Do you believe in extraterrestrials?

[Grave_n_idle]

...it got me to thinking - we tend to think of our 'habitable zone' pretty much entirely in terms of distance from the sun, but our habitable zone may be much more specific than that. In fact, it pretty certainly is. [...]

I know I've mentioned somewhere recently on a forum (this one, in this thread?) the possibility of a "Galactic Goldilocks Zone". Another thing that's not my idea, but looks like you have the same sort of one. Too close to glactic centre and allthat Cygnus X-1 thing and the radiation in amongst the mass of close-knit stars isn't good for (our kind of) life, and there's probably no stability of planets if you've got a dozen stars between an otherwise likely sun and its equivalent of our neighbouring Alpha Centauri, whizzing about like nobody's business and gravitationall ypurturbing all the debris.

Too far out and nebulae may just not have enough purturbation to recoallesce into the next generation of stars (or at least with not the right mix of matter).

Similar patterns perhaps within the core of spiral arms and definitely in the gaps between them, and obviously zones that aren't "stellar nurserys" are going to have to do with whatever stars and planets they got the last time their area was a stellar nursery (and deal with the slow death of the stars that are dying), at least until the next good nova stirs things up again.

And of course we're a spiral galaxy. Other types (already different ages from our own, with different suns also representing different points throughout the standard stellar evolution graph, and some apparently with hyperactive cores that might make the entire span of that galaxy uninhabitable to radiation-sensitive life¹) will have their own problemaic/advantageous areas. Especially if the potential life would have been arising just about the time that the neighbouring galaxy in the cluster starts its deathly-slow 'collision' with your own, bringing in a hail of 'fast'-moving stars through one's neighbourhood. (Mostly them all missing, I presume, given how big space is, even compared to stars, but I bet it's spectacular when you get a direct collision, and even more so with a glancing hit, from the right angle... )

(But by the time we're talking about looking for life in other galaxies, I tend to go "Of course its there," (above-mentioned 'dead zones', possibly excepting), "but we'll probably never know of it, even if Humanity lasts faaaar beyond the lifetime of our own sun." The same may be true of life from the other side of the Milky Way, but at least if we compartmentalise our own galaxy into more and less likely areas to find life (as we know it!) we can get a good idea of how long we might have to wait (or, ourselves, travel, barring breakthrough shortcuts that would be a game-changed on every level) to meet the 'neighbours'.)


¹ Or inhabitable to life that demands it? That couldn't have arisen in our neck of the woods because the conditions were too quiescent?

Sounds like we're on the same sort of wavelength, yes.

One thing I wanted to point out - I'd imagine that 'radiation-sensitive' is probably going to be a fairly common ingredient in the make-up of life, to some extent or another - because adaptability requires variation, and variation is favoured by mutation.

[Grenartia]

(Thank god for the scrollable Topic Review bit below the editor, otherwise I'd lose track. My large posts, your large responses... I'm sure everyone else is thinking TL;DR;...)

1. I don't see how that enters the equation. It just seems like a neater way to organize the various known systems of life on each planet. I.E., simply saying that planets 1, 4, 36, 78, and 285 have right-handed life, while planets 5, 6, 908, and 10432 have left-handed life.

I understand now. Sorry, I was thinking of you looking at each individual planets systems and making up a new Kingdom-set (or using their existing one, if they have made one themselves), but that a super-set of Kingdoms would be "universals" that applied regardless of the fine details of the local trees.

1. Only can we say for sure that a given LH/RH sugar (say, as a base-line for the dominant chirality on a given planet) always maps to other chemicls being LH/RH (respectively, or always anti-respectively)? It might not work like that. Or it might. Not enough data, yet!

2. Well, its because of that tumbleweed example that I'm opposed to motility-based classification.

2. To be honest a tumbleweed isn't self-directing, OTOH plants as we know them do have movement, w.r.y. heliotropic behaviour, so it isn't a long stretch to imagine that an alien motile creature is still, technically, a plant. But it's Triffids all over again. (Whoops: again, not enough data yet.)

7. The main problem with 1L4A with hopping/leaping/jumping as a form of locomotion is that its inherently unstable, and more likely to cause injury.

3. Probably why I'm imagining Leaping Lemurs, using their 'leaping and prancing' ground movement only when not swinging between trees.

8. Or perhaps a decentralized semi-autonomous nerve cluster dedicated to motor control (kind of like how paleontologists once thought Stegosauri had two brains).

4. Consider the octupus, as well. Apparently 2/3rds of their nerves are in their arms, and after detatchment (forced or volountary, upon being attacked) they retain some self-autonomy and trained reflexes.

10. So long as you have metallic skin, I don't see much of a reason it itself can't act as a receiver.

5. My electronics isnt top-notch, but I'm fairly sure you need some sort of 'spark gap' to receive, otherwise a continuous skin is just going to equalise electric/magnetic potential across itself (Faraday Caging in the process) and neutralise the receptivity. Also if phase-arraying you need multiple 'aerial heads' separated by non-conducting material, wired into whatever 'comparitor' you have that works out the phase difference and possibly recombines (with differing time-lags) the received signals to create the full-quality signal for the source being 'aimed at'. BICBW about all that.

13. I'm not familiar with them, actually.

6. Well, I've done my bit for selling Jack (Cohen) and Ian (Stewart)'s works already, for the day, so I won't go on about them (Jack Cohen and Ian Stewart, that is). But rest assured that Professors Stewart (Ian) and Cohen (Jack) are not only fully qualified in their respective fields of Biology (Jack. Jack Cohen) and Mathematics (ian. Ian Stewart) but work well together (Jack with Ian and, interestingly, Ian with Jack) in various collaborative works. And they've also been made Honorary Wizards of the Unseen University (this being within the Earthly/Roundworld power of Terry Pratchett of Discworld fame).


(3,4,5,6,9,11,12: Really nothing more than general agreement and/or happy acknowledgement of the information, accordingly.)

I know, really?

1. Indeed.

2. Again, spot on.

3. Of course, we're ignoring the possibility of organisms that have limbs capable of acting as both arms AND legs, and ignoring things like prehensile tails.

4. And my mind went straight to naughty tentacles.

5. I'm not that knowledgeable in electronics, either, but it sounds reasonable. Perhaps a hair analogue that acts like anntennae?

6.

...it got me to thinking - we tend to think of our 'habitable zone' pretty much entirely in terms of distance from the sun, but our habitable zone may be much more specific than that. In fact, it pretty certainly is. [...]

I know I've mentioned somewhere recently on a forum (this one, in this thread?) the possibility of a "Galactic Goldilocks Zone". Another thing that's not my idea, but looks like you have the same sort of one. Too close to glactic centre and allthat Cygnus X-1 thing and the radiation in amongst the mass of close-knit stars isn't good for (our kind of) life, and there's probably no stability of planets if you've got a dozen stars between an otherwise likely sun and its equivalent of our neighbouring Alpha Centauri, whizzing about like nobody's business and gravitationall ypurturbing all the debris.

Too far out and nebulae may just not have enough purturbation to recoallesce into the next generation of stars (or at least with not the right mix of matter).

Similar patterns perhaps within the core of spiral arms and definitely in the gaps between them, and obviously zones that aren't "stellar nurserys" are going to have to do with whatever stars and planets they got the last time their area was a stellar nursery (and deal with the slow death of the stars that are dying), at least until the next good nova stirs things up again.

And of course we're a spiral galaxy. Other types (already different ages from our own, with different suns also representing different points throughout the standard stellar evolution graph, and some apparently with hyperactive cores that might make the entire span of that galaxy uninhabitable to radiation-sensitive life¹) will have their own problemaic/advantageous areas. Especially if the potential life would have been arising just about the time that the neighbouring galaxy in the cluster starts its deathly-slow 'collision' with your own, bringing in a hail of 'fast'-moving stars through one's neighbourhood. (Mostly them all missing, I presume, given how big space is, even compared to stars, but I bet it's spectacular when you get a direct collision, and even more so with a glancing hit, from the right angle... )

(But by the time we're talking about looking for life in other galaxies, I tend to go "Of course its there," (above-mentioned 'dead zones', possibly excepting), "but we'll probably never know of it, even if Humanity lasts faaaar beyond the lifetime of our own sun." The same may be true of life from the other side of the Milky Way, but at least if we compartmentalise our own galaxy into more and less likely areas to find life (as we know it!) we can get a good idea of how long we might have to wait (or, ourselves, travel, barring breakthrough shortcuts that would be a game-changed on every level) to meet the 'neighbours'.)


¹ Or inhabitable to life that demands it? That couldn't have arisen in our neck of the woods because the conditions were too quiescent?

And you knocked it out of the park, yet again. Stellar explanation, no pun intended.

I know I've mentioned somewhere recently on a forum (this one, in this thread?) the possibility of a "Galactic Goldilocks Zone". Another thing that's not my idea, but looks like you have the same sort of one. Too close to glactic centre and allthat Cygnus X-1 thing and the radiation in amongst the mass of close-knit stars isn't good for (our kind of) life, and there's probably no stability of planets if you've got a dozen stars between an otherwise likely sun and its equivalent of our neighbouring Alpha Centauri, whizzing about like nobody's business and gravitationall ypurturbing all the debris.

Too far out and nebulae may just not have enough purturbation to recoallesce into the next generation of stars (or at least with not the right mix of matter).

Similar patterns perhaps within the core of spiral arms and definitely in the gaps between them, and obviously zones that aren't "stellar nurserys" are going to have to do with whatever stars and planets they got the last time their area was a stellar nursery (and deal with the slow death of the stars that are dying), at least until the next good nova stirs things up again.

And of course we're a spiral galaxy. Other types (already different ages from our own, with different suns also representing different points throughout the standard stellar evolution graph, and some apparently with hyperactive cores that might make the entire span of that galaxy uninhabitable to radiation-sensitive life¹) will have their own problemaic/advantageous areas. Especially if the potential life would have been arising just about the time that the neighbouring galaxy in the cluster starts its deathly-slow 'collision' with your own, bringing in a hail of 'fast'-moving stars through one's neighbourhood. (Mostly them all missing, I presume, given how big space is, even compared to stars, but I bet it's spectacular when you get a direct collision, and even more so with a glancing hit, from the right angle... )

(But by the time we're talking about looking for life in other galaxies, I tend to go "Of course its there," (above-mentioned 'dead zones', possibly excepting), "but we'll probably never know of it, even if Humanity lasts faaaar beyond the lifetime of our own sun." The same may be true of life from the other side of the Milky Way, but at least if we compartmentalise our own galaxy into more and less likely areas to find life (as we know it!) we can get a good idea of how long we might have to wait (or, ourselves, travel, barring breakthrough shortcuts that would be a game-changed on every level) to meet the 'neighbours'.)


¹ Or inhabitable to life that demands it? That couldn't have arisen in our neck of the woods because the conditions were too quiescent?

Sounds like we're on the same sort of wavelength, yes.

One thing I wanted to point out - I'd imagine that 'radiation-sensitive' is probably going to be a fairly common ingredient in the make-up of life, to some extent or another - because adaptability requires variation, and variation is favoured by mutation.

Hell, there's probably planets where life not only survives high levels of radiation, but literally NEEDS it to survive. We already have examples of such here on Earth.

http://en.wikipedia.org/wiki/Radiotrophic_fungus

[Northwest Slobovia]

An interesting speculation...

How unfamiliar? Not fitting our existing cladistic "orders" would hardly surprise me, but nothing like our "kingdoms" would. What else... Lack of bilateralism? Biochemistry we don't initially recognize as living?

I guess I'd also be surprised by a lack of eyes we recognize. There don't seem to be too many image-forming systems we can think of, even allowing abiological ones.

What springs to mind for me is some of the creatures that have been discovered in some of the depths of our own oceans, and how profoundly alien they are to us. The difference between our land-world of mammals and their world of crushing pressure and absolute darkness is only a sliver of difference compared to what we will find if we start comparing our planet to other planets.

Sure. Actually, if you want "difference", black smokers and other extremely hot, salty, and/or acid environments are probably the places to look. Wierd stuff lives there...

So to answer your specifics, I think the lack of bilateral symmetry would go hand in hand with radically different biochemistry; the way we develop, and the reasons why it is "easier" to produce a symmetrical organism than an asymmetrical one, would not necessarily remain constant if the underlying molecular interactions were different.

Hm. I'd say the same machinery supports a whole bunch different body plans. We're bilateral, echidnoderms are radially symmetric, and plants are, well, dendric. Hell, dicots start out bilaterally symmetric, but they're not consistently so after that.

Still, I'd be surprised if motile critters didn't frequently end up bilateral. It seems very convenient for movement. But, um, that's the whole point of looking.

As for eyes, we already know of plenty of life forms which have no particular need to perceive the spectrum of energy we know as visible light. I would not be at all surprised by alien life which finds such receptors similarly unnecessary, particularly since there's no reason to assume said life would be surface-dwelling.

Yeah, badly phrased on my part. I shoulda said something like, "if we find anything which sees the same light we do, I expect them to have eyes like ours because of physical constraints.".

While I'm at it: any opinion on on whether we'll life other life in our solar system? I'm opimistic: I give better than 3:1 odds in favor (25% chance there's life). There's four big, damp moons with plausible conditions, and I suppose Mars might still have something home (though I think that's a real long shot).

[Northwest Slobovia]

Mostly minuses. Si-Si bonds are surprisingly weak and easily cut by water (and other common polar solvents).

That's something I meant to address, given that Si-Si 'organics'-friendly (<-originally typed "orangics".. ) environments are likely waterless, so what might be the equivalent "universal solvent" (which doesn't, as you point out, destroy the polysilicates)? If we're just dropping a level on the periodic table then H₂S might be our man, but something tells me it isn't... *cough*

You mean "silanes", and I'd have to look it up. "Silicates" are rocks. The problem with hunting for suitable solvents is that excluding stuff we think is relatively common around stars means the odds of finding incompatible life is low.

Also forgot to deal with the issues of the eye that you mentioned. Don't they say that (on Earth) it has been independently developed at least seven times, in different evolutionary branches? That's all forms of eye, not just our (pre-)mammallian one, although the cephalopd one is surprisingly similar to ours (only without some of its flaws).

Dunno. There's only three designs that I know of, however: simple, lensed eyes like ours; compound, lensed eyes like insects have, and pinhole eyes, which as far as I know are restricted to Nautiloids.

Anyway, I imagine that as long as visible light has been a useful thing to detect (i.e. not if the aliens developed within a somewhat photo-opaque atmosphere¹) that we'd see eyes of some kind or another. Although how recognisable they would be is another question, e.g. are they still paired? Are they still upon what passes for the alien's head? (Assuming that there is a 'head', c.f. Niven's "Puppetteer" race.)

Excellent questions! We'll have to see. The only good argument I know WRT where eyes go is that vision takes a lot of bandwidth, which tends to argue that they go near the brain. 'course, there may be different brain architectures out there, and I can imagine critters with, say, a "visual cortex" right near the eye(s), but the rest of the brain further away. Bottle would have a better guess than I would, since neuro is her thing and I'm a biochemist.

But if visible (or near-visible, from our perspective) light has not been useful, perhaps electrosensitivity is the dominant 'sight'-equivalent sense, perhaps not needing obvious eye-like features. I forget if this is supposed to be part of their biology, but the "Alien" aliens are conspicuously eyeless (well, all natural ones anyway) and may be thus differently-sensing of prey (or, on their original home world, all the very much nastier things that they are prey for) in such ways.

Works for electric eels, so why not? But water's a good dielectric, which makes signal transduction for biochemistries similar to ours easier. Dunno about weirder stuff, though; I don't know much about RF.

And if we're still welded to the idea of "metalliform" creatures,

Dry sense of humor y'got there...

arising from a vague and admitedly unproven assumption of a silicon-based biology, might that make wandering off into the radio-wave areas of the EM spectrum a viable sense-equivalent? Of course, if your skin is metal-based you're probably effectively shielding internal aerials/parabolic dishes from radio waves, so either external ones (which may be obvious) or radio-opaque patches of skin (which, again, may be obvious, just like the eyeball pokes out through our own skin) perhaps ought to exist. But it still may not be anything like that.

See above, though image-forming radar takes big apertures. Might work for large critters, cf. Clarke's "Meeting with Medusa".

¹ Of course, if an alien atmosphere is photo-opaque to us, it's possibly not so at far infrared or ultraviolet, so actual eyes tuned accordingly could/should/would still develop.

Why not? Tho for UV much smaller than, oh, 200Å or so, ya gotta wonder how it's getting through to the ground, since that raises a bunch of questions about the atmosphere...

Also s/atmosphere/ocean/ if you can either explain or hand-wave away what the equivalent "discovery of fire" moment is in a locale with no fire. e.g. using geothermal vents and the like as natural campfires (and later, natural forges from where there are magma extrusions?). Although if we're already talking about alternate biochemistries then we can look for something else that's equivalent in the alternate environment.

Well, in addition to fire providing heat -- which is a big win for us, especially cooking -- it provides a convenient way of driving a bunch of metal-reducing reactions (eg, MOx + C → M + CO).

[Breadknife]

You mean [poly-]"silanes",

Yup, knew I'd messed that up.

Don't they say that (on Earth) it has been independently developed at least seven times, in different evolutionary branches?

Dunno. There's only three designs that I know of, however: simple, lensed eyes like ours; compound, lensed eyes like insects have, and pinhole eyes, which as far as I know are restricted to Nautiloids.

I meant "however many designs, independentantly arrived at (one design or another) <foo> times." (I've seen figures as high as 12 mentioned for the 'arrivals at' figure, and sometimes eight or more 'eye types' to which they have arrived, though this latter figure definitely includes closely-related developmental variants rather than full paradigm shifts.)

It is said that octopus eyes are very similar to ours (except better!?), but seem to have arisen (or at least done most of their development away from the original "light sensitive patch" on whatever Latest Common Ancester we have) independently from our own. Perhaps with so few destinations being reached by so many more 'wandering drunkards' this means we have most (or all?) of the possible solutions randomly arrived at. At least for visual-spectra (and near-visual, relative to our own particular baseline).

And if we're still welded to the idea of "metalliform" creatures,

Dry sense of humor y'got there...

I don't just throw these posts together, you know! (Well, I do, somewhat, hence the perpetual sprawl, but I'm glad you picked up on one of the few bits that was more carefully crafted upon my traditionally-styled (but actually 'modern replica') wordsmith's anvil. )

[Liberated Counties]

They estimate there are 100,000 million planets in the galaxy and I believe at least a couple of hundred maintain life.

[Jessjohnesik]

I do think this is out of question as Drake's equation proved extra terrestrial life.

[Abatael]

I conjecture that there are quite a lot of extraterrestrials such as this:

(Image)

But comparably few extraterrestrials such as this:

(Image)

I believe there might be extraterrestrials of the first part and none of the second part.

[Abatael]

I do think this is out of question as Drake's equation proved extra terrestrial life.

How?

Edit: I looked into this. This equation is based completely and entirely on conjectures, which makes this equation meaningless. It can range from trillions of civilizations to none. And all current estimations--or, rather, guesses because, to be frank, that's what they are--become more inaccurate as time goes on.

Now, I am not picking a fight with the equation itself, but to say that it somehow proved extraterrestrial life is simply wrong because every value in that equation is nothing more than guesswork. It can mean anything once it is all multiplied out, which ultimately means nothing.

[Cameroi]

i believe in i sort of are one, who had to have myself born here to avoid the non-cultural interference regs.
yup there's a whole universe of worlds on which people evolved to look funny to people on every other world.
(and generally can't breathe the air of each other's world either, so forget about solving population problems by exporting them to other worlds, even if it were practical to migrate an entire world's population out of its gravity well)
but yeah, universities on various worlds do send grad student exporation teams to pre emergence worlds like earth. and then there's a few stray rogue worlds out there to. but they're still a tiny minority. (and please have the good sense not to become or be exploited by one of them)

[Breadknife]

I do think this is out of question as Drake's equation proved extra terrestrial life.

How?

I believe Jessjohnesik means that by plugging realistic figures into the equation it shows that there's more than us out there (by a considerable amount). I believe your objection is that this does not 'prove' anything, and probably also that we don't even know what 'realistic' figures are for several of the terms, and possibly even so far as to say that the error-bars on such figures that we're estimating could conceivably come up with less than one civilisation (i.e. not even ourselves, by dint of mere objective probability, ignoring or the moment that we are here to ask the original question) exists in the entire galaxy.

To which I would suggest that Drake is overly-pessimistic (too anthropocentric and terracentric and concentrating on detectable civilisations, or ones that we would meet), also that adding all the assumed bell-curves together you still get a maximum point far above 1 (even if it does encroach upon zero at the lower end), also that the question in the OP is potentially so open that it means any extraterrestrials, in any galaxy and not necesarily right now in history and actually visiting our little abode whilst we inhabit it, so some of the fractional Drake Equation terms are in reality much less so than traditionally used, or even unnecessary altogether when answering such a looser question.


OTOH, if the question is specifically about (near-as-damnit present day) Visitors, then it skews in the other direction. So each side of the argument needs to better define their terms, and not suggest (or require) 'proof' as forthcoming until the actual moment we get an actual tête-á-braincase moment between us and Them.


Have I summarised that all to everyone's satisfaction?

[Grenartia]

I do think this is out of question as Drake's equation proved extra terrestrial life.

How?

Edit: I looked into this. This equation is based completely and entirely on conjectures, which makes this equation meaningless. It can range from trillions of civilizations to none. And all current estimations--or, rather, guesses because, to be frank, that's what they are--become more inaccurate as time goes on.

Now, I am not picking a fight with the equation itself, but to say that it somehow proved extraterrestrial life is simply wrong because every value in that equation is nothing more than guesswork. It can mean anything once it is all multiplied out, which ultimately means nothing.

Actually, its not completely and entirely based on conjecture. We already know a fair bit of the numbers called for in the equation. Perhaps at the time it was created, it was entirely based on conjecture, but that is no longer the case.

[Cameroi]

we're also getting to where we can discover planets circling other suns that have the proper conditions and ingredients for what we think we know of life. although we're still limited to finding somewhat over large ones.

earth has a big sign hanging over it, that can only be seen from other solar systems, that says "danger, keep out, infested area". not in a literal physical sense of course, but in a form recognizable as a signal to that effect, by the advanced worlds in the rest of our galaxy.

so they come deeply stealthed, when they come at all. sometimes the stealthing fails. and then there are relationships with some of the more powerful earth nations. though i personally suspect it is the minority of rogue worlds that have done the latter, and not for the best of reasons.

[Abatael]

How?

I believe Jessjohnesik means that by plugging realistic figures into the equation it shows that there's more than us out there (by a considerable amount). I believe your objection is that this does not 'prove' anything, and probably also that we don't even know what 'realistic' figures are for several of the terms, and possibly even so far as to say that the error-bars on such figures that we're estimating could conceivably come up with less than one civilisation (i.e. not even ourselves, by dint of mere objective probability, ignoring or the moment that we are here to ask the original question) exists in the entire galaxy.

To which I would suggest that Drake is overly-pessimistic (too anthropocentric and terracentric and concentrating on detectable civilisations, or ones that we would meet), also that adding all the assumed bell-curves together you still get a maximum point far above 1 (even if it does encroach upon zero at the lower end), also that the question in the OP is potentially so open that it means any extraterrestrials, in any galaxy and not necesarily right now in history and actually visiting our little abode whilst we inhabit it, so some of the fractional Drake Equation terms are in reality much less so than traditionally used, or even unnecessary altogether when answering such a looser question.


OTOH, if the question is specifically about (near-as-damnit present day) Visitors, then it skews in the other direction. So each side of the argument needs to better define their terms, and not suggest (or require) 'proof' as forthcoming until the actual moment we get an actual tête-á-braincase moment between us and Them.


Have I summarised that all to everyone's satisfaction?

That would still prove nothing.

[Abatael]

How?

Edit: I looked into this. This equation is based completely and entirely on conjectures, which makes this equation meaningless. It can range from trillions of civilizations to none. And all current estimations--or, rather, guesses because, to be frank, that's what they are--become more inaccurate as time goes on.

Now, I am not picking a fight with the equation itself, but to say that it somehow proved extraterrestrial life is simply wrong because every value in that equation is nothing more than guesswork. It can mean anything once it is all multiplied out, which ultimately means nothing.

Actually, its not completely and entirely based on conjecture. We already know a fair bit of the numbers called for in the equation. Perhaps at the time it was created, it was entirely based on conjecture, but that is no longer the case.

What then do we know?

[Tayrona]

Nope. I'm one of those "need proof" guys. Lights moving in the sky is not proof of extraterrestrials I'm afraid.

Extraordinary claims need extraordinary proof.

[Jessjohnesik]

Nope. I'm one of those "need proof" guys. Lights moving in the sky is not proof of extraterrestrials I'm afraid.

Extraordinary claims need extraordinary proof.

Except we are not taking about the lunatic fantasies of little green men.

How?

I believe Jessjohnesik means that by plugging realistic figures into the equation it shows that there's more than us out there (by a considerable amount). I believe your objection is that this does not 'prove' anything, and probably also that we don't even know what 'realistic' figures are for several of the terms, and possibly even so far as to say that the error-bars on such figures that we're estimating could conceivably come up with less than one civilisation (i.e. not even ourselves, by dint of mere objective probability, ignoring or the moment that we are here to ask the original question) exists in the entire galaxy.

To which I would suggest that Drake is overly-pessimistic (too anthropocentric and terracentric and concentrating on detectable civilisations, or ones that we would meet), also that adding all the assumed bell-curves together you still get a maximum point far above 1 (even if it does encroach upon zero at the lower end), also that the question in the OP is potentially so open that it means any extraterrestrials, in any galaxy and not necesarily right now in history and actually visiting our little abode whilst we inhabit it, so some of the fractional Drake Equation terms are in reality much less so than traditionally used, or even unnecessary altogether when answering such a looser question.


OTOH, if the question is specifically about (near-as-damnit present day) Visitors, then it skews in the other direction. So each side of the argument needs to better define their terms, and not suggest (or require) 'proof' as forthcoming until the actual moment we get an actual tête-á-braincase moment between us and Them.


Have I summarised that all to everyone's satisfaction?

Yes, that's what I meant. I should've phrased correctly.

[Jessjohnesik]

Actually, its not completely and entirely based on conjecture. We already know a fair bit of the numbers called for in the equation. Perhaps at the time it was created, it was entirely based on conjecture, but that is no longer the case.

What then do we know?

That life exists beyond Earth.

[Abatael]

Nope. I'm one of those "need proof" guys. Lights moving in the sky is not proof of extraterrestrials I'm afraid.

Extraordinary claims need extraordinary proof.

Except we are not taking about the lunatic fantasies of little green men.

I believe Jessjohnesik means that by plugging realistic figures into the equation it shows that there's more than us out there (by a considerable amount). I believe your objection is that this does not 'prove' anything, and probably also that we don't even know what 'realistic' figures are for several of the terms, and possibly even so far as to say that the error-bars on such figures that we're estimating could conceivably come up with less than one civilisation (i.e. not even ourselves, by dint of mere objective probability, ignoring or the moment that we are here to ask the original question) exists in the entire galaxy.

To which I would suggest that Drake is overly-pessimistic (too anthropocentric and terracentric and concentrating on detectable civilisations, or ones that we would meet), also that adding all the assumed bell-curves together you still get a maximum point far above 1 (even if it does encroach upon zero at the lower end), also that the question in the OP is potentially so open that it means any extraterrestrials, in any galaxy and not necesarily right now in history and actually visiting our little abode whilst we inhabit it, so some of the fractional Drake Equation terms are in reality much less so than traditionally used, or even unnecessary altogether when answering such a looser question.


OTOH, if the question is specifically about (near-as-damnit present day) Visitors, then it skews in the other direction. So each side of the argument needs to better define their terms, and not suggest (or require) 'proof' as forthcoming until the actual moment we get an actual tête-á-braincase moment between us and Them.


Have I summarised that all to everyone's satisfaction?

Yes, that's what I meant. I should've phrased correctly.

This still proves nothing.

[United Furry Alliance]

Of course extraterrestrials exist and that is my opinion.

[Abatael]

What then do we know?

That life exists beyond Earth.

How? Nothing you have ever said in your entire life has proven this.

[Lemonius]

Most certainly.

Ranging from microbes/bacterial lifeforms to highly sophisticated creatures such as ourselves, with technology equal or even greater than ours.

[Sahrani DR]

Extraterrestrial life does exist somewhere, but UFOs are definitely not extraterrestrial vehicles.

[Grenartia]

we're also getting to where we can discover planets circling other suns that have the proper conditions and ingredients for what we think we know of life. although we're still limited to finding somewhat over large ones.

1. earth has a big sign hanging over it, that can only be seen from other solar systems, that says "danger, keep out, infested area". not in a literal physical sense of course, but in a form recognizable as a signal to that effect, by the advanced worlds in the rest of our galaxy.

2. so they come deeply stealthed, when they come at all. sometimes the stealthing fails. and then there are relationships with some of the more powerful earth nations. though i personally suspect it is the minority of rogue worlds that have done the latter, and not for the best of reasons.

1. Nah. Studies suggest that our radio signals become indistinguishable from background before even Alpha Centauri.

2. Got any proof? Because we can knock some holes in the notion of stealth in space. Its not just an "it sometimes fails" thing. Its an "it never works" thing. Its like trying to sneak a fully-trimmed, lighted Christmas tree into the basement of the White House, with no help from the inside.

[Grenartia]

Actually, its not completely and entirely based on conjecture. We already know a fair bit of the numbers called for in the equation. Perhaps at the time it was created, it was entirely based on conjecture, but that is no longer the case.

What then do we know?

We know the average rate of star formation in our galaxy.
We have some reasonable figures for the fraction of stars with planets.
Everything else is, admittedly, conjecture.