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

There Have Probably Been Aliens

nytimes.com

Post reply on HN
Print view View original

121–130 of 163 posts

Re: There Have Probably Been Aliens

#121

Post by Houshalter »

titzer wrote: post #100
Houshalter wrote: post #38

Earlier quoted context omitted.

"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.

You are postulating the existence of only a single universe, ours. But there could be any number of universes, and so far we have no scientific way of testing that. The anthropic principle and the possibility of multiple universes puts all probabilistic arguments to dust: anything with non-zero probability happens in an infinite number of universes. > A million monkeys typing on keyboards will eventually write shakes…

I agree with you completely about the anthropic principle. But we are talking about the probability of aliens. If the anthropic principle is true, then we should expect aliens to be really really unlikely.

Re: There Have Probably Been Aliens

#123

Post by Houshalter »

andbberger wrote: post #104
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…

Your assumption that the odds of abiogenesis is given by `~1/2^n, where n is the complexity in bits' is utterly, completely false. Statistical mechanical entropy and information theoretical entropy ('complexity in bits') are not the same quantities! But even if they were, your expression would still be incorrect because living system are definitionally not at equilibrium - so equilibrium statistical mechanics (whose…

This has nothing to do with physics. He's saying if a first self replicator requires a very specific sequence (of something like RNA) to form by chance, then it can easily be incredibly unlikely to happen.

As an analogy, if I make a huge number of random files on my computer and execute them, the probability of getting a self replicating computer virus is really low. And one that successfully spreads itself to other computers over the internet should never happen.

If the first successful computer virus is 100 bits long, then probability of finding it in a single random search is 1/2^100. Which is just incredibly small and should never ever happen.

Re: There Have Probably Been Aliens

#124

Post by ende »

greggman wrote: post #93
ThePhysicist wrote: post #30

Earlier quoted context omitted.

I think what will really help us to get at a better estimate is to answer the question whether there exists life in our solar system that evolved independently of that on Earth. If we should find traces of bacteria on Mars or another planet, that would immediately take the corresponding probability factor in the Drake equation to a number close to 1 (i.e. most solar systems with planets in the habitable zone produce…

what if life didn't evolve here but arrive on other space debris? Has that theory been ruled out?

The term you're looking for is panspermia. Nothing can necessarily be ruled out but it seems both 1) highly unlikely from a mechanistic perspective and 2) unnecessary to the explanation of life origin.

Re: There Have Probably Been Aliens

#125

Post by yoha »

dave_sullivan wrote: post #96
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 of my favorite explanations and counterpoints come from Neil deGrasse Tyson: It took modern astrophysics to determine the origin of the chemical elements. We observe stars (and) we know what goes on in their center. They explode, laying bare their contents. And what we have discovered is that the elements of the periodic table -that which we are made of- derive from the actions of stars that have manufactured the…

Most common elements in the universe [1]: Hydrogen, Helium, Oxygen, Carbon, Neon, Iron, Nitrogen

Most common elements in the human body [2]: Hydrogen, Oxygen, Carbon, Nitrogen

I agree that we can skip helium and neon since those are noble gases, but I do find the lack of iron interesting.

[1] https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...

[2] https://en.wikipedia.org/wiki/Composition_of_the_human_body#... (look for table, sort per atomic percent)

Re: There Have Probably Been Aliens

#126

Post by gpsx »

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 don't know enough to know if the range you specify is right, but I agree that it is silly to say 10^-22 is a ridiculously small number. For one thing, when talking about the size of probabilities, we should talk about the size of the exponent. -22 is not a ridiculously small number.

People base the idea that there should be other life in the universe on the fact that life developed at least once, which is here on earth. The odds are it would happen either 0 times or many times, but not exactly once.

This argument is reasonable if there is one universe. Another scenario is that there is some god awful large number of universes (for round numbers let's say 10^1000 raised to the 10^10000 power, which would be a huge underestimate), and that most of these universes contain no life, because the odds of life developing are also very, very small. We ARE special in that we are viewing one of the small fraction of universes that has life, because if it didn't we wouldn't be viewing it. This allows for life to exist exactly once in our universe. There could also be universe where life developed independently more than once, but the odds of us being in that universe are very small relative to the odds of being in a universe with one life.

But how would there be many universes? Here is one possibility that is surely controversial. In quantum mechanics, things happen in parallel. Is that electron spin up or spin down? It is both, but the electron in one state is not influenced by the electron in the other state. Each exists wholly on its own. This is true whether you believe the Stockholm or the Many Worlds interpretation of quantum mechanics. These two cases only differ when some special life form makes an observation, in which cases something very dramatic happens in the Stockholm interpretation (which is observationally indistinguishable from the "nothing different" that happens in the Many Worlds interpretation). If we think about the simplest form of life that can not make observations rather than looking for human-like life, the distinction between Stockholm and Many Worlds is mute. These parallel states of the system form our many universes, some that contain life and some that do not.

Re: There Have Probably Been Aliens

#127

Post by cookingrobot »

Houshalter wrote: post #123
andbberger wrote: post #104

Earlier quoted context omitted.

Your assumption that the odds of abiogenesis is given by `~1/2^n, where n is the complexity in bits' is utterly, completely false. Statistical mechanical entropy and information theoretical entropy ('complexity in bits') are not the same quantities! But even if they were, your expression would still be incorrect because living system are definitionally not at equilibrium - so equilibrium statistical mechanics (whose…

This has nothing to do with physics. He's saying if a first self replicator requires a very specific sequence (of something like RNA) to form by chance, then it can easily be incredibly unlikely to happen. As an analogy, if I make a huge number of random files on my computer and execute them, the probability of getting a self replicating computer virus is really low. And one that successfully spreads itself to other…

Purely hypothetical: where N is the fewest number of bits for a successful virus.

There could be 10 different ways to make a virus N bits long. There could be 1000 ways to do it in N+1 bits, and a billion ways in N+2.

The relationship between how many possible successful viruses exist to number of bits doesn't have to scale by any obvious pattern.

Re: There Have Probably Been Aliens

#128

Post by Houshalter »

cookingrobot wrote: post #127
Houshalter wrote: post #123

Earlier quoted context omitted.

This has nothing to do with physics. He's saying if a first self replicator requires a very specific sequence (of something like RNA) to form by chance, then it can easily be incredibly unlikely to happen. As an analogy, if I make a huge number of random files on my computer and execute them, the probability of getting a self replicating computer virus is really low. And one that successfully spreads itself to other…

Purely hypothetical: where N is the fewest number of bits for a successful virus. There could be 10 different ways to make a virus N bits long. There could be 1000 ways to do it in N+1 bits, and a billion ways in N+2. The relationship between how many possible successful viruses exist to number of bits doesn't have to scale by any obvious pattern.

I don't see why adding more bits would make the program significantly more likely. Yes in theory that is possible, but I don't think it's relevant.

Re: There Have Probably Been Aliens

#129

Post by ulmus »

lisper wrote: post #101
ulmus wrote: post #58

In estimating a probability for the occurrence of life in the universe, the authors essentially claim to know the probability of their own existence. For me, that's a red flag. I can't know the probability of a phenomenon which my existence depends on just by observing my existence alone, because I can't observe all of the cases where the phenomenon does not occur and I do not exist.

The quantity of interest in any probability problem can always be re-cast as the conditional probability of the event given that the person asking the question exists, which is necessarily 1.

Pardon me, but I'm not sure what you mean by quantity of interest. If the quantity of interest can always be re-cast as a value which is necessarily 1, isn't "quantity of interest" the same for all probability problems?

Re: There Have Probably Been Aliens

#130

Post by Houshalter »

tyingq wrote: post #92
Houshalter wrote: post #73

Earlier quoted context omitted.

Why would they want to hide? You are making a very strong claim about the motivations of aliens.

SciFi usually offers this sort of explaination: https://en.wikipedia.org/wiki/Prime_Directive

That's a very forced explanation by science fiction writers to justify it. I wouldn't expect actual alien civilizations to invent such an arbitrary rule.
Post reply on HN