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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

#301

Post by rolenthedeep »

booleandilemma wrote: post #264
rolenthedeep wrote: post #160

Earlier quoted context omitted.

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 existenc…

It really is nothing short of wondrous and awe-inspiring.

We could very well be one of the first species on the galactic stage, how absolutely awesome is that??

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

#302

Post by random314 »

whatshisface wrote: post #187
random314 wrote: post #173

Earlier quoted context omitted.

SD is defined by dividing by the square root of the number of samples. It is never divided by the mean - as this metric has no relevance. The SD as it relates to the central limit theorem is the confidence in the estimation of the average E(X) of a distribution. It means that the SD reduces i.e. confidence increases as the number of samples increase. You don't need the central limit theorem for this. It follows from…

The variation in the random variable relative to the value of the random variable goes away for large sums.

The variation in the random variable relative to the value of the random variable is fixed. It doesn't change, no matter how many times you sample the random variable. It's called the per-sample standard deviation.

If 2 people A and B have a salary difference of 100K$ , then their salaries will not start to cluster together if you add C,D,E,F and more into the mix because of Central Limit theorem. Their salary difference will stay exactly at 100K as before.

The variation/standard deviation in the sum of random variables increases as the square root of number of samples, not on the basis of how large the sum is. This follows from the definition of standard deviation.

If you divide this "sum of random variables" which is itself a new kind of random variable (that is different from the per sample random variables you are starting out with) by number of samples then as

alpha*sqrt(n)/n = alpha/sqrt(n)

the variation in the summation random variable reduces(if divided by n) by a factor of 1/sqrt(n)

Once again, all of this simply follows from the definition of standard deviation. Central limit theorem doesn't come into the picture.

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

#303

Post by random314 »

dragonwriter wrote: post #215
dragonwriter wrote: post #155

Earlier quoted context omitted.

If you assume that they vary independently , yes.

Incidentally, my statement above is incorrect on a couple of levels: first, I was thinking of the law of large numbers not the central limit theorem, and second, even the LLN would only say that about the average step length, not the total time to the end of any step.

Correct

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

#304

Post by jjoonathan »

withinboredom wrote: post #266
jjoonathan wrote: post #210

Earlier quoted context omitted.

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…

> 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 just need to wait for the prime asteroids to be claimed.

> the speed of light is quite limiting in every aspect

Yes, exactly, and the non-interaction limit only needs one ship of space mormons to become exponential growth

Diffusion-limited exponential growth, to add the next layer of modeling sophistication, but the ultimate point is that you still don't need all that many generations before the galaxy is full. Just multiply the number of steps by generation time, and if you are tempted to pick a really long generation time, remember that space mormons get a vote.

> 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

Come on, the reason is resource competition.

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

#305

Post by whatshisface »

random314 wrote: post #302
whatshisface wrote: post #187

Earlier quoted context omitted.

The variation in the random variable relative to the value of the random variable goes away for large sums.

The variation in the random variable relative to the value of the random variable is fixed. It doesn't change, no matter how many times you sample the random variable. It's called the per-sample standard deviation. If 2 people A and B have a salary difference of 100K$ , then their salaries will not start to cluster together if you add C,D,E,F and more into the mix because of Central Limit theorem. Their salary differ…

https://en.wikipedia.org/wiki/Law_of_large_numbers

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

#306

Post by rolenthedeep »

thrown1212 wrote: post #194
rolenthedeep wrote: post #160

Earlier quoted context omitted.

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

The anthropic principle would hold that we as a species and our circumstances of existence are entirely average and not at all special.

Being one of the first species, at the relative dawn of the universe is very special.

I'm not such a huge fan of the grabby alien model. It's internally logically consistent, but I think it's too rooted in human psychology. Plus I have serious doubts about the ability of any species to maintain a multi-planet empire, let alone a multi-system one. Barring something like a hive mind I suppose.

Ultimately it's just conjecture and we'll probably never know within our lifetimes.

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

#307

Post by [deleted] »

oAlbe wrote: post #287
Valgrim wrote: post #284

Earlier quoted context omitted.

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?

[deleted]

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

#308

Post by random314 »

whatshisface wrote: post #305
random314 wrote: post #302

Earlier quoted context omitted.

The variation in the random variable relative to the value of the random variable is fixed. It doesn't change, no matter how many times you sample the random variable. It's called the per-sample standard deviation. If 2 people A and B have a salary difference of 100K$ , then their salaries will not start to cluster together if you add C,D,E,F and more into the mix because of Central Limit theorem. Their salary differ…

https://en.wikipedia.org/wiki/Law_of_large_numbers

I am not really sure what you are on about. So I will stop responding here.

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

#309

Post by shireboy »

pfdietz wrote: post #232
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's very likely life exists elsewhere How can you support this statement? It requires that Origin of Life is sufficiently probable, and we cannot conclude that from the known evidence (that life originated early on Earth is not sufficient, as we don't know how long the conditions suitable for OoL persist in a new solar system.)

well, for some values of “very likely”. ;) I base it on extremophiles. Life exists in volcanic vents and freezing waters. So it seems possible that at least microbial life exists somewhere else in the universe. Either way, “is/has there been at least microbial life on Venus, Mars, or Jovian moons” seems like a solvable question in the next 100 years or so. The conditions for intelligent life seem much more narrow.

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

#310

Post by Enginerrrd »

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…

That's really not much of a rebuttal.

The simple truth is, if a clone of the human race existed on proxima centauri, long enough for signals to propagate, we'd have no idea and that's an extremely optimistic scenario.

Why would a race be casually pointing terawatts of laser at every star around them. Tremendous waste of resources for essentially no gain within human scale lifetimes.

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