He may try to go on the evidence, but his deductions from that evidence are flawed. Or would be, if we had evidence yet.

But I think you're on the right track.To my mind, it's a hypothesis along the lines of the Moon Hoax hypothesis

Well, frankly, I don´t see him adding anything new, besides the [cool expression] 'great filter'. He does not advance onto anything that hasn´t been thought before about the lack of evidence of alien intelligence. And he also throws around old concepts like techs going awry.

__________________
What brings us together is stronger than what pulls us apart

Why would they do that? Do they fear that they might be discovered? That seems to imply that something out there is worth hiding from.

In that case they are rare, or have only emerged recently, and have not existed long enough to get here. In both cases, one has to wonder 'why'?

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Yes, he writes well, and frames his reasoning in an interesting evolutionary perspective, but most of his ideas can be found in science fiction. His article reminded me of Lem's book Fiasco.

__________________
"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

I tend to put it in the same category as the Carter Catastrophe, actually;
http://en.wikipedia.org/wiki/Doomsday_argument
a thought experiment that might indicate something, if only how little we know.

If and when we explore more locations in the universe. the realities behind the Great Filter (or filters) might make themselves known.
But fairly soon we might start finding evidence of biospheres on terrestrial exoplanets; if these are commonplace, but intelligent life isn't, then we should ask ourselves how this might be explained.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

I said;

1.To mask themselves before another gigacivilization that can be agressive.
2.To not contaminate lesser civilizations developement.
3.To maintain their own privacy.
4.Anyways how can you know how they can think?

Why they would be hiding?We are worried that our TV broadcasts will reveal us, they could have the same fear.

I think the godlike billions year old civilizations would hide because they want to manipulate the lesser civs. w/o suspicion and/or to protect themselves from another similar civs, and to keep their godtech from falling into bad hands.

Why they would be rare?Sry, LOL, do you understand that evolution is not something that "makes organisms perfect", but just natural selection, breeding and the founding of new spieces?Only on a fraction of living planets with advanced life organisms needs intelligence to survive.There was complex life on Earth for cca 800 million years, we have evolved only in the recent 100 000 years.

Anyways, we'd better start exploring space more and build better instruments, not be like ants trying to understand Empire State Building.

Actually, that was the first thing I thought of when I started to read the article! I thought maybe it was another discovery of that. Personally, I place that in with the Moon Hoax too.

Here's an old discussion on BABB

This is one of the answers I am looking for. Perhaps the fear of warfare itself prevents expansion- it may be that there exists a balance of terror betweem myriad different species in our galaxy. One wonders how stable that balance might be.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Well, I did not mean not expansion.

Galaxy could be all colonised, but these colonies sophistically hidden and creating in not obvious ways that only supercivilization can come up with and create.

For example, turning sentients into an intelligent picodust that takes power from radiation and that appears to anyone else just as normal interstellar dust do, but it hides something else... + nano to pico or even planck sized Von Neumann style machines that convert entire planet interiors into computing substrate and repair it.

My point is that it is entirely possible that there are megacivs. with "megastructures", just not these too obvious like classical Dyson shells, rings etc., but much more advanced and clever designs that provide secrecy as a side effect (a desired one).

For example, would you consider planets that are appearing normal on the surface, but with interior of computronium or some other strange ultratechnology thing designed to mimic normal planet interiors (at least from the outside) as detectable by any technology?!

Even if they colonised many planets and covered half of them with solar collectors they would be still invisible for us.
Even if they use radio they would be probably careful enough to jam it to not go anywhere where it is not supposed to go (even w/o it we simply cannot detect unidirectional radio signals of communications power because they are ruined in noise around at the distance of Pluto).

Well,but you all seems to forgot that billion year old civs. would probably have intellect at least 12 orders of magnitude better than us and understanding them would be probably like expecting bacteria to learn the principles of nuclear fission.
Billion year civ. = existed 100000x longer than our civilization (if you take the dawn of our civilization as cca 8000 B.C).
I strongly suspect that civ. that's been around for so long can manipulate strings to create FTL speeds, store their information in cosmic dust and gas, master godtech plancktech, create virtual universes in planet interiors filled with immeasurably dense computing substrate etc.

With 400 billion stars in our galaxy, I suspect that at least a few of these "masters of the universe" quietly lurk our galaxy.

BTW I've read in one of our popular science magazines roughly before a year or so, that research on "intelligent dust" being able to function as little cameras, tracking devices etc. is being taken, so I guess that it would be extremely trivial for billion year old civilizations to basically make everything smaller than atom, only not the computing substrate clusters.
Also I think that blocking all the EM, electron etc. radiation would be as easy for them as pickin up a coin for us.

You have enormous energy radiating structures in your scifi OA universe, but that's 20000 years, not a billion year old civilization.
I think reasonable civilization would be cautious and never build things so obviously, instead developing the best ways to do it.

We can speculate endlessly, everything is possible.
What if we are in a simulation, bubble universe etc...

But one thing that angers me, is when someone says "we are alone because we don't see funky Star Destroyers with huge jets everyday in the sky" or "hope there is no one else because I am paranoid and I cannot never understand that a defeat is always possible and let's kill everyone alien just for safety" or "Aliens do not exist because if they existed they would have colonised the Earth even if it would be totally unfit to them and they would have no interest of watching its biosphere from distance and study its uniqueness because they don't have 400 billion systems just in this galaxy systems to colonise and 10000000000000000000000 stars to explore, oh, and ofcorse they would leave bones in the earth as dinosaurs did because they sure have bones and bury their bodies in the Earth because even trough capable of travelling 100000 ligh years they cannot extent their lifespans".

And what if there are even stranger forms of life, intelligence and civilisation, such as neutron star dwelling creatures in a rich wonderful biosphere using nuclear and electrical reactions in place of chemical, with time being that microsecond is like a minute for them, with size of molecules, living on a body with 1 mm thick neutrino atmosphere where time goes slower on the poles than on the equator, with hundred billion G gravity being normal for them, and their biology gradually evolving and their metabolism slowing dowing as the neutron star cools?
These creatures would not even recognise Earth at a first glance, rock being hard vacuum for them.

I can imagine that some very advanced alien civilisations might adopt a low profile for reasons other than fear. Perhaps they prefer to blend into the background out of politeness; they might prefer the appearance of a galaxy which looks as if it is uninhabited.
They might even hide in this way for our benefit, so that we can continue to behave as if they did not exist, which for all intents and purposes they don't.

This leads on naturally to the Zoo hypothesis; we don't see them because we are being kept as specially preserved examples of our kind
http://en.wikipedia.org/wiki/Zoo_hypothesis
An ideal zoo might provide an environment in which the zookeepers were entirely invisible.

What does the Great Filter hypothesis tell us about such a situation? Well; there would obviously be a barrier for us to pass to move from the status of zoo exhibits to that of zookeepers. It may be the case that we would not be allowed to ever make that transition. We would remain as exhibits forever - and a filter which could potentially prevent us from passing to a higher status in the Galaxy would exist.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Sorry, but stop this "Great filter" nonsense.
I said that even if they don't want to hide, the most advanced technologies would be virtually invisible.
Zoo hypothesis?It seems strange to me, why they would keep us in same state?What if they just want to watch and secretly guide our developement and not disrupt it by revealing themselves, then accept us into the "gods club" once we will be developed enough?What if advanced civilizations in this universe are watching and guiding the developement of sentients and then accept them as brothers and in turn watch another civilization etc.
What if there is actually no war between advanced civilizations simply because everyone achieved it's status due to someone other?
It is really a coincidence that our solar system seems to be litararly designed for life of our kind?

Possibilities are endless, and I am not claiming any of my speculations as sure facts, just possibilities and speculations.
But I think that when you wanna speculate about godlike civs, it is really stupid to assume that they would be detectable by us and postulating some type of galactic plague that prevents civs. from developing, and to assume that civilizations that manage to live for billions of years would have the same level of ego and narcissm as our human race has (let's face it) and that they would just wanna to control lesser civilizations as "exponates" preventing their growth and developement.

I am not saying they would be benevolent angels, just that evil, violence and dishonesty loving creatures would not survive to the stage of being gods.
Their malevolent ways would backfire on them, just as Hitler lost his narcisstic mad genocidal conquest.

It tells us nothing?

The hypothesis itself gives no useful information. I'm not sure where you derive the zoo thing from the hypothesis. I guess that comes from the zoo hypothesis, completely.

I have that feeling too.

I am suggesting that the Great Filter concept also might have a benign interpretation, where advanced civilisations dissapear from view because they become invisible on purpose. This invisibility could be explained by the Zoo hypothesis, or by civilisations which hide inside terrestrial planets, stars, neutron stars or black holes; it could be explained by civilisations patterened into the quantum foam, or into the strings that make up matter, or decanted into baby universes.

All these invisible states may be possible, and would represent a Filter in our future which prevents the existence of an observable, galaxy wide civilisation. But instead of being a negative filter, destroying all civilisations, this presumed transogrification merely makes them invisible, and perhaps intangible as well.

But it stil is a filter which removes observable civilisations; and for some unknown reason it removes all of them, which to me is the intriguing part. The option to become invisible may exist - but why, among all the physically and psychologically diverse species of intelligent aliens that may be out there, why do they all follw this path? Why are there no civlisations which chose to take the option of an expansive, visible,comprehensive empire?

Do the invisible civilisations stop them?

That too would be a filter of sorts, one which explains the absence of archaeological remains on our planet. If civilisations are a common phenomenon, and some are expansive and visible, we might expect to find tangible evidence of their presence on our planet in the past. Not just a few traces of metal or glass technology, but whole cities. They are not there. So something seems to prevent expansive and visible civiilisations from occuring.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Then again, there could be interstellar civilizations that, through no exotic means, simply have yet to be observed. Considering that our own star wouldn't be obvious to any great distance, it doesn't seem that there would be a need for exotic methods to remain unobvious.

__________________
I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

If there are a lot of dead civilisations out there, and they all died from different causes, then it simply becomes a matter of chance. And such chance disappearances begin to look a little improbable. Once a civilisation spreads to more than just a few stars, it is insulated from any localised disasters. The possibilty that a large number of interstellar civilisations have each been removed in turn by chance alone is difficult to explain.

I did at one time think that Gamma-Ray Bursters might sterilise whole volumes of a galaxy on a regular basis; but the current theory suggests that GRBs send out tightly focused beams of death, which are great for observing across the universe, but not so good for sterilising a galaxy.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

But how "tightly focused".
"Tigtly focused" could mean 10000 light years wide maybe.

Why there are no visible god civilizations?Because it is much safer, wiser, better to be quiet and hidden than to shout all over the universe, it prevents cultural contamination of lesser civilizations and the most advanced technologies are simply invisible by principle?
What is better, build a billion km wide sphere with star inside radiating half of energy as waste heat and shouting all over the galaxy or a swarm of invisible nano solar collectors?Being in a form which requires exact conditons, temperature, atmosphere, pressure and has limited slow movement, couldn't move in free space,depends on expansive bulky energy eating machines to just move a few hundred kilometers....or to be a free swarm of nanobots that is even capable of engulfing any enermy and "eat" him like a Von Neumann machine, can building anything without aid provided it has enough avilable materials, and can travel at incredible speeds all over the universe due to each it's constitutent particle having at least molecular sized nano rocket engine?Oh, and by the way, such thing could be capable of easily turn into humanoid or any other form, a brilliant forms of mimicry.They might even be here amongst us...It is billion of times more comprehesive and better civilization than your visible civilization.You still seems to expect civs like in popular scifi, where there are kilometers long starships with gamma ray emiting engines and weapons that can be detected over light years everywhere.

The one things that is important to realize when you want to discuss extremely advanced civilizations is that expecting them to waste materials and energy just to sustain their former biological form and to build stupendously huge structures that will reveal themselves to half the universe and are extremely inefficient is very naive.

The final answer in my opinion is; no civilization is stupid enough and when it is at the point when it can make inefficient megastructures, it already knows that there are billions of times better methodes to live and develop that do not involve extreme energy and matter wasting and risk of revealing themselves to some bloodthirsty predator civilization that makes it's living from razing other civs.And this would be more like 20000 years old civilization, not billion, so billion year old civilization = not even try to find, they will not reveal themselves if they do not want to, and they surely will not to do it to some baby civilization that cannot even build collonies on their nearest satellite.

Your idea is based not on psychological diversity of aliens, sorry, but by common human imagination about future.
Certainly no such "builds gigacities consumming pettawats each second and dyson spheres, and billion ton weighting spaceships that cannot do 20 percent of lightspeed" civs exist, just as we are ridiculing 19th century imaginations about 21th century now we will ridicule our common 21th century imaginations about aliens when we will encounter them, I think.

You seems to pretend that they would be technologically advanced, but extremely idiotic.

Would you leave easy use atomic bombs and autopilloted bombers for caveman?

We could erase the most obvious of our traces even now - just launch our stockpiles of nuclear weapons at all big cities, set them to burst at impact, wait until the fallout gets cleared and anyone alien would think that we never build cities with more than 500000 population.
If we had capabilities of interstellar travel and a bit developed nanotechnology, we would be capable of quickly destroying all traces and leaving home for another planet.

What prevents them from occuring; Simple, their own intelligence.

Please, I know my posts are long, but read them entirely and think about it.
Maybe you will come to same conclusion as mine.

The question then becomes- why do they feel the need to 'cover their traces', so to speak? Every alien civilisation which has ever visited the Earth has subsequently eradicated all evidence of their existence. Why would they do that?

Are they hiding their traces from us, or from something else?

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

I came to an interesting web page;


http://www.dailymail.co.uk/pages/liv...n_page_id=1770

We are finding fossils just because they were protected by sediments, cities will become dust after not a very long time.
Please, think more.
Saying that there would be cities because we can see dinosaur fossils is like saying that a fly can live up to 120 years because humans can.

Are my posts not obvious enough?
I have written in my previous post that it would be like leaving nukes for caveman.Why delete traces?Because native sentient life can evolve on that planet and you don't want them to have the most advanced technology and planet destroying weapons when they do not have the responsibility.

Sorry, your questions seems very trivial.

I have to advise to you, use more common sense and think more about some question, only if you really cannot solve it, ask it.
No offense, but I've answered the questions already in my previous posts.

Assuming civilizations have, for some reason, visited earth, time can take care of a lot of things. Most of our stuff wouldn't be obvious a few million years down the road, and an ET visit need not leave anywhere near as much evidence as we have.

__________________
I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

This is another subject I believe we have discussed in the past on this forum. Most metal and plastic artifacts will probably be unrecognisable after a few hundred thousand or million years; but glass, diamond-type materials indicative of nanotech, and certain kinds of stone artifacts would survive. My wife is an archaeology graduate, and tells me that the most difficult evidence to get rid of is a hole in the ground- you have to remove the whole layer the hole is in to obliterate it.
So underground car-parks and subways, cellars and wells, mines, nuclear waste dumps... all these might be expected and are absent.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Not completely, not yet.

The first Earth-like planets might have been formed in our galaxy twelve billion years ago or more; the first civilisations might have arisen a few billion years after that. Wave after wave of empires could have crossed our galaxy, and each might have come to Earth and left a trace. Some may have missed us, by chance- Geoffrey Landis has written an interesting paper on this possibility.
http://www.sff.net/people/Geoffrey.L...ercolation.htp
But all of them?

But more importantly why are none of them still here? To explain this one must invoke the unlikely coincidence that they all disappeared for different reasons, or suspect a filter of some sort.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

eburacum45, but as I said, no advanced aliens would leave high tech artefacts on a planet where sentient life could develop

And why do you expect them to settle here at all?Advanced civilization has lot of space, why they would dirsrupt the natural developement of unique biospheres?Mines?Nuclear waste?I've said, no such things.Nano civilization would have no use of planets other than converting their interior into a computing substrate or some other strange thing and even then they would not gonna do it on living worlds because a developing sentient civ. may discover it and scavenge and study the technology.

A sort of Prime Directive.

I ask again for the third time, would you allow cavemen to acess nukes?No, and that's why aliens are not gonna leave their ultra energy sources and weapons here even if they colonised Earth?

Evidence erasure hard for a billion year old civ? HA HA HA HA HAHA
Sorry.
They would surely even disassemble a planet if they wanted to without it's inhabitants even knowing, making molecule sized holes and creating more of themselves while the dirt under your foot will disappear.

Are we even talking about the same thing here?As I said, godtype civilization would be probably basically nanodust that can accelerate itself to almost c and hypercomputers created from planet interiors.Car parks?Nuclear waste?When your parts are as small as molecule and can independently move at, nearby the speed of the light you can do ANYTHING.Doo you even who billion year old civilizations are?They are GODS.

The most efficient mode of existence for an advanced civilization is nanoswarm of Von Neumann machines connected by string or wormhole FTL communications to billions of brain-worlds that appear normal from the outside, but their interior is computronium.
Energy is from radiation (for individual nanobots) and the brainworlds can use energy either from fusion or some another high energy reaction or from energy emitted by spiecialised nonsentient swarms of nanobots that collect energy orbiting extremely close to the host star.
Yeah for humans it is hard to imagine being nanodust because we have predisposition of seeing everything "machine" as "inferior", "cold", "artifactal" etc., but billions of year old civilization will certainly have no such predijuces and will certainly opt for the best option allowing the most freedom and things to do without requiring extreme energy and matter requirements.
This way, no Dyson sphres in the ordinary sense are ever needed.

Here's a somewhat older expression of the Great Filter concept, from Robin Hanson in 1998
http://hanson.gmu.edu/greatfilter.html
To explain the GF, the explanation must be comprehensive; if the filter has already occurred and we are past it, then advanced, visible, expansionist civilisations are likely to be rare, since none has apparently arisen yet. If the filter is in the future we have yet to face it, and trying to anticipate it can't do any harm - although such speculations might be in vain, depending on how 'unexpected and subtle' the filter turns out to be.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Btw search of Dyson spheres is stil ongoing and your megastructure model of advanced civs. may well be true;
http://home.fnal.gov/~carrigan/infra...lab_search.htm

Finally,
Let's face it.

Every argument and the Fermi paradox also has the same fundamental flaw,
We don't know anything and we are overestimating our instruments.
What if they simply use thermal shielding to use some waste heat and so we don't detect anything.
You all foolishly belive that our instruments are strong enough.
Wrong.

I don't know, but imho this discussion is not productive and all of it is pure speculation.

We may talk again when we'll have some evidence for or against advanced intelligent civilizations in this galaxy.
And better instruments and not so small knowledge of the universe.
We are in diapers.

I know that an advanced civilisation could cover its tracks- but the question still is -why? Why would a civilisation a hundred million years ago erase all evidence of its existence? Why would it leave in the first place? A good answer. If there is an option that all advanced civilisations find more attractive than visibility and expansionism, then they will follow it. But this must assume that every section of every advanced civilisation chooses to follow that option. Just how likely is that? Do all advanced civilisations converge upon a single ideal state, an attractor of some sort? That is certainly possible; but it is difficult to imagine how this attractive condition could mop up all the diverse forms of intelligent life that might emerge.

__________________
New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set