Earth Sized Planets!

[YellowSubmarine]

We don't know how life started yet, but we have figured out there are potential mechanisms, and we've figured out there are things called evolutionary processes that make it easier than we've ever imagined. We aren't certain that it is not excruciatingly difficult, but even if it is it very very unlikely it still leaves a very big possibility for at least one other instance of life in the universe, because the number of planets would be insanely huge too.

And just to point out: The statement that “no life at all” and “life in almost every reasonable place” are equally likely implies that almost certainly the universe is quite abundant in life (equally likely would imply a probability smaller than one over a billion). If I was to make an argument against life in the universe, I'd point out that life on no other planets at all is much more likely than life on just a few planets, because there are lower rates even after you reach zero planets. You can have life in one out of a sextillion universes.

 

[RoJoHen]

I'm just saying, as far as statistics go, you can't predict the exist of life anywhere else in the universe until you have more examples of life actually existing.

If I give you a giant bag of marbles and you pull out a red one, what is the likelihood that the next marble you pull out will also be red? You know nothing about the contents of the bag. Maybe all the marbles are red. Maybe none of the other marbles are red. Without more information, you simply can't guess one way or another.

 

[YellowSubmarine]

No. You can calculate what was the probability to pull a red one for any distribution of red marbles. The data that you just observed would be incredible if this was the only red marble in the bag, and so you're expecting that it isn't. In fact, at this point you're expecting that all marbles in the bag are red until you pull another colour, though the probability that it is actually so is still small.

 

[Crazy Eddie]

That's only if you assume that we are likely to be extinct in much less than a billion years.

Why not? Most OTHER species on Earth last a tenth as long as that, either because they are exterminated or because they evolve into something else. I have alot of faith in human ingenuity and all, but not enough to bet on our perpetual survival for half a billion years. The best you could say is that some of us might evolve into a distinct new species that is no loner biologically "human," but I doubt that species will have any connection--or really, any MEMORY--of us.

 

[Crazy Eddie]

I'd say it is likely there is intelligent life elsewhere, but, no, we can't estimate it. That would imply being able to predict evolution in alien ecosystems that only theoretically exist. We can predict the number of probable planets with life, but I don't think we can go much farther than that.

That's kind of the point I was making. We can certainly estimate the number of planets that might be capable of supporting life, but until we actually find life out there and get a better understanding of how life begins, we can't predict how much life there is. We don't even know how life started here. We certainly can't make a reasonably guess at how life started elsewhere or how much of it there might be.

But that, again, is speaking in the PRESENT tense. Even assuming life exists in one other place in the universe, the chances of it existing--and proliferating over interstellar distances--is considerably higher than the chances of this happening in TWO places at the same time, especially considering the timescales involved.

There could, for instance, have been intelligent life in a planet 300 light years away from here controlling a sphere of influence that included what later became the Earth... four billion years ago, when Earth was still just a baren lifeless rock. There could have been an entirely different one in a totally different system three and a half billion years ago; they might have briefly explored (what was still, at the time) the almost-habitable planet Mars. In between, on a dozen different planets in a dozen different eras, civilization could have risen and fallen without ever leaving their own solar system (or even their own world) and passed into extinction or even burned out of existence entirely when their suns burned out.

It's far less likely for these civilizations to all have evolved AT THE SAME TIME, however, considering the timescales involved (a few thousands or tens of thousands of years) out of millions or billions of years is a scale almost as vast as the stars themselves.

 

[YellowSubmarine]

Why not? Most OTHER species on Earth last a tenth as long as that, either because they are exterminated or because they evolve into something else. I have alot of faith in human ingenuity and all, but not enough to bet on our perpetual survival for half a billion years. The best you could say is that some of us might evolve into a distinct new species that is no loner biologically "human," but I doubt that species will have any connection--or really, any MEMORY--of us.

The extinction of species and the end of a civilization are different things. Homo sapiens will almost certainly be extinct in a billion years, but the human civilization will hopefully still be there, just the humans won't be homo sapiens anymore, they will be homo bigusboobickus.

 

[MattWallace]

No. You can calculate what was the probability to pull a red one for any distribution of red marbles. The data that you just observed would be incredible if this was the only red marble in the bag, and so you're expecting that it isn't. In fact, at this point you're expecting that all marbles in the bag are red until you pull another colour, though the probability that it is actually so is still small.

We don't know how many red marbles or marbles of any other color or even how many marbles are in the bag. We don't even know if the red one was the only marble in the entire bag. It's hard to calculate a trend using one data point.

 

[YellowSubmarine]

What good would knowing those numbers do? They have no effect on your estimation of the proportion of red marbles. Having one of those numbers is useful only to estimate one of the other numbers.

 

[Pavonis]

^The bag either contains nothing but red marbles, zero red marbles (after removing the only one), or any number in between. The probability of drawing a red marble can be calculated for any or all of the possible mixtures in the bag, but with only one point, there's no way to know which of the possibilities is realistic!

 

[YellowSubmarine]

If I gave you a bag and you pulled out a walnut out of it, you'd think it's a bag of walnuts.
If I gave you a bag and you pulled out a red marble out of it, you'd think it's a bag that has some red marbles in it.

In a real world situation you won't really consider the option that there are no other walnuts/red marbles inside the bag, at least not as your first choice.

Though I personally have no idea what the marbles have to do with anything. We have not yet pulled a single marble out of this bag (no aliens is no aliens), and all reasoning about their abundance is pretty much indirect. Being indirect doesn't make it invalid, I see no reason why my reasoning is invalid, although I admit it's not very good either because there's guesswork in it - particularly how easy is for life to form, and that knowledge of the general process suggests it's not so extremely difficult.

 

[Pavonis]

Though I personally have no idea what the marbles have to do with anything. We have not yet pulled a single marble out of this bag (no aliens is no aliens),

Yes, we have pulled one marble out of the bag. Our planet definitely is one sample of a life-bearing planet. It just doesn't tell us about the probability of the existence of other life-bearing worlds.

If you assume one red marble drawn from a bag means the bag is full of red marbles, that's fine, but you don't really know the bag has more than one red marble.

 

[Crazy Eddie]

Why not? Most OTHER species on Earth last a tenth as long as that, either because they are exterminated or because they evolve into something else. I have alot of faith in human ingenuity and all, but not enough to bet on our perpetual survival for half a billion years. The best you could say is that some of us might evolve into a distinct new species that is no loner biologically "human," but I doubt that species will have any connection--or really, any MEMORY--of us.

The extinction of species and the end of a civilization are different things. Homo sapiens will almost certainly be extinct in a billion years, but the human civilization will hopefully still be there, just the humans won't be homo sapiens anymore, they will be homo bigusboobickus.

In which case, to what extent will they have any knowledge--or any reason to care--about their connection to homosapiens?

If you think about it, WE could just as easily be the descendants of another sapient race that underwent a dozen million years of evolution only to eventually become us. We wouldn't really know it either way, but it's unlikely those ancient forefathers would recognize us as the inheritors of their civilization since we are nothing like them and don't remember anything about them.

 

[YellowSubmarine]

I always thought homo erectus were sapient?

Unless our descendants are racist, I don't see why they would make any difference whether they make up the same or a different species as us. Memory will be independent of speciation.

 

[Crazy Eddie]

I always thought homo erectus were sapient?

And if we found a planet populated by an industrialized species of homo erectus, do you think we would begin to look at ourselves as merely an extension of their civilization here on Earth and we, therefore, the ultimate continuation of their species?

Or would we say "It's amazing that those evolutionary throwbacks managed to survive all this time! What are the odds? Well, let's try to talk to them and see whether or not coexistence is possible."

Unless our descendants are racist, I don't see why they would make any difference whether they make up the same or a different species as us. Memory will be independent of speciation.

Memory is also fleeting, and highly inaccurate even when it DOES last. On a scale of two million years, on encountering our evolutionary derivatives, so much culture and so much language and so much history and so much biology has changed that at that point we might as well be talking to Klingons or Cardassians. Coexistence is eventually possible, but not from an ancestors/descendants relationship, but from a "your people, my people" relationship.