And SOME races may not give a rats buttocks. Sure it may not be wise, but they may not CARE. Besides, to an advanced civilization atomic bombs could be approximately as advanced as stone tools. They may not consider the implications, They may be arms merchants. They may be genocidal. A billion year old civilization may have capabilities that seem god like, but me with a bic lighter may seem god like to a people who are still stealing fire form the sky, as in lightning strikes. If there is a bigger threat sure, I can see why a billion year old civilization would want to hide their traces. But if they are the numeruo uno, they just may not CARE. In fact, if they have lasted over a billion years, then they could be selfish to the hilt, not caring to make grand stands, but also not caring what happens to other species. Also, they will be not wanting competition, so giving atomic bombs to cavemen, would be a perfect strategy for erasing competitors. You won't even have to worry about any OTHER life form arising on that planet to supplant you. Brilliant. The way I see it, if they are hiding, it means there is a bigger dog out there, and that means they are not gods, and if there isn't, they would have no reason to hide themselves.

__________________

I wouldn't be surprised if some Dyson swarm-like structures were found in the next few decades- but I would suspect they would either be distant or very partial, or they would already have been noted. A partial swarm might look very similar to a thick dust cloud- and several of those have been seen already, around Vega and Fomalhaut for instance.

__________________
Orion's Arm . The Starlark . Voices: Future Tense . OA Flickr set

I think that when you are evil you will be doomed to extinction no matter how smart at lying are you.
The civilization what you describe would not even survive 20000 years, it will destroy itself.
And as "God like" I MEAN GOD LIKE.I mean THE MOST ADVANCED DEGREE OF DEVELOPEMENT POSSIBLE not what may seem "Godlike" to us.
Such civilization is perfect, technologically, morally, intelligently, whatever.
Why they would do anything bad anyways if they already have everything?
Yes, if they had the capabilities from the beginning they could be evil.
But to survive billions of years you had to be pure good.
Before 20 years there was still a threat of humanity being destroying in a nuclear war and we a young and not too evil civilization.
This is the reason why they would be rare, to achieve that you must erase all agression, stupidity etc. totally completely from your brain and mind FOR EVER.
"Evil gods" simply don't work.
When someone attempts to be the greatest by killing and hurting another, everyone will ally and destroy them.

These civilizations may not even use nanobots or gigabrains or whatever...they finally find a way how to live without normal material form and be totally invisible except for another similar beings.
I do not mean spirit wowoo, but things like storing ourself in a quantum foam, strings, elementary particles, pure spacetime curvature, dark matter or whatever.

And evil is a human concept, some beings may not even have concept for evil, these would be most likely to achieve godhood status, or no concept of good, in which case they wil mostly last extremely short.

Or very sophisticated?Nano satellites appearing as transparent?

"When it rains, it rains on the just
And also on the unjust fella;
But chiefly on the just, because
The unjust has stolen the justs umbrella."
Lord Bowen.
Why would they have to erase these nasty attributes? What is the mechanism that takes out the evil ones? What we call evil often depends on whether it happens to us or someone else. A billion year old civilization is going to care about one thing, survival. There is no way they are going to let some whippersnapper race take their place as prima donna's of the universe.Sure, they just might be peaceful and cooperative, within culture/species, but so are ants,who are quite xenophobic.
I don't believe in Utopias, and efforts to create them tend to end in failure. Not in a million years, not in a billion years.

__________________

The mechanisms is nuclear weapons in the Information era.
I belive in Utopia and the only reason why we have not achieved it is because we are too stupid and we care too much about human rights of henious psychopathical criminals while neglecting people who need help.

A transparent satellite sort of defeats the object of a Dyson swarm, which is to collect photons and use the energy. But a very large dyson swarm or sphere would radiate at the same temperature as the cosmic ray background, making it practically invisible; otherwise it could just disguise itself as a dust cloud, and appear natural.

Hmm; perhaps it is an aesthetic choice- just as some cell phone masts are disguised as trees for aesthetic reasons, perhaps some dyson swarms are disguised as dust clouds so as not to spoil the scenery.

__________________
Orion's Arm . The Starlark . Voices: Future Tense . OA Flickr set

Those 'henious psychopatalogical criminals' are also human beings. Humans beings who need help, but still people. Many are 'incurable' at this present time, but I see no reason to stop looking. Your 'utopia' frightens me.
'Let not the perfect be the enemy of the good.'

__________________

It can be transparent in the visible light but not in another wavelenghts, absorbing another.

Psychopaths lacks any sense of conscience or morale and they are capable of hurting anyone to achieve their own selfish goals and fake emotion while they don't have any.They cannot be helped because their psychology is like...eh, I have to say, non human, they have the appearance, but no substance.But they have free will, nobody forces them to hurt people and they are perfectly sane if they do not have another mental illness, so that's why I think we should never have mercy on them when they do horrendous crimes.So what we must do according to you?Leave them until we find a cure for their soulessness?They are sane, but completely amoral.

"Evil" is the characteristic that defines them most closely.
That's why they're giving me creeps and honestly I think the world would be better if we at least locked them up all.
They have no compassion to others, no heart, no soul, but they are not insane.

When cure to this will be developed you will basically solve the problem of evil in the human race.
Normal people do evil, but they have boundaries.
Psychopath never has any such thing, if he killed your child brutally he will not feel absolutely anything, no regret, no nothing, that's why I hate them as abominations and a carcerous growth on any civilization.
Please do not have sympathy for psychopaths, because they are not capable of feeling anything.
A psychopath simply has no concern for anyone expect him and his immediate gratification.
Psychopaths appear as normal and most of them never do any really serious crime but they hurt people in many other ways.
They leave empty wallets and broken hearts and they infiltrated our human culture to than point when some of the psychopathical behaviors are actually seen as "competive" and "desirable" and moral relativism is seen as acceptable.
A sad, sad thing.
And a disturbing portion of the population are psychopaths.
I think that every civilization starts with a bit of good and evil because social civilization cannot be governed by evil.Only when flawed individuals that do not mind raping and murdering someone with a smile take control, a civilization can become truly evil but then it would destroy itself due to wars, because everyone will want to have the most and don't mind killing other do get it.

You didn't understand me, I am saying that because you simply cannot have long lived evil civilization, because everyone would care only for himself, not for the civilization, but just him, him, him ,him....
Egomania and narcissm are the basis of evil.
Psychopath is not a madman in the common sense of that word, just a being in which there is no good and evil has overtaken.
But yes, they are ill because they are not capable of feeling any good, it is not their fault.
But you can judge them morally because they are still sane.

Perhaps this is the sad explanation for the rareness or nonexistence of really advanced civilizatiions, that psychopaths lie their way over and overtake, in turn start a period of massive wars that will go WMD and destroy the entire civilization.
Coincidentally this means that we will encounter many pre-WMD or our nowadays technology level civilizations, but very rarely those that survived this critical stage.
That''s because before WMDs there are no artificial means of how could civilization start a seft destructive fatal war.
And WMD+psychopaths at charge = bad news.

I am not taking about any poor people who hurt someone because they are insane or beliving that they are actually helping, but parasites that can sponge you off in a minute or worse.

I think immortality can be this attractor. And if you become immortal it change all your motivations. You don't need to reproduce and so don't have to colonize. And if you are immortal you cannot evolve in the traditional way , generation after generation , so you must evolve yourself ,taking over the evolution process. (Intelligent design !!! ) So you are not very interested in moving to an other star.
An other point , may be planets are not so interesting for very evolved civilizations. they are full of dirt , winds , bad weather , nasty insects , bacterias , virus and . . . nasty aggressive monkeys !! . . . What awful places they are !
Better to live in artificial dwellings !

And finally I think Argos has a point , a Civilization able to travel to the stars , may be much less matter oriented than our.

I think that there would be many strange types of civilizations, each taking it's own unique path.

The only natural, obvious, simple answer to the Fermi paradox is the one no one really wants to consider: Starfaring civilizations are just very rare - and/or they last only for a very short time. (very rare = civilizations/galaxy <<< 1, very short = lifetime civilization <<< lifetime galaxy)

This interpretation is the only one consistent with all our observations and needs no "god-of-the-gaps"-like reasoning why we don't see any aliens. There is not a single observation that implies that civilizations must be plentifull in the universe...

This solves also the following problems/observations:

- absence of any artifical signals from interstellar space
- absence of any signs of former colonization of the Earth or the solar system
- absence of any megastructures
- Late occurence of civilization on Earth (compared to the lifetime of the Earth's biosphere): typical observation if average time for evolution to develop a civilization >>> typical lifetime of a biosphere
- Typical observer argument ("Doomsday argument"): if we are typical observers*, it is unprobable that the number of people being born after us >>> people being born before us
- Typical observer argument aplied to interstellar colonies: if we are typical observers*, and we are living on the original homeplanet of our species with the galaxy still untouched by our own colonization efforts, then it is unprobable that people living in colonies >>> people living on homeplanets (otherwise the typical observer would live in a colony)

(*which is probable, as most observers are by definition typical observers...)

This view may be deemed "pessimistic", but it is not: it is just based on realism and observation. If this weren't such an emotional topic, we would have adopted this rational explanation long time ago. The belief in many "contactable" civilizations has a quasi-religious ring to it: if we don't find any evidence for it, lets find some insightfull "excuses" why they are out there but we still can't see them...

By the way, I am not suggesting to shut down SETI or the like, although I guess it will never be successfull. SETI is an experiment to test the predictions made from observations: but as far the null-result it has delivered only supports the view I have expressed here.

The author of all that clearly thinks he knows it all.

I'm not satisfied with religion or the concept of "GOD".

How could anyone say there can't be life out there, what do they know. They haven't been out there.

Mr. think he knows it all, same like the religious.

Exploring space is a reason, to try avoid destroying ourselves.

__________________
http://www.geocities.com/theydidgotothemoon/

I can't help but picture an Incan philosopher in 1491 explaining carefully to his students why there could be no greater civilization than the Incan on Earth, because if they were they would be in America by that point, and theorizing that any culture more technologically advanced than the Incan must also have learned to be peaceful, and would undoubtably be protective of the distinct Incan culture if such a culture were to appear.

__________________
"You miss 100% of the shots you don't take" - Wayne Gretzky

To be fair, that is more or less what Bostrom is saying; by including the term 'and/or' you include a wide range of possibilities. If the correct solution is simply 'they last only for a short time', the question becomes 'why?'.

In writing our fictional history of the galaxy for Orion's Arm, we happily included many extinct species that rules the galaxy, or a part of it, for a few tens of millions of years at most.
Here is a summary of the fictional empires which rose and fell over the lifetime of the Earth in that scenario (there were probably a few before the Earth was formed, but they are not listed)
http://www.orionsarm.com/timeline/preterragen.html
But the one notable feature that is common to all but the most recent is that they all died out.

If one day we can make a similar history of the real galaxy over its lifetime, will we find numerous dead civilisations to put on the list? And if we do, the question resurfaces- why are they all vanished? Once a civilisation spreads itself out over a sufficient number of stars what could cause it to fall?

In the past I've answered this question with 'all things must pass' or 'all good things must come to an end', nowt but platitudes. But on an interstellar scale I can't really guess why every such civilisation must eventually fall, assuming they come to exist in the first place.

Of course any suggestions would be welcome...

__________________
Orion's Arm . The Starlark . Voices: Future Tense . OA Flickr set

Great Post, Best of this entire thread, though eburacum45's posts are sensible also. The next to last paragraph says much, just look at the most immediate replies.LOL. I have normally refrained from posting about this subject throughout the years because of the emotion and quasi-religious tone.

Perhaps I should address the 'typical observer argument'; that only works if there is no selection bias when you choose your typicial observer. The 'typical observer' is an assumption also made in the Carter Catastrophe; and I have argued in a different thread that it is wrong to assume that we are typical observers.

Instead, we are observers who exist at a particular point in time, just after the first development of such logical confections as the Carter Catastrophe argument and the Great Filter hypothesis. We could not exist before today, because we did not have enough information and suitable logical and mathematical tools in the past to frame these arguments.

We could not live in