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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

#311

Post by gcanyon »

AlbertCory wrote: post #225
gcanyon wrote: post #206

Earlier quoted context omitted.

> There is no such thing as a "probability" of any of those terms... > That said, there probably are intelligent civilizations somewhere in the universe ...pick one :-)

I gather you're getting all triumphant there: "Hah! A contradiction! So there." Not really, sorry. "Probability" as in "something you can assign an exact number between 0 and 1 to." "Probably" as in "I dunno, maybe."

First, I was gently poking fun, not seriously criticizing. But since this is apparently that sort of conversation: no.

> There is no such thing as a "probability" of any of those terms...

There is a probability for each term in the Drake equation, but I assume you mean that we don't have a way of judging what it is. I agree.

> That said, there probably are intelligent civilizations somewhere in the universe

"there probably are" does not equal "I dunno, maybe" -- I'd argue it's a direct summarization of the nonsense that is the Drake equation, but just semantically it at least means greater than 0.5 probability, which we clearly can't establish.

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

#312

Post by 29athrowaway »

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 does the interstellar medium interact with communication signals like radio waves?

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

#313

Post by patentatt »

aortega wrote: post #258
yourapostasy wrote: post #74

Earlier quoted context omitted.

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…

With correct encoding you can detect signals way below the noise floor. Thats how GPS work, you detect a satellite signal orbiting at 400 km with an antenna the size of a chip. The Curiosity rover communicates with Earth from Mars with an antenna the size of a soda can.

But the receiver has to know the encoding to be able to detect it. Maybe the aliens are using a different type of spectrum spreading technique that makes a lot of sense to them but is unknown to us.

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

#314

Post by Balgair »

aortega wrote: post #252
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…

Your calculation is likely wrong. See, you can build a laser in a spectrum not generally emitted by stars, and point directly to another star system. You dont need much power, yes, perhaps some terawatts, but it can be pulsed, total energy would be low. And getting a low power signal doesnt means its impossible to detect, but that the bandwidth is short. Instead of 200 bits per second, you would get 1 bit per hour. B…

All beams will broaden and distort though. No matter the wavelength or pulsing, anything made by not-a-pulsar is likely to get garbled and shifted beyond comprehension. You can fix this with some really really big fancy lenses, maaaaaybe. But you'd have to know the distance of the point you're trying to image the laser onto first. Collimated light over those distances just isn't ever going to stay that way.

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

#315

Post by Balgair »

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…

Just want to point out the currently known composition of the universe:

~5% matter. The stuff you and I are made of. Most of this is H and He though, bit of Li in there too. And it's all mostly burning in a star. Like, 99.99999% of it.

~25% dark matter. We know little about it. We do know that it falls down though and doesn't like to touch other stuff. But that's kinda it.

~70% dark energy. We know pretty much nothing about it. It falls ... up (?!).

Considering that the stuff we're all made of is the 5%, and even then most of that is down in a deep gravity well and on fire, I think we may need to look at the other 95% of the stuff out there too if we want to find friends.

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

#316

Post by _tom_ »

mcculley wrote: post #178
_tom_ wrote: post #82

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.

There won’t be anything artificial about such intelligences. I have taken to calling them synthetic intelligences.

"Next step intelligences"

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

#317

Post by _tom_ »

yreg wrote: post #267
_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…

If someone built Dyson spheres / swarms, they cannot hide from us even now. Unless it's possible to cheat thermodynamics.

Yeah, there would be mass and nothing visible. Like a black hole, dark matter, etc. :-)

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

#318

Post by yreg »

_tom_ wrote: post #317
yreg wrote: post #267

Earlier quoted context omitted.

If someone built Dyson spheres / swarms, they cannot hide from us even now. Unless it's possible to cheat thermodynamics.

Yeah, there would be mass and nothing visible. Like a black hole, dark matter, etc. :-)

There would be also the heat of a star.

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

#319

Post by withinboredom »

jjoonathan wrote: post #304
withinboredom wrote: post #266

Earlier quoted context omitted.

I doubt a civilization could survive being multi-starred. If you can expend that kind of energy, a pilot with a bad day can destroy the whole planet. A pissed off colony in the asteroid belt can sling asteroids at the home planet, etc. I also think you’re making a lot of assumptions but the speed of light is quite limiting in every aspect. If it takes 40 years to send a message, you need to either live a ridiculously…

> A pissed off colony in the asteroid belt can sling asteroids at the home planet If planets become indefensible then people simply won't colonize them. Problem solved. They'll stay in artificial habitats, and I would expect this to accelerate the colonization of the galaxy, if anything, because then they wouldn't need to wait for a planet to fill up before sending out the next generation of colony ships, they would…

> If planets become indefensible

Planets are indefensible, as is most of space if your orbit is predictable. All you need is a body bigger than your margin of computational error, and reaction mass.

> exponential growth

My point is that in order for civilization to be multi-starred, they'd need to communicate. Once a new star is colonized, due to the constraint on light speed, they become two separate civilizations. This means each star basically starts from the beginning, each time. So, if you estimate a couple of million years for a civilization to just to consider expanding... it'd take awhile. A lot more than a few million years to colonize the galaxy because not every star will consider expanding.

> the reason is resource competition.

Resources for what, exactly? Populations self-govern growth. It isn't always pretty, since over-population means a lot of deaths. But hungry people aren't going to say "I'm hungry so I'm going to build a space ship and hunt Space Cows. Who's coming with me?"

Further, there is no evidence that dinosaurs left this planet. They had 165 million years to do so. So, it doesn't 'just take' a few million years and there is no guarantee that a civilization will expand beyond a star. Sure, you could argue that dinosaurs probably weren't intelligent, but there's no evidence for that other than a small cavity size for brains; which doesn't necessarily mean they were stupid. Whales have bigger brains than humans, but I don't see them leaving the earth any time soon either.

My point is, even if you decide to colonize another planet, you are effectively cut off from your home. Technology WILL be lost since you basically have to restart manufacturing from nothing, with a small population at that, and there are a whole different set of filters to pass through. The odds of that civilization growing to the point of wanting to move on, without dying out itself, is remarkably low.

Interestingly, colonization of stars beyond a certain distance might even be impossible without some kind of artificial gravity or cryo. Especially if it requires multiple generations to arrive.

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

#320

Post by dromenkoning »

lapcat wrote: post #246
friend_and_foe wrote: post #235

Earlier quoted context omitted.

Really? You don't see how our civilization is stronger than it's ever been? You don't see how we are on the verge of expanding beyond our home planet? Just, don't see it huh? Perhaps you're not the person that should be explaining to everyone what is painfully obvious and what is not then.

> Perhaps you're not the person that should be explaining to everyone what is painfully obvious and what is not then. You didn't even understand my comment. I meant it's painfully obvious to me. It should have been obvious that I didn't mean it was obvious to everyone, but obviously some people can't see the obvious. I could write a long essay on why we're not on the verge of expanding beyond our home planet, but I f…

> I could write a long essay on why we're not on the verge of expanding beyond our home planet

The reason that essay would be long is because you'd have to explain away so much progress from multiple independently operating space industries.

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