Ancient Astronauts.

[tnjrp]

Assuming the alien visitors indeed were similar enough to us to wear "Gemini spacesuits" (a known point of debate in astrobiology - would an intelligent alien necessarily be a "Star Trek humanoid" or not) they might even have found hairy primates brandishing big sticks at them specifically interesting. Never mind a Cro Magnon or an ancient Egyptian. Given a reasonable tech level and enough time to study Earth they most likely would've found our ancestors out too.

But, as I said earlier, there is still no evidence available that they were. Here, or interested.

[iquestor]

Assuming the alien visitors indeed were similar enough to us to wear "Gemini spacesuits" (a known point of debate in astrobiology - would an intelligent alien necessarily be a "Star Trek humanoid" or not) they might even have found hairy primates brandishing big sticks at them specifically interesting. Never mind a Cro Magnon or an ancient Egyptian. Given a reasonable tech level and enough time to study Earth they most likely would've found our ancestors out too.

But, as I said earlier, there is still no evidence available that they were. Here, or interested.

why wouldnt us "smart Apes" wouldn't be interesting to an advanced race ?

Honestly, if Curiosity (The next Mars Mission ) finds compelling evidence of ancient or current microbial life, I beleive we would be all over getting there to study it. And then if we found some evidence of life in Titan's ocean, or Europa, we would find a way to get there too.

Any aliens who could get here would have most likely encountered other life, but that doenst mean they arent interested in finding and studying more.

If Aliens did develop interstellar travel, there has to be a reason. For humans its our curiosity and quest for resources that drives us. It has kept us alive and prospering, and I'd assume Alien evolution did impart some driving motive to eventually travel in space.

Therefore they would very likely be interested in coming here, maybe for familiar reasons, maybe not.

[Paul Wally]

If aliens have been here they must have kept a record of their findings somewhere. Perhaps in some ancient library there is a record of this planet Earth, of course it will go by a different name. But if there is some library with information about the Earth then any civilization having access to that information will know about us, but why aren't they here then? I mean, if aliens have been here before, word should have gotten around of our existence, and spread all over the galaxy. It really seems then that knowledge of our existence didn't spread around the galaxy.

[IsaacKuo]

If aliens have been here they must have kept a record of their findings somewhere. Perhaps in some ancient library there is a record of this planet Earth, of course it will go by a different name. But if there is some library with information about the Earth then any civilization having access to that information will know about us, but why aren't they here then? I mean, if aliens have been here before, word should have gotten around of our existence, and spread all over the galaxy. It really seems then that knowledge of our existence didn't spread around the galaxy.

If this library gives them all of the information about us that they're really interested in, why should they be here? Maybe they send probes every once in a while to update their information, or maybe not.

I just don't see how "they know we exist" translates to "they must come here and stay here and be obviously visible to us".

[ravens_cry]

Indeed. So far our ability to detect other worlds far outpaces our ability to visit them, a trend that begun when we first noticed that some stars didn't move like other stars and has continued to the detection and direct imaging of extrasolar planets. Assuming this trend continues, we are potentially more likely to detect life on planets around other stars from a distance long before we can even send robotic probes to see them, let alone in person.

[Luckmeister]

Why do some think it's a given that spacefaring beings must be aware of us?

First, FTL travel is impossible for objects with mass.
The current mainstream physics view assumes that, so I will too.

Second, I assume that no beings from another galaxy have ever traveled to ours.
Traveling near the speed of light, it would take them well over two million years to get here from our closest neighbor, Andromeda -- very unlikely to have happened.

Third, I'm assuming there are billions of planets within our galaxy.
If there were spacefaring beings within our galaxy, it is by no means a given that they would even be aware of Earth let alone have an interest in coming here. Unless they were very close, right now, they would not nor would ever have detected signs of technology here and the odds are very high against there being a spacefaring ET that close just by chance.

For these reasons, I feel further (more advanced) SETI studies are our best hope of finding we are not alone in the universe.

[wolver99]

Now, my big problem with the Erich Von Daniken-type theory of "ancient astronauts", apart from the gaping flaws, misdirection and downright falsehoods often present in those arguments, is that it gives ancient peoples absolutely no credit at all. Humans are ingenious, and quite capable of building impressive structures with stone-age technology. Humans are incredibly imaginative. Our imaginations fill the world and beyond with mythical beings with supernatural powers, which we then go paint on cave walls. They do not have to be depictions of spacemen in fish-bowl helmets.

The Skeptics Guide to Erich von Daniken


Charioteer of the Gods

[Gomar]

if aliens have been here before, word should have gotten around of our existence, and spread all over the galaxy. It really seems then that knowledge of our existence didn't spread around the galaxy.

Good point. I've met many tourists from lands where there is no snow; Africa, Australia, South America, etc. These people come
to the U.S. in the Winter(LOL) to check out something they've never seen before. Now, say, word spreads that you can ski, and
make snowmen then others will come. Certainly, if I've seen snow before, I would run off to Australia in February instead.

Possible that aliens have seen it all before and have no interest in flying across the galaxy to investigate a bunch of primates
attempting to resolve their economic troubles. I am sure trees, fish, ants, birds, roaches, spiders, primates are all pretty much
the same across the galaxy.
Unless, ifcourse there are no intelligent species anywhere but on Earth.

[tnjrp]

why wouldnt us "smart Apes" wouldn't be interesting to an advanced race ?

If these completely speculative aliens were wildly different from us (perhaps to a point where they wouldn't be interested in coming down to Earth for an extended period) they might not have taken note of a few peculiarly behaving apes. Assuming they'd been here in the very early stages of our evolutionary divergence from the other chimpanzees that is. Of course one could speculate on sapience so different from our own - and indeed very many have - that it wouldn't take any note of us even now but that does seem a fairly unlikely prospect.

[Paul Wally]

If this library gives them all of the information about us that they're really interested in, why should they be here? Maybe they send probes every once in a while to update their information, or maybe not.

I just don't see how "they know we exist" translates to "they must come here and stay here and be obviously visible to us".

I suppose it depends on how common complex life is in the galaxy. If they came here and found just another planet of thousands with life on it, I suppose they would have the been there done that attitude, but suppose that complex life is relatively rare and they had to travel past several, perhaps thousands of lifeless star systems to get here, then I'm sure they should find the Earth an interesting place to study, and perhaps establish some kind of outpost. Maybe they would even contact us if they've left in the meantime.
Even if they have some ethical code of non-interference, like a "prime directive", I think the discovery of a planet like Earth would be of importance to them, that is if intelligent life is rare.

If these completely speculative aliens were wildly different from us (perhaps to a point where they wouldn't be interested in coming down to Earth for an extended period) they might not have taken note of a few peculiarly behaving apes. Assuming they'd been here in the very early stages of our evolutionary divergence from the other chimpanzees that is. Of course one could speculate on sapience so different from our own - and indeed very many have - that it wouldn't take any note of us even now but that does seem a fairly unlikely prospect.

If they took all the trouble of getting here, why wouldn't they take note of what is here, and study the planet in detail? It's seems like a awful waste of resources to come here and just leave without any clear objectives or purpose. If aliens came here and found nothing special about the Earth, it must mean that inter-stellar travel is walk in the park for them and it would also mean that intelligent life is abundant in the galaxy. But then why come here, if there are 200 Billion other star systems to explore. What are they looking for then?

[tnjrp]

You'll note I was primarily talking about the "Black Monolith period" in human history when humans were not very clearly more sapient than chimps are today. Ignoring humans becomes progressively harder to explain the less time you want there to be from the visitation.

The objection already raised a few times to both "arrogance" and "a whole lot of trouble" statements is of course that the Ancient Aliens (AAs) didn't specically come here and definitely weren't looking for us (or our ancestors, as the case may be). Sol system may have been a waypoint on the way to something more important and interesting to them. Thus, specifially because interstellar travel probably isn't "a walk in the park" and/or if AAs were very different from us they might have been "forced" to make a fairly passing note of Earth fauna and flora instead of sticking around long enough to notice that there is indeed something a bit special about the more upright-standing variety of chimpanzee.

The counterargument you used above is that Earth is truly rare to the point where it makes sense to specifically come here to study it for centuries, even millenia -- maybe even worth devoting several round trips from some "home system" to here. That certainly would give time to notice the very likely faster cultural evolution, possibly even the physical evolution of early humans. However we don't know if Earth is indeed so extraordinary, less than "Turing 1 grade" intelligence may be pretty common in the cosmos and only the truly technological civilizations may be rare.

[ravens_cry]

Sorry, but with the known laws of physics, that doesn't wash. The amount of energy it takes to accelerate a given body to a speed to make a trip doable, even by a species with a life span ten times ours, mean a stop over wastes huge amounts of energy, you're not saving anything by stopping to refuel.
And even if it were an incidental visit, the odds of that are likely literally astronomical. You have to include all the time the solar system has existed as well as the odds of how common an Interstellar civilisation is, a major, major unknown, but with a known example of none.
Coupled with a complete lack of evidence of Others visiting this solar system at any point in our history and you will have to forgive me for being a little sceptical.

[iquestor]

Just so I am clear, I do not believe we have ever been visited; I wish we had, but I just don't see the evidence.

However why couldnt the scenario be that the Aliens knew there was life here through specroscopy and other remote detection equipment, sent a few probes, then decided we were interesting enough to come and research for a while.

I keep hearing on this thread how humanity and our ancestors arent interesting enough for someone to take the time to come here specifically. One post even said words to the effect that the flora and fauna here would be pretty much the same everywhere. I think that is all unfounded and not well though out. Evolution on Earth will be unlike evolution elsewhere and each world will likely be vastly different due to this. I am sure there will be animals with legs and wings and beaks, but just look at the diverity we have today, and throughout the ages.

Of course we are interesting and deserve to the be destination for such a hypothetical trip, not just a 'forced' stop over until they can get to the real attraction.

[neilzero]

Just as we travel to the next town (perhaps repeatedly) to see what is different or interesting, ET is likely also curious, but most of us don't visit Mecca, as it dangerous, costly and difficult, somewhat like visiting Earth would be for ET. If we did visit Mecca we would try hard to blend in, much as ET would, when and if he comes to Earth for sight seeing or as a scientific expedition.
I agree there is lots of low grade evidence that ET has visited Earth. Assuming ET is smarter than humans, he likely has technology to insure the evidence remains low grade. There is a slight possibility that human society is infiltrated by ET whose mission is to make sure the evidence remains low grade or the evidence gets debunked. More likely, no ET have visited Earth. Neil

[skep155]

If this library gives them all of the information about us that they're really interested in, why should they be here? Maybe they send probes every once in a while to update their information, or maybe not.
.

Hypothetically they could also have taken zoological specimens from Earth home with them. Unlikely, but perhaps they have an Earth themed nature reserve in a large bio-dome on their own planet, complete with Giant sloths and Dodo's.

[Gomar]

I suppose it depends on how common complex life is in the galaxy. If they came here and found just another planet of thousands with life on it, I suppose they would have the been there done that attitude,

Looks like that is indeed the case. Suppose I go to Miami and see an ant colony. I would not take notice of it because ants exist
in LA, NYC, Boston, London, Tokyo, etc. As do pidgeons, dogs, cats, etc. Now for ants to travel from LA to Japan is ifcourse
not possible, thus they go about their own business without bothering to establish contact with ants in other states nor countries.

If the aliens could travel from their planet to other parts of the galaxy just as easy as I could from NYC to London, and if many
planets have life, ants, fish, birds, primates, etc. then they'll just say heck it's another one we found out here, and just move on.

Unless, ifcourse, science, medicine, technology or natural resources on other worlds are of any interest to them. Perhaps they'll need to re-fuel by mining for coal or gold or diamonds. Maybe elephants or kangaroos are a prized possession, or they
consider human flesh a tasty treat. Either way, I am glad I wont be around for an alien invasion as either we'll be eaten,
enslaved, or converted to some alien religion worshipping a god born unto a mother with 6 eyes, 56 tentacles, a tail, and a tongue the size of a VW beetle.

[Sardonicone]

the median age of all civilizations is also the median age of our nearest neighbor. There’s a fifty/fifty chance it will be either younger or older than that, but there’s a 90% chance it will at least be 10% of the median, which means that in all likelihood our nearest neighbor will be hundreds of millions of years older than us. And, if you want to find an ETC of approximately our own age, say within a thousand years of ours, you will on average have to pass by a million older to vastly older civilizations.

Am I the only one who read this completely differently than how it seems to be argued here? If a civilization is 10% of our own civilizations median, that only puts it on what, and order of a thousand years ahead of us? If you take sustained agriculture as the jumping off point for modern civilization (7000BC, give or take), we're talking about civilizations either being in the "dark ages" or being where we *might* be in the 30th or 31st century. Where is this "billion years older" assumption coming from?

[CounterWeight]

My first college courses in astronomy, physics, math, chem in the mid 70's... I had no clue I'd be taking better images from my back yard with a small telescope in the early 2000's(and it was absolutely NOT even postulated to be possible)... and really the same goes for other disciplines with other things. The proposed age of the universe has changed... does that make me proportionally older or long lived? There are many titanic questions unanswered but the greatest error is in not asking them to begin with. I think everything we say we 'know' should be replaced with "current thinking is that..."

After spending most of my working life in research and development, I'm often surprised at just how much folks seem certain of. "Don't believe everything you think"...

[eburacum45]

Am I the only one who read this completely differently than how it seems to be argued here? If a civilization is 10% of our own civilizations median, that only puts it on what, an order of a thousand years ahead of us? If you take sustained agriculture as the jumping off point for modern civilization (7000BC, give or take), we're talking about civilizations either being in the "dark ages" or being where we *might* be in the 30th or 31st century. Where is this "billion years older" assumption coming from?

The median age of civilisations in the galaxy is likely to be very different from the age of our own civilisation, unless for some reason most civilisations only last for twenty thousand years or so. An advanced civilisation could be billions of years old; there is no reason to assume that advanced civilisations would be limited to a few thousand years of duration. If the median age of an advanced civilisation is a billion years, we are more likely to meet civilisations hundreds of millions of years old.

If, on the other hand, civilisations are limited to a few thousand years, we are unlikely to encounter any, unless they emerge very frequently. In a galaxy that is thirteen billion years old, there would have to have been many millions of civilisations over its long history if we stand a chance of coexisting with a respectable number of short-lived civilisations.

[whimsyfree]

The median age of civilisations in the galaxy is likely to be very different from the age of our own civilisation, unless for some reason most civilisations only last for twenty thousand years or so. An advanced civilisation could be billions of years old; there is no reason to assume that advanced civilisations would be limited to a few thousand years of duration.

You're not using the word "civilization" in the conventional sense that would distinguish, say, Carthage, the Medes and the Mayans. The sense you're using it in is more like settled, intelligent tool making species. It's rather hard to pin down. Chimps make tools by stripping the leaves from branches and even crudely sharpening them. Are chimps a civilization? I'll follow your usage in anyway.

I tend to agree but most writers on the topic seem to presume that civilizations have a short average life and even a relatively small upper bound on their lifetime. IMHO this is mostly because in reconciling themselves with the Fermi paradox they don't want to conclude that the "birth rate" of civilizations is very small so they have to make the "death rate" very high. I don't buy this. While I can imagine that many or even most civilizations burn-out for one reason or another, I find it much harder to believe that if the galaxy has hosted millions of civilizations that every single one of them killed itself off without leaving a trace.

[iquestor]

there is no reason to assume that advanced civilisations would be limited to a few thousand years of duration. If the median age of an advanced civilisation is a billion years, we are more likely to meet civilisations hundreds of millions of years old.

I disagree with the idea of a civilization lasting millions of years -- I don't think they can. Evolutionary changes occur over that timespan and even if a population survived and maintained its identity over that timespan, I would think different civilizations would rise and fall rather than one continuous civilization existing the whole time.

To be clear, I am defining a "civilzation lasting millions of years" here as a "continuous civilization with a relatively linear progression of society, economics, technology as well as retaining the same basic identity as a biological species for the duration." I made the distinction "biological species" because if it were a machine intelligence, then I think they would be less prone to having the start over because of their ability to survive and thrive in many more diverse environments without the pesky need to breathe, eat and destroy each other.

when we talk about civilizations being millions of years old, it seems to be a basic assumption that they have has some linear progression in social, ecomonic, political, and technological sectors. Sure, they might have temporary setbacks, but assumed they didnt lose too much, and were able to recover, and thrive each time after a period. So a civilization with technology that had been steadily advancing for a million years would be daunting indeed; but if it were an intelligent species on a given planet where civilizations rose and fell, and each time there were major setbacks for each sector, than the level of progress would be much, much less after millions of years. We might be looking at a species which has had intelligence for a couple million years but only has the equivalent of 19th century technology, or maybe 25th century technology.

I think it's also self-limiting -- if a biological species were to survive and progress in technology, at some point they would naturally want to overcome their biological shortcomings, such as the need to eat, breathe, and eradicate disease, sickness and death, just like we humans would love todo. I think these desires would arise naturally from any biological intelligence since most of our definition of life is that it eats, breathes and dies. The end result of this advancement is machine intelligence, where we overcome all biological shortcomings. At this point, the species has lost its original identity as a species and is no longer the same civilization -- since much of the motives for biological societies is borne from our identity as a species and our shortcomings (food, sex, illness, death) then the resulting machine society would be vastly different, evolve more quickly, and lose touch with its roots. One of the answers to Fermis Paradox is that all intelligent civilixzations naturally migrate to machine intelligence then lose interest in contacting "meat intelligences". If this were the case then it supports my theory here.

Im not saying it can't happen, it just seems very unlikely that a single civilization could survie and progress linearly over that time span and retain its identity.

[eburacum45]

I'm pretty sure you are right. An advanced civilisation could be so altered from its biological roots that we might fail to recognise it as a civilisation. In addition, they may disregard our biological race as insignificant. But if we are only able to have meaningful contact with biological civilisations we are likely to fail to find many nearby examples, since they are likely to either change beyond all recognition or disapear in a relatively short period.

It is an interesting exercise to try to imagine a long-lived biological civilisation; ants and bees might provide a model for such an entity, since they have existed for many tens of mllions of years with little change. But such civilisations are likely to be extremely conservative.

[whimsyfree]

I'm pretty sure you are right. An advanced civilisation could be so altered from its biological roots that we might fail to recognise it as a civilisation. In addition, they may disregard our biological race as insignificant. But if we are only able to have meaningful contact with biological civilisations we are likely to fail to find many nearby examples, since they are likely to either change beyond all recognition or disapear in a relatively short period.

Well whatever they change into seems to never be interested in exploiting the galaxy. This leads me to the think they don't exist, at least not in large numbers.

[Van Rijn]

when we talk about civilizations being millions of years old, it seems to be a basic assumption that they have has some linear progression in social, ecomonic, political, and technological sectors. Sure, they might have temporary setbacks, but assumed they didnt lose too much, and were able to recover, and thrive each time after a period. So a civilization with technology that had been steadily advancing for a million years would be daunting indeed; but if it were an intelligent species on a given planet where civilizations rose and fell, and each time there were major setbacks for each sector, than the level of progress would be much, much less after millions of years. We might be looking at a species which has had intelligence for a couple million years but only has the equivalent of 19th century technology, or maybe 25th century technology.

Another common assumption is that significant scientific and technological progression can continue for very long periods, but we don't (and can't) know how many more scientific and technological advances are ultimately possible. Maybe a species with a million years with no setbacks simply could not have much more advanced technology than would be possible by the 25th century.

[iquestor]

Another common assumption is that significant scientific and technological progression can continue for very long periods, but we don't (and can't) know how many more scientific and technological advances are ultimately possible. Maybe a species with a million years with no setbacks simply could not have much more advanced technology than would be possible by the 25th century.

Yes, I'm sure there is some limit to what we can know -- who knows when we will find it? I remember seeing a quote around the turn of the century where the scientist felt we had discovered much of what could be discovered and the twentieth century would be spent cleaning up the decimal places. Then of course, we found out about Quantum Dynamics.

Whimsy said:

Well whatever they change into seems to never be interested in exploiting the galaxy. This leads me to the think they don't exist, at least not in large numbers.

I haven't given up hope -- I'd much rather the 'machine intelligence' scenario than 'Rare Earth'... what would it do to human psyche to learn we are truly (or at least effectually) alone ... however if the machine intelligence theory is correct then I'd think we should find some VN probes or something.

Even if we hit the limit of what we can know, I don't think that limits us to how we can exploit the knowledge. And I think machine intelligence is something we will reach before we hit that limit. I think maybe 300 years from now it's possible we will be able to download our consciousness to a machine, or upload it to a new body.

[whimsyfree]

Another common assumption is that significant scientific and technological progression can continue for very long periods, but we don't (and can't) know how many more scientific and technological advances are ultimately possible. Maybe a species with a million years with no setbacks simply could not have much more advanced technology than would be possible by the 25th century.

I don't think technology has a limit because technology begats technology. Invent the wheel and soon you need wheel nuts, wheel balancing machines and those little lead weights they put on the rim. Similarly if science is merely knowledge I do not believe it is possible to know everything that can be known. For example, however large your telescopes there will always be an unimaged planet somewhere. Fundamental physics may have a limit.

Whether technical progress stops in the 24th, 25th or 1000th century is irrelevant to our arguments because we have no idea what level it will have reached by those times.

Whimsy said:

I haven't given up hope -- I'd much rather the 'machine intelligence' scenario than 'Rare Earth'... what would it do to human psyche to learn we are truly (or at least effectually) alone ... however if the machine intelligence theory is correct then I'd think we should find some VN probes or something.

It seems to me that machine intelligences just make the Fermi Paradox worse, not better. It's much more plausible for MIs to exploit the galaxy's resources than it is for animals to do so. Animals have short life spans and are made of delicate squishy stuff. In principle machines could last for a very long time and they can travel through space without carrying massive supporting environments along with them, which implies they can go much faster for a given energy budget.

Even if we hit the limit of what we can know, I don't think that limits us to how we can exploit the knowledge. And I think machine intelligence is something we will reach before we hit that limit. I think maybe 300 years from now it's possible we will be able to download our consciousness to a machine, or upload it to a new body.

That seems an anthropomorphic view to me.

[astromark]

To say.. " We do not know." Is not to say it might not be, or even. It must be..

That we have not found proof is accepted as the fact at this time.. That could and might one day change..

We also do not need to say we can ever know it all. We can never, know it all.

For that word 'all' could be a infinite term.

From the safety of my fence post I have been watching this thread going no place at all..

There is NO shame in not knowing the whole history of life on planet Earth.

Most of the historic record has been ravished by the changing environment..

Some speculative guess work is required to fill the gaps which are many..

My contribution is nothing at all but a simple conclusion

supported by nothing more than what I can not say 'I know.'..' I do not know...

That the historic record of humanity has endured and arisen despite mass extinctions and Ice ages..

Leeds me to conclusions I can not yet prove... Back to my fence post....>>>>>>>> Mark.

[eburacum45]

Another common assumption is that significant scientific and technological progression can continue for very long periods, but we don't (and can't) know how many more scientific and technological advances are ultimately possible. Maybe a species with a million years with no setbacks simply could not have much more advanced technology than would be possible by the 25th century.

Rather than a continuous process of scientific progression, I think that an advanced civilisation would advance by increasing their fine control of the physical world. An advanced civilisation would not be able to travel faster than light, overcome the uncertainty principle, or reverse entropy, but it could build processing substrates capable of very detailed modellng of the universe, the past, distant locations, and different possible versions of the future. These modelling tools would allow such a civilisation to have remarkable a control over their own environment, their economy and their well-being.

Would such fine control over the unpredictable unverse make them happy? I'd like to think it would, but there is no real guarantee of that. Perhaps they would just use these multiple simulations of possible worlds to plan battle tactics in a series of increasingly desperate conflicts.

[Paul Wally]

I'd like to separate the concept of civilization from whatever it supervenes on. There are several possibilities.
One species can have multiple civilizations at the same time.
One civilization can consist of multiple species at the same time.
One species can have a succession of different civilizations.
One civilization can have a succession of different species.
Any combination of the above will also do.

Civilization is a higher level structure or organization supervening on the biological/mechanical base and any changes in the base can leave the identity of the civilization unchanged. A particular civilization is a distinct kind of organization that transcends the material base and can persist through time and space, as long as there is a base to supervene on.

I see that in this thread, species is being equated with civilization, but that would be like equating a novel with ink and paper.

[astromark]

Lets just try to drag this back onto topic...

I suspect, and trust that most of us science minded people expect that species will be found..

That they might be cockroaches and a long way from here.. is a expectation not unreasonable..

There is well reasoned argument that civilisations as we might want to find are rare...

We may NEVER find human like civilizations.. that is a well reasoned argument..

Facts supporting that this Earth has EVER been visited by intelligent beings has not been found.

and that I should add the word YET...