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#71




Horizon 2017: Strange Signals from Outer Space
On 15/07/2017 15:03, Johnny B Good wrote:
Don't forget, as some proponents for the idea that life pervades the whole universe would prefer you to believe, anyone is quite free to plug their own values (best guesses) into this equation to obtain their own guestimate. :) Most people treat the Drake equation as timeinvariant. They take no account of the evidence that massextinction events  even galactic mass extinction events  were more frequent in the past. So the answer to Fermi's Question may be "just hang about a bit longer".  Robin replyto address is (intended to be) valid 
#72




Horizon 2017: Strange Signals from Outer Space
On Sat, 15 Jul 2017 10:55:49 +0100, Norman Wells wrote:
On 15/07/2017 10:42, Roderick Stewart wrote: On Sat, 15 Jul 2017 00:09:11 GMT, Johnny B Good wrote: The more I've learned about the series of very *fortunate* accidents that lead to the Earth's environment that so swiftly became benign to the evolution of life, the more I think that Drake's famous equation represents an outrageous level of optimism in discovering other intelligent species in the Universe that we can actually interact with. I've always thought exactly the same. The Drake "equation" is just a string of estimated probabilities multiplied together. Some of those estimates appear to be reasonable ones, based on facts, and since the equation was first proposed we've discovered a few more facts  but not (yet?) the most important one. We can make guesses at how life might progress, but it's meaningless as long as we know nothing about the probability of life appearing *at all*. Multiply several numbers together, and no matter what they represent, if just one of them is an unknown quantity then the whole thing is unknown. It looks like mathematics, which makes it look clever, but really it's still just wishful thinking. It's not 'wishful thinking' but a best estimate based, as everyone involved accepts, on certain informed guesswork. You're free to make any other different assumptions you want and come up with a different answer. Quite true but, understandably, the SETI proponents will concentrate on their own best guesses and play down the ones where the result tends towards unity (i.e. Just Us!). But your assumptions would have to be pretty wild to come to the conclusion that intelligent life on earth is unique. They'd have to exclude the possibility that the chemical processes leading to life here could not or would not happen anywhere else at all. And I wonder if you could possibly justify that. Putting aside the question of *intelligent life* capable of producing radio signals, from the evidence so far I doubt any scientist would harbour such an extreme view as that. Indeed, our current understanding of biochemistry suggests that whatever life forms which may arise elsewhere outside of the Solar system, it's extremely unlikely that they'd all be based on anything other than Carbon. Limiting our scope to just that of Carbon based biochemistry might seem a rather parochial attitude to the question of 'Life elsewhere in the Universe' but, quite frankly, even with all of Carbon based compounds' advantage of 'unstable complexes' throughout the liquid phase of water, we're struggling to fathom out how in Ghod's name such precursor complexity required to construct cellular life was able to arise in the first place let alone how such cells managed to spring into being at all. It seems a pretty safe bet that if life is to arise anywhere else in the Universe, it will inevitably be Carbon based. Although it may become possible to theorise about life based on a different key element to Carbon, I suspect such a possible alternate life form would probably require several lifetimes of the stellariferous phase of the Universe in which to allow such an accumulator bet to pay off, instead of the mere 10 billion years or so that it took for Carbon based life to collect on its own accumulator bet. When Einstein expressed his dislike of the new fangled quantum mechanics theory by claiming "God does not play Dice!", I reckon he had the whole concept of an omnipotent deity, responsible for everything in the universe (including the Universe itself), totally arse about face. :)  Johnny B Good 
#73




Horizon 2017: Strange Signals from Outer Space
On Sat, 15 Jul 2017 12:47:04 +0100, Jim Lesurf
wrote: The more I've learned about the series of very *fortunate* accidents that lead to the Earth's environment that so swiftly became benign to the evolution of life, the more I think that Drake's famous equation represents an outrageous level of optimism in discovering other intelligent species in the Universe that we can actually interact with. I've always thought exactly the same. The Drake "equation" is just a string of estimated probabilities multiplied together. Some of those estimates appear to be reasonable ones, based on facts, and since the equation was first proposed we've discovered a few more facts  but not (yet?) the most important one. We can make guesses at how life might progress, but it's meaningless as long as we know nothing about the probability of life appearing *at all*. Multiply several numbers together, and no matter what they represent, if just one of them is an unknown quantity then the whole thing is unknown. It looks like mathematics, which makes it look clever, but really it's still just wishful thinking. Yes and no. :) We should distinguish between the *equation* which includes a series of variables and the question of how we might decide actual values for each variable in order to get an overall figures. True, but for this equation we don't have an actual value for the most important variable  the probability of life appearing spontaneously independently of the life that we are aware of here on Earth, or the number of times this has happened, whichever way you want to express it. Without this value, the rest of the equation is useless as a means of estimating the probability of life appearing elsewhere. Its virtue as an equation is that it lets us divide the question into a series of subquestions about the value of each variable. We can amuse ourselves as much as we want considering as many subquestions as we can think of, but without the answer to the most important one  see above  we know nothing. We can then look for ways to get plausible values for each variable as a way to build a way towards the result the equation would then give. Good. Let's do that. Let's try to find life that has arisen elsewhere and thus provide a value for the missing variable, but in the meantime let's recognise that we haven't found it yet. If anybody, even a respected scientist (and they really ought to know better) says they are "hopeful" of discovering extraterrestrial life, then that's all it is  hope  not science, and certainly not an indication of the probability of it happening. We won't be able to calculate the probability of discovering extraterrestrial life until we've actually discovered some extraterrestrial life, and then we won't need to calculate it because then we'll know. This would appear to render the Drake equation pointless, but that's life. At least it's life as we know it. Rod. 
#74




Horizon 2017: Strange Signals from Outer Space
On Sat, 15 Jul 2017 14:03:16 GMT, Johnny B Good
wrote: It's true enough that most of the variables are just 'best guesses', some of which may or may not be relevant (such as the need for a planet in 'the Goldilocks zone' to suffer a collision with a Mars sized planet in order to get a spin axis stabilising moon which will also provide tidal forces to create interesting habitats to help drive evolution) but this list of possible factors, if nothing else, provides targets for research which may prove essential to determining whether or not there is life elsewhere in the universe. The equation is part of the process in gaining a better understanding of the problem. Indeed. It gives us a better understanding of just how many variables there could be, and to wonder how many of them might or might not be relevant. That's an interesting set of concepts to wonder about in its own right. For those of us who understand that that's all it is, there isn't a problem, but unfortunately the Drake equation is often put forward as a way of estimating the actual probability of finding extraterrestrial life, and it cannot possibly be this until we have credible values for *all* of its variables. As things stand at the moment, one absolutely vital value is missing. Rod. 
#75




Horizon 2017: Strange Signals from Outer Space
On 15/07/2017 17:55, Roderick Stewart wrote:
Good. Let's do that. Let's try to find life that has arisen elsewhere and thus provide a value for the missing variable, but in the meantime let's recognise that we haven't found it yet. They have found "organic matter" in some meteorites, but nobody has yet put their head above the parapet and said it demonstrates life rather than a chance combination of chemicals. So there is a reasonable assumption that organic chemistry exists somewhere other than Earth, but it is perhaps a step too far to assume that such an occurrence is an example of life elsewhere. Jim 
#76




Horizon 2017: Strange Signals from Outer Space
On 15/07/2017 17:55, Roderick Stewart wrote:
snip We should distinguish between the *equation* which includes a series of variables and the question of how we might decide actual values for each variable in order to get an overall figures. True, but for this equation we don't have an actual value for the most important variable  the probability of life appearing spontaneously independently of the life that we are aware of here on Earth, or the number of times this has happened, whichever way you want to express it. Without this value, the rest of the equation is useless as a means of estimating the probability of life appearing elsewhere. I do not know what you mean by "the most important variable". If you mean "the smallest one" then it is just your assumption that that is the probability of life arising. It might for all we know be the length of time that communicative civilizations release detectable signals. Its virtue as an equation is that it lets us divide the question into a series of subquestions about the value of each variable. We can amuse ourselves as much as we want considering as many subquestions as we can think of, but without the answer to the most important one  see above  we know nothing. We can then look for ways to get plausible values for each variable as a way to build a way towards the result the equation would then give. Good. Let's do that. Let's try to find life that has arisen elsewhere and thus provide a value for the missing variable, but in the meantime let's recognise that we haven't found it yet. If anybody, even a respected scientist (and they really ought to know better) says they are "hopeful" of discovering extraterrestrial life, then that's all it is  hope  not science, and certainly not an indication of the probability of it happening. We won't be able to calculate the probability of discovering extraterrestrial life until we've actually discovered some extraterrestrial life, and then we won't need to calculate it because then we'll know. This would appear to render the Drake equation pointless, but that's life. At least it's life as we know it. Pedantic but important (well I would say that, wouldn't I?) point: the Drake Equation (at least in its original form) does not deal with the probability of *discovering* life, only the existence of active, communicative extraterrestrial civilizations. Discovery depends on other factors  eg how long do we listen? how hard? how?  Robin replyto address is (intended to be) valid 
#77




Horizon 2017: Strange Signals from Outer Space
If it wasn't for the strange fact that electromagnetic waves will
propagate though a vacuum we would have no idea that the universe existed other than the Earth. But since life would never have started on Earth it wouldn't matter much. Bill 
#78




Horizon 2017: Strange Signals from Outer Space
On Sat, 15 Jul 2017 18:54:21 +0100, Indy Jess John
wrote: Good. Let's do that. Let's try to find life that has arisen elsewhere and thus provide a value for the missing variable, but in the meantime let's recognise that we haven't found it yet. They have found "organic matter" in some meteorites, but nobody has yet put their head above the parapet and said it demonstrates life rather than a chance combination of chemicals. So there is a reasonable assumption that organic chemistry exists somewhere other than Earth, but it is perhaps a step too far to assume that such an occurrence is an example of life elsewhere. Jim "Organic chemistry" just means big molecules with carbon atoms, so yes, the discovery of the chemicals alone is no guarantee that they ever have or ever will develop into life. I remember the first lesson of Organic Chemistry A Level, which began with the alkanes  methane, ethane, butane, propane and so on. They all burn nicely but are a long way from developing intelligence. Rod. 
#79




Horizon 2017: Strange Signals from Outer Space
On Sat, 15 Jul 2017 18:54:25 +0100, Robin wrote:
We should distinguish between the *equation* which includes a series of variables and the question of how we might decide actual values for each variable in order to get an overall figures. True, but for this equation we don't have an actual value for the most important variable  the probability of life appearing spontaneously independently of the life that we are aware of here on Earth, or the number of times this has happened, whichever way you want to express it. Without this value, the rest of the equation is useless as a means of estimating the probability of life appearing elsewhere. I do not know what you mean by "the most important variable". If you mean "the smallest one" then it is just your assumption that that is the probability of life arising. It might for all we know be the length of time that communicative civilizations release detectable signals. The variables in the Drake equation are to do with the probabilities of life developing in particular ways, becoming intelligent, inventing radio, etc  all except one. That one variable is the probability of anything that can be called life appearing *at all*. This is what I mean by the most important variable, because until we can give a numerical value for it, the others are useless. [...] Pedantic but important (well I would say that, wouldn't I?) point: the Drake Equation (at least in its original form) does not deal with the probability of *discovering* life, only the existence of active, communicative extraterrestrial civilizations. Discovery depends on other factors  eg how long do we listen? how hard? how? Discovery of anything depends crucially on whether it is there to be discovered in the first place. Until we know that, all the rest is speculation. Rod. 
#80




Horizon 2017: Strange Signals from Outer Space
On 16/07/2017 08:56, Roderick Stewart wrote:
The variables in the Drake equation are to do with the probabilities of life developing in particular ways, becoming intelligent, inventing radio, etc  all except one. That one variable is the probability of anything that can be called life appearing *at all*. This is what I mean by the most important variable, because until we can give a numerical value for it, the others are useless. Well, it's certainly happened here, on the only planet we know that much about. What you have to consider is really the probability of it *not* having occurred anywhere else in all the incredible vastness of the universe. You may think you're special and unique, but you're still just a bunch of chemicals made up of a very low number of elements that are abundant everywhere and are perfectly capable of combining anywhere in the same way as in you. Even your DNA contains just five of those: carbon, hydrogen, oxygen, nitrogen and phosphorus. 
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