Interstellar travel?

[hobbsyoyo]

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

News just broke today that Curiosity found a rich deposit of organic materials in a drill sample under a lakebed it traversed. Unfortunately the drill can't reach depths where high-quality organics would survive (radiation) and doesn't have the equipment for directly detecting life but it's still a good sign for life. The European ExoMars rocer has a 2 meter drill and the right detection equipment for detecting life so here's hoping it has a successful launch.

Oh and it detected a seasonal variation in Methane production (peaks in summer) which is also good for the potential for there to be life underground.

 

[Broken_Erika]

If there are warpus fossils on Mars I will have to probably go into hiding from the CIA

If there are, the CIA isn't the agency you should be worried about....

 

[El_Machinae]

Me? Nothing.

There is little that could be done and then there is the question, why should I do anything?

Well, I was originally asking about anyone he wanted to answer, not just you. Personally, I think that the question is worth a little bit of my attention and effort. For this reason, I run the seti@home software on my home computer.

 

[Lexicus]

Oh and it detected a seasonal variation in Methane production (peaks in summer) which is also good for the potential for there to be life underground.

I saw that too. It's not clear to me how big a deal it is as far as the possibility of life.

 

[warpus]

News just broke today that Curiosity found a rich deposit of organic materials in a drill sample under a lakebed it traversed. Unfortunately the drill can't reach depths where high-quality organics would survive (radiation) and doesn't have the equipment for directly detecting life but it's still a good sign for life. The European ExoMars rocer has a 2 meter drill and the right detection equipment for detecting life so here's hoping it has a successful launch.

Oh and it detected a seasonal variation in Methane production (peaks in summer) which is also good for the potential for there to be life underground.

Are you saying that there could be life on Mars that's not just a fossil but actually an organism farting out methane?

 

[Perfection]

I tried walking somebody through the math a while ago and it didn't go anywhere, just pages of back and forth nonsense. Let me try again, maybe I can explain it better this time:

That was me, I saw your math. I disagreed with it. Here's the thread: https://forums.civfanatics.com/threads/how-much-intelligent-life-is-there.302505/

Apparently awhile ago is almost 10 years. BTW, you also still have to reckon with that 10 year bet you lost in the cool unbuilt structures thread: https://forums.civfanatics.com/threads/the-cool-unbuilt-structures-thread.196126/page-4

I agree that your new argument is better put, but I still think you're succombing to issues regarding selection bias. So let's reletigate for old times sake.

Say that you have a die with an X number of sides. Say that you will roll this die once for every single planet in the universe. You have no idea how many planets and you have no idea how big X is.

Each time you roll a very specific number (Let's say 581,658,618,115,618,681,688,683,111,687,863,238) for a planet, that means life arose there.

Even though all the probabilities are a mystery to you, in this scenario it is more probable for you to roll this number twice or more, if you have already rolled it once. It's possible that the number will never ever come up again and you end up with a grand total of 1 roll, but statistically speaking you can expect to roll it multiple times, assuming you've already rolled it once.

It's possible we are the only life that ever arose in the universe anywhere, ever. But it's more likely that it also arose elsewhere. P(1) is just one singular data point while P(2) + P(3) + P(4) + P(5) + ... is a combination of probabilities. In some cases yes, P(1) will be more likely, if you set up your variables just right. But in most situations it wouldn't be. We have no idea which situation we are in, but we can't just assume we are in the situation where P(1) is more likely.

Anyway, if this doesn't make sense then I won't be able to convince you. And that's fine, but I'd put $100 on other life existing out there somewhere. It would be really statistically improbable for it to just happen once, ever, although sure, it could happen, just like Yeovil Town can win the English Premier League.

So let's say I'm God, and you getta be my archdemon (I'm an evil God )

I'm sitting around on my throne and I get a bug up my butt and say. Gosh darn it, imma make me a big ol' batch of universes (let's say 10^75 of 'em).

So here's what I do, first I make a barren universe with 10^25 stars. Then for each star I roll a fair n-sided die, if it's 1 I put some life on it, if not I move on without the life.

But what dice should I use? I have in my dice drawer 10^50 fair dice a D1 a D2 a D3 all the way up to a D10^50. Well if I picked one at random that would almost certainly be greater than 10^48, thats' not very sporting. So instead here's what I do, I take a tape measure 50 units long and pick a random point on it x and measure it to divine precision. Then I take 10^x, round to the nearest integer and use that dice from the drawer. You'll note that this produces a distribution of n such that when written in scientific notation has a 2% shot of having any particular exponenent.

You'll note that that there are roughly 3 different types of batches I can produce:
If I'm using a D10^23 or less. Almost all the universes will have stars with life. Moreover almost all will have multiple stars with life. This is group has a 46% chance of occuring. (let's call this a "life-rich" batch)
If I'm using a D10^27 or more. Almost all the universes will be devoid of life. Moreover almost all with life will be the only ones in their universe with life. This is group has a 46% chance of occuring (let's call this a "life-poor" batch).
If I'm using a D10^23 to D10^27 things get complex. You'll see significant numbers of universes devoid of life, and with life. In this group a significant minority have only 1 star with life. This group has an 8% chance of ocurring. (let's call this a "intermediate" batch)
(I think this is a relatively fair distribution for the purposes of my argument though not a particularly realistic one. The salient properties of this distribution are that there is a significant possibility of the die being over and under the amount of stars in the universe with it being about the same a distinct but rare possibility. I believe that such a wide range of possibilities should be considered prior to attempting any statistical argument)

So let's say I whip up that batch of 10^75 universes and pick a universe at random. Then I ask you "what is the probability there is life in that universe?" Well if it's a life-rich batch you're almost certainly going to find life, if it's life poor it's almost certain you won't, in the intermediate batch there's a significant fraction of both. Your calculation is going to be about 50%. Now let's say I tell you, "actually in this universe there is life on at least one star" then ask "what do you think the probability of finding life on multiple stars is?". From this information you can pretty much rule out the possibility the batch is life-poor (because you probably wouldn't have found life on it), so you only only got life-rich and intermediate batches to worry about. Almost all the life rich ones have multiple stars with life. Most of the intermediate batch with life also have multiples, though a significant fraction don't. So overall you'd have to say the probability is something like 99% that there are multiple instances of life. I believe this is the sort of intuition you're using to come up with the above argument.

But what if instead of picking a universe at random after whipping up the batch I list all the stars with life and pick one at random, then ask you the same questions about the universe it's in? Well the first question "what is the probability there is life in that universe?" is pretty easy. It's 100% gaurenteed (ignoring the extraordinarily insignificant possibility that all universes are devoid of life) because if it didn't have life there'd be no stars on the list. Now if "what do you think the probability of finding life on multiple stars is?" the calculation is different. You don't get to rule out all those life-poor batches, because even though the chances in any particular universe is small, it's all but certain that that list is going to have at least some stars with life. So all options are back on the table again. So let's go through 'em. If it's a life-rich batch, you're probably going to find multiple instances. If it's a life poor batch, it's probably alone. And the intermediate batches have a mix of both. So you're going to come up with an answer of about 50% of multiple and 50% alone.

I argue that when assessing these probabilities we should be thinking about the latter not the former. The reason being that since we come from a star with life we will not find ourselves in some random universe from the batch, instead we will only find ourselves in universes that have at least one star with life. Without further information we should presume we're on a random star with life. If we are open to a significant possibility that dice has more sides than there are stars in the universe, then we must be open to the significant possibility that we are alone. I have thus far not seen any particularly solid argument that should preclude the probability of life being that low so accept that as a distinct possibility and with that accepting I accept that there's a significant possibility we're alone in the universe.

 

[Akka]

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.

Sorry, but no, 50/50 as a default probability isn't a good guess, it's just lazy
My whole post is about the point that we have a bunch of hints which lend more toward a "life should be rather common" than "life is so exceptionnal it might only happen once".
Let's remember that most of what we "know" about the universe IS MADE OF such kind of assumptions which are just "not yet disproven" and are constantly refined.

The most typical comparison I can remember is how, barely, what, 20 or so years ago, it was considered a possibility that our solar system was an outlier with so many planets and that most other solar system might have none (because at that time we only had detected a very small number of gas giants).
It was a possibility, which was seriously entertained, but yet the educated guess was that "nah, we just haven't been able to detect other planets".
Lo and behold, a few years later, we discover planets by the thousands and show that our solar system is nothing special.

 

[Perfection]

Some other random thoughts.

There is nothing to do, but to keep our eyes open in case we have the incredible luck to observe a glimpse of life on another planet. Otherwise there are not going to be any answers.

Another longshot is if we find a plausible biochemical pathway that we could demonstrate is likely to occur multiple times in the universe.

Of course, it only really counts when we see it.

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.

We have good theoretical reasons to believe that there are only a finite amount of configurations for a particular universe. Thus if we believe in an infinite number of universes everything in it should be repeated an infinite number of times.

But to get wilder, are multiple identical warpuses really different warpuses or just the same warpus in different locations?

...I think about these sorts of questions too much.

But, where did these conditions disappear to? Again, by all indications all life as a process is derivitive from a single initiation of the process. Why did this process start once, and not continue to start? The circumstances, if they aren't unique and are happening on mudballs everywhere, should have happened repeatedly right here. But they aren't. Life the process started on earth once, and has apparently just ticked along ever since. Even application of the vaunted intelligence that has evolved in that process can't get it to initiate a second time, under any circumstances. However this process initiated, it appears very arguable that the initiation of the process is unique. No matter how repetitiously the process spreads and diversifies, there is only one known starting point.

We certainly do not know these questions. But after life has formed once, it might eat the stuff needed to form it again.

Your sample size is one. You don't get to make a statistical analysis about diamonds out of one diamond and a bunch of rocks.

You can make some reasonable assertions with a sample size of one. If you scoop up 1000 rocks and find 1 diamond, you can make some tentative inferences. Diamonds to other rocks ratio probably aren't a billion to 1 nor 10 to 1. The problem is life on earth doesn't count as a sample at all because samples need to be arbitrarily selected. As living on a planet with life is pretty much a necessary condition to ask annoying existential questions we can glean no statistical information from it.

 

[gozpel]

So you all talk about possible others and not ourselves?

Well, I blame myself for starting this thread as it sits in dead water. Everyone talking about anything but the sole purpose of this thread. For 10 pages!!

We have a Big Fu**ing Rocket coming online soon, that might give us answers or just be another fail. More countries are trying to reach out there, without talking about possibilities of alien life.

Well, no one cares what an OP says today anyways, just highjack the thread and carry on.

 

[Timsup2nothin]

As living on a planet with life is pretty much a necessary condition to ask annoying existential questions we can glean no statistical information from it.

That's pretty much the point. There is literally no information to apply to the question, and yet people span a spectrum from "oh, it's a sure thing" to "as any reasonable person can see" to " if you weren't so lacking in education you would know" and right on down the line.

So you all talk about possible others and not ourselves?

Well, I blame myself for starting this thread as it sits in dead water. Everyone talking about anything but the sole purpose of this thread. For 10 pages!!

We have a Big Fu**ing Rocket coming online soon, that might give us answers or just be another fail. More countries are trying to reach out there, without talking about possibilities of alien life.

Well, no one cares what an OP says today anyways, just highjack the thread and carry on.

Sorry, but your OP question just didn't have any answers. There's an old joke:

How many super advanced space aliens are monitoring us right here, right now, in this room, without us being able to detect them?

Spoiler :

As many as want to be.

 

[red_elk]

But what if instead of picking a universe at random after whipping up the batch I list all the stars with life and pick one at random, then ask you the same questions about the universe it's in? Well the first question "what is the probability there is life in that universe?" is pretty easy. It's 100% gaurenteed (ignoring the extraordinarily insignificant possibility that all universes are devoid of life) because if it didn't have life there'd be no stars on the list. Now if "what do you think the probability of finding life on multiple stars is?" the calculation is different. You don't get to rule out all those life-poor batches, because even though the chances in any particular universe is small, it's all but certain that that list is going to have at least some stars with life. So all options are back on the table again. So let's go through 'em. If it's a life-rich batch, you're probably going to find multiple instances. If it's a life poor batch, it's probably alone. And the intermediate batches have a mix of both. So you're going to come up with an answer of about 50% of multiple and 50% alone.

Technically, if you are picking stars at random instead of universes, the chance that it will get us to the universe with multiple habitable planets becomes even higher. Because it's much more probable to pick a star from universe with abundant life, than from the one where it is unique.

Consider a toy example with exponential distribution. Let's say we have 7 universes where numbers of habitable planets are 1,1,1,1,2,2,4. If we pick a universe, the probability that there will be multiple habitable planets is 3/7. If we pick planet at random, then the probability that other habitable planets exist in this universe will be 2/3.

 

[Timsup2nothin]

I saw that too. It's not clear to me how big a deal it is as far as the possibility of life.

The martians were doing a good job of hiding, but their farting cows are giving them away.

 

[Hrothbern]

Another longshot is if we find a plausible biochemical pathway that we could demonstrate is likely to occur multiple times in the universe.
Of course, it only really counts when we see it.

Only when we see real life... yes.
But not so clear when we find for example organic molecules !

If we see amino acids ? The building blocks of proteins, the versatile toolkit elements that enable any kind of macromolecule that can catalyse desired (bio)chemical reactions ? No.
If we see fatty acids ? the building blocks for cell membranes ? No.
If we find enzymatic proteins that for example make certain di-peptides, or cut certain di-peptides in two ? No.
If we find strings of RNA ? No.
They can all be made at random in the right circumstances without anything that deserves the word "life"

When we start finding organic molecules that are NOT in random proportions, there is more likelyhood that they indicate life.
For example if we find a meteorite with 80 amino acids.
Organic material on Earth shows 20 amino acids (if you add 2 for the Sulphur amino acids that can also be Selenium acids, that becomes 22).
There are thousands and thousands of different kinds of amino acids possible. Whereby the simple ones are more likely in comparison. So why only 20 on Earth ?
The answer is that we have life on Earth that breaks down continuously all amino acids and builds up only those 20.
Ok, but why not more being build up ?
On plausibility: good enough is good enough: you use the differing amino acids to construct a 3D protein structure that has the right shape to catalyze reactions. When you can construct all that is needed from 20, why use more kinds ? When 26 letters of the alfabet are good enough. Why use more ?
So back to that meteorite with 80 amino acids: assuming above is plausible enough, that 80 means: unlikely to indicate life.
And you can use this "random" argument with most of the organic material to be found on missions to planets.

That longshot will work, perhaps faster than at first sight:

If we understand how our own origin of life was here on Earth..... we have a base line likelyhood from at least one category of planets and type of possible alien life forms.
Adding more biochemical pathways can only increase that base line likelyhood.

For that biochemical origin of our own life.... for now our computing power and basic insights what to simulate are inadequate.
But a strong increase of computing power comes for free driven by our general development, and the little money needed for more scientific insights is peanuts.

 

[Perfection]

Technically, if you are picking stars at random instead of universes, the chance that it will get us to the universe with multiple habitable planets becomes even higher. Because it's much more probable to pick a star from universe with abundant life, than from the one where it is unique.

Consider a toy example with exponential distribution. Let's say we have 7 universes where numbers of habitable planets are 1,1,1,1,2,2,4. If we pick a universe, the probability that there will be multiple habitable planets is 3/7. If we pick planet at random, then the probability that other habitable planets exist in this universe will be 2/3.

that is correct and i am aware of this. Since it only has a significant impact if were in the intermediate batch range the effect on the overall math is small. I felt it wasn't worth getting into in what was becoming an overly large post.

 

[hobbsyoyo]

I saw that too. It's not clear to me how big a deal it is as far as the possibility of life.

It's actually a big deal because while it does not prove life itself, it disproves several non-biological theories for current methane production and also helps show that at least in the past this lake could have supported life.

Are you saying that there could be life on Mars that's not just a fossil but actually an organism farting out methane?

Yes that is what NASA is saying. So there are several different mechanisms that could explain Martian methane including, but not limited to, life. Several of the non-biological origins of the methane fall apart when if a seasonal variation is invoked whereas we would expect living organisms to have a seasonal variation of methane output that peaks in summer - which is what they found. Now there are still non-biological mechanisms that involve thawing subsurface water interacting with rocks to generate methane, so this finding does not definitively prove life by itself. However, because it discounts some of the non-biological methane mechanisms and also boosts the biological methane mechanisms, it's a big deal.

The finding of organic molecules doesn't mean much for current life, unfortunately. Apparently the molecules they found could easily have non-biological origins. However, it's still a good sign and highlights the need to send more capable missions or humans to Mars to get to the bottom of it. Basically these molecules just make it more likely that this lake could have supported life in the distant past.

 

[warpus]

That was me, I saw your math. I disagreed with it. Here's the thread: https://forums.civfanatics.com/threads/how-much-intelligent-life-is-there.302505/

Apparently awhile ago is almost 10 years. BTW, you also still have to reckon with that 10 year bet you lost in the cool unbuilt structures thread: https://forums.civfanatics.com/threads/the-cool-unbuilt-structures-thread.196126/page-4

Holy crap.. we're old

What was that bet? Checking.. now... Haha damn, as if you remembered that. Looks like you were right. What do you win?

I will have to read your rebuttal to my "life in the universe" argument later unfortunately, as I have a busy day ahead of me today, and after this coffee is finished I will be off the grid for a while. I welcome an opposing view disecting my argument though! I won't be around much today but wanted to respond before I get buried in work

 

[Manfred Belheim]

That was me, I saw your math. I disagreed with it. Here's the thread: https://forums.civfanatics.com/threads/how-much-intelligent-life-is-there.302505/

Apparently awhile ago is almost 10 years. BTW, you also still have to reckon with that 10 year bet you lost in the cool unbuilt structures thread: https://forums.civfanatics.com/threads/the-cool-unbuilt-structures-thread.196126/page-4

I agree that your new argument is better put, but I still think you're succombing to issues regarding selection bias. So let's reletigate for old times sake.


So let's say I'm God, and you getta be my archdemon (I'm an evil God )

I'm sitting around on my throne and I get a bug up my butt and say. Gosh darn it, imma make me a big ol' batch of universes (let's say 10^75 of 'em).

So here's what I do, first I make a barren universe with 10^25 stars. Then for each star I roll a fair n-sided die, if it's 1 I put some life on it, if not I move on without the life.

But what dice should I use? I have in my dice drawer 10^50 fair dice a D1 a D2 a D3 all the way up to a D10^50. Well if I picked one at random that would almost certainly be greater than 10^48, thats' not very sporting. So instead here's what I do, I take a tape measure 50 units long and pick a random point on it x and measure it to divine precision. Then I take 10^x, round to the nearest integer and use that dice from the drawer. You'll note that this produces a distribution of n such that when written in scientific notation has a 2% shot of having any particular exponenent.

You'll note that that there are roughly 3 different types of batches I can produce:
If I'm using a D10^23 or less. Almost all the universes will have stars with life. Moreover almost all will have multiple stars with life. This is group has a 46% chance of occuring. (let's call this a "life-rich" batch)
If I'm using a D10^27 or more. Almost all the universes will be devoid of life. Moreover almost all with life will be the only ones in their universe with life. This is group has a 46% chance of occuring (let's call this a "life-poor" batch).
If I'm using a D10^23 to D10^27 things get complex. You'll see significant numbers of universes devoid of life, and with life. In this group a significant minority have only 1 star with life. This group has an 8% chance of ocurring. (let's call this a "intermediate" batch)
(I think this is a relatively fair distribution for the purposes of my argument though not a particularly realistic one. The salient properties of this distribution are that there is a significant possibility of the die being over and under the amount of stars in the universe with it being about the same a distinct but rare possibility. I believe that such a wide range of possibilities should be considered prior to attempting any statistical argument)

So let's say I whip up that batch of 10^75 universes and pick a universe at random. Then I ask you "what is the probability there is life in that universe?" Well if it's a life-rich batch you're almost certainly going to find life, if it's life poor it's almost certain you won't, in the intermediate batch there's a significant fraction of both. Your calculation is going to be about 50%. Now let's say I tell you, "actually in this universe there is life on at least one star" then ask "what do you think the probability of finding life on multiple stars is?". From this information you can pretty much rule out the possibility the batch is life-poor (because you probably wouldn't have found life on it), so you only only got life-rich and intermediate batches to worry about. Almost all the life rich ones have multiple stars with life. Most of the intermediate batch with life also have multiples, though a significant fraction don't. So overall you'd have to say the probability is something like 99% that there are multiple instances of life. I believe this is the sort of intuition you're using to come up with the above argument.

But what if instead of picking a universe at random after whipping up the batch I list all the stars with life and pick one at random, then ask you the same questions about the universe it's in? Well the first question "what is the probability there is life in that universe?" is pretty easy. It's 100% gaurenteed (ignoring the extraordinarily insignificant possibility that all universes are devoid of life) because if it didn't have life there'd be no stars on the list. Now if "what do you think the probability of finding life on multiple stars is?" the calculation is different. You don't get to rule out all those life-poor batches, because even though the chances in any particular universe is small, it's all but certain that that list is going to have at least some stars with life. So all options are back on the table again. So let's go through 'em. If it's a life-rich batch, you're probably going to find multiple instances. If it's a life poor batch, it's probably alone. And the intermediate batches have a mix of both. So you're going to come up with an answer of about 50% of multiple and 50% alone.

I argue that when assessing these probabilities we should be thinking about the latter not the former. The reason being that since we come from a star with life we will not find ourselves in some random universe from the batch, instead we will only find ourselves in universes that have at least one star with life. Without further information we should presume we're on a random star with life. If we are open to a significant possibility that dice has more sides than there are stars in the universe, then we must be open to the significant possibility that we are alone. I have thus far not seen any particularly solid argument that should preclude the probability of life being that low so accept that as a distinct possibility and with that accepting I accept that there's a significant possibility we're alone in the universe.

I think that's a really good post (I think quoting it in full should be alright with the "new" forum format).

However, I still think even in your emboldened paragraph example the odd sill still be overwhelmingly in favour of their being lots more life in the universe you select this way, just because those universes will be contributing so many more (as in orders of magnitudes more) stars to your overall list, so the chances of picking a star off that list that comes from your batch of universes with only 1 or 2 populated stars in it is infinitesimal, even though those universes make up 50% of your sample.

But of course for all we know God might have used his 10^45 sided dice for every one of his universes

 

[Perfection]

I think that's a really good post (I think quoting it in full should be alright with the "new" forum format).

However, I still think even in your emboldened paragraph example the odd sill still be overwhelmingly in favour of their being lots more life in the universe you select this way, just because those universes will be contributing so many more (as in orders of magnitudes more) stars to your overall list, so the chances of picking a star off that list that comes from your batch of universes with only 1 or 2 populated stars in it is infinitesimal, even though those universes make up 50% of your sample.

But of course for all we know God might have used his 10^45 sided dice for every one of his universes

My premise is that we are only concerned with one batch of universes and for said batch the dice rolled remain the same for every universe, if God rolled a 10^45 for one stars in one universe, he rolled it for stars in all universes. If we had many batches and compiled a list based on that (a batch of batches) then your analysis would be correct. However I don't think we should think of it like a batch of batches.

The reason to choose a batch rather than a batch of batches is because for universes with the same set of physical laws the probability shouldn't change from universe to universe, it should be considered a constant. My random method of choosing the dice is not representing some chance laden physical process that produces a spectrum of outcomes but the great uncertainty of our knowledge about what the probability of life is for given portion of a universe with our physical laws. We also have compelling reasons to believe that there are plenty of universes with the same physical laws as ours beyond the cosmic horizon. Thus it's a good starting point.

Now you might ask what about universes with different physical laws? After all universes with different physical laws should be rolling a different dice, should we treat it like a batch of batches? I would argue that attempting to do that would be likely to mislead. We are uncertain not only of the probability of life for a given portion of a universe with our physical laws, but we are also uncertain of the distribution of probabilities of life for a given portion of a universe within a certain set of possible physical laws. These uncertaintities are likely highly related. If we come to find out that life is very rare for a universe with our physical laws, that would provide some evidence to support the notion that life is very rare for a universe with physical laws from a particular set of possible physical laws. Conversely if we find out that life is common for a universe with our physical laws then that would provide some evidence to support that life might be common in universes with different physical laws. Life could generally be easy or hard to make. I restricted our analysis only to universes like ours because it makes it much easier to analyze the probabilities at play, for a complete picture we should add universes unlike ours to the analysis (presuming they exist) but then you run into all sorts of issues. For the sake of carity and brevity I chose not to delve into that.

 

[warpus]

From this information you can pretty much rule out the possibility the batch is life-poor (because you probably wouldn't have found life on it), so you only only got life-rich and intermediate batches to worry about.

That's my argument though, that we can pretty much rule out that we are in a life-poor universe. I mean, it's possible, but the claim is that it is likely that we are the only life here. As likely as there being life elsewhere! That means we are in an extremely life-poor universe and got super lucky to have ended up being seeded.

Given all the scenarios it is far more likely we are in one of the other types of universes, whether it's "life-rich" or "life-super-scarce-but-it-appears-twice-or-thrice" or "life-kinda-poor-but-each-galaxy-has-1" or whatever you can imagine. There are so many more options out there in way of probability, it towers way above the "we got lucky with the die throw and are in a life-only-once" universe. The way you described the set-up helps illustrate that concept better than my write-up earlier

 

[uppi]

That's my argument though, that we can pretty much rule out that we are in a life-poor universe. I mean, it's possible, but the claim is that it is likely that we are the only life here. As likely as there being life elsewhere! That means we are in an extremely life-poor universe and got super lucky to have ended up being seeded.

Given all the scenarios it is far more likely we are in one of the other types of universes, whether it's "life-rich" or "life-super-scarce-but-it-appears-twice-or-thrice" or "life-kinda-poor-but-each-galaxy-has-1" or whatever you can imagine. There are so many more options out there in way of probability, it towers way above the "we got lucky with the die throw and are in a life-only-once" universe. The way you described the set-up helps illustrate that concept better than my write-up earlier

This is a logical fallacy, because you know nothing about the underlying distribution. The argument falls apart if the distribution the probability of life arising in a universe is a long-tail distribution and I don't think you can make a good argument that it is not such a distribution.

Let me make an example where this type of reasoning falls apart: Suppose you have two bags of marbles with 10 marbles each. One of them has 10 white marbles, the other one only 1. Now you chose one bag at random, take one marble out and it is white. The probability that the bag you chose was the one with 10 white marbles is 10/11 = 91%. But now consider the situation when there is one bag with 10 white marbles and 1000 bags with 1 white marble. Again you chose one bag at random and take out a white marble. In this case, because there are so many of the 1-white-marble-bags, the probability that you chose the one with 10 white marbles is only 10/1010 = 1%.

So, if there were nearly infinite life-poor possible universes and only few possible life-rich universes, the probability could be much higher that we are in a life-poor universe, just because there are so many of them. Any of the life-poor universes would be less probable than any given life-rich scenario, but in total the life-poor situation would be more likely. Since we don't know anything at all about the underlying distribution, you cannot make any argument at all whether it is more probable that our universe is life-rich or life-poor.