guess best forward.

The first few have some reasonable guesses, which together create some finite likely bound of a number of planets suitable for life to occur.

There are of course WAGs about how many of those DO develop life, and for the sake of discussion assume a high fraction.

Then that intelligent life emerges. Unknown fraction. Personally I look at the fact that life has existed here WITHOUT our level of intelligent life for the entire time except for a relative microsecond to date, as evidence for a low number there, but some may want to place it high. Go with a high one if you want but there is no basis for that.

Then fc, the fraction that develop technologies that we can detect. Outside of a fairly small radius the fact that signals weaken by a square of the distance means that such posits the capacity for stronger omnidirectional signals than we put out is realistically possible, that other civilizations have reached the point (in the past in time for the signals to reach us), and that they had an interest in doing so. I do not claim that such a term is zero, and neither would I assume it is large.

Last is L, how long each civilizations produce such signs. Also an unknown. Do all survive long term? Do a majority break themselves to a lower technological level before too long? Do they decide to hide their ability to produce such signs? Again unknown.

I read an article last week that took a position just a bit more fully fleshed than mine:

LIFE may be widespread but intelligent life, let alone intelligent life with civilizations that reach our level without self-destruction, is rare. That being the case an intelligent technologically advanced civilization may be uninterested in looking for life on other planets as they see it lots even nearby, and have concluded that intelligent life, let alone technologically advanced civilization, is very rare. They’ll wait to hear from us first.

269

You need to build an Ansible.

Be careful who you call, it’s a dangerous universe out there.

270

Right, and I also want to keep things civil and on point.
I just got slightly annoyed in my last post because I have had to repeat myself a lot in this thread.

Personally, I am not a fan of the Drake equation. It’s not incorrect, but I think often it gives the wrong impression. Most of the terms of the equation can be broken down into many, many separate unknowns, and grouping them up under one number makes the whole issue appear simpler than it really is.
Anyway, I guess that’s an aside here, because I’m happy to talk about the situation from a Drake equation point of view.

I think any intelligent species is likely to find itself in that position. Once a sentience emerges, it’s essentially a “stop the clock” moment, as the speed a sentient species develops is orders of magnitude faster than natural selection.

The only other option is that an intelligence emerges, wipes itself out, then another emerges in its place. But evolution being what it is, the new intelligence is more likely to be a nearby branch of the tree than elsewhere. So they may still consider themselves the “first”, as the old species was a step towards their existence. Just like we do.

But here the term “signals” does a lot of work, as it’s everything from a deliberate message beamed at us to just any visible activity (e.g. Dyson swarm, flower megastructure).

Agreed. And based only on what we know today, this seems the most likely option.
Life started on earth pretty much immediately; while it had barely finished forming. Then it took billions of years to evolve cells and then multicellular life. On this data, we might posit that “slime worlds” are common, but rich ecosystems of complex lifeforms are rare.

Sure, but I don’t think that paper makes a great case for this. They say that it would be “pointless” to beam out radio waves. However it would also be trivial to do so; proportionately cheaper than me putting a message in a bottle.
And, like I say, psychological solutions to the Fermi paradox require making a claim about the behaviour of all ETIs. So we’re saying, no intelligent civilization ever thinks to send a signal, when the one example of intelligent life that we know of, have already attempted to do so? Doesn’t seem very plausible to me.

Plus, like I say, “signal” does not only mean deliberate messages.

271

And repeating myself, no it doesn’t. It merely says that of the finite number that may have existed, far enough in the past for their signals, of any sort, to reach us, none have, in any window of time able to have been seen by us at this point in time, occurred. Maybe one did for a period of time in the distant past for some finite period that we missed. Maybe one has happened and has not reached us yet. Maybe one will occur in the future. Those are all included in “all”.

You are right that each term of the Drake Equation actually is an umbrella for many items, each one a filter. Thing is I think the psychological impact on the WAGs created is to overestimate the odds of getting past each one.

The bit that I find misleading is the phrase “Great Filter”.

More multiple filters none of which are great barriers on their own. The proper metaphor is one popularized during Covid in reference to layers of protection: stacked slices of Swiss cheese. No single slice is or need be great protection, a great filter, but getting past each and every one is unlikely.

272

And repeating myself, the concept of a “signal” in the Fermi paradox does not only mean a one and done Arecibo-type message. It includes, for example, just about any kind of megastructure built for any purpose. Or probes. These things wouldn’t vanish with a civilization.

Yes, I’d agree with that. The true situation may well be multiple difficult “filters”, and they need not be entirely uncoupled.

273

How long would it take for a sturgeon to migrate from Lake Baikal to a freshwater lake in France? A few extra million years isn’t going to help because every fish that tries will die 5 minutes into this month long journey.

Is a 1,000 ly journey the technological equivalent of walking for 1 hour on a pleasant day, or swimming for a month over dry land?

274

Well we don’t know, and therefore we are not justified in citing it as the solution to the Fermi paradox.

Based on our understanding today, there are significant engineering challenges in making technology that could survive the radiation and micrometeors over that distance.
However engineering challenges just aren’t sufficient in this context, we need it to be physically impossible.

275

Why? The only argument I know of that would imply that says, “Hey, so long as even one civilization gets to the point of sending out self-replicating probes, they should be everywhere”. If we accept that, then yes we can’t tolerate any highly advanced civilization probabilities without running into the Fermi paradox.

But we don’t know any of that. We don’t know if self-replicating probes at this scale are even possible, or if they are only possible at such high levels of tech that no one has actually made it there yet. The energy requirements for sending large probes to other stars are immense, and the challenge of building a probe that can build a copy of itself (including electronics, fuels, etc) is so far beyond what we can do that I have no idea how long - if ever - it would take to get there.

And what’s the self-replicating probe FOR? What does it do once it’s spawned a copy of itself? Why would you even build such a thing? So you can die happy knowing that you’ve set a course for machines to eat the galaxy? Just because we can imagine something doesn’t mean someone out there will do it. There may be fundamental limits we have yet to understand that make such probes impossible.

Without self-replicating probes, the Fermi Paradox falls apart. We could have 1,000 civilizations near us (say within 1,000 light years) and never know about it. Even Dyson Spheres are extremely hard to detect. Tabby’s Star is about 1170 light years away, if I recall, and we thought maybe it had some kind of Dyson swarm around it. If it had been a Dyson sphere, 10 years ago we would have had no idea it existed. And galactically speaking, it’s in our backyard. We have since have found other stars dimming and brightening in similar ways, and don’t kow what they are.

There could be a million Dyson Spheres in the galaxy, and we could miss all of them.

I still think the core problem here is perception. We greatly overestimate our ability to detect other civilizations, underestimate how hard it would be for those civilizations to colonize the galaxy, and then wonder why we can’t see them all. The answer may simply be that they are really hard to see, none of them have built successful self-replicating probes that don’t die out after a generation or two, and one of these days we will improve our detection capability and suddenly we’ll hear them or see them.

276

I’ve explained this previously, but basically because of how old the universe is.
The chance of another random ETI being within mere millenia of us, technologically-speaking, is astronomically low. It’s far, far more likely for them to be millions of years of equivalent progress separation.

We’re not talking rayguns and shiny silver suits. We’re talking hundreds or thousands of times greater separation than between us and cavemen.

Now, bear in mind we’ve been building spacecraft for mere decades (Sputnik 1 was only in 1957).
Perhaps the things that look difficult to us would still be difficult after millions of years of technological progress. But I certainly wouldn’t bet on it.

Physically impossible? Sure. Some of the things which we think are impossible may still be impossible to such a species. But engineering challenges just aren’t going to cut it.

If you want to posit that this is the sticking point then fine. But again: decades in to the task of building spacecraft, we’ve already landed a probe on an asteroid. Where can I place my bet that within millions of years we might figure out how to get one to mine materials from asteroids?

It depends how quickly you want to get there. Even slow probes cause the same issue for the Fermi paradox, if they can self-replicate.
But as I say, we know for a fact that humans have not scratched the surface of the energy potential of matter.

I wouldn’t say the paradox “falls apart”. It’s not making a positive claim.
It’s pointing out what we don’t know.

And Tabby’s Star being an equivocal finding for a time doesn’t tell us anything. We can detect pulsars from whole other galaxies, which illustrates that a very clear signal of a Dyson swarm could in principle be detected from very far indeed.
Or indeed many other tech. Remember, I am not claiming to know what aliens would or would not build. This solution of the Fermi paradox relies upon asserting that no civilization ever makes anything noisy or big enough to be seen.

Or that they aren’t there.

I would certainly prefer ETIs to be common, but the lack of empirical evidence is an important set of data, not something to be handwaved.

277

Just to give credit to someone who is always unjustly neglected.

Willy Ley created the so-called Drake equation a full decade before Drake.

In the 1952 sf anthology Travelers of Space, edited by Martin Greenberg, Ley wrote it out in his Foreword.

We can reason like this: Our island universe, our galaxy, contains at least 15 billion suns. … Being as pessimistic as is consistent with good sense we’ll put the number of suns with planets down as one billion, or 1,000,000,000. Each of these can be expected to have at least two planets of the type of Earth and Mars. This gives us two billion planets in our galaxy that can be expected to harbor life.

If we say that just one out of a hundred of these planets has progressed far enough to produce intelligent life of some sort, we arrive at the fantastic figure of twenty million planets with intelligent beings. Again, if only one out of a hundred of these intelligent types have progressed as far in the engineering sciences as we have, we get two hundred thousand planets on the verge of space travel.

And if, again, one out of a hundred is no longer just “at the verge” – but here begins the realm of science fiction.

That this is overlooked is criminal. Ley is not mentioned in the Wikipedia article on the Drake equation, not even in the 85 footnotes. Nor was he obscure. He probably was the leading writer on rocketry and space for the decade after WWII. I can only guess that because he wrote in a book of science fiction and despite all the talk about scientists reading science fiction, it really was a despised and ignored genre in 1951 that was wildly overoptimistic about the possibility of intelligent life making contact.

Nothing really has changed since then. We don’t know anything. We don’t know the odds about anything. We don’t know what humans or any other life are capable of. We don’t know if Earth has been visited in the past or is being invisibly visited or probed or studied today. All suppositions are equal, equally bad.

But if we’re going to talk about the subject, start with Willy Ley. He’s worth paying attention to.

278

This is basically an argument from incredulity. “Surely, if we could go from horses to spaceships in a few decades, a civilization that’s been around for millions of years must be able to…”

The problems with the argument:

  1. We don’t know how long technological civilizations last. For all we know we are already way above average and in the history of the universe no technological civilization has lasted for more than a few thousand years. Or a few hundred years. We really have no idea.

  2. Extrapolating short-term curves into the future is suspect. Rather than a constant series of improvements, perhaps there are just step functions. For example, Futurusts used to have fun drawing curves of the maximum speed attained by mankind, and then using it to ‘show’ that we’d break the speed of light within a few decades. But we didn’t. The exponential curve was an ‘infant industry’ artifact that had a hard limit, and once we hit it, progress stopped or at least slowed down dramatically.

In fact, our fastest vehicles still date back 50 years, and we’ve made virtually no progress on the speed front since. Our history of speed improvement is really just a series of step functions from animal power to steam power to fossil fuel power - harnessing increasingly dense energy sources. Airplanes went from props to jets. From jets to rockets to chemically powered spacecraft. It’s not a continuous function, and there is no evidence that the steps will continue indefinitely. We know we can go faster with nuclear propulsion, and maybe one day fusion. Neither of those gets you practical interstellar travel. Maybe a million year old civilization figures out another way, or mybe we are already close to the last practical step. We don’t know.

We are married to the idea of continual progress, but there is no reason to believe that’s true. We have slid back in progress many times in humanity’s history. We may be doing so again as we speak. Maybe civilizations that last a very long time only do so by going through a continual process of destruction and rebirth, always hitting the same limits after a time which causes them to contract again. Again, we just don’t know.

What we do know:

  1. There don’t appear to be Kardachev Type III civilizations. We’ve done a pretty thorough galaxy survey and have yet to see one modified by an intelligence. And we should be able to see those.
  2. Nobody within a few light years appears to be intentionally signalling us.

I think that’s about it. Every other null result has multiple possible explanations.

I think the difference between landing on an asteroid and building a self-replicating probe that travels to the stars is so vast that our speed in getting from horses to asteroid landings may be completely irrelevant. We can’t even build a truly self-replicating machine on Earth, and have no idea how to do so. We don’t know if we ever will.

And this may not just be an engineering challenge. It might be a ‘breakeven’ problem where it turns out that you need so much energy to send a self-replicating probe to another star system and build a copy of itself there that any civilization capable of that has no need for the probes in the first place. It might be like if you needed fusion power to build a solar power satellite: If you have fusion power, why are you building solar power satellites? The enabling tech is already better than the thing you were going to use it for.

Except now we are assuming that it makes sense for any civiliaation to build self-replicating probes that take tens of thousands,of years to travel between stars. And maybe that length of time brings its own challenges in terms of keeping a probe alive and healthy for that long in a harsh environment. Again, all of this speculation is just riddled with unknowns.

279

I didn’t use the word “must”. Perhaps we’ve developed the pinnacle of space technology within decades of starting. Who knows? I just wouldn’t bet on it personally.

Right. However, the one intelligent species that we know of, is aggressive, and on the cusp (cosmologically-speaking) from making replicating probes. It seems a rather dubious claim that ETIs might be common, yet none ever advance farther than we have.

Everyone in this debate is necessarily extrapolating from known data to unknown data.
I believe that my extrapolation is the safer one at this time, as I am not suggesting any new facts beyond what we already know. There’s nothing in physics that renders replicating probes, megastructures or noisy beacons impossible.

Really? You really believe that? We already have digital fabricators and I expect to live to see the day when a crude fabber can be made that given the right materials can make a copy of itself. Let alone millions of years.
This is not to claim that the issue of making a ship that flies to an asteroid and copies itself is somehow easy. It’s likely centuries away. Maybe millenia. That’s still small fry compared to the age of the galaxy though.

I’m making no such assumption, you are. I’m pointing out all the ways that evidence would be extant of ETIs and you are handwaving them all as “Why would they want to do that!?”
I don’t presume to know the minds of aliens. Meanwhile you need 100% of them to all behave in the same way.

280

I absolutely believe that. Think about what true replication means: Exploring for, mining, smelting, and purifying chemicals and minerals. But also somehow being able to build the machines needed to explore, mine, and refine the materials needed to build the machines. Building some sort of chip foundry. Somehow engineering or finding all the lubricants, glues and such that are needed. And on, and on, and on.

These things have supply chains of thousands of specialized businesses and millions of people. The only ‘self replicating’ we’ve done is with simple 3D printers that can print their own structural parts out of plastic or metal, but need highly refined feedstock. And they can’t hope to make the wires, the chips, the screws, and all the other parts that go into a printer.

The day we can drop a complex, computerized machine by parachute into a random place on Earth and have it cough up a second identical copy from local materials is the day I will agree that we might be getting close to such a device. We aren’t even in the ballpark in terms of being able to build such a thing. We may not ever be in that ballpark. We don’t even have autonomous mining or exploration, let alone assembly.

And how much would such a probe have to weigh? It has to go into an unknown solar system, descend down to a planet, hope to find all the stuff it needs to replicate, then build a launch rocket and fuel it, and somehow build a space drive from scratch to send it on its way. In the meantime, it has to collect enough energy to do this, which would be immense, and it has to never break down over thousands of years. And, I assume that in addition to all that it has whatever functionality you wanted the probe to do in each system as well, or there’s no point sending them.

Such a probe would likely be gargantuan. The energy you’d need to move it between the stars might be so high that if you’ve got it you can just terraform your entire system, move mass from the equivalent of the Kuiper Belt or Oort cloud, build a Dyson sphere, whatever. What do you need with another star system if you can build your own out to almost infinite size if you wield that amount of control over matter and energy?