From NewScientist, "Aliens need a lot more time to find us". From Bjork's paper

In the summer of 1950 in Los Alamos, Fermi and three of his friends sat down to a lunch. They were discussing the possibility of extraterrestrials. Fermi asked, "Where is everybody?" He paused a few moments, making a series of rapid calculations. His friend, York, recalled Fermi concluded that we should have been visited long ago and many times over. In other words, our galaxy should be swarming with extraterrestrial civilizations. But we see no sign of them. This is the Fermi paradox. Where are they? It is said that Fermi himself probably believed in the existence of extraterrestrial intelligence. But his paradox certainly leaves open the possibility that we are the only advanced civilization in our galazy and maybe even in the universe. For me, the numbers are staggering in favor of ETI's out there.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge. --- Enrico Fermi ---

Article
Fermi paradox is a myth (urban legend)

I'm very sorry but this article is only in italian language.

Use Babel Fish for translation. ;-)

Clear and dark skies!

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73 & clear skies from Bruno IK2WQA
Founder SETI ITALIA Team G. Cocconi

One member of these boards who goes by Sleestak said "Its like an ant trying to extrapolate the number of blades of grass on the Earth without knowledge of the oceans or deserts."

Also if I were to use the logic of the Fermi paradox I could conclude that no elephants exist on Earth. I have never seen any around my neighborhood. Even though they have had plenty of time to wander here. If you are an alien exploring solar systems they all look equally inviting for exploration. Theres nothing that makes ours stand out.

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Article
Fermi paradox is a myth (urban legend)

I'm very sorry but this article is only in italian language.

Use Babel Fish for translation. ;-)

Clear and dark skies!

Babel Fish Translation

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Join TeamACC

Sometimes I think we are alone in the universe, and sometimes I think we are not. In either case the idea is quite staggering.

One member of these boards who goes by Sleestak said "Its like an ant trying to extrapolate the number of blades of grass on the Earth without knowledge of the oceans or deserts."

Also if I were to use the logic of the Fermi paradox I could conclude that no elephants exist on Earth. I have never seen any around my neighborhood. Even though they have had plenty of time to wander here. If you are an alien exploring solar systems they all look equally inviting for exploration. Theres nothing that makes ours stand out.

I see your point. However, if there are others out there, most certainly they are more advanced than we. Where are they?

Also, taking into account all the variables that concur to allow us to exist, I can see how someone might conclude that we are alone in the universe. But for me....they got to be out there!!!!

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge. --- Enrico Fermi ---

what is the Fermi paradox

from Widipedia

The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence of contact with such civilizations.

The extreme age of the universe and its vast number of stars suggest that extraterrestrial life should be common. Considering this with colleagues over lunch in 1950, the physicist Enrico Fermi is said to have asked: "Where are they?"[1] Fermi questioned why, if a multitude of advanced extraterrestrial civilizations exist in the Milky Way galaxy, evidence such as probes, spacecraft or radio transmissions has not been found. The simple question "Where are they?" (alternatively, "Where is everybody?") is possibly apocryphal, but Fermi is widely credited with simplifying and clarifying the problem of the probability of extraterrestrial life.

There have been attempts to resolve the Fermi Paradox by locating evidence of extraterrestrial civilizations, along with proposals that such life could exist without human knowledge. Counterarguments suggest that intelligent extraterrestrial life does not exist or occurs so rarely that humans will never make contact with it.

A great deal of effort has gone into developing scientific theories and possible models of extraterrestrial life and the Fermi paradox has become a theoretical reference point in much of this work. The problem has spawned numerous scholarly works addressing it directly, while various questions that relate to it have been addressed in fields as diverse as astronomy, biology, ecology and philosophy. The emerging field of astrobiology has brought an interdisciplinary approach to the Fermi paradox and the question of extraterrestrial life.

for Info only

Hit Me
Greetings from Germany NRW
Ulli

Jeannot, wow!! Thank you very much for this info. Do you think a layman like me could understand much of the International Journal of Astrobiology? Do you personally know much about this journal?

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge. --- Enrico Fermi ---

Do you think a layman like me could understand much of the International Journal of Astrobiology?

Hi,
I am a layman too ! and that's the reason why I read the Newscientist article first.
You could see that they talk about SETI somewhere else Unfortunately the complete article is only available for subscribers.
Maybe I'm going to buy a paper version.

Maybe aliens exist outside our light cone and we shall never be able to communicate with them.
Tullio

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If you consider the fact that if there is other life out there some where, it doesn't mean that we will ever find each other by looking for something that we know of...

What if they took a different direction with technology... Maybe the long distance communication uses something different than radio waves, or anything else we use for that matter...

We have animals on this planet that have abilities that we can't even describe...

How does a animal return to where it was born to reproduce???
My guess is that the animals have a ability that we either lack, or ignore...

One of the best examples of hidden communication is when an entire flock of birds turns at the same time...
This has been studied for years, yet we are no closer to knowing the answer, than when we started...

If Fermi was right and there is an civilization somewhere that is highly advanced and that they should have visited by now, why would they even bother to let us know they existed???
Imagine that you are one of the beings from this advanced civilization... Would you risk exposing yourself to us??? With all of the radio transmissions floating around in space that we send out, they would already know that this is a planet that is constantly in turmoil, and worse yet, has all sorts of nasty bacteria and viruses floating around...

I am all for finding someone else out there, but I am not so sure that a highly advanced civilization would feel the same way about us... What could they possibly have to gain from us???

I would be willing to bet that if there is a civilization out there that is much more advanced than we are, they probably know we are here, and have already looked to see the pros an cons of announcing their presence...

They are probably just sitting back and watching to see what we do...

Just my two cents...

I think that aliens will not be ignorant of radio waves, even if they use something completely different. It's a phenomenon that is present throughout the whole universe and impossible to miss. In fact, knowledge of the electromagnetic spectrum is just about the only thing we can assume of them, and the only thing they can assume of us. It's the obvious medium for making contact.

Even if they intended to not contact us, they might still leave tell-tale signs of their existence. It might be possible to detect unintentional emissions that are a product of their industry or communications.

As for aliens being cautious of our germs and viruses, I don't think that's going to be a problem. After all, humans don't catch tree diseases or fish diseases and the genetic differences between aliens and earth life will be vastly greater than between humans and trees.

I have some observations about why the Galaxy is apparently not populated. We have been searching now for maybe 30 years or so and as such we can be somewhat sure that there are no purposive electromagnetic emissions or transmissions out to almost 100 light years.

Let's say though that the distance to a "habitable" planet is just 10 light years. At one tenth the speed of light it would take a journey of 100 years to reach the next habitable planet. (ignoring relativistic effects that would not be too great at this speed This would require a multi-generational commitment on a ship that carried all of the life support and knowledge that the explorers would need both on their trip and to start anew on the next planet--let's assume that : the Aliens are about as long lived as us, that they know where they are going and they have solved the cosmic ray problem.

Implicit in this scenaro is the fact that they would probably need to regenerate their food, water and "air" and probably have a nuclear source of ion propulsion.

Let's assume that a civilization would be willing to undertake this 100 year odyssey and continue it with future generations after several hundred years of colonizing a given planet. I assume that they would not try to colonize a planet that was alredyknown to have intelligent life--would they undertake a 100 year journey just to visit --even if they announced their intentions and were welcomed 100 years into the future.

Knowing where a habitable planet is would be a difficult thing to achieve. They probably wouldn't set off not knowing where they would wind up . This is all the more apparent when you consider that the nearest star (not necessarily nearest habitable planet ) is more than 4 light years away.

It is not likely that they would wander around looking to find a suitable place for colonization--although we sort of did that here on earth with iur early explorers.

[It is with some certainty now after 30 years of looking, that there are no emissions or transmissions out to 10 light years. It is also apparent that there may not be any out to 100 light years.

The band of habitability for an Earth-like planet is very narrow. The conditions are finely balanced that give us our liquid water, atmosphere and temperate climates. This delicate balance gives rise to what some consider to be evidence of a DESIGNER.

None the less, let's assume that there is an Earth-like planets suitable for habitation every 100 light years --even though we haven't heard from them. The amount of stars in this distance is not large . The "MILKY WAY" Galazy is 100,000 light years across and only 1000 light years thick outside the central bulge. It contains between 200 Billion and 400 Billion stars (here Billion =10**9 or 1GIGA)

If we assume homogeneaity in star and planet distribution that would mean that there are still 250 million habitable planets.

Sounds like a lot of planets refining this to one habitable planet every 1000 light years drops the number to 2500 planets in the galazy. Check my math on this --.


This would require a trip of 10,000 years at one tenth the speed of light.
So that's why I think "THEY" are not here--but maybe some day we can hear"THEM"

[More fuzzy math :

Let's design a ship that would undertake a multi-generation trip to a planet that is many light years ahead. I am assuming that it could be assembled in orbit and weigh about the same as the new Airbus which I will conveniently assume would weigh 320,000 pounds (all the rest of the world will have to convert to the KGS system).

Using Newtons F=ma lets see how a force of 10,000 lbs thrust would accelerate a mass of 320,000/32 =10,000 slugs (yes slugs!)

Ignoring any relativistc effects we have:

a=m/f
a=10,000/10,000 =1 foot per sec per sec of acceleration

one tenth the speed of light would be 18,600 miles per sec or:
18,600 times 5280 = 98,208,000 seconds

now there are 365 x 24 x 60 x 60 =31,536,000 seconds in a year

so in a little over 3.5 years (factoring in relativity) this ship could be cruising to the stars at one tenth the speed of light. It would take this long to turn the engine around and then slow back down to zero velocity. So a trip out to 1 light year would be a "snap" out to 100 or 1000 would be quite an undertaking.

As we have siad on this board before the Cosmic ray problem would have to be solved. We are probably not too far from being able to build this kind of ship right now--don't know how long it would be before we know where to send it.

I believe that if there is what we call an Earth-like, habitable planet then life will start on that planet. If the planet has been there for 5 billion years, then I believe that the life that started would evolve intelligence.

Since the Galaxy is perhaps 12 Billion years old then many such planets probably have already evolved intelligent life. Of course one does not know how long a civilization can exist without destroying itself after acquiring the means to do so.

We may have no place to go even if we could get there.

I believe that if there is what we call an Earth-like, habitable planet then life will start on that planet. If the planet has been there for 5 billion years, then I believe that the life that started would evolve intelligence.

Since the Galaxy is perhaps 12 Billion years old then many such planets probably have already evolved intelligent life. Of course one does not know how long a civilization can exist without destroying itself after acquiring the means to do so.

We may have no place to go even if we could get there.

And we may not be able to talk back to them if and when we receive their signal because they will be "dead." But it will be a great day on earth when we do know for certain that someone else is out there!!! I get goose bumps just thinking about it.