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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

#261

Post by dredmorbius »

credit_guy wrote: post #177
m4rtink wrote: post #166

Earlier quoted context omitted.

We might be able to see their drive plumes if they use some of the theoretical high performance reactive drives we know of on big crafy. Eq. various fusion plasma drives, Orion, Nuclear Salt Water Rocket release so ludicrous ammounts of energy that they might be visible over interstellar distances, especially if pointed in our general direction when running. Massive solar sails as well would be very very big and very…

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.

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

#262

Post by krapp »

yreg wrote: post #254
withinboredom wrote: post #244

Earlier quoted context omitted.

And what if we broadcast and whomever hears us wants us dead? Maybe it’s so quiet because to be loud results in death of the entire civilization.

If you are an advanced civ that fears new competition, you don't wait for hearing random radio transmissions. You build replicating factories to build relativistic kill missiles and preemptively destroy all the planets in the galaxy.

Given that planets currently exist in our galaxy, either no advanced civilizations exist that fear competition or... apparently not?

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

#263

Post by btilly »

JauntTrooper wrote: post #170
btilly wrote: post #122

Earlier quoted context omitted.

BS. Filter 1. If we had no large moon, roughly every 30 million years or so our axial tilt would become too extreme for life. We do not have another example of a planet with a moon to rival ours in relative size. Filter 2. Without Jupiter acting as a cosmic vacuum cleaner, we'd predictably be hit by enough asteroids and comets that we'd never have evolved. In thousands of solar systems that we've found, we've found l…

Good comment. I would add that our Sun is alone, while up to 85% of solar systems are at least binary. It's possible multi-star systems make life more difficult. Similarly, Earth's magnetosphere may be uncommon, since we don't see a similar one on Mars or Venus. And maybe Earth's rotation is uncommon and many planets are tidally locked. I wonder, though, how this stacks against the sheer size of our galaxy. There are…

We don't know how rare either actually is. For both we have just one example - us. This suggests odds of no more than one in several thousand. But it doesn't take too many filters of that order of magnitude for a few hundred billion to become a handful, and the handful to become just one.

Your point about binary star systems is interesting. Orbital dynamics have a well-known tendency to be chaotic. In a single star system, this chaos is significantly less of a problem. But in a double star systems, the odds of moving in/out of the habitable zone over time are much higher. So that's probably a filter. But not as big of one as the ones I listed.

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

#264

Post by booleandilemma »

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…

we are extremely close to the beginning of all existence

This is the one that always causes me to wonder.

I was born in a major metropolitan area, which makes sense, statistically. I'm a native speaker of the 3rd largest language on the planet. That also makes sense. The 3rd largest country by population. Nothing out of the ordinary statistically speaking.

But to exist extremely close to the beginning of all existence

Huh? What are the chances that I, or any of us, would exist now? It's like being born on some island in the Pacific. Sure, it happens, but only to a few.

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

#265

Post by denton-scratch »

topaz0 wrote: post #195
denton-scratch wrote: post #130

Earlier quoted context omitted.

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 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.

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

#266

Post by withinboredom »

jjoonathan wrote: post #210
puglr wrote: post #192

Earlier quoted context omitted.

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…

It routinely bothers me a bit that, IME, most IRL discussions of the Fermi Paradox settle on this rather simple explanation when the whole idea was that this "simple explanation" was extremely unlikely, pushing speculation to more complicated and interesting hypotheses. Emergence of life on Earth took 13.7 billion years, galactic colonization should only take millions of years. We should not expect to find the galaxy…

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 long time — in which case your birth rate will be quite low — or figure the colonization as a one-way trip. No one would colonize another star system just for kicks, there would need to be a reason and I can’t think of a reason to colonize an entire galaxy that would make sense for a whole civilization, especially when it takes multi-decades just to send a message one way.

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

#267

Post by yreg »

_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.

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

#268

Post by yyyk »

alfiedotwtf wrote: post #257
withinboredom wrote: post #244

Earlier quoted context omitted.

And what if we broadcast and whomever hears us wants us dead? Maybe it’s so quiet because to be loud results in death of the entire civilization.

If an advanced civilisation was so advanced that it could hop around the galaxy on a whim, why would they come here to destroy us? It's not like the would possibly need any of our resources

It's not difficult to think of realistic (if not necessarily sensible) motivations if we try.

Maybe they're religious fanatics and there's no we can satisfy their tenants so.. Or maybe the local alien boss doesn't want to deal with their EPA equivalent and decides to deal with the problem before anyone notices. Or the Grand Poobah just acts whimsically and everyone must do as it says.

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

#269

Post by yreg »

krapp wrote: post #262
yreg wrote: post #254

Earlier quoted context omitted.

If you are an advanced civ that fears new competition, you don't wait for hearing random radio transmissions. You build replicating factories to build relativistic kill missiles and preemptively destroy all the planets in the galaxy.

Given that planets currently exist in our galaxy, either no advanced civilizations exist that fear competition or... apparently not?

Yep, I think it makes little sense for them to fear competition (if they exist). I suspect that intergalactic warfare is impractical and there is nothing to gain.

Reasons being: There is no stealth in space, there is no FTL, resources are abundant everywhere, destroying planets/megastructures is rather easy.

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

#270

Post by withinboredom »

anotherman554 wrote: post #216
saalweachter wrote: post #202

Earlier quoted context omitted.

So a fun thing to try to think about is "What's missing from our intelligence?" Our brains may just be made up of lumps of neurons, but we can break out various capabilities we have: * language * tool use * memory * ability to think about hypothetical situations * ability to think about abstract concepts * theory of mind We can think about what alien creatures or civilizations are like that lack them. A civilization…

If you look at animals on earth, they just aren't curious about many of the things we are curious about. My cats for example don't find television interesting. Suppose there's some property of physics that looks like random noise to us (maybe like a TV looks like random noise to a cat) but to a different species they see it's something they can model and understand while our species just ignores it?

Your cats don’t find the tv interesting because they can’t even see it. Their visual refresh rate is different enough from humans that they just see flashes of images (a refresh rate above 100hz is needed for cats to watch tv or see a screen, IIRC).
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