This is exactly what kind of thing my “eyeblink” alluded to, but I think I get what you’re saying.
I think you’re saying that colonies spreading by generation starship would not be detectable.
Maybe generation starships (and colonies) are all over the Galaxy and we can’t see them yet.
But… It again has an issue with the replicating probes. If (multiple) species can build ships capable of ferrying whole communities around, the sending thousands of probes, or self replicating probes, is childs play. Why do we not see any?
Depends on what you mean by eyeblink. We are talking in cosmological scales, where an eyeblink is a million years.
Except, as explained, it doesn’t require going faster than the speed of light.
We are not seeing any is the problem here.
If an asteroid world ship pulled into our solar system and started dismantling the planets for materials, we would most likely be able to detect that.
Light speed is not the great filter if it doesn’t prevent us from expanding out into the galaxy, and there is no reason why it has to be done at such a high speed. We could take our time, move at .1% the speed of light, and have the entire galaxy filled up in a few hundred million years.
Are the plethora of challenges of reaching other habitable planets less complex than simply building a new planet in a desired location? Perhaps super-intelligent species just build their own, and thus have no reason to travel great distances?
Habitable planets don’t matter here. They will be extremely rare, if they exist at all. What civs would be going for is just the raw resources contained outside of their solar system.
The problem is that if given, say, a million years, we probably WOULD have done all these things.
Now, life could have probably existed in our universe billions of years before it started on earth, but let’s be generous and say life could not have evolved anywhere until it did on Earth.
Well, here on Earth, once multicellular life evolved, we ended up with a familiar pattern - ecosystems diversify and life becomes varied and widespread; mass extinctions destroy most of that variety; the survivors rediversify into new complex ecosystems.
The main cycle we evolved in started when the dinosaurs died out 65 million years ago; since then, despite ups and downs, the land has mostly been dominated by mammals.
The cycle before that started around 251 million years ago, and was dominated by reptiles. At no point during that time did intligent life arise.
But that was just luck. Imagine another world where life evlolved around the same time as us. Intelligent life couls just as easily evolved in an earlier cycle (just as it could have never arisen until life on the planet ended completely).
If these aliens had a million year head start on us - much less 65 million - they’d have had eons to colonize the stars
But once again, for the Fermi paradox it is not enough to posit that a species has good reason to do something other than interstellar travel (and other than anything else detectable, like a big ass laser light show).
We need those things to basically be out of reach. Because if 9/10 species decide to only build planets, but 1/10 has one faction that decides to launch probes, or just be noisy, that could leave evidence across the galaxy and/or within our own star system.
Forgive these unwieldy posts, this thread is moving so fast…(so fun!)
Okay I think here’s my disconnect. Somebody else said something similar about would we notice when they entered our star system or something.
In my mind, space is very big. The reason they haven’t been here is because we’re one of 100 billion stars in the Milky Way galaxy. Statistically speaking, it’s unlikely they would ever come to our particular star or even look at it.
Right now on earth, what percentage of land is dark at night? The unpopulated part? Maybe our star system just happens to be in the equivalent of the middle of Wyoming, while the rest of the galaxy is lit up like the rest of the earth is at night.
I guess the response would be we would see that, but would we for sure? I’m asking; I don’t know.
That doesn’t sound like a civilization we would have any particular reason to be able to detect, though.
That doesn’t sound right to me. Google says the radius of the Milky Way galaxy is 50,000 light years. At 1/1000th the speed of light it would take us 50 million years just to go halfway across the galaxy without stopping to colonize anywhere else along the way. Surely each of those colonizations take several hundred years before they are ready to send out more colonizations. Does the math check out?
What if there are actually around 2,000 interstellar civilizations, but they all started out within the last hundred million years. I say the galaxy is big enough that they could have all still never run across any of the others in this conventional speed strip mining model.
Aside: Was that just luck? For some reason I seem to think that reptile physiology wouldn’t be able to sustain a large brain. Something about regulating body temperature. Do I have that wrong? Could a cold-blooded creature theoretically have a large brain? Actually, are octopus cold-blooded?
It’s interesting that whenever the Fermi paradox comes up on SD, or forums like it, by far the most popular explanations are psychological: Perhaps ETs are out there, and have the means to explore or leave evidence, but just choose not to… How can we be so arrogant as to guess what they would do?
But such propositions are very much at the back of the list among astrophysicists and astrobiologists. For the reason that I said: that psychological explanations require every individual of every civilization of every species to always come to the same conclusion, for billions of years.
Given the variety of behavior we see among the one sentient species we know of, this looks like quite a stretch.
But what are the detectable signals we should be seeing in any of these hypothetical examples? If they’re not colonizing planets, what should we be seeing?
In any example of us expanding to billions of stars, would we be easily detectable to every single star in the galaxy?
Unless aliens solve the light speed problem they’d have to be close by. They would have had to detect us long enough ago through radio noise to have an expedition heading in our direction, or else heading here by random chance. And even if we are detected it will be a long time until they get here, and unless the mission includes aliens and is not just a machine then it may be a long time until the aliens find out about us back on their home world.
So no light speed travel and we’re not likely to meet any aliens anytime soon. But the odds improve over time. Eventually there should be a lot of technologically advanced aliens and eventually we and some aliens will run across each other. As long as we don’t wipe ourselves out anyway.
That was quite a popular explanation for the Fermi ‘paradox’ at one time; there are hundreds of billions of stars in our galaxy alone, so why would they come here?
In 1980, Frank Tipler suggested that a civilisation could launch a relatively small number of self-replicating probes, and thereby explore every system in the galaxy within the space of a few million years, so the question now becomes ‘why have they not launched self-replicating probes?’
Statistically speaking, it’s extremely unlikely that a particular worm will crawl under the rock in your front yard, and yet, if you pick up the rock, there’s a worm.
We are not talking about an individual coming over to visit, we are talking about a growth curve of an entire species.
If you look at it that way, it’s the other way around, as our star is larger and brighter than the vast majority of stars out there. But, once again, look under a rock in Wyoming, see those worms there? They didn’t crawl all the way from Ohio.
If other civs were out there stellarforming, putting up dyson spheres, and lifting the materials out of the stars, we would see that, for sure.
Easy enough to detect when they land on Earth and start taking it apart and shipping the resources back home. Or even the moon, a planet or an asteroid. What is so special about our solar system that wards them off entirely?
Sure, for a couple reasons. One is that I used those same numbers and math to come to a few hundred million year timescale. And why do you think that everyone will stop at every star system? If you have dandelions in your yard, they don’t invade your neighbor’s yard, then go from there to their neighbor’s yard, one at a time. The dandelion seeds get blown all over the neighborhood.
If you set out from Earth to colonize another system, why would you go to the next one over, when you know that there are already others going there? You don’t, you go on to the next. If you are part of a interstellar colony, and your faction decides to move on, you aren’t going to just hit the next star over, it’s probably already inhabited. You are going to push on past a number of them to get to one that is unclaimed.
Why do you think that for the first 13.6 billion years, there was nothing, and then all of a sudden in the last .1 all these civs came up at once?
And I’ve shown the math that says that we would. Not only would we see them in our back yard, but we would also see as they dismantle solar systems over a thousand light years away.
For the same reason we haven’t and likely won’t, is my guess: Without a solution to the light speed problem, there is no point.
I really don’t see humans doing one-way expansion. That’s not really our bag. When we discover new worlds, the point is to connect them to our existing world, to make the world bigger. That’s what I think of as the human drive.
Sending an ark 4 light years away (the closest!) means writing off everyone and everything on the ark, and for those on the ark, writing off everyone and everything back home. Forever. I don’t think it’s in the human psyche to do something like that.
Who knows? Again, I’m not positing any particular behavior of aliens, the critical thing is just what technology is at their disposal and the likely cost of said technologies.
For example, let’s say we discover a massive helical structure, radiating a complex pattern of gamma waves. We’d absolutely consider this potential evidence of ETs even while having no clue whatsoever of what such a structure is for.
However, we see no such helices. We see nothing at all in fact. No deliberate signals, no incidental ones either.
