The Fermi paradox revisited: Technosignatures and the contact era • Hacker News Board

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

#81

Post by YurgenJurgensen » Tue, Dec 20, 2022, 5:43 PM UTC

bnralt wrote: post #79

YurgenJurgensen wrote: post #76

Earlier quoted context omitted.

The fact that you're talking about Saturn Vs and landing on planets and taking off again shows that you're considering the wrong paradigm entirely. If you're landing on planets you're already doing it wrong. Atmosphere and gravity wells are the enemy. Remember, even the non-self-replicating probe still needs to be self-repairing, since in your scenario it has to last for probably a million years' worth of radiation a…

I brought up Saturn V's to give people a sense of the mass we're talking about, not because I thought the probes would be actual Saturn V's (and I don't think we'll be sending 1.5 million of them to a single star). As I said, the reason I talked about landing on planets is because you mentioned rare metals, and I don't know how _reliably_ they could be found if you're only looking at asteroids. But maybe that's not a…

The problem wasn't that you thought they would be actual Saturn Vs, the problem is that you think the mass of a Saturn V is remotely enough to send a probe to the other side of the galaxy. Designs for intra-galactic probes typically include meters of shielding because of how nasty hitting even a grain of sand is at interstellar velocities, and in your case this is even worse, since said shielding doesn't have to stand up to a century of ablation, it has to hold up for a million years. You're exceeding the mass of a Saturn V on shielding alone, and the tyranny of the rocket equation still applies. Building bigger means building everything else bigger.

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

#82

Post by _tom_ » Tue, Dec 20, 2022, 5:43 PM UTC

My other pet theory is that organic life forms are an intermediate step in the development of intelligence.

No one will bother with us, until the inevitable artificial intelligences develop.

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

#83

Post by AnimalMuppet » Tue, Dec 20, 2022, 5:45 PM UTC

AlanSE wrote: post #50

causality0 wrote: post #36

The universe we find ourselves in isn't very compatible with a species like our surviving for an extended period. If humans exist for millions of years we're going to either spread out to fill the galaxy or our machines will. The fact earth was free to develop us means that no other species like us existed long enough to beat us to it. We ought to hope that's because species find some other priority besides expansion…

That argument seems to violate the basic rules of exponentials. If an advanced species did settle on an stasis, then that will only last until some subset of the population decides to go beyond the stasis. Particularly for a space-faring civilization, the time scales and resources are so fast, that any multiplication factor beyond unity will eventually go bananas. Any individuals with the prerogative to multiply will…

But in real life, it never actually is an exponential. There always is some limiting resource or saturation point or something, that turns it from an exponential into an S curve. An argument based on "the basic rules of exponentials" typically ignores second-order effects (there seem to always be some, even if we may not be able to see them in advance).

> that will only last until some subset of the population decides to go beyond the stasis.

You are assuming that they can go beyond the stasis. I'm not sure that's a valid assumption.

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

#84

Post by TheOtherHobbes » Tue, Dec 20, 2022, 5:46 PM UTC

yourapostasy wrote: post #74

spuz wrote: post #44

This paper seems to explore a question I've had for a while which is: What is the maximum distance an Alien civilisation could eventually detect life signatures from Earth assuming their detection technology matches ours? I know that our current radio signals extend 100 light years or so but at which distance could these eventually be detected? I ask because I've read that in order for the SETI program to make a dete…

Our electromagnetic shell drops below the noise floor around 15 light years out for say 5 MW military radars. For coherent signal decoding into carrier wave and payload waveforms as opposed to being able to point to a signal and say, yep that's not natural, probably around 5 light years out. Some discussion here [1] to get you started. Even assuming super duper alien technology that violates what we know of the physi…

I would guess advanced civs don't bother with radio and look instead for direct visual and spectrographic evidence.

We're very close to being able to look for spectrographic evidence and maybe 50-100 years from building a telescope that uses a planet's gravity well for optical enlargement.

Earth already looks quite distinctive spectrographically because of the free oxygen, water, and CO2. In the general case you look for chemistry that is far from equilibrium.

Hubble already has the sensitivity to analyse exoplanet spectra, and Webb can do much better.

But some way beyond that, I'd imagine it's possible to look for spectral technosignatures directly. Artificial lighting, heat sources, and unusual non-biosignature gas combinations would all be clues that life exists.

I'm also fascinated by Przybylski's Star, which must be one of the weirdest objects in the galaxy. It doesn't take much imagination to wonder if it's an artificial beacon.

https://en.wikipedia.org/wiki/Przybylski%27s_Star

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

#85

Post by AnimalMuppet » Tue, Dec 20, 2022, 5:49 PM UTC

actionfromafar wrote: post #66

1970-01-01 wrote: post #25

Until SETI locates something like a pulsar braking and accelerating to signal prime numbers we're really really really unlikely to stumble onto more life. Space is just too big.

I think it can be done cheaper than that, and with technology we have access to. Detonate a handful of large hydrogen bombs in deep space, set apart by minutes. Say hello to our fellow Aliens.

How far away do you think such a thing could be detected? Say someone set off a 100 megaton nuke in space within the Centauri star system. Could we detect it?

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

#86

Post by kiba » Tue, Dec 20, 2022, 5:55 PM UTC

cortic wrote: post #68

marcosdumay wrote: post #43

Earlier quoted context omitted.

> because otherwise the reason we're free to exist is because species like us always wipe themselves out before they spread That's a complete non-sequitur. There can be plenty of reasons for a species like us never appearing on the first place, and they are way more reasonable than postulating that life like us always destroy itself.

We are actually running out of places in our history to fit a great filter. Most of the events in our evolution seem probable, even inevitable. In fact the only place IMO that's really left is the emergence of the first self replicating RNA molecule. But even that seems too probable to be a great filter. And if its not behind us, it has to be in-front of us or we are under a great misapprehension about the nature of…

Probably, inevitable based on what sample size?

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

#87

Post by AnimalMuppet » Tue, Dec 20, 2022, 5:57 PM UTC

api wrote: post #12

antirez wrote: post #5

The first alien we will ever encounter is likely a neural network we built with our hands.

If something visits us from another star system it's also likely to be an AI. Hibernation for thousands of years to travel between stars would be almost trivial for machine intelligence. Just turn yourself off. It'd be easy to tie this directly to solar power. Have an array of solar panels that powers you near a star and in interstellar space you just naturally go to sleep. When you approach the next star system the…

Even for an AI, you'd need storage media that are stable for thousands of years, and hardware that will still turn on after thousands of years, and solar panels that are still functional after thousands of years. Oh, yeah, and a fair amount of those thousands of years will be exposed to radiation, including relativistic iron nuclei (fun stuff).

Your AI may not quite be itself when it arrives.

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

#88

Post by kiba » Tue, Dec 20, 2022, 5:59 PM UTC

_tom_ wrote: post #80

The Fermi paradox assumes that "intelligent" is one threshold, and we are beyond it. We couldn't communicate with the most advanced primates from a million years ago. A civilization a million years past ours would be unlikely to want to talk to us. The average star in our galaxy is a billion years older than our sun. You can only communicate with civilizations near your level, which are inherently much rarer. We aren…

We couldn't communicate with the most advanced primates from a million years ago. A civilization a million years past ours would be unlikely to want to talk to us. The average star in our galaxy is a billion years older than our sun.

Based on what? Just because a civilization is extremely sophisticated doesn't mean we have nothing to offer.

We still study primates and ants. Hell, we even desire that we could communicate with chimps and dolphins.

Communication is impossible with primates and ants simply because they lack the hardware to engage in abstract communication.

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

#89

Post by messe » Tue, Dec 20, 2022, 6:02 PM UTC

ben_w wrote: post #62

chii wrote: post #8

Earlier quoted context omitted.

But that wouldn't technically be an alien, since it's not extra-terrestrial.

"Alien" doesn't only mean "extra-terrestrial", for example: https://travel.state.gov/content/travel/en/us-visas/immigrat... And: https://www.theguardian.com/society/2013/dec/12/gender-segre...

Ok, but right here, in this context, everybody else in the thread is quite obviously referring to extra-terrestrials.

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

#90

Post by russdill » Tue, Dec 20, 2022, 6:04 PM UTC

eloff wrote: post #37

1970-01-01 wrote: post #25

Until SETI locates something like a pulsar braking and accelerating to signal prime numbers we're really really really unlikely to stumble onto more life. Space is just too big.

But is it? We can detect things about the chemical makeup of the atmospheres of extra solar planets. Our own atmosphere is broadcasting the likely presence of life, plus near certainty of industrial civilization. We could detect that up to some distance with our technology. What could advanced aliens detect? What if they used gravitational lensing to magnify the signal? We can’t rule it out. Let’s hope the dark fores…

Our signal for oxygen and other bio-signatures is so much stronger than the signals we have been sending recently and it's been going out for...quite some time.