I suspect @Jim_B has become a willing victim of Google’s & Facebook’s algorithms. The internet he sees is full of this garbage. So of course he thinks it might well be mainstream thought.
Unlike the internet I see which has none of this silliness. Zero. Zip. Zilch. Nada. Instead my internet is full of obscure bits on geography, ships, weird one-off airplanes, and railroad mishaps. Plus Motown & disco music vids. And yachts. The ads on yacht websites are hilarious; I can’t afford the props in the background much less whatever they’re selling. Much less the yacht it’s shown on.
You think yachts are real?
You think people pay millions of dollars for a wet Winnebago, then thousands of dollars each day just to rope one to some decking? What part of Duran Duran’s Rio video seemed like reality to you?
Some people are far too gullible.
The answer to Fermi’s Paradox that makes the most sense is the one expressed in a sci-fi trilogy that I won’t name out of spoiler concern -
Most civilizations are hiding from each other, understanding that other civilizations that find them may be more advanced than them and want to destroy them before they represent a threat to them. And those that haven’t hidden well enough are found by the more advanced ones and destroyed … quietly … without wanting to call another more advanced civilizations’ attention.
Again, behavioral or psychological answers to the Fermi paradox all suffer from the same issue of every individual of every species always coming to the same conclusion forever.
For example, let’s go back to the self reproducing probes. One individual or group can litter the galaxy with such probes. And then what? Who is going to go to the trouble of trying to clear up that litter when it won’t really affect the safety of anyone?
So, why don’t we see any evidence of such probes?
Eh, not necessarily. Even if a species has sufficient tech to make interstellar travel possible, it probably still isn’t easy. You don’t need every individual to agree not to do something; you just need every sufficiently rich group of individuals to agree.
It’s like the question of why New York has never been nuked. It’s possible, after all, but nobody has ever chosen to do it. There are plenty of people out there who would want to, but none of the people who want to have nukes. And then there are going to be some people who would want to, but still don’t, because they don’t want the consequences that others will impose on them as a result.
Humans launched an interstellar probe less than 2 centuries after a horse and buggy was our most advanced transportation technology.
However, in this context it doesn’t even matter when self replicating probes become technologically feasible, only that such a state is arrived at significantly before interstellar genocide (even of species that are moving targets such as generation starships, diffuse colonies etc) is feasible.
If there were interstellar civilizations capable of quietly crossing interstellar space and destroying other civilizations, they’d also be able to monitor planets for biosignatures in the atmosphere, etc… this is something we are already trying to do using our very limited capability of monitoring exoplanets, and will likely be able to accomplish in the next couple of decades for nearby planets. At the level of tech and resources it would possess, an interstellar empire should be able to monitor every planet in the galaxy for signs of life.
In other words, no matter how quiet we try to be, and even if we invent our own technologies that enable us to hide any signs of life in our atmosphere, we’d be screwed in the scenario you present, because these mighty interstellar civilizations would have noticed when Earth’s atmosphere filled up with oxygen during the Great Oxidation Event 2 billion years ago and sent a fleet to wipe out all life on Earth BEFORE it evolved into sentient beings who could even think about hiding.
You can only hide to the degree you’re far enough from who you’re hiding from. Monitoring every star in the galaxy is a tall order and requires a LOT of monitors in a lot of places. And lots of time for the various signals to propagate. Inverse square law for radiation propagation and inverse cube law for search volume are our friends.
Whether they’ll prove to be good enough friends depends on where the nearest advanced-vs-us civilization happens to be. Nearby? We’re screwed. Diametrically across the galaxy? We’re OK for a long time to come, perhaps for the duration of our natural existence as a species / civilization.
Problem with that is that we have already announced ourselves to anyone who is out there. It’s far too late to hide now.
So, I suppose we should expect a quiet extermination any day now.
That can still be a staggering number. If we start colonizing the solar system, then any colony capable of self sustenance is also capable of launching interstellar probes. It’s capable of becoming an interstellar vessel itself, in fact.
All it would take is one to decide that the solar system is too crowded, and set off on a voyage to another star. Sure, it may take tens of thousands of years, but so what? We’re not talking about a ship with hundreds or thousands of people and limited resources. We are talking a self sustaining colony with millions or more. At a certain point, what’s the difference between hanging out on Spaceship Earth for ten thousand years, and heading to another star over that same time period?
That’s a bad analogy, as New York is populated with a bunch of infrastructure, and nuking it would piss a whole lot of people off. Anyone who did so would face massive retaliation.
Since, as far as we are aware, space is uninhabited, a better analogy would be nuking uninhabited areas, just because we can, and we want to see what it would to.
And we certainly have done that.
I do wonder about that sometimes. The biggest threat I see to humanity is humanity. The only thing that can stop us is ourselves.
I can see a situation where the people of Earth consider space colonies a threat, and they are, as it would be trivial for any space colony to wipe out life on Earth. With the kind of technology required to move about in space and colonize it, the technology to destroy such colonies could also be available.
You wouldn’t necessarily be able to target every ship, but anything large enough to be self sustaining may be doable.
Any answer to the Fermi Paradox that puts the Great Filter in our technological future has to show that all civilizations would be affected by it. I can accept that the requirements to get to our level of technology requires a certain amount of competition, which means paranoia, meaning that it could be universally applicable.
Our collective EMR since the advent of radio is less than thermal noise or the CMB at the distances that matter.
As to physical probes, again the inverse cube law applies to search volume. We now have 2 robots beyond Pluto. “Big space little probe” applies pretty well. Sure, somebody could stumble upon it, but that’s not the way to bet.
If you mean that anyone watching our planet can detect atmospheric oxygen (and now burgeoning CO2 if they’re within maybe 150 LY of here), yeah, that’s a problem. But I’d argue two ways against that.
Is atmospheric oxygen the telltale signal aliens are looking for? We have no way to know. If they’re silicon based, maybe they’re looking for silane-rich atmospheres and Earth’s atmosphere looks totally dead/innocuous to them. Etc.
Secondly, if their rubric is:
Atmospheric oxygen → life → spacefaring life (eventually) → danger to us aliens → Must. Destroy. That. Planet. Right. Now!!
then on any planet there’s a pretty long time interval from step 1 to becoming a danger to others in step 4. Which implies that planets can’t hide. Only at about stage 3 do they become aware of their need to hide, and by then it was millions of years ago that they needed to start hiding but didn’t. Oops.
The aliens will be very busy squashing millions of planets. The vast majority of which won’t ever be an actual threat. In a totally post-scarcity society that might be doable, albeit slowly. But even in a post-scarcity world there’s still opportunity cost.
If we’re already on their “Must. Destroy.” list but they won’t get around to it for a couple million more years because of their backlog, well that’s enough for you and me.
Depends on what you mean by distances that matter. We could barely pick up the Earth at a distance, but if we had 1km space radio telescopes, we could pick ourselves up at quite a distance.
If there is life, then I doubt that the Earth is the only one that uses an oxygen atmosphere to metabolize carbon. These are abundant elements, and the chemistry involved is pretty simple and straightforward. Even if they evolved differently, they would still recognize that high levels of oxygen means life.
That’s kinda where I’m going with this. With James Webb, we will likely be able to tell the atmospheric content of planets dozens of light years away. Further advances in space telescopes will expand that.
If we can build a multi kilometer space telescope, we would be able to tell the composition of atmospheres hundreds, maybe thousands of light years out. Tens of thousands of light years is not undoable, and I see no reason why we wouldn’t. It would be much easier to build such a telescope than it would be to actually travel to the nearest star, after all.
If civs can see tens of thousands of light years, it doesn’t take many to have eyes on the whole galaxy.
IMHO, species capable of interstellar travel are either exceptionally rare, where you wouldn’t expect to see more than one in any multi-billion lightyear radius, or they are extremely common, where we should be seeing them develop in any conducive environment. The thing I always find most unlikely in the Drake equation is the fine tuning required so that there is more than one (us), but not more than a dozen or so.
Depends on how paranoid they are. They may just keep a closer eye on them, or they may be proactive about it.
One of the campaign worlds that I made for a space based RPG was one where they would just lob large asteroids at life bearing worlds every few tens of millions of years, to keep life from getting too advanced on them. (Our last regularly scheduled shot missed.)
If you need to sterilize a planet, it’s not that hard to turn an average sized star into a massive laser that can strike from hundreds of light years away.
It’s also enough for hundreds of other civilizations to have sprung up and started populating the galaxy.
If they’re an interstellar empire, I’m sure they can keep an eye out for more than one class of potentially life-bearing planets.
Mind you, I’m not arguing that any of this is actually likely. I’m pointing out that IF the reason we cannot see any aliens is that alien empires wipe each other out and hide, then the first alien empire that decided to do this could ensure that no other empire rises to their level in the first place.
Monitoring every planet in the galaxy is hard, but we’re talking about Kardashev 2 civilizations at the least here, who are harnessing the power of multiple solar systems, traveling to other starts, and wiping out life there. Monitoring all planets in the solar system is a monumental task that would take enormous resources and manpower, but a civilization like this has access to a staggering amount of both. You could have billions of people working with trillions of instruments to monitor planets and this would represent only a tiny chunk of the resources available to a civilization with control of even one star, let alone many. And that’s without considering AI (although whether you want to build an AI with the express goal of wiping out all other life in the galaxy is debatable - seems like it could easily forget/misinterpret the “other” bit and wipe you out, too).
Not to very much of the universe, we haven’t. We have been producing things on the EM spectrum for a bit over a century, so even in theory only within 120 LY or so will anyone out there possibly have heard us. That’s a really small ball of the universe. There aren’t that many stars close to us that are likely to host planets with life.
Right, but as has been mentioned, the fact that we have an oxygen atmosphere has been out there for hundreds of millions of years.
But in any case, those signals will continue to travel, as well as the changes in our atmosphere that indicate technological life. Even if they haven’t seen us yet, it’s too late to hide the evidence, anyone out there looking, as they would be in the Dark Forest hypothesis that @DSeid alludes to, would pick it up eventually.
This is a good point. There’s no real reason why a different species couldn’t have taken a path to sentience in Earth’s history - just because it didn’t happen doesn’t mean it couldn’t have - and any space-based detection method from a few solar systems over wouldn’t notice that Earth of 2021 is any closer to spaceflight than Earth of 65 MYA. We went from basically animals to early space exploration in 2 million years, and there’s no reason to suspect we were unusually fast about it.
Hell, if some theropod dinosaurs started down the sapience path 75 million years ago and went at it at half our own pace, they’d still have plenty of time to build a massively advanced technological civilization in time to deflect the asteroid that wiped out the dinosaurs in our timeline. With 6 million years to spare.
My point is, on these time scales, by the time you see that a planet’s atmosphere is indicative of complex life, you may actually be rather short on time before space-faring life arises. You just can’t tell. So if you’re trying to wipe out advanced civilizations, your best bet is to wipe out the first signs of life.
At the scale of a galaxy and limited to speed-of-light travel or instrumentation, change and progress on a planet actually happens pretty quickly compared to the speed of news about the change or the speed of your own ability to influence / destroy it.
This reminds me of the “dilemma of mobilization” back around the onset of WW-I.
Mobilizing up an army from a standing start was enormously disruptive to your economy and very expensive. So not something you want to do unnecessarily or as a precaution.
At the same time, the exponential growth of your capability over time as you train and equip the first group who trains the second group who trains the third group … means that if you start mobilizing even a week after some neighboring potentially hostile country does, you’ll be hopelessly outgunned real soon and ripe to be overrun. So you have an incentive to mobilize ASAP upon the slightest hint your neighbor is about to do the same. And, once mobilization is underway on both sides, to attack as soon as your advantage is large enough to be decisive in the early days.
In modern deterrence theory terms you have an unstable equilibrium prone to flashover into hot war. As 1914 proved to be.
My thought is that there doesn’t actually have to be other more advanced destroyer civilizations, just the reasonable fear there would be, just a frequent conclusion among technologically advanced world that the assumption the only other civilizations out there would be no threat to any specific “us” (whether due to beneficent ethics or technological inferiority) is dangerously naive. Better to not be the nail that sticks up. Lots of planets might develop life and some prioritizing by threat risk would make sense.
Sure they could already be on their way … even in our neighborhood it would take some time.
But then you are back to relying on psychological or behavioral solutions to the Fermi Paradox, which aren’t viable, because it would only take 1 subgroup of one alien race not to take the predicted path, and boom, the entire galaxy is crawling with colonists 100 million years later (ie a blink of an eye on a galactic scale)