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The Fermi paradox revisited: Technosignatures and the contact era

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Re: The Fermi paradox revisited: Technosignatures and the contact era

#191

Post by janee »

superposeur wrote: post #102

In my opinion, the excitement occasioned by the discovery of so many exoplanets has clouded our collective judgement on the Fermi Paradox, leading the overwhelmingly most probable resolution to be underemphasized. Namely: there is no life out there. Not due to baroque mechanisms such as techno-self-destruction but just due to its sheer unlikeliness. As large as the number of stars in the observable universe is (let’s…

In a hypothetical total universe timeline of something like 100 trillion years, say till the degenerate era...we're not really very far in right.

If we were near the end and had the same paradox I'd say you're probably right in that the answer is there is no life.

But we're really really early, so either we're a total fluke and the first or there's another reason.

Basically what I'm saying is if you're right and the probabilities are so low then I'd think we should either not exist or the timelines I've sketched are very very off

Re: The Fermi paradox revisited: Technosignatures and the contact era

#192

Post by puglr »

shireboy wrote: post #183

Yeah, this is where I've landed on Fermi. It's very likely life exists elsewhere - possibly even on moons in our solar system. And it's somewhat likely intelligent life exists in other solar systems. But physics is such that it is much less likely two intelligences will be able to talk to eachother much less reach eachother. To quote Douglas Adams: Space is really big. You just won't believe how vastly hugely mind-bo…

It routinely bothers me a bit that, IME, most IRL discussions of the Fermi paradox tend to omit this rather simple explanation.

Half the time it's brought up, FTL is offered as the solution. Which as best we can tell is fundamentally impossible.

That squishy or otherwise organic bodies are generally unable to travel interstellar distances has always seemed to me to be the simplest solution.

Assuming intelligent life is out there, surely there are civilizations that have destroyed themselves and so on. But lack of FTL travel would be a common constraint, regardless of all other scenarios.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#193

Post by m4rtink »

wokwokwok wrote: post #40

Good grief, did anyone read the paper, or are you all just sprouting your own personal Fermi paradox theories? > The basic assumption of this work is the hypothesis that alien civilizations do not bother to explore merely biotic planets, so that the radiosphere criterion becomes the main trigger for alien civilizations to send interstellar probes The tldr; in this work is that they assume there’s a finite (short) dur…

Even a very efficient and radio quiet civilization would still have to release obscene amounts of heat if they do any serious stuff in space. Unless they somehow hack thermodynamics there is really no way around that.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#194

Post by thrown1212 »

rolenthedeep wrote: post #160
thereddaikon wrote: post #92

Earlier quoted context omitted.

I think the answer is pretty obvious, we are the precursor species. Or it could be any number of things other than nobody out there. For example, advanced life could be out there but it might be rare enough that you only end up with a handful of space capable civilizations at any one time. The milky way is a big place. If we assume that ultimately there isn't a clever way around the speed of light then two civilizati…

Us being (one of) the first species is the most likely answer IMO. It violates the anthropic principle, but that doesn't account for everything. By all estimates of the age and expected lifespan of the universe, we are extremely close to the beginning of all existence. We know that life takes an extremely long time to evolve, and life on Earth is young compared to the age of the system. That we don't see a sprawling…

It violates nothing. Your intuitions are expanded at length here http://grabbyaliens.com

Re: The Fermi paradox revisited: Technosignatures and the contact era

#195

Post by topaz0 »

denton-scratch wrote: post #130
topaz0 wrote: post #109

Earlier quoted context omitted.

If the intervals are relatively prime, it wouldn't take much to work out what the intended time unit was.

OK, that makes a bit of sense. But I don't know what it means for two real quantities to be relatively prime. Primality is about factoring, right? And you can only factor integers. So to observe primality, you'd have to partition interval measurements into an integral number time-units. Can two reals be relatively prime no matter how you partition them into integers?

You're looking at the sky and you see a bright and otherwise unexpected signal. Then you see it again, some time later. You write that time down as T_1. You don't know of any astronomical phenomena with period T_1, so you wonder whether this could be a weird rare event. Then you see it again, spaced by T_2 this time, and you start to wonder whether it could be a purposeful signal. Then T_3 etc. How could they be linked? They're getting farther and father apart, so maybe it is a sequence with some significance. Maybe it's the fibonacci sequence for example. So you try dividing all the intervals by T_1. And you get 1,1.503,2.496,3.500,5.506... huh, lots of nearly-half-integers in there, maybe T_1 was supposed to be 2 units actually?

Re: The Fermi paradox revisited: Technosignatures and the contact era

#196

Post by theptip »

Perhaps I'm missing something, but this seems to get the Fermi Paradox backwards. It explains why we haven't been visited by aliens (the light-cone of our radio transmissions is small and therefore aliens outside of it couldn't send probes to us), but the key observation of the Fermi Paradox is in the other direction; why can't _we_ see _other_ civilizations, in all of the billions of years of history in our light-cone?

If extra-terrestrial civilizations exist, we expect to be able to see some trace of them with our telescopes. Particularly at Kardashev type II and above (star-scale structures like Dyson Spheres).

Fortunately if you fix the Drake equation, the paradox dissolves: https://arxiv.org/abs/1806.02404.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#197

Post by m4rtink »

throw1234651234 wrote: post #10
Mistletoe wrote: post #7

Earlier quoted context omitted.

I feel the same way. How do the SETI people explain this away and justify their search? One light year is tiny, I think it would take an incredibly generous Drake equation estimate to make that contain intelligent life. Same for 100 light years too. But I lean towards pessimistic Drake equation values. Life is even more rare and precious the more I dig into the equation. > The true stellar density near the Sun is est…

There are other techno-signatures to look for: Dyson swarms (marked by irregular dimming). Infinitely more powerful transmitters - i.e. irregular pulsars. Oumuamua type fly-bys. "Unnatural" gasses in atmospheres. All purely theoretical, of course. As far as we know, we might not even notice life on Alpha Centauri planets 4ly away.

I think a big Orion drive powered spaceship flight profile would be widely noticeable. Like, nature rarely produces hundreds of sequential nuclear detonations in deep space in quick succession, possibly perfectly matching high energy transfer orbits.

Just not sure what would the other party thing about builders of such craft.

On the other hand, its clear what would they think about anyone running a Nuclear Salt Water Rocket - eq. riding continuous fission detonation for minutes or hours! They would definitely think they are batshit insane! :D

Re: The Fermi paradox revisited: Technosignatures and the contact era

#198

Post by pmontra »

puglr wrote: post #192
shireboy wrote: post #183

Yeah, this is where I've landed on Fermi. It's very likely life exists elsewhere - possibly even on moons in our solar system. And it's somewhat likely intelligent life exists in other solar systems. But physics is such that it is much less likely two intelligences will be able to talk to eachother much less reach eachother. To quote Douglas Adams: Space is really big. You just won't believe how vastly hugely mind-bo…

It routinely bothers me a bit that, IME, most IRL discussions of the Fermi paradox tend to omit this rather simple explanation. Half the time it's brought up, FTL is offered as the solution. Which as best we can tell is fundamentally impossible. That squishy or otherwise organic bodies are generally unable to travel interstellar distances has always seemed to me to be the simplest solution. Assuming intelligent life…

Even with FTL you have to know where to go. Let's say you do 100 solar systems per year (going somewhere close to the star and some local jumps to look around.) There are 100 billion stars in the Milky Way. It takes a billion years to sequentially scan the galaxy. Optimizations in the search algorithm to cut that number down to 100 years are left as an exercise ;-)

Re: The Fermi paradox revisited: Technosignatures and the contact era

#200

Post by superposeur »

Ancalagon wrote: post #171
superposeur wrote: post #102

In my opinion, the excitement occasioned by the discovery of so many exoplanets has clouded our collective judgement on the Fermi Paradox, leading the overwhelmingly most probable resolution to be underemphasized. Namely: there is no life out there. Not due to baroque mechanisms such as techno-self-destruction but just due to its sheer unlikeliness. As large as the number of stars in the observable universe is (let’s…

Abiogenesis happened Way too early in earths development for there not to be life elsewhere imho

Here is a plausible alternative scenario. As planets form, there is a certain window of opportunity where conditions are right for life to get going (among other extraordinarily unlikely accidents that must come together, the phase of planetary evolution must be just right). Almost always, this too fails. After all, every attempt to date to recreate primordial conditions in the laboratory have failed to produce any life.

I return to the key point: the number of planetary systems in our observable universe is not infinite. It is not much larger than atoms in a macroscopic chunk of matter. It is entirely possible that the probability of life forming on a given planet is much too small for it to have happened in the last 13.7 billion years. This is just like the fact that the probability of radioactive decay of an atom (even in a sizable sample) becomes unlikely if the half-life is too long compared with the time scale of observation.

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