The Great Silence

[neufer]

In Brief

* Within decades advances in computing power will allow astronomers to scan enough stars in our galaxy to have a reasonable chance at detecting a signal from an extraterrestrial civilization.
* News of the discovery of an extraterrestrial signal will reach the public almost immediately. A conspiracy to hide or suppress the evidence of alien intelligence would be all but impossible.
* The content of the signal may never be understood. The assumption that mathematics or physics could serve as a cosmic lingua franca among civilizations may be misguided.
* Would revealing our existence to the universe at large attract the attention of hostile aliens? Such fears are probably groundless, despite the warnings of some prominent scientists.

<<One day last spring Frank Drake returned to the observatory at Green Bank, W.Va., to repeat a search he first conducted there in 1960 as a 30-year-old astronomer. Green Bank has the largest steerable telescope in the world—a 100-meter-wide radio dish. Drake wanted to aim it at the same two sunlike stars he had observed 50 years ago, Tau Ceti and Epsilon Eridani, each a bit more than 10 light-years from Earth, to see if he could detect radio transmissions from any civilizations that might exist on planets orbiting either of the two stars. This encore observing run was largely ceremonial for the man who pioneered the worldwide collaborative effort known as SETI—the search for extraterrestrial intelligence. As a young man, Drake had half-expected to find a cosmos humming with the equivalent of ET ham radio chatter. The elder Drake did not expect any such surprises from Tau Ceti or Epsilon Eridani. The Great Silence, as some astronomers call the absence of alien communiqués, remains unbroken after five decades of searching. And yet so does Drake’s conviction that it is only a matter of time before SETI succeeds.

“Fifty years ago, when I made the first search, it took two months—200 hours of observing time at Green Bank,” says Drake, who is now chairman emeritus at the SETI Institute in Mountain View, Calif. “When I went back this year, they gave me an hour to repeat the experiment. That turned out to be way too much time. It took eight tenths of a second—each star took four tenths of a second! And the search was better. I looked at the same two stars over a much wider frequency band with higher sensitivity and more channels, in eight tenths of a second. That shows how far we’ve come. And the rate of improvement hasn’t slowed down at all.”>>

[owlice]

The Great Silence

Huh. I thought this referred to the times when you are asleep!

Oh, wait... maybe that's me...

[neufer]

The Great Silence

Huh. I thought this referred to the times when you are asleep!

Oh, wait... maybe that's me...

Either way, it takes about four tenths of a second to glean all the intellectual content from one of our posts.

[Beyond]

The Great Silence

Huh. I thought this referred to the times when you are asleep!

Oh, wait... maybe that's me...

Either way, it takes about four tenths of a second to glean all the intellectual content from one of our posts.

I was going to make a comment, but i realized i can not improve on neufer's last remark. I am awed at his Genius

[owlice]

Either way, it takes about four tenths of a second to glean all the intellectual content from one of our posts.

You are far too generous, sir!

[Céline Richard]

There are hypothesis explaining the "Great Silence" in wikipedia (article "Fermi paradox"):

Few, if any, other civilizations currently exist

No other civilizations have arisen: Rare Earth hypothesis

It is the nature of intelligent life to destroy itself: Doomsday argument

It is the nature of intelligent life to destroy others: technological singularity and Von Neumann probe

Life is periodically destroyed by naturally occurring events

Human beings were created alone

They do exist

Communication is impossible due to problems of scale: Relativity of simultaneity

It is too expensive to spread physically throughout the galaxy: Project Daedalus, Project Orion (nuclear propulsion), and Project Longshot

Human beings have not been searching long enough

Communication is impossible for technical reasons

Civilizations only broadcast detectable radio signals for a brief period of time

They tend to experience a technological singularity: Sentience Quotient and Matrioshka brain

They choose not to interact with us

Earth is purposely isolated (The zoo hypothesis)

It is dangerous to communicate: An alien civilization might feel it is too dangerous to communicate, either for us or for them.

They are too alienAnother possibility is that human theoreticians have underestimated how much alien life might differ from that on Earth.

They are non-technological : It is not clear that a civilization of intelligent beings must be technological.

They are here unobserved


Céline

PS: picture from: http://webiswell.fr/wp-content/uploads/ ... restre.jpg

[RJN]

Background: http://asterisk.apod.com/vie ... 39&t=22045

[Céline Richard]

Hello

Thank you a lot for the video about SETI

About the "Great Silence", are the Nazca lines related to any extraterrestial intelligence? It might be a myth. Actually, i didn't find scientific details on the Internet over this subject (maybe because i didn't seek well).
In wikipedia (article "Nazca lines"), i have read this:

Swiss author Erich von Däniken suggests the Nazca lines and other complex constructions represent higher technological knowledge than he believes existed when the glyphs were created. Von Däniken maintains that the Nazca lines in Peru are runways of an ancient airfield that was used by extraterrestrials mistaken by the natives to be their gods.

Maria Reiche's protege Phillis Pitluga, an astronomer at the Adler Planetarium & Astronomy Museum, believes, based on computer aided studies of star alignments, that the giant spider figure is an anamorphic diagram of the constellation Orion. She further suggests that three of the straight lines leading to the figure were used to track the changing declinations of the three stars of Orion's Belt but does not take into account the other twelve lines.

Have a very nice day,

Céline

[Chris Peterson]

Swiss author Erich von Däniken suggests...

Lets not overlook the fact that von Däniken is, to put it as charitably as possible, stark raving insane. Basically, if he says something you may rest assured it's a crazy idea.

(The Nazca lines are perfectly explainable without invoking exotic theories.)

[Céline Richard]

You convinced me Chris, i am reluctant to read anything more about it by now
Have a very nice day!

Céline

[bystander]

Interstellar Predation Could Explain Fermi Paradox
Technology Review | The Physics arXiv Blog | KFC | 2011 Apr 08

If alien civilisations compete for scarce resources, the process of evolution may ensure that the survivors keep as quiet as possible

In a casual chat over lunch back in 1950, the Italian-American physicist Enrico Fermi posed a now famous question. If intelligent life has evolved many times in our galaxy and beyond, why do we see no sign of it?

There are a number of standard reposts to this paradox. The first is that life is actually quite rare and humanity is the first species to become advanced enough to contemplate other civilisations.

Another argument is that intelligent species have been common throughout history but end up destroying themselves or their habitat with their own technology, such as with nuclear weapons or fossil fuel burning.

Yet another approach is that advanced civilisations are common and aware of us but keep themselves hidden for fear of disturbing our delicate culture.

Today, Adrian Kent at the Perimeter Institute in Waterloo, Canada, puts forward another possibility. His idea is that civilisations are common, that they have interacted many times in the past but end up competing for scarce resources. When that happens, the process of evolution, operating over vast time scales, ensures that the survivors learn to keep quiet.

That's not an idea that can be easily dismissed. Kent says that one counter argument might be to point to the way evolution works on Earth. This usually operates on ecosystems in which species become interdependent in complex ways.

Although many species develop ways of camouflaging themselves, they do not end up hiding in isolation. So by this measure, Kent's fears are unfounded.

But evolution on a cosmic scale would be very different, he says. Cosmic evolution must operate over vast distances and that the scarce resources offered by habitable plants would be very rare.

Kent puts it like this: "If cosmic habitats are widely enough separated that they are very hard to find, by far the best strategy for a typical species to avoid defeat in such competitions may be to avoid entering them, by being inconspicuous enough that no potential adversary identifies its habitat as valuable."

That raises important questions about whether humanity is wise to advertise its existence. Various attempts to send messages to the stars have already been made and many scientists have pointed out that this could be a serious mistake, even a suicidal one.

Kent says the risk is easy to misconstrue. I'll leave you with his conclusion:

"One can summarise the essential point simply enough. If there are no aliens out there, any efforts at communication were obviously wasted. Thus we can assume for the sake of discussion that there are aliens out there likely to receive the messages at some point.

"The relevant parameter, then, is not the probability of our messages being received by aliens who might potentially do us harm: it is the conditional probability of the aliens who receive the messages doing us harm, given that the messages are indeed received (and understood to be messages).

"Can we really say that this probability is so negligible, bearing in mind that any such aliens appear to have made no reciprocal attempts to advertise their existence?

"The arguments considered above suggest that we cannot."

A sobering thought.

Too Damned Quiet? - Adrian Kent

• arXiv.org > physics > arXiv:1104.0624 > 04 Apr 2011

[bystander]

The surest sign that intelligent life exists elsewhere in the universe is that it has never tried to contact us. — Bill Watterson (Calvin and Hobbes)

[Orca]

Interesting list, Céline. Here are some thoughts on a few of them:

Few, if any, other civilizations currently exist

Probably true, and assuming they are roughly spread out evenly through the universe, there is a lot of 4D universe between them.

No other civilizations have arisen: Rare Earth hypothesis

Possible, but what makes our little corner so special? This brings up the Anthropic Principle. The odds are small that in any given corner of the universe a civilization would form. But if it hadn't, we wouldn't be here to contemplate those odds. Still, I find it hard to believe that our planet is "special" in the larger picture of the universe.

It is the nature of intelligent life to destroy itself: Doomsday argument
It is the nature of intelligent life to destroy others: technological singularity and Von Neumann probe
Life is periodically destroyed by naturally occurring events

If civilizations are commonplace, perhaps some of them do end up destroying themselves; I hardly see this behavior as unavoidable. Natural disasters on a planetary scale can indeed be a threat to life but such events are rare. A planet that suffers disasters often - such as wild climate shifts or continuous bombardment - would likely not be stable enough for intelligent life to progress toward civilization in the first place.

Communication is impossible due to problems of scale: Relativity of simultaneity

Our collective attention is often lost within a generation or two; maintaining communication with a planet hundreds or thousands of light years away seems impractical at best. As for travel I'd say humanity - and any other civilization out there - is in all likelihood physically confined to our home system.

Civilizations only broadcast detectable radio signals for a brief period of time

This is because in all likelihood individual civilizations exist for brief periods on the universal time scale. As if the physical distances aren't a large enough problem, civilizations probably rise and fall in short order. Again, assuming that intelligent life is spread roughly randomly throughout the universe, the odds that two civilizations in close physical proximity would exist within a tiny slice of time - a few thousand years - seems astronomically improbable. I think this is the single best explanation for "The Great Silence."

They choose not to interact with us

Is this a choice? We were using radio waves for communication long before we realized the possible ramifications. Is it reasonable to assume that other species might follow a similar pattern? Might they discover EM radiation, play with radio waves, start using them for practical applications, then realize "hrmm, we've been broadcasting our existence into space for a long time." Here's where cultural differences might exist. On our planet, I think you'd be hard pressed to get people to completely stop using RF transmissions on the grounds that aliens might notice the transmissions! But on another world, who knows? We don't know how other species think, so maybe such a mandate wouldn't be so crazy. Even if a civilization could manage to stifle all its EM transmissions you'd probably just be narrowing the already tiny window that we'd no doubt miss by thousands or millions of years due to the argument in the last paragraph.

They are too alienAnother possibility is that human theoreticians have underestimated how much alien life might differ from that on Earth.

They are non-technological : It is not clear that a civilization of intelligent beings must be technological.

It is entirely possible that intelligent life exists but doesn't ever develop technology of any sort, or perhaps develops a certain level of technology and doesn't advance beyond that point.

An intelligent species could be so well adapted to its environment it never needs to make fire or create clothing and weapons. However, what if physical deficiencies are the pressures that develop intelligence? Would we have developed fire, clothing, and weapons if we'd had claws and thick fur? Going further, are certain fundamental discoveries of nature required for technological development? For example, on a planet with a low oxygen content or one covered in water, the discovery of fire couldn't happen. Would this mean that such a species would never take those initial steps? Or perhaps I am simply anthropomorphizing?


I've had a quote from Douglas Adam's Hitchhiker's Series running through my head since I started thinking about this thread:

“Man has always assumed that he was more intelligent than dolphins because he had achieved so much...the wheel, New York, wars and so on...while all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man...for precisely the same reason.”

[BMAONE23]

Celine,
Here is another possibility
Radio transmission is much too slow for interstellar communications so they have developed a method to communicate instantaneously accross vast distances and so do not listen for nor communicate via radio frequencies. We are alone in the silence because we do not have the technology to listen to the chatter.

[rstevenson]

And there are other possible reasons why we seem to be alone, so far. David Brin's website has an article about this which he oroiginally published back in 1983. The whole article is worth reading, and down near the bottom of it he lists a few more interesting reasons.

And then there's this article, about the "Great Filter".

Rob

[Orca]

Celine,
Here is another possibility
Radio transmission is much too slow for interstellar communications so they have developed a method to communicate instantaneously accross vast distances and so do not listen for nor communicate via radio frequencies. We are alone in the silence because we do not have the technology to listen to the chatter.

I doubt that breaking the laws of physics is just a matter of technological skill. Star Trekian "sub space transmissions" aren't going to happen!

Also, if there were lots of civilizations out there, wouldn't there be a wide range of tech levels? Also, you'd hear a civilization's transmissions in the order they were sent - starting with the most rudimentary methods.