Interstellar travel?

How about a slightly more mathematical, but really hand wavy answer. Note I am not a mathematician or anything really relevant, but I do use bayesian stats a bit. Feel free to critique it.

If we assume there are 10^21 stars in the universe, and 10^21 universes. Let us also say that our prior probability for intelligent life around 1 star (P) is a uniform distribution bounded by 10^-2 and 10^-100.

We then take our 1 observation, there exists 1 universe with at least 1 star with intelligent life. How does this change our knowledge of the probability function? It reduces our estimate of the probability at P = 10^-100, because at that level the probability of our observation happening is 10^-58 (I think). However it does not say anything about the relative probabilities of P = 10^-27 (1 intelligent life per 1,000,000 universes) and P = 10^-15 (1,000,000 intelligent lives per universe) because the probability of our observation under both these conditions ~ 1.

Therefore I believe that the observation that life exists on earth does not do much to inform us on the chance of meeting ET.
Lexicus said:
The inconceivable size of the multiverse means it is near-certain there is another warpus out there somehwere.
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I do not think this is true, but it is really getting into maths I only know about through osmosis from real mathmaticians I know socially. Even if there are infinite planets with life on them, this does not mean that every form of life possible exists somewhere. As an explaination, consider there are an infinite number of integers, and there are an infinite number of real numbers. Does that mean that if I take one real number for every integer, eventually I will pick an integer? No, because there are aleph-naught integers but aleph-one real numbers, and aleph-one is infinitely larger than aleph-naught. Equally if there are aleph-naught stars in the multiverse, but aleph-one (or aleph-two, or aleph-42) configurations of life, then you will not get another warpus.
 
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I really hope there isn't another warpus out there. Imagine me arguing with him about stuff. I already hate him just thinking about

El_Machinae said:
Manfred, are you familiar with the example of the "bag with numbered marbles in it?" I think that's what warpus is leaning on while misunderstanding your point.

There are two bags, each with sequentially numbered marbles in them. One bag contains 100 marbles, the other a thousand.

You pull a random marble out of one bag. It's labeled a "eleven". One data-point.

Is it more likely that you pulled a marble out of the bag of ten, or the bag of one thousand? With your next draw from the same bag, what are the odds that you pick a "one"?

That's the statistical exercise they're drawing upon. They're positing two universes, one with only a small window in which life could appear or only with a long window in which life could appear. One where life has to begin in the first 100 billion years, or one in which life may begin in the first 1000 billion years. We pulled into the bag, and pulled out an "11" (or whatever).

I think it's a misapplication of that exercise to think this means that "there is probably other life", but I think that's what's being drawn upon.
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I'm not quite sure if that aligns with what I'm trying to say, but it could simply be a case of me not having enough coffee in me yet.

Imagine you have a random number generator. It's somehow actually random and does not rely on your computer's internal clock or whatever.

You run this random number generator once for every planet in the universe. Yeah, that's a lot of times, but assume that it would be feasible to do this.

You actually have no idea if the random number generator is generating numbers between 1 and 10 million or 1 and 10 billion or 1 and 10 trillion. You have NO idea what the upper limit is, only that each number you receive is completely random.

Now, before running any of this you make a point to pick out a very specific number. Let's say it's 581,681,686,333,678,678 followed by 15 zeroes. Or whatever. Any number, even if it's higher than the random number generator's upper limit. You have no idea what that is, remember.

You start running the generator for each planet in the universe, and each time this special number comes up, you mark the planet as special, i.e. life arose on it.

What is the expected number of times this special number will come up during this exercise? It is unknown, since we don't know the upper limit of the random number generator, and we don't even know the number of planets in the universe.

The only thing you can do is write:

P(x=0) = 0 (since we already have our data point, this is the only probability we actually know)
P(x=1) = a
P(x=2) = b
P(x=3) = c
...
P(1858925187267812367329867438673486) = whatever

P(1) reading as "The probability that this number comes up exactly once"
P(2) reading as "The probability that this number comes up exactly twice", and so on

Since we have no idea what these probabilities are.. you can't just assume that P(1) is more likely than P(2) or P(3) or P(4) or ... or P(13789768763289067283067)

That wouldn't make any sense to assume, since there is no data to imply that. You have no idea what the probability is that this will only ever happen once, or twice, or three times, or four times..

Assuming that it's more likely for it to happen once than all the other (insanely large number) of possible scenarios, is like assuming that it's more likely for it to happen exactly 8 times. Or exactly 568 times. The key word here is "Exactly".

You can't just pick one of those probabilities and hail it as the most probable. There is no data there to support that. The only thing you can do is say

"It's probably more likely for this to happen {not x} number of times than x number of times"

X in this case being 1. Replace that 1 with any other integer and the same thing will be true. You can't say that it's more likely for the number to be rolled 658,115 times than all the other possible scenarios. Or 58 times. Or 12 million times. Or whatever number you can think of. 1 is not a special number in this case, it's just one of (very) many possibilities

I think this conversations has probably been pounded into the ground. Where else can we take this?
 
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warpus said:
I really hope there isn't another warpus out there. Imagine me arguing with him about stuff. I already hate him just thinking about
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Once you get into the realm of parallel universes; Imagine, an infinite number of parallel universes, with an infinite number of Warpuses. Although, unless there is some kind of weird rupture in the fabric of space-time, i don't think you'll have to worry about it.
carter%2Bripple.JPG
 
We really need to set all this aside for a bit, until we get the really important issue resolved. Are they Warpuses, or Warpi?
 
Manfred Belheim said:
If we do I would genuinely love to know what it is because I don't know of any and I haven't seen any presented yet :/
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That's literally the content of the message I posted above :

There is tons of things we don't know about life, but it's still made out of rather mundane elements that just require a set of factors which are barely on the "uncommon" side.
So unless we discover an especially incredibly rare and restrictive requirement, it's a given there is a big bunch of planets hosting life in our very galaxy, and probably hordes of planets with the potential.
And that's just with the version of life we know of, so not counting the potential different way life can emerge.

All the building bricks of life as we know it are pretty common in the universe. The conditions for life as we know it to survive are not really exceptionnal. The only unknown is the "kickstart" of life, and we already have some informed guesses (oldest traces of life rather similar to those that can be found close to undersea heat vents, spontaneously-forming proteins, etc.).
We also know that life started very soon after the planet could support it (between 3,7 to 4,3 billion years ago).
All this allow to make an educated guess.

And remember : all that is only about life as we know it. It's probable there is also a number of lifeforms which are pretty different and come from fundamentally alien origins.

---

Timsup2nothin said:
Life, the process we are familiar with, has persisted for a mighty long time. A sample size of one, but it doesn't argue for "the process started a bunch of times, but only one is still going." It also appears to be a divergent process rather than convergent.
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Life being, as its core, a self-sustaining chemical process drawing resources from the environment, it's much more rational to consider that it emerged from a general environment as a critical mass of loosely-related chemical construct that ended up forming the basic forms of life, instead of a single ancestor which only appeared once and miraculously survived and reproduced and had all the biosphere descending from it.
Consider that my position in the argument really hasn't changed. It isn't that I'm committed to "life started once on Earth," any more than I am committed to "there is no life anywhere else." I started out challenging @warpus over his assumption that life is not unique, for which he had no evidence, and now I'm challenging the assumption (which I respect that you are not claiming as a fact) that these multiple starts that could have happened actually did.
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As I said, we still don't know, but we can make a good educated guess. There is a lot of factual hints that say that life should be pretty common in the universe, and very few that it's unique.
I'm just following Ockham's Razor here (as I'm fond to do so).
I started out by mentioning the absurdity of two. As long as you have one and only one example you have to deal with the possibility of uniqueness, one way or the other. As soon as you have a second sample uniqueness as a possibility is eliminated. At that point, logically, no matter how long it took you to find a second example there are going to be more.
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Agree on this one, but having to consider the possibility of uniqueness doesn't mean it's an EQUAL possibility.
 
Akka said:
Life being, as its core, a self-sustaining chemical process drawing resources from the environment, it's much more rational to consider that it emerged from a general environment as a critical mass of loosely-related chemical construct that ended up forming the basic forms of life, instead of a single ancestor which only appeared once and miraculously survived and reproduced and had all the biosphere descending from it.

As I said, we still don't know, but we can make a good educated guess. There is a lot of factual hints that say that life should be pretty common in the universe, and very few that it's unique.
I'm just following Ockham's Razor here (as I'm fond to do so).

Agree on this one, but having to consider the possibility of uniqueness doesn't mean it's an EQUAL possibility.
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Unique, or not unique. In the absence of any real information to quantify probabilities I'd say 50/50 is as good a guess as any and better than some. But I want to repeat that I'm not going to quibble with you because I respect that you aren't the one presenting assumptions as facts.

However, the current leaning is towards exactly that common ancestor that seems so unlikely. Too much commonality in the DNA of every currently known organism to not have a common root. Perhaps prior to that point life was a convergent process, but by all indications it has not been convergent since. I think Occam's razor would suggest that such a reversal is odd, at best, but it's certainly possible.
 
El_Machinae said:
The debating is helpful, but what are people actually doing to help us get answers?
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Agitating for a socialist future so that people's potential can be unlocked and we have a much larger base of educated/technically skilled people to work with.
 
El_Machinae said:
The debating is helpful, but what are people actually doing to help us get answers?
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I'm debating for fun, not out of some illusion that I'm being helpful. The origins of life on earth are lost...there isn't some "new information" that is going to end the debate. The question of "is there/was there/will there be other life" is not important enough for me to be concerned, beyond the entertainment value. If I am doing anything that could be helpful in some way it comes from challenging possibilities presented as facts, which might help keep a mind open here and there.
 
Europa and Enceladus are the first places we should look. It's also probably worth checking out Titan before Mars.
 
Yes, water oceans look more promising than Mars deserts. Drilling several kilometers of ice though was very challenging task even in Antarctica, so may be we should try to analyze volcanic eruptions in near future.
 
warpus said:
If we find fossilized life on Mars, that could provide some answers, whether the fossil contains Earth-like DNA or not. Personally I don't think we will, but who knows. It's the first place we should look
Click to expand...

If we find a Warpus fossil then we'll really know what's going on.
 
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