I believe there are any number of intelligent life forms in the universe.
I also believe that all of them are alone.
Charlie_Tan and Acenray—there are at least 10 other instances of JWST mentioned in this thread. I’ve listed them below.
Was it only my use of it that confused you? I suspect not.
Modnote: Considering the context of their post and the thread, it sure looks a lot like your baiting a poster known for complaining about the use of acronyms.
Stop it.
This applies to anyone else wanting to be funny also.
I am skeptical.
To be honest, I haven’t read every post in the thread closely, so it could just be my inattention.
[Bolding mine]
Thank you for the note. I feel I must point out: I do not complain about the use of acronyms. That would be obnoxious and I use acronyms myself all the time (see: this thread). Instead, I have complained about people posting terms, including various initialisms and acronyms, that other Dopers could not reasonably be expected to know and thus are akin to posting in a foreign language which is a violation of Board rules.
Fair enough but also enough of this side issue in this thread.
Please all, back to your regularly scheduled program now.
Long story short, it’s obvious there’s no galaxy-spanning civilization out there because surely we would have seen some sign of it by now. That doesn’t preclude life generally speaking, which we’ve only just now barely begun to be able to detect remotely, or technological civilizations like our own. Other civilizations could pop up as quickly as ours and snuff itself out just as quickly as ours might.
I have no reason to believe the universe isn’t teeming with life, as many have pointed out already abiogenesis occurred on earth almost immediately as soon as conditions were right. There is no reason to believe these conditions aren’t likely to occur on other planets. Furthermore, we’ve only truly begun to be able to detect other civilizations over the last 100 years. This is peanuts to space. There could be countless pre-industrial intelligent civilizations out there, our own ancestors spent tens of thousands of years huddled around fires despite having brains physically identical to ours. It’s also possible that an alien intelligence could manifest in ways we barely recognize.
Many folks in this thread have also pointed out how trying to crunch the numbers breaks down to what assumptions you make about unknown variables and likelihoods, so attempting to use math to prove or disprove the existence of extraterrestrial life seems like a waste of time. I say we wait until we make contact with at least one other intelligent species, then maybe with our two data points we can make more accurate assumptions and get a better idea of how many others might be out there.
I don’t think that’s remotely obvious. If non-relativistic generation ships prove the only realistic option for interstellar travel, a civilization that has expanded across the galaxy but only colonized 1% of the stars is likely still invisible to us. Especially if their biochemistry is different enough that they wouldn’t be interested in Earth.
Hmm, why? Well, Dyson spheres come to mind. They’re all about efficiently harnessing a star’s energy and they are what Kardashev thought makes a Level 2 civilization. (I think he says type 2 but level 2 is better).
So if a species is a lvl 1 on the Kardashev scale, it should be able to outcompete a lvl 0 like Earth, and the same with lvl 2. The higher the level, the higher the efficiency of energy harnessing. Of course, maybe I’m wrong.
Aside from the question of whether what Kardashev thinks is anything like what aliens would think:
that’s efficiency in a particular area, use of energy; which is what Kardashev was specifically talking about. That’s not what I’d mean by a “most universal value”. Energy’s used for a purpose; it’s the things a person, or a species, choose to use it for that they value.
Maybe we’re just using the terms differently.
I couldn’t find the source but there’s a quote from the 1950s to the effect that nuclear energy won’t just make spaceflight possible, it will make it necessary.
Also, I’m reminded of a short story where a group of physicists stumble upon a way that anyone with access to hardware store tools and chemicals could build a planet-destroying bomb. This presents a dilemma; as one of them puts it, if the information was leaked the Earth wouldn’t survive a week.
It’s a fun idea, but physicists are confident for a number of reasons that dark matter can’t be baryonic.
Well firstly, several of the scenarios; megastructures, self-replicating probes etc may have been visible from day one of Homo sapiens’ existence.
Also of course, our scientific enquiries being recent doesn’t constrain the timeframe of the evidence itself. If a species existed hundreds of millions of years ago and built megastructures around our galaxy, we could still see them now.
Thousands of years is peanuts. If humans are any guide on how intelligences evolve and develop then it is extremely unlikely that there are many pre-industrial civilizations.
Finally found it: “Obviously Suicide” by S. Fowler Wright.
One of the biggest risks we face, imo, is that our power to destroy is growing at a rate faster than our ability to control it. I wouldn’t even choose nuclear as the risk. Nuclear weapons can cause devastation, but in the hands of terrorists will not end civilization.
Bioweapons are much more likely. CRISPR and future tech like it make gene editing cheap. Imagine if we did to people what we’ve tried to do to mosquitos - imagine a virus that replicates without immediate symptoms, but which ensures that the next generation is born sterile. Or one that simply damages our immune systems so badly that we all start dying of cancers, colds, whatever. Or one that simply changes us in some way that makes us stop striving and growing.
Who knows? When the tech is so available that high school kids in labs or terrorists with a few thousand bucks can start manipulating genomes or biomengineering viruses, that may be the beginning of the end for the race.
Perhaps that is the fate of all technological civilizations. They grow to the point where they become powerful enough that the power can’t be contained and they destroy themselves from within.
But even if civilizations are expanding outwards, that doesn’t imply that they would have colonized the entire galaxy. The argument you often hear is, “The galaxy is onky 30,000 light years across. Any expanding civilization should have, by now, expanded into the entire galaxy.”
I don’t see how that follows. First of all, accelerating close to the speed of light uses ungodly amounts of energy. A civilization expanding for respurces might balk at the energy requirements for travelling anywhere near the speed of light. For example, if you accelerated something the size of the ISS to 50% of the speed of light, you would need the equivalent of 400,000 megatons of nuclear explosions assuming a magic drive that doesn’t use reaction mass.
But it’s much worse than that, because the rocket equation means that a ship that size would have be almost all fuel, with a tiny payload. Moving large payloads between stars is something that just may not be possible without consuming so much energy that the trip isn’t worth it, or it’s only worth it if you go so slowly that colonizing the galaxy is not a reasonable goal.
Travelling between stars quickly is insanely energy intensive, The rewards at the other end would have to be extremely valuable. And even then, it’s going to take many, many years to get anywhere. If you want to do it with reasonable amounts of energy you are going to be traveling at a tiny fraction of the speed of light and it will take thousands of years to get anywhere. Engineering something that can stay working for such a duration is not trivial. maybe not even possible. But if it is, it still means an expansion rate of thousands of years per star. So if a civilization expanded linearly one star at a time, in a billion years at say 1,000 years per star, that’s a million stars. If that happened on the other side of the galaxy, we’d never know.
Maybe civilizations expand to other stars occaisionally when critically necessary, but never geometrically expand throughout the galaxy because it’s just too hard and too pointless for the expenditure of time and energy.
The rebuttal to this is always ‘but self-replicating probes!’. We don’t know how feasible it is to create probes that can travel through space for thousands of years, then not only build copies of themselves at a destination but collect enough energy for the next probe. Maybe they work, but they are the speed of Voyager and take 40,000 years to get to the nearest star. And maybe 99% of those fail on the trip, and of the ones that arrive 99% fail to replicate and launch from their destination.
And maybe only one civilization in a hundred ever gets to the technological level to create such probes, and of those only one in a hundred has thr desire to launch them.
It’s all speculation, but as long as we can come up with feasible scenarios for how there could be other advanced life in the galaxy we kmow nothing about, the Fermi Paradox has a rational answer that does not equate to ‘we must be alone’.
Why would that be the assumption? It doesn’t make any sense for it to be linear.
If the civilization can manage slightly more than one new generation ship per colony, it will grow exponentially. If slightly less, it will fizzle out. But constant linear growth has to be less likely than either of those two possibilities; it would mean the rate is exactly 1.0.
The radius of the sphere of expanding influence will grow linearly. But the timeframes are not very long; only a million years to get from one size of the galaxy at 1% c. The limiter would be if new colonies can pump out >1 new ship on average. It doesn’t require self-replicating probes unless you consider a generation ship that kickstarts a planetary civilization capable of producing more generation ships to be “self replicating”.
Why would it still be the same civilization, over a million years and thousands of planets? A million years is a species’ lifetime, not a civilization’s. And if the speed of light is the speed of communication, what’s to hold them together? By the time there’s a dozen planets colonized, will the ways they’re living even be recognizable to each other? I’d love to try to have a conversation with someone from even ten thousand years ago – but I think we’d have a hell of a time trying to understand each other, and not only because they wouldn’t speak English.
Aliens might be better at this than we are, I suppose. Or they might not. But I think there’s a reason why all those ‘galactic empire’ stories out there have FTL ships and FTL communications – two reasons. One is that there’s no way any civilization would hold together without (I doubt it would with.) The other is that the authors are trying to write a Galactic Civilization as if it were, say, the British or Roman Empire. Which fell apart within a handful of centuries, despite communications and travel which took days or months, not thousands of years.
Valid points, but there are some possible workarounds. A civilization could make a concerted effort to preserve the genetic and cultural state that they had when their generation ship was launched, and make an effort to launch future colonists in that state. It might be a good idea anyway, since if the ship actually arrived successfully, it must have been in a state that was compatible with long-term interstellar travel. So even if the civilization has moved on from their initial state (say, because it took 10,000 years to grow from the starter colony to a Type 1 local civilization), sending out the ship acts as a kind of reset button. There will still be some divergence of course, but it would be much less than it would be otherwise.
That is a grim and plausible theory indeed…
Because of that, I would think the only way it makes sense to expend the effort for a short-lived species like ours would be to send it without expectation of ever gaining information back, or profiting from it before we die. I am reminded of Voyager’s golden record as a primitive equivalent.
Things may change if your species lives for billions of years but it’s hard to ascertain the possibility of such a thing. Is it possible for any being to dodge huge space “explosions/energy bursts” for long enough to live for a billion years?
Silver lining is interstellar aggression may make no sense at all because no space-faring species would ever pose a threat to any other because they’re all trapped in their own solar systems.
There are a few clever tricks that may help reduce the amount of fuel required for this sort of journey. To avoid the use of rockets during the acceleration phase, you can accelerate the vessel using beamed power. Powerful lasers and very large sails could accelerate the ship to interstellar speeds; this process could be made even more efficient if the laser beams were swapped for beams of small, massive particles that can be caught using large magnetic sails.
This doesn’t help decelerate the ship though; you would need to carry enough fuel to slow down at the destination. There is one technology that may reduce this fuel burden, however; the magnetic sail we used to accelerate the ship in the first place could be reconfigured to form a magnetic brake - using the same process that Bussard described in his ramjet concept, but to decelerate rather than accelerate.
- I would point out again that a civilisation that possesses giant lasers or particle beams also possesses weapons that could deal death at vast distances, and is living on an existential knife-edge.
I have found many people seem to believe in, for lack of better words, ‘infinite technology’.
There is no reason to believe technology is infinite. It is likely there is a limit and we might actually be closer to that limit than when we started. The difference between a canoe and the Space Shuttle might be greater than the Space Shuttle is to what is possible.
Eventually we are likely to ‘tap out’ and the only increase in technology will be incremental…slight increases in efficiency that will get less and less as time goes on. I don’t think we are there yet but it could happen in 100K years, or 1000 years, or 100 years. I do believe we have a leap or leaps left, like fusion etc, but it could then just…end. There ARE no more new technologies to discover.
This seems to happen with the discussion of FTL - they just assume technology is ‘infinite’ and eventually we will find a way…or civilizations a billion years ahead of us will have a huge technology advantage.