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.

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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'?

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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.

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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.

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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.

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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.

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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.

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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.

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

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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.

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