Combined with the recent witnessing of evolution of multicellular life[0] the Great Filter seems more and more menacing.
[0] - https://www.sciencealert.com/scientists-have-witnessed-in-re...
[0] - https://www.sciencealert.com/scientists-have-witnessed-in-re...
Great Filter is neat because it bundles many different solutions together into one class. Any solution saying that civilizations in the Milky Way are incredibly rare is basically a variation on Great Filter.
>why should we assume anything about our ability to determine life beyond our Solar System?
It isn't farfetched to assume that sufficiently expansionist/numerous Kardashev type 2+ civilizations should be easier to detect from Earth than bacteria on Venus.
I think you are in fact laundering the very large assumption you're making.
However, it does seem that the Milky Way is not collonised (not even the other galaxies as far as we can tell), and if that's truly the case, then it would suggest that there is some kind of filter barring all civilizations from ever doing it.
I consider interstellar travel not ever being viable a legitimate filter.
Of course there is a plethora of other solutions as well.
I also wanted to point out that life on Venus would not even necessarily move the great filter. It is possible, though not experimentally proven, that lifeforms could survive a cataclysmic ejection from one planet after an asteroid impact and float to another planet in the same system. In other words, the life on Venus may have come from Earth or vice-versa.
"ANY AND EVERY" is not remotely a part of any plausible premise of either the Great Filter or the Fermi paradox. Please be charitable in stating assumptions of theories you disagree with.
Space is difficult, interstellar space exponentially more so. It isn't necessary to make any claims about any or all civilizations if the nature of physics alone makes it extremely unlikely for any species, however curious, to ever make it out of their local gravity well, much less sustain the technological infrastructure, knowledge base, energy consumption, unified political will (despite vast cultural and biological evolution) and control over every other variable across millions of years as a species to be able to stumble across our planet even once among the billions upon billions of galaxies' worth of stars in the observable universe.
One might say "it only has to happen once." I submit that it could have happened a thousand times and we could still never know.
So it seems reasonable that if any interstellar civilization were out there, one would have found us by now, or their presence would be obvious to us. After all, Rome knew of China, even if they never directly interacted, and Spain eventually stumbled across the New World. Von Neumann probes make sense because it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero. We look up at the night sky and we can see so many of them, and they seem so close together, obviously you'd run into one no matter which way you went, sooner or later. Right?
It's more comforting to make up rationales as to why we might be alone than deal with the ramifications of being surrounded by life we may never see in a universe in which the entirety of physical reality amounts to a rounding error in a zero.
[0]https://en.wikipedia.org/wiki/Hubble_Deep_Field
[1]https://www.theatlantic.com/technology/archive/2014/12/the-c...
There's a point where it's all just "big". A million and a billion seem equally big. Even though, as it has been said before, that the difference between 1 billion and 1 million is about 1 billion.
There are so many fundamentally difficult problems with deep space exploration, that it may never be logistically possible to over come them. And that's of the ones we know about.
If a single civilization in our galaxy made a machine capable of replicating itself and going to other star systems less than a billion years ago, we should have seen that.
> it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero
I fail to see how this is a strong critique of Von Neumann probes, maybe you can clarify.
Allow me to attempt to clarify.
Let's say a civilization creates Von Neumann probes. Ignore whether such devices are even technically feasible. It sends these Von Neumann probes out into the universe in all directions.
The chances of any one of them ever encountering anything larger than a grain of dust before the heat death of the universe is practically zero. In almost all possible universes, all of the probes are swallowed up by the void. In almost all of the rest, one probe finds enough material to be able to replicate, and all of those are swallowed up into the void.
The scenario whereby a stable chain of exponential reproduction and growth via interstellar transfer occurs lasting long enough for a significant amount of stellar matter to be consumed and for an obvious trace to be left which just happens to be visible to us, is not the most likely scenario in a universe where such devices exist, it is still so unlikely that its feasibility borders on requiring sorcery. Because the universe is just that empty.
It's the sort of idea that only works on graph paper assuming a "perfectly spherical cow in a frictionless vacuum" kind of universe. The lack of a universe awash in Von Neumann probes is not a strong argument against the existence of life or advanced civilization in the universe, it is, itself, a strong argument against the feasibility of Von Neumann probes.
If the goal is to mine the resources of one specific location, then a targeted probe makes sense. But if the goal is to proliferate and explore (or consume) as much of the universe as possible as efficiently as possible, then targeted probes seem less likely to succeed over the scale of time necessary.
I'd argue that your argument is either
a. not intrinsically true of complex probes or
b. just a modified version of the great filter argument
You could imagine an advanced civilization that creates an artificially intelligent probe that is pretty effective at problem solving and resilient to these sorts of failures. Even if targeted probes have to remain active, there is no reason they couldn't consume energy harvested from their origin world to course correct.
If your claim is that every form of intelligence will inevitably fall to mechanical or software failure, etc. then that claim seems to just be identical to the great filter claim.
> targeted probes seem less likely to succeed over the scale of time necessary.
Your own GP seems to provide a very compelling reason why this is not true.
>But if the goal is to proliferate and explore (or consume) as much of the universe as possible as efficiently as possible, then targeted probes seem less likely to succeed over the scale of time necessary.
Less likely than non targeted ones that you say wouldn't get past the first generation?
Haha okay. I think most would view this as a pretty uncharitable assumption (appears contingent on these civilizations not having telescopes or AI), but if that's your view I can understand why we disagree.
This is why no civilization would randomly fire off Von Neumman probes in random directions. They would understand that this is a problem.
If you want to efficiently use them, you fire them at nearby stars. They will either find materials and restart the process, or they won't (and potentially report this, but it's not required). A non-zero number of them may encounter sufficient material (given how plentiful planets seem to be, that's a fair assumption). Those star systems would now fire off a bunch of probes, at near stars. Rinse and repeat. It's a slow process, initially, but given the exponential nature, it should be surprisingly quick.
"Aiming" at star is not something that's too complex even for us. It might require mid-course corrections to account for errors, but we could build a probe that would conceivably reach a star. Ensuring it would be alive and operational by then is more challenging, but it is an engineering one. Actually entering the star's orbit might be even trickier depending on relative speed. But that's peanuts for a civilization that could build such things.
> The lack of a universe awash in Von Neumann probes is not a strong argument against the existence of life or advanced civilization in the universe, it is, itself, a strong argument against the feasibility of Von Neumann probes.
It is. But that's assuming we can even recognize one.
Given modern technology, we would be able to observe both without being noticed. It would be pretty trivial from space. It wouldn't be quite so trivial close up, but it would be possible.
A time difference of ten thousand years? The invisibility would be rather more effortless, and might even include direct memory manipulation in the victims.
A million years? Can anyone even imagine what a million year difference would look like? Never mind the technology - we can't even imagine what its motivations would be.
So assuming an advanced civ is going to do what we'd do - build ships, colonise, hoard and transform resources - is more than a little naive and unimaginative.
It's not unlike a protohominid assuming that life is about hunting, and any other two legged creature they meet is going to want to talk about flint knapping and these new arrowhead shapes.
The assumption is weaker than you suggest. It's not that your typical advanced civ will do what we'd do, just that some proportion (perhaps extremely small) of civilizations will be expansionary.
Any process that involves replication will eventually need more resources.
The idea is that "probability mass they'll cross paths with another and each can mutually grok the other exists" is a monotonically increasing function of the number of other civilizations, which bridges the problem you've identified.
> 1. it extremely unlikely for any species, however curious, to ever make it out of their local gravity well
ie. it is more likely that they would go extinct before making it out of their local gravity well, which means the discovery of other life local to us would make it substantially more likely that filter preventing us from attaining interstellar travel is ahead of us.
As we can see by this announcement they wouldn't have detected the first primal soup that formed life (we don't have any probes), but given enough time they would have sent a probe to our planet and detected single celled life, and they would have seen evidence of life.
At 5 light years (the closest start is just less than that) they wouldn't have had a chance before about 1900, and they might needed until 1960 (I give a range because there is room for debate on exactly what would be proof, they might have not been sure) to detect out radio transmissions. We would probably have made contact with them in the 1970s.
At up to 100 light years the above applies with more of a timeshift. After 200 we don't have the ability to detect ourselves (the technology of 1820 didn't give any emissions to go on.) I'm not sure if they would know there is a planet with water where we are (There has been great progress in detecting small planets but I don't know what their abilities are).
The farther out you go the harder it gets. Eventually they are still seeing the big bang form our galaxy and so have no idea life will eventually happen here (or where we will be as the universe is moving all along in directions that they cannot predict)
Back when we started broadcasting radio, we needed very powerful transmitters since the receivers were pretty primitive - you could make receivers with no power source at all (Galena radios).
Then we started using them for other purposes. Powerful radars appeared. TV was invented. Later on we added digital signals and most traffic shifted to binary for computer to computer communication.
Now we have things like WIFI and 5g. The problem is that the technology has advanced so much that cellular antennas can talk to puny transmitters from miles away, while the transmitters are only outputting milliwatts. We can also electronically 'steer' transmissions so they will 'point' at the other party (beamforming).
Long range communication is shifting to satellites and fiber optic cables. Those are pretty directional and not very strong signals, by comparison (and fiber optic of course has none). We have been slowly shutting down TV stations in favor of internet streams.
Civilian radars still exist but they are relatively weak. They are also slowly being phased out in favor of technologies like ADS-B, which broadcast a fraction of the power. GPS signals are very weak.
Military radars are also more sensitive than before - and increasingly look like background noise. Given the high emphasis on stealth, they are also more directional and lower power than before. And may not even be on all the time.
Given this, it is possible that, if you are taking a SETI approach, there's only a very small window before a civilization switches to more efficient and less noisy RF comms.
> At up to 100 light year
At 100 light years you'll have very faint, possibly undetectable signals, as the strength decreases with distance squared. Unless they are pointing at us.
A galactic civilization is expected to leave traces. The most advanced civilizations are expected to use a huge amount of energy (information is energy too). Even if we don't find spaceships, we could see otherwise unexplained high/low entropy regions. In fact, there is a theory that says that life is the most powerful entropy generator, and that Earth has a distinct IR glow because of it.
Currently, it doesn't seem there is anything preventing us from colonizing interstellar space in the far future. Lots of unanswered questions but the laws of physics don't exclude it.
The Great Filter theory is that because we don't see any sign of a galactic civilization, there is something in the way. It can be behind us (ex: the appearance of life) or ahead of us (ex: civilizations tend to get wiped off before they can colonize other star systems).
And even if the great filter is simply that even the most advanced civilizations can stay undetected (so no real filter), finding evidence that the great filter is less likely to be behind us make it more likely to be ahead of us (or inexistant).
I don't think simple multicellularity has ever been something that seemed like a likely candidate as a particularly strong filter (although you could argue that it's a weaker filter combined with others)
Do we know what were the necessary atributes of those early multicellular organisms without which animals wouldn't be possible?
Now, broadly, I think (in my capacity as an armchair biologist) what we care about here is an nervous system, or something like it that is capable of fast communication and complex feedback loops that can be built into complex "computation". Interestingly, nervous systems aren't present in sponges, which are most likely the basal animal group (and which are immobile), but are present in all other animals. I'm therefore speculating that "able to develop a nervous system" could be the filter we care about for behavioural complexity.
Being non-photosynthetic (so more advantage to being able to move around and find food), not having cell walls (so potentially more able to be motile, and form flexible structures), as well as just whether there are existing cellular pathways that control ion gradients in a way that can be co-opted for communication (which are present in sponges) all seem like plausible things that could predispose a multicellular organism to develop nerves, but if it is a filter, it could well also be that it's really hard to develop something as complicated as nerves, and an early animal got very lucky.
Reminds me of a documentary I once watched, watching a timelapse of a vine growing upwards. It grows spiraling, and it looks like it is "looking" for where the walls are, adjusting its trajectory whenever it touches a wall.
It's fascinating, and for me it definitely does have some quality of "intelligence" to it.
> Imagine we knew God flipped a coin. If it came up heads, He made 10 billion alien civilization. If it came up tails, He made none besides Earth. Using our one parameter Drake Equation, we determine that on average there should be 5 billion alien civilizations. Since we see zero, that’s quite the paradox, isn’t it? No. In this case the mean is meaningless. It’s not at all surprising that we see zero alien civilizations, it just means the coin must have landed tails.
Just spent the time to read this whole paper, I think you're misstating some of the claims. A lot of people seem to be confused as to what is stated by the Great Filter/Fermi paradox/Drake equation.
First, let's define some terms (from wikipedia!): "The Great Filter, in the context of the Fermi paradox, is whatever prevents non-living matter from undergoing abiogenesis."
To be clear, the Great Filter is a solution to the Fermi paradox. If the Great Filter is true, then there is no paradox. The statement that there is no Fermi paradox is not the same as saying there is no Great Filter.
This paper suggests that there is a huge amount of uncertainty in $f_l$ and it actually can be quite small, meaning that it is not unlikely that we would see no alien life. (I won't comment on their choice of log-uniform priors, which does not seem intrinsically justified and lets them get much smaller results than if they had just picked uniform)
But that is the Great Filter argument! If there is a great filter, that would be a reason why $f_l$ would be lower and the fermi paradox doesn't occur. The paper never suggests that there is no great filter.
Now contextualizing to this discovery. If there is life on Venus, that changes our estimate of $f_l$, reducing our uncertainty and increasing the posterior probability mass towards life developing, which means that the fact that we haven't seen life must push the probability of development beyond that stage down or our current state of affairs is more unlikely than it was before.
Does that make sense?
> First, let's define some terms (from wikipedia!): "The Great Filter, in the context of the Fermi paradox, is whatever prevents non-living matter from undergoing abiogenesis."
I think you ended this sentence early. Wikipedia continues that sentence "...from undergoing abiogenesis, in time, to expanding lasting life as measured by the Kardashev scale."
In the context of the Fermi Paradox ("where are they?"), Bostrom is saying that he hopes the Great Filter is "whatever prevents non-living matter from undergoing abiogenesis" ($f_l$), but it might not be. The Great Filter might be a thing that is ahead of us, says he. And, yeah, the prior that it isn't abiogenesis is higher if we find life in our backyard.
So, you're right, finding life on Venus reduces some uncertainty with $f_l$ and pushes some of the probability mass down the Drake equation, which remains a chain of expected value multiplications, which is a bad way to combine probability distributions.
Bostrom's whole argument is predicated on the proposition that the galaxy "should be" teeming with life, and if the argument that it "should be" teeming with life is bogus (boiling down bathtub curved or otherwise not-normally distributed probability distributions to means/point estimates and then multiplying them, even if we had $f_l$ nailed down exactly), then I think that's a win for not worrying about Bostrom's argument so much.
But you are right, it's hard to say "don't worry about it!" if I don't well and clearly define what "it" is, or worse, define it wrong ("the great filter!"). Thanks for pushing this into better clarity.
Perhaps the paper wants to say that the problem with the Drake equation is intrinsic to multiplying expected probability, but what they're really doing is laundering their great filter assumptions upwards in the Bayesian hierarchy (ie. into their prior distribution hyperparameters and choice of distribution)
ie. they are still using expected values, they're just using them
This discovery would totally undermine the thesis of this paper. Here's the paper:
> While the analysis above required us to make our own judgment calls about how to represent the state of scientific uncertainty for each of these parameters, our qualitative result is robust to many of these assumptions and can be driven by our claimed uncertainty in f_l alone
This is much less impressive than it sounds. What this means is that if we could verify there is alien life on Venus that independently evolved, then the prior they have for f_l is massively off and their claimed uncertainty is way off. Using a log-uniform + the lowest estimate for f_l they can find in the literature already explains most of their results, not the mere process of multiplying expected probabilities.
> So, you're right, finding life on Venus reduces some uncertainty with $f_l$ and pushes some of the probability mass down the Drake equation, which remains a chain of expected value multiplications, which is a bad way to combine probability distributions.
The only reason they get such a low result is because they push a lot of the probability mass of $f_l$ super super super super far to the left. By their model, the probability that $f_l$ is less than 0.0001 is something like 42%... if we discovered independently evolved life on venus that would shift extremely far to the right and change their results completely.
There are two types of naive thinking one is we are children of god and god would never kill all of us and we are deeply rational beings when things get critical we will snap out of it and get things done. I believe in gospel of doubt and that there will be no miracles here. Environmentalists are already abandoning their field and reskilling not only because of lack of funding but lack of public attention and change.
That tells me that they weren't all together convinced/interested/passionate about it, so good for them for switching. One thing I've noticed from people who love their field of research and are absolutely convinced of it -- they don't care how much it pays or who believes them. They do it partly because ego (want to be the first or among the first for groundbreaking studies) but mostly because of genuine interest and curiosity and the desire to show the world what they've learned.
The biggest argument in favor of climate change being a true existential risk is if the conflicts it would spawn would result in a global war.
It's far more of a threat to human culture and knowledge than to human DNA. The latter is likely to survive it in some form - albeit probably not a very interesting one. The former is already showing signs of stress and climate change has barely started.
Frankly, my belief is the only thing needed to parlay climate change into an accelerant for human progress as opposed to believing it's a hurdle to leap over is for us to see it that way, and use it as an excuse to build energy generation technologies 100x better than our current ones. The focus on renewables is depressing, and the memes around the solution to climate change to be "use less, consume less, focus on more clean energy" are equally so, since they creates a cynical belief there is a tradeoff between energy use and conservatism. We can have both.
Alternatively, you can compare France to China, which has a greater CO2 footprint per capita, and half the GDP per capita.
https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...
https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)...
Many climate change activists aren't even countenancing nuclear power, known to be sustainable as well as much safer now than even in the recent past. I strongly agree that we can have both, we just need to build it.
These aren't insurmountable problems, but they are pretty big. With solar, a person can stick it on their house. A grid-level installation can be built over time and starts paying for itself as soon as the things are plugged in.
Our current plans are targeting 2030 for massive carbon reductions, right? I don't see how starting a bunch of nuclear plants now really helps there. The most enthusiastic proponents of preventing global warming have always wanted to target 10-15 years out, so the energy isn't there for nuclear. Unfortunately. It would have been nice if we'd built a bunch of nuclear reactors 30 years ago.
PV manufacturing is complex and expensive. Most of the cost of PV is in the manufacturing machinery, since the raw materials are cheap. Adding new manufacturing capacity takes time.
It may be that PV can be ramped up faster than nuclear, but some of the new nuclear designs (NuScale and Oklo) could be cranked out pretty fast also.
As for time, the majority of this 20-30 years estimate consists of inertia and bureaucracy. As a country, we've built far more complicated (Apollo Project) and high-risk (Manhattan Project) things in the past in a compressed time frame, we had no choice then because we've faced clear existential risks. Our inability to countenance all this today says more about us as a society, than it does about the do-ability (within say a decade) of the task at hand.
I guess I can agree with you, but only as pessimist, which is a darn shame really.
Thank god. We need people who are logical and pragmatic, not ideological and dogmatic. I don't think anyone has done as much damage to the climate as environmentalists, by opposing nuclear power. Fortunately the climate (no pun intended) slowly seems to be turning.
I do think we should reinvest in nuclear power at the same time we're making other reforms to the energy sector and economy.
I think suburban homeowners and their organized interests have had much more to do with nuclear power. I am an "environmentalist" and am largely pro-nuclear power (although less than before due to increasing cost competitiveness of renewables).
Actual environmentalists (ie. people who are passionate about saving the environment and also analytical thinkers) like Stewart Brand have been on top of this for a while.