There Have Probably Been Aliens • Hacker News Board

Re: There Have Probably Been Aliens

#31

Post by kbenson » Sat, Jun 11, 2016, 9:59 AM UTC

andrewstuart2 wrote: post #14

nielsbjerg wrote: post #11

Earlier quoted context omitted.

You got the units of the borehole wrong, it's in meters not kilometers.

Well, we've certainly drilled more than 12 meters. :-P (Note the decimal point: 12.262km; I just converted to km to keep it consistent with the other measurements I cited) Could be confusing if you're used to the inverse comma/period from what we use in the US (comma=thousands, period=decimal).

It would be far less confusing if you only reported the depth to the hundredths place, as it them both disambiguates the period/comma (in the case where it's reversed by locale), and makes it immediately recognizable.

Re: There Have Probably Been Aliens

#32

Post by Houshalter » Sat, Jun 11, 2016, 10:01 AM UTC

>unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.... the degree of pessimism required to doubt the existence... of an advanced extraterrestrial civilization borders on the irrational.

After working with probability theory and combinatorics a bit, you realize probabilities much smaller than this occur naturally all the time. It might be hard for people not familiar with that to appreciate this, and be wowed by such a small number.

The thing is that independent probabilities multiply together, and so approach 0 exponentially fast. The probability of winning the lottery is of course very small. But there are so many people, that someone wins a lottery every day.

But the probability of winning the lottery twice is really small. The set of people that have won twice is a very small set indeed. And the probability of winning 3 times is so small that we should expect it to be a sure sign of corruption of the lottery, or intervention by supernatural forces. It's also about 1 in 10 billion trillion.

It seems to me that the evolution of intelligent life from nothing, also requires many things to go right. We don't know what all these things are, and we can only guess what their probability is. But if even a few of them have relatively small probabilities, then the probability of all of them happening could easily be much lower than "1 in 10 billion trillion".

There are many candidates for this so called "great filter". Some ideas I think are plausible are the evolution of multicellular life. The Earth was around a very, very long time before multicellular life formed. And it's believed to have required some weird coincidences like a parasite evolving into mitochondria.

Another candidate is the evolution of intelligence itself. Most animals aren't intelligent. Intelligence doesn't actually seem to be very correlated with fitness beyond a certain point - and reducing brain size is actually beneficial. Animals with brains were around for a very, very long time before anything like humans appeared. Some scientists believe that humans required a really weird set of conditions to evolve. There are theories that we are a case of accidental runaway sexual selection, like the peacock's feathers.

And there are many other factors we can't possibly know, that might be unique to Earth and rare on other worlds. We also don't know a huge amount about the evolution of early life. Getting from RNA self replicators to the complicated machinery of the most recent ancestor was no small feat.

Re: There Have Probably Been Aliens

#33

Post by nielsbjerg » Sat, Jun 11, 2016, 10:08 AM UTC

andrewstuart2 wrote: post #14

nielsbjerg wrote: post #11

Earlier quoted context omitted.

You got the units of the borehole wrong, it's in meters not kilometers.

Well, we've certainly drilled more than 12 meters. :-P (Note the decimal point: 12.262km; I just converted to km to keep it consistent with the other measurements I cited) Could be confusing if you're used to the inverse comma/period from what we use in the US (comma=thousands, period=decimal).

It was indeed the thousand separator which confused me, thanks

Re: There Have Probably Been Aliens

#34

Post by mrob » Sat, Jun 11, 2016, 10:10 AM UTC

rl3 wrote: post #5

houseofshards wrote: post #2

Content of the article is pretty information, but worst clickbait title of the year. At the risk of alienating some fraction of HN community (no pun intended), I'm going to say this is what you get when trying to chase the likes of Gawker (again, no pun intended).

The irony here is that Gawker's relevant clickbait is actually far superior: http://io9.gizmodo.com/11-of-the-weirdest-solutions-to-the-f...

I read a good short story recently about a weird Great Filter:

http://www.begoodenough.com/the-great-filter/

Re: There Have Probably Been Aliens

#35

Post by throwaway_yy2Di » Sat, Jun 11, 2016, 10:11 AM UTC

apsec112 wrote: post #9

"In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational." This is terribly silly. It reminds me of the Onion talks: "Step 1: Devise an idea to create a car that runs on compost. Step 2: Create the car. We’ve already compl…

"One in 10 billion trillion" sounds like a very large number, and it's put in italics for emphasis,"

And the author even asserts it's "irrational" to think real-world probabilities are this small!

It's easy to construct "unreasonably" small probabilities: take a few small ones and multiply them. If you path-sum all the evolutionary state transitions summing to P(intelligent life|planet), is it a shallow graph with many alternatives (additive probabilities), or a deep graph dominated by long, conjunctive sequences (probabilities multiply)?

Re: There Have Probably Been Aliens

#36

Post by raverbashing » Sat, Jun 11, 2016, 10:13 AM UTC

reso wrote: post #22

apsec112 wrote: post #9

"In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational." This is terribly silly. It reminds me of the Onion talks: "Step 1: Devise an idea to create a car that runs on compost. Step 2: Create the car. We’ve already compl…

I had a similar intuition reading the article. I don't think we understand much at all about the probabilities of life forming even under the ideal circumstances. The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. Nevertheless the progress on the other factors in the Drake equation is very interesting and impressive.

> . The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number.

I disagree with this.

It seems that, from what happened to other planets on the solar system, that nothing happened on Earth too much out of the ordinary. Mars had a similar story (except for the whole Moon coming out of a giant collision), and had water. But maybe it was too small to keep warm for enough time

Earth had 5 mass-extinctions, that "reset the game" before we got to humans. Doesn't seem too far fetched to me

I really don't buy that Earth is one in a billion unless Mars is one in a billion as well. Maybe one in 1000? One in 100000?

And that's limiting intelligent life to what we know. Yes, maybe the ideal speed of chemical reactions (for intelligent life) happen around 273K, or maybe there's another way

Re: There Have Probably Been Aliens

#37

Post by Houshalter » Sat, Jun 11, 2016, 10:20 AM UTC

dacompton wrote: post #8

There have been aliens -- and they don't care about us. To assume that a collection of beings which have obtained the ability to travel amongst the stars would focus their attention on a single species on a single planet is fundamentally selfish. What resources does our earth contain that are not (more easily) obtainable elsewhere? If Drake's equation "holds", then what novelty do _we_ provide?

There are many reasons alien races would interact with primitives.

Morality - they might be utilitarian and desire to relieve the suffering of other sentient beings. Or force their weird alien morals onto them.

Competition - we might not be a threat now, but given a sufficiently long time, we could evolve into one. If they really don't care about us, it would cost them very little to exterminate us early.

Re: There Have Probably Been Aliens

#38

Post by Houshalter » Sat, Jun 11, 2016, 10:22 AM UTC

qaq wrote: post #27

jkeler wrote: post #10

> a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic I think people underestimate how low probabilities can really be. According to wiki the shortest self-replicating RNA is 165-bases long. Even if you convert all observable universe in RNA this is still not enough for this RNA to form by chance (4^165 is much larger than number of atoms in observable universe).

Given enough time anything can form out of random fluctuations if it has >0 probability no matter how small.

"Enough time" can easily be longer than the age of the universe. A million monkeys typing on keyboards will eventually write shakespeare. But it will be longer than the universe before they even type a single sentence of it correctly.

Re: There Have Probably Been Aliens

#39

Post by jkeler » Sat, Jun 11, 2016, 10:25 AM UTC

raverbashing wrote: post #36

reso wrote: post #22

Earlier quoted context omitted.

I had a similar intuition reading the article. I don't think we understand much at all about the probabilities of life forming even under the ideal circumstances. The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. Nevertheless the progress on the other factors in the Drake equation is very interesting and impressive.

> . The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. I disagree with this. It seems that, from what happened to other planets on the solar system, that nothing happened on Earth too much out of the ordinary. Mars had a similar story (except for the whole Moon coming out of a giant collision), and had water. But maybe it was too small to keep…

It's not about how probable are these conditions but given these conditions how probable is that life will appear.

Re: There Have Probably Been Aliens

#40

Post by coldtea » Sat, Jun 11, 2016, 10:29 AM UTC

sktrdie wrote: post #29

By pure probability, if we're the first intelligent species here on earth (that is able to build radio communicators) out of what, ~4 billion species that ever existed, what are the odds of us being the first in the entire universe? My logic is that intelligence (as defined above) is clearly rare here on earth where life is prolific, hence by no means a certain development of evolution. I wouldn't be surprised if we'…

>And then you can say, "us being the first is egocentric". Well, but we're the first when it comes to building radio stations, so we clearly won that lottery big time.

Who told you we're "the first when it comes to building radio stations"? There could be 200 other explanations for "radio silence" from advanced civilizations (if they exist).