Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Fermi paradox revisited: Technosignatures and the contact era

arxiv.org

Post reply on HN
Print view View original

281–290 of 353 posts

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

#281

Post by omnicognate »

floxy wrote: post #208
credit_guy wrote: post #149

The Fermi paradox is good for a nice chat at a party. But it's not a paradox at all. Imagine there's an alien civilization in our galactic neighbor Proxima Centauri. How would we know they are there? To make it more plausible. Let's say we figure out a way to send a space probe to Proxima Centauri. How do we communicate with that probe? Easy, you say, just like we communicate with the Voyagers: they point a reasonabl…

>How would we know they are there? How about pointing an optical telescope at them to take a look? Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravity Lens Mission https://www.youtube.com/watch?v=NQFqDKRAROI https://arxiv.org/abs/1802.08421

Which is absolutely amazing and I desperately hope it happens in my lifetime.

But we haven't done it yet, so it's hardly relevant to the "why haven't we seen any?" part of the "Fermi" "Paradox".

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

#282

Post by actionfromafar »

DesiLurker wrote: post #277
AnimalMuppet wrote: post #85

Earlier quoted context omitted.

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?

its inverse square falloff for radio energy dissipation so I'd say it goes away really really quickly. also you have the problem of overcoming Sun's 'blaring' background signal unless you took your signal generator and placed it outside of oort cloud or further.

Yes, why not the oort cloud! It might take a decade or two to get them out there, but completely within our current technical capabilities.

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

#283

Post by Mistletoe »

friend_and_foe wrote: post #219
Mistletoe wrote: post #22

Earlier quoted context omitted.

For me it boils down to- would an advanced civilization beam out a very strong locating signal on purpose? They would have to be very certain they were the baddest strongest civilization in the galaxy. I can’t think of a way intelligence and that idea go together.

With one single data point, we presume that life is ubiquitous in the universe and that intelligent civilizations probably exist in more than one place, yet we assume that everyone else is scared to give away their position, even though we aren't. If we can presume intelligent life is out there even though up to now we only know of ourselves, why not presume that that life behaves like us in at least this one way? Se…

I don’t think we are that intelligent obviously. When I watch the news this is confirmed. And when we send out a “look here and come plunder” beacon it is confirmed as well. We just exited the campfire stage a hundred years ago or so. An alien civilization could be millions or billions of years ahead of us with weapons that we can’t even imagine.

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

#284

Post by Valgrim »

twawaaay wrote: post #165
credit_guy wrote: post #159

Earlier quoted context omitted.

Only if they are in our own Solar system. But you can easily imagine a supercivilization visiting lots of solar systems, but not establishing permanent colonies everywhere. As I said, what if 5% of the solar systems are teaming with life? That would still be tens of millions of solar systems in our galaxy. The diversity of life could be something to make Star Wars look unimaginative. And we'd have no idea they are ou…

What kind of argument is this "only if they are in our own solar system"? Even at the speed of Voyager 2, (15km/s), in a billion years it would cover about 4 * 10^17 km or about 40 thousand light years. I am pretty sure people who have been developing for hundreds of millions of years can do better than that, by orders of magnitude. Also you put a totally strange assumption that all civilisations will only restrict t…

If the dark forest hypothesis is true, you can bet any civilization advanced enough to detect us will go out of their way to avoid being detected by us.

For all we know, there could be a gigantic tungsten rod slowly and purposefully accelerating toward us that would destroy all life on earth in ten thousand years, and we'd have no way of knowing.

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

#285

Post by actionfromafar »

denton-scratch wrote: post #265
topaz0 wrote: post #195

Earlier quoted context omitted.

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 link…

> so maybe it is a sequence At that point, you introduce the assumption that the interval is quantized. Up until then, you're dealing with an arbitrary period of time, which is a real, and can't be made into sequences. Once you have sequences you have integers, and so you can have primes. But you can't just switch from reals to countable numbers without explanation, and then say that two reals can be relatively prime…

So begin with a sequence of 1 1 1 1 1 1 1 1 1 1. That establishes a baseline cadence of minutes, or hours or whatever. A clock signal if you will.

Then switch to primes. I think anyone looking at that kind of message will figure it out eventually. It can't be mistaken for a natural occurence.

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

#286

Post by DesiLurker »

friend_and_foe wrote: post #212
cletus wrote: post #163

Focusing on radio communications for SETI purposes and as a solution to the Fermi Paradox I find to be incredibly outdated thinking. Let me summarize: 1. Planets are incredibly inefficient in creating living area per unit mass; 2. Orbitals are incredibly efficient at creating living area per unit mass. IIRC 1% of Mercury's mass could create a full Dyson Swarm around the sun and have billions of times of the living ar…

You're ignoring the temporal aspect. A dyson swarm would be visible thousands of light years away, thousands of years after it happened. Humans current technological kick start has only been going on for a hundred or so years. Our entire known history, complete with dark ages, is a few thousand years. By the time something even sees it, who knows how much such a civilization will have changed. Would the dyson swarm e…

> A civilization could be born, evolve and die

I feel this line is doing quite a bit of heavy lifting there because this in itself is a solution to fermi's paradox. if a type-2 civilization could 'just die' then we should probably think about possible way in which they could completely (& i mean completely as in the last humans w/o the ability to bear & raise children) be wiped off. the only way I can imagine that besides an AI is a planetary gray goo scenario. but even that does not works for a type-2 civ. & if an AI wipes us out then there is a good chance that the AI itself will be around to take over the leftovers.

The only realistic solution for the paradox IMHO is that intelligence (not life) is really really rare and has happened here on earth with humans by accident. I mean Dinosaurs existed for about 160M years but the did not develop intelligence and we only developed in last couple of million years only.

the other rather handwavy solution I can imagine is that all intelligent civilizations ultimately give up meatspace and evolve into some hybrid quantum-foam dwelling semi-temporal beings because that gives them most amount of 'freedom'.

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

#287

Post by oAlbe »

Valgrim wrote: post #284
twawaaay wrote: post #165

Earlier quoted context omitted.

What kind of argument is this "only if they are in our own solar system"? Even at the speed of Voyager 2, (15km/s), in a billion years it would cover about 4 * 10^17 km or about 40 thousand light years. I am pretty sure people who have been developing for hundreds of millions of years can do better than that, by orders of magnitude. Also you put a totally strange assumption that all civilisations will only restrict t…

If the dark forest hypothesis is true, you can bet any civilization advanced enough to detect us will go out of their way to avoid being detected by us. For all we know, there could be a gigantic tungsten rod slowly and purposefully accelerating toward us that would destroy all life on earth in ten thousand years, and we'd have no way of knowing.

Why a tungsten rod in particular?

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

#288

Post by fernly »

yamtaddle wrote: post #136
spookthesunset wrote: post #111

Earlier quoted context omitted.

I think the probability of there being other life is much closer to 100%. There just has to be. Our universe offers way to much of the correct “stuff” that can create life that it just has to exist elsewhere. Why haven’t we seen it? Well that is one of life’s great mysteries. But the idea we are all alone in this giant thing called the universe… it just doesn’t feel right. The more we learn about things the more we r…

I think life's probably fairly common. Like, bacteria-type stuff, maybe something like moss. I think complex life, and life that lasts as long as that on Earth has, is probably extremely rare. There's a lot more that's special about Earth that lets it support large fauna over long spans of time, than just orbital position and basic composition and such. Our weird moon plays a role, tectonic activity is vital , not ju…

If you grant moss and bacteria, then more complex life forms become inevitable. There are _advantages_ to be being multicellular, or multicellular life wouldn't exist. It's energetically advantageous for a plant to acquire a woody stem and stand up above the moss, or for a simple organism to work out how to have eyes, or teeth, or legs, or an exo- or endoskeleton. Assuming an environment that affords nutrients and is stable over a long time, once life kicks off it should keep complicating itself. It wouldn't stop at simple forms.

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

#289

Post by postalrat »

nobody9999 wrote: post #278
postalrat wrote: post #184

Earlier quoted context omitted.

The paradox is that the our solar system should have been visited. But so we haven't been able to detect anything. It's much closer than the centauri system.

>The paradox is that the our solar system should have been visited. But so we haven't been able to detect anything. >It's much closer than the centauri system. That assumes there have been other(s) technological civilizations in our galaxy. Which isn't necessarily the case. We may well (or not) be one of the first space faring (for some values of that term) civilizations in our (part of) the galaxy. A recent discussi…

That is a possible solution for the paradox. The comment I replied to was talking about a different star system.

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

#290

Post by credit_guy »

dredmorbius wrote: post #261
credit_guy wrote: post #177

Earlier quoted context omitted.

Space is large. If you don't look in some direction, you don't see what's there. Big, or not. Let's take the Orion engine. It keeps blasting away thermonuclear bombs. Are we looking straight at it? Why? Ah, maybe because they are in the neighborhood of a star. But then we are also looking at the star, which is trillions or quadrillions times brighter. Same for fusion plasma drives or anything else. If the Orion engin…

If they're approaching us, they might be using the Orion engine to decelerate on long final.

Here's an amusing thing. Even if they were within Jupiter's orbit and decelerating and pointing straight at us, we wouldn't be able to detect them.

Nuclear bombs produce a fireball here on Earth. In the first microsecond when the explosion actually happens, they produce gamma rays and X rays. The atmosphere is opaque to those rays, which is to say, it absorbs them. Their energy is enormous, so the part of the atmosphere that absorbs them becomes superheated. That's what the fireball is. That's what produces the bright flash.

In space it goes without saying that there's no air. The fireball doesn't form. The explosion itself will produce gamma rays and x-rays (the blackbody radiation at 100 million degrees).

They will go in all directions, including towards Earth. But once they get to Earth, they'll be absorbed by the upper layers of the atmosphere.

As seen from Earth a nuclear explosion happening somewhere in the vacuum of the Solar system will be invisible.

But we do have gamma ray and X-ray telescopes. On satellites in space. Only not that many of them. If they don't look in the right direction exactly when the explosion happens, they see nothing. Another difference between a nuke detonated in space and one on Earth is that on Earth you can see things (like the mushroom cloud) for hours after the explosion. In space, the explosion happens, and one second later nothing. There is absolutely nothing happening one second after the nuke goes boom. So our telescope needs to point exactly in the right direction, exactly at the right time to have a chance to see something.

Post reply on HN