Do you believe in extraterrestrials?

[Icirus]

It is impossible for Aliens NOT to exist. The wise-people(through centuries) has said that the universe is ever-expanding...which means, that in theory: Planet Earth2 is out there.

[Anachronous Rex]

It is unpossible for Aliens NOT to exist. The wise-people(through centuries) has said that the universe is ever-expanding...which means, that in theory: Planet Earth2 is out there.

Right...

That's not what they mean when they say the universe is expanding. It is stretching outwards, similar to a balloon. Increasing it's size doesn't increase the amount of material the balloon is made of.

[Ucropi]

It is unpossible for Aliens NOT to exist. The wise-people(through centuries) has said that the universe is ever-expanding...which means, that in theory: Planet Earth2 is out there.

Right...

That's not what they mean when they say the universe is expanding. It is stretching outwards, similar to a balloon. Increasing it's size doesn't increase the amount of material the balloon is made of.

It does however increase the volume

[Anachronous Rex]

Right...

That's not what they mean when they say the universe is expanding. It is stretching outwards, similar to a balloon. Increasing it's size doesn't increase the amount of material the balloon is made of.

It does however increase the volume

Yeah... that's what I said.

[Breadknife]

It does however increase the volume

Yeah... that's what I said.

...and. if anything, that could spread out all potential star- and planet-forming materials beyond the range of enough like matter to get new stars and planets out of the remains of old stellar explosions.

(To an extreme, look for information on "The Big Rip", I think it's been referred to, which is where the accelerating expansion of the universe sends every molecule (then every atom of every molecule (then every particle within every atom)) beyond the "Observable Universe" of every other... But that's if certain cosmological conditions are met, and won't be for a loooooong time.)

Right now, though, Ucropi, the point is that there's not really any "new material" out there, and doesn't therefore create so much in the way of further copies of the Earth just because there's an increasing chance that everything comes together exactly the same, again. Although as every star dies and throws out spent material it gives potentially a cloud of 'newer' material (more doped with heavier atoms, at the expense of the volume of lighter ones, although still enough hydrogen to get new stars started for the 'immediate' future, i.e. a good few recyclings yet) and it's a bit of a simplification to suggest that this keeps everything constant (expansion of the universe aside, but don't forget that locally things like star clusters, galaxies and galaxy clusters tend to keep their constituent parts together regardless of how far apart the 'next level out' gets dragged), but once enough very early stars had 'salted' the new nebulae with more advanced elements then something similar to our own situation (rocky planets, icy mons, gas-giants) should arise fairly regularly and keep on doing so until a loooong time in the future where the doping gets 'top heavy' and there's critically less amounts of hydrogen in order to form the stars, etc..

(Which is not to say that there might not be life-forms that work with 'light element loads' and 'heavy element loads', as compared to our own which likes this 'mid-life' position in stellar evolution, but we re-enter all those speculative realms that I've raised previously of "Life, but not as we know it!", Captain. Of course, as different areas of a galaxy might have fewer or more levels of stellar recycling behind its current generation of stars, there'll have been "like now" areas earlier than our bit was like it is, and there'll be other "like now" areas far in our own future when what's left in our area is mostly luke-warm remnants of what once was, all these ripe for "like us" lifeforms¹. Or, conversly, we might be able to see 'now' (or at least at whatever time it was the light left them) proof of civilisations of 'light life' or 'heavy life' from such younger or older regions of space.)



¹ No, not humanoid except perhaps with rubber foreheads. But something probably carbon-chain-based, maybe, making use of the same sort of chemistry as DNA and RNA does (but probably not exactly the same). I doubt that we'd find our proteins compatible, etc, never mind that any given triple-set of exactly the same (ACGT/U) bases means the same thing to our inner molecular-machines.

[Creativalsia]

I believe it is mostly celled organisms.

[Uieurnthlaal]

I do not "believe" or "not believe" in extraterrestrials. I suspect that there is life in some planets, and I have no idea whether or not there is intelligent life, but until we find actual scientific evidence, I will not "believe" in extraterrestrials.

[The Orson Empire]

It is impossible for Aliens NOT to exist. The wise-people(through centuries) has said that the universe is ever-expanding...which means, that in theory: Planet Earth2 is out there.

No. The universe isn't that big to where you would start seeing copies of planets. The observable universe is 14 billion light years long. In order for copies to start happening, it would have to be 1 googol light years long.

[New Krikkit]

I believe that there must be some sort of extraterrestrial life out there, considering the sheer size of the universe. However, life is such an improbable phenomenon that chances are these planets are most likely scattered much to far apart for any extraterrestrials to meet us. I agree that these life forms are probably bacteria mostly, but even if any are sentient there is little to no chance that they will (a) develop the necessary space technology to reach us and (b) happen to stumble across our little planet in the vast emptiness that is space. I don't see any kind of alien contact (be they like ET or Mars Attacks!) in humanity's future.

[Breadknife]

Why do people insist on overly-fussy anthropocentrism when it comes to envisaging the basic nature of aliens, yet utterly ignore that the resulting (xeno-)anthropecentric search criteria used by such aliens would probably give these aliens a short-list of planets to look at that most definitely contains our own particular ball of rock?

One way or another, please...

[Grave_n_idle]

Right...

That's not what they mean when they say the universe is expanding. It is stretching outwards, similar to a balloon. Increasing it's size doesn't increase the amount of material the balloon is made of.

It does however increase the volume

Which is equally an argument AGAINST an 'earth 2', because it means planets that might once have been in the 'habitable zone'... will have moved out of it.

[Wind in the Willows]

Yes, but I believe that extraterrestrial life would all be primitive.

[Zilam]

Intelligent life? Not likely.
Basic life, such as single cell organisms? I'd put money on finding some out there somewhere.

[Shnercropolis]

I believe that there is extraterrestrial life. I don't think we will ever be able to contact any of it, since it'll all either be bacterial or too far away.

[Mkuki]

I do believe in extraterrestrial life. Why? Because I find it arrogant to believe that Earth is the only planet in such a vast and diverse universe that can support life.

[Terran Faction]

I believe that there must be some sort of extraterrestrial life out there, considering the sheer size of the universe. However, life is such an improbable phenomenon that chances are these planets are most likely scattered much to far apart for any extraterrestrials to meet us. I agree that these life forms are probably bacteria mostly, but even if any are sentient there is little to no chance that they will (a) develop the necessary space technology to reach us and (b) happen to stumble across our little planet in the vast emptiness that is space. I don't see any kind of alien contact (be they like ET or Mars Attacks!) in humanity's future.

ET and Mars Attacks! is a horrible example. Especially Mars Attack! I cannot stand the depiction of extraterrestrials in that film. Most films suck with their depiction of possible extraterrestrials.


I do agree that life around a single galaxy where it won't be impossible, but hard for foreign lifeforms including us to meet each other.

[Grave_n_idle]

I do believe in extraterrestrial life. Why? Because I find it arrogant to believe that Earth is the only planet in such a vast and diverse universe that can support life.

Is it 'arrogant' to believe that Mauritius was the only location populated by Dodos?

Arrogance is irrelevant. Whether we are alone or not, it won't be determined by how egotistical we are.

[Breadknife]

I do believe in extraterrestrial life. Why? Because I find it arrogant to believe that Earth is the only planet in such a vast and diverse universe that can support life.

Is it 'arrogant' to believe that Mauritius was the only location populated by Dodos?

Arrogance is irrelevant. Whether we are alone or not, it won't be determined by how egotistical we are.

That's the difference between observed actuality and blind assumptions, though.

There are any number of individual species found (in nature) only in one geographic location, and often there are good reasons (being flightless birds, etc). There are also ones that (perhaps with slight difference) are found all over the planet (e.g. bears). And then there are those that are spread all around the planet, for one reason or another (cats, rats, dogs, and of course humans). And life is all over the planet.

Of course this is probably quite different from space. Life having arisen once (at least once, but one that 'arose' having dominated via its various descending branches such that all extant life appears to come from a single source) and spread and diversified it has found niches (and entire swathes of niches) and inhabitted them on Earth, from the depths of the ocean to the mountaiside, from the lush plains to rock fissues, from desert sands to glacial ice. But, barring panspermia or even deliberate seeding of life by an ancient space-faring civilisation (neither of which are impossible), for the distribution of life around space we're looking at whether individual pools of life can have arisen in each and every little isolated rockpool. All we know is that our rockpool (the Earth) managed it, but that might be selection bias. Still, I'm among the people who expect that given that there is a possibility of various self-organising and self-replicating molecules arising in the huge parallel chemistry experiment that would be a virgin planet (or something even more exotic, from our anthropocentric and terracentric point-of-view) it's almost certainly a given that life will independently develop.

(Of course if our rockpool didn't manage it, but was subject to panspermia, etc, this hints that other pools that were similarly unsuccesful in their own right might still have life abundant.)

Then the argument is whether that ever becomes intelligent civilisation, etc. Which again I bend towards the "probably" POV, for, on the assumption that a subset, at least, of simple life will find benefits from becoming more successful life, at each point up the hypothetical ladder, and intelligence and civilisation is... if not the pinnacle of development, one of the many pinnacles available. (Look at life on our planet. We apparently dominate it. But the same can be said about rodents and beetles and bacteria and even viruses, if you want to count them, in their own way... and I don't imagine it would be a dissimilar 'himalayan' profile upon a different planet with a localised form of biology. I anticipate intelligence and plagues will co-exist, at least until intelligence gets good enough to wipe out the plague or the plague finds itself having gotten rid of the intelligence.)

Then the argument is for longevity of such civilisations, and onwards as to whether they've ever visited us (or will ever do so, or 'contact us by phone'/etc) which is where I start going dubious (though still optimistic). But their current non-presence, or more specifically absence (various unconfirmed stories aside) either from the skies above our collective fleet of hick pick-up trucks or the airwaves is not, as far as I'm concerned, anything to do with the basic question of whether they do exist, or have done, so I feel my general opinion untempered by such notes. (Ask me about flying saucers, and I'd probably say "no". But ask me about UFOs and I would of course say "yes", for purely semantic reasons that you doubtless already understand.)

[Man this is awesome]

I believe there might as well be intelligent life out there, considering the large number of unexplored galaxies and the infinite range of possibilities for a primitive unicellular organism to later on develop to become a new species. It is all a matter of possibility. Our existence on Earth, regardless of what subjective views we may hold as people, was nothing more than a possibility and was the only one to have worked out of many others, and as such there must be intelligent life out there.

But if these intelligent extraterrestrials do visit us, I doubt ordinary people like us would ever hear about it, most of these 'visits' would be kept under wraps by the government (And we've seen how trustworthy the government is in the last couple of decades) but then again that's just my opinion.

[Grave_n_idle]

Is it 'arrogant' to believe that Mauritius was the only location populated by Dodos?

Arrogance is irrelevant. Whether we are alone or not, it won't be determined by how egotistical we are.

That's the difference between observed actuality and blind assumptions, though.

There are any number of individual species found (in nature) only in one geographic location, and often there are good reasons (being flightless birds, etc). There are also ones that (perhaps with slight difference) are found all over the planet (e.g. bears). And then there are those that are spread all around the planet, for one reason or another (cats, rats, dogs, and of course humans). And life is all over the planet.

Of course this is probably quite different from space. Life having arisen once (at least once, but one that 'arose' having dominated via its various descending branches such that all extant life appears to come from a single source) and spread and diversified it has found niches (and entire swathes of niches) and inhabitted them on Earth, from the depths of the ocean to the mountaiside, from the lush plains to rock fissues, from desert sands to glacial ice. But, barring panspermia or even deliberate seeding of life by an ancient space-faring civilisation (neither of which are impossible), for the distribution of life around space we're looking at whether individual pools of life can have arisen in each and every little isolated rockpool. All we know is that our rockpool (the Earth) managed it, but that might be selection bias. Still, I'm among the people who expect that given that there is a possibility of various self-organising and self-replicating molecules arising in the huge parallel chemistry experiment that would be a virgin planet (or something even more exotic, from our anthropocentric and terracentric point-of-view) it's almost certainly a given that life will independently develop.

(Of course if our rockpool didn't manage it, but was subject to panspermia, etc, this hints that other pools that were similarly unsuccesful in their own right might still have life abundant.)

Then the argument is whether that ever becomes intelligent civilisation, etc. Which again I bend towards the "probably" POV, for, on the assumption that a subset, at least, of simple life will find benefits from becoming more successful life, at each point up the hypothetical ladder, and intelligence and civilisation is... if not the pinnacle of development, one of the many pinnacles available. (Look at life on our planet. We apparently dominate it. But the same can be said about rodents and beetles and bacteria and even viruses, if you want to count them, in their own way... and I don't imagine it would be a dissimilar 'himalayan' profile upon a different planet with a localised form of biology. I anticipate intelligence and plagues will co-exist, at least until intelligence gets good enough to wipe out the plague or the plague finds itself having gotten rid of the intelligence.)

Then the argument is for longevity of such civilisations, and onwards as to whether they've ever visited us (or will ever do so, or 'contact us by phone'/etc) which is where I start going dubious (though still optimistic). But their current non-presence, or more specifically absence (various unconfirmed stories aside) either from the skies above our collective fleet of hick pick-up trucks or the airwaves is not, as far as I'm concerned, anything to do with the basic question of whether they do exist, or have done, so I feel my general opinion untempered by such notes. (Ask me about flying saucers, and I'd probably say "no". But ask me about UFOs and I would of course say "yes", for purely semantic reasons that you doubtless already understand.)

The point I was making is - it's not 'arrogant' to think we might be the only planet in the neighbourhood, galaxy, universe, etc that might have had JUST the right conditions for life.

Suggesting we COULD be the only planet with life isn't arrogant - it's observation, based on the small sample we've examined in a little detail, so far.

[Breadknife]

I believe there might as well be intelligent life out there, considering the large number of unexplored galaxies

...just to say that while I don't disagree with you, and this does indeed support both your and my opinions on the subject, it's not so much the large number of unexplored galaxies as the large number of unexplored stars within our own galaxy.

All but one of them are unexplored (i.e. unvisited, if we decide to term our native residency of this planet a "visit", and also conflating "being on a planet" with "understanding an entire planetary system") and while we can make broad-sweep generalistions about those that we have studied from afar (e.g. assuming that non-singleton stars cannot have stable planetary systems, although that's not actually as absolute as once was imagined) to rule out stars that are too young and active or old and bloated or too close to other systems, it's still a lot less than are actually out there.

There's (conservatively) 100 billion stars, in the Milky Way (maybe up to four times that, but let's keep the estimate low) of which maybe a fraction are known well enough to rule out planets in the vicinity, but a number (latest figure: ~713 systems, but growing all the time as we're looking further) can already be shown to be conducive to planets. albeit that includes Hot Jupiters, but ~925 bodies in total gives plenty of scope (it's out of date, but see http://xkcd.com/1071/ for a comparative view of what had actually been discovered a short while ago) to hint at locations where life may have arisen/be arising/will arise given the chance. And even if not on the discovered planets, for whatever reason, on the undiscovered ones hidden in the noise of those systems.


I suppose one really needs to compare graphs such as "discovered exoplanetary systems, per distance from Earth" and "star systems, per distance from Earth" to get an idea of local frequency and the tendency for such discoveries to tall off by distance, thus building a half-way decent figure of the glaxy-wide circumstances (accounting for fluctuations in star density and average ages within and without spiral arms, ideally). I don't have that at hand but, still, let's say there's one one thousandth of a percent of the stars in our galaxy with (suitable, e.g. with liquid water) planets, which I think is vastly pessimistic given a prior estimated of 15 billion or so having planets of some kind or another. But that's still a million stars represented!

Now assume the suitable planets are Earth-like, so that's half a billion square kilometres each of surface. 7/10ths covered with water? No let's make it a half, on average... So perhaps 250 million square kilometres of ocean floor(/surface?) or shoreline per planet, where pre-organic chemistry can happen in a random manner.

A quarter of a sextillion metre-square plots (for want of any other arbitrary subdivision) where something might happen with the local mix of chemicals, in the presence of whatever energy is available, etc... So surely it has. Numerous times. (Ok, so plot-ID XK34-2707-9295 on planet 954,321 creates life but gets squished by an alternate form of life that arose in plot-ID XK34-2708-9294 on the same rock, and plot-ID DF391-2845-8265 on planet 340,949 created life but was then at the centre of the impact from a stray bit of asteroid that still hadn't been mopped up by the local Jupiter, but I stand by my assertion of "numerous times", even after some rather pessimistic culling and merging of the chances...) And by "numerous", I'm talking loads... Albeit vaguely so. But I'd be surprised to see our select few 'suitable planets' (that's the one million from the pessimistic and rather restrictive estimate, mind you) not be more than 50% life-bearing.

Half a million planets with life. We could now say we assume that 10% get complex life and 10% of those get sentient life and 10% of those get social life and 10% of those get technological life (which would give us 500 worlds perhaps one step away from space travel), but I wouldn't care to justify those figures. And, besides, I'm still using pessimistic ones, and if I'd been using 90% instead (still below my expectation, which is somewhere in the 99.something% range for the earlier proportions, at least) we'd be talking more than 30,000. From still arguably pessimistic figures!


Factor in life expectencies of civilisations, and communication (or commuting!) times necessary for contact, if you will, but that's the whole "They are among us" (or at least have shouted in our direction) situation, rather than the "They are, or at least have been, out there..." one.


(Ah well... if I can't explore the galaxy physically, at least I can do so philosophically, statistically and hypothetically. It's a fascinating place, the one in my head, and maybe one day I'll find out how the reality actually compares. I suspect it'd be far more interesting, if that comes to pass.)


Oh, and...

The point I was making is - it's not 'arrogant' to think we might be the only planet in the neighbourhood, galaxy, universe, etc that might have had JUST the right conditions for life.

Suggesting we COULD be the only planet with life isn't arrogant - it's observation, based on the small sample we've examined in a little detail, so far.

In response to Mkuki's "I find it arrogant to believe that...", the issue is belief, and thus an arrogance in being special. (Which, as indicated, I cannot imagine to be true, perhaps with a form of arrogance in the opposite direction.) The "observation of one sample" just doesn't permit any proper analysis.

OTOH, choosing the example of the Dodo from amongst all the creatures that weren't constrained merely to Mauritius was self-selecting of a special case. To illustrate a point, maybe, but I just didn't see it as a valid illustration.

I think we're generally in agreement in these things we're discussing here, I just found the way you put it not to my liking, I'm afraid. Which is arrogent of me, doubtless..

[Dumb Ideologies]

There is no positive evidence but the existence of extraterrestials is feasible given the vastness of space and the fact that life has demonstrably arisen on at least one planet.

Just as an FYI, this is rather different to the case of believing in an all-benovelent invisble man who will sentence you to endless pain if you don't believe in him and follow a set of 10 rules.

[Gallup]

We have no idea. The universe is so vast.

[Ifreann]

We have no idea. The universe is so vast.

Who's we? Got a mouse in your pocket?

[Bottle]

Based on my background in biology, I think 1) It's almost certain that life exists on other planets, and 2) It is vanishingly unlikely that said life will resemble anything familiar to us.