Likelyhood of Extraterrestrial Intelligence

[DrChinese]

Originally posted by drag
Greetings DrChinese !

I don't know. How narrow and why ?
After all, the "surge" of complex life forms
on the planet began just a few million years
ago. I don't know what triggered it (there was
a lot of orgamisms for billions of years before
that). Also, if it weren't for that Yukatan
astroid, you'd probably have huge dino-cities
covering the planet by now and dinos expanding
in the galaxy. I recently saw a program where
they were talking about a dinosour just a bit
larger than us that had a brain as complex as
that of our pets. It evolved "just" before the
above "accident".

Mammals started about 120+ million years ago. I don't see anything that requires that an intelligent species would come to dominate a planet as we do (I guess "dominate" may be subjective). Anyway, what I am saying is that there could be 1000 planets with tigers and monkeys as the highest intelligent lifeforms for every one that ends up with intelligent civilizations.

Hmm... I suppose that the Moon did help a bit,
but I think that surface instabilities and
planetery rotation have considrable roles too.

According to the latest estimates that "some"
buried ice could've covered the entire planet's
surface (if it were flat) and be 100 meters deep.
There's also the part about oxygen on Earth
being freed by microbes or something over the years.

Logically, buried ice itself means very little. Look at Antarctica - not exactly a hotbed. And the oxygen on Earth came from our CO2 atmosphere. So there is clearly a minimum size of planet - so as to provide an atmosphere.

As for the tides, I admit that rotation of the planet makes a difference. The planet would then need to rotate, which it probably does anyway to insure that the temperatures don't get too extreme. So I am not certain I am right about the moon being necessary.

But I think the ocean is a requirement so as distribute early life forms over the planet to give them new areas to evolve. Patches of water would essentially require all of the early evolution - before the advent of legs - to occur in a tiny area.

Mars is too far-away from the Sun and hence
too cold, and it has a lower mass which also
makes the atmosphere part problematic.

BTW, if all the CO2 that is estimated to be in
the "dirty" ice covering its poles is relased
into the atmosphere the planet can "heat up"
considrably, I think.

An atmosphere from buried ice? I think you watched "Total Recall" too many times. (Just a little joke.) That's definitely a stretch, because it would have to melt, release an entire planet's worth of gas, and then not blow out into space. Considering we are trying to talk about the probabilities, not the possibilities, I say that doesn't fly.

I would be the last person to deny the possibility of another intelligent species in the universe. Obviously, what was possible on Earth is possible elsewhere.

I'm not certain about the range being so limmited.
If Earth was as far as Mars it is possible that
life could form and exist there. (Denser CO2
atmosphere - higher tempratures.) And, like I
mentioned before, there are other options
(like the case of Europa).

As for eccentricity, I don't have the scientific
data and calcs to support this, but I think that
planets at relativly close proximity to the star
(below say half a billion miles for Sun-like and
smaller stars) would not ussualy have very eccentric
orbits becuase of the way they are formed.

Live long and prosper.

I would grant that life could possibly exist on a planet whose orbit went out farther than Earth's, not sure about all the way to Mars. But it couldn't go much farther in, either. Maybe the range is 80-110 millions miles from the Sun. That would need to be the limits for the eccentric orbit as well.

 

[drag]

Greetings !

Originally posted by DrChinese
Mammals started about 120+ million years ago. I don't see anything that requires that an intelligent species would come to dominate a planet as we do (I guess "dominate" may be subjective). Anyway, what I am saying is that there could be 1000 planets with tigers and monkeys as the highest intelligent lifeforms for every one that ends up with intelligent civilizations.

Ooops... Did I say "a few million years" ?!
I meant "a few hundred million years"(400-500).

But, after that I made a point about the
dinasours heading in the big brain direction too.
So, this may not be a must, but I think that
given sufficient time (say up to a billion years),
complex life is likely to evolve "intellegent"
(at similar to our level) beings. It took a lot
less on Earth, after all.

Then again, dolphins have brains that are larger
than ours and yet you don't see them building
civilizations. I guess this is an open question
until we get some alien "examples".

Originally posted by DrChinese
An atmosphere from buried ice? I think you watched "Total Recall" too many times.

Arnold Shwartzneger rocks !

Originally posted by DrChinese
That's definitely a stretch, because it would have to melt, release an entire planet's worth of gas, and then not blow out into space. Considering we are trying to talk about the probabilities, not the possibilities, I say that doesn't fly.

Yeah, it's a VERY long shot, but I once considered
what would happen if we nuked the poles
"big time". All that CO2 got'ta add a degree
or two...

Live long and prosper.

 

[Pauly Man]

I remember having a huge debate with one of the Physicists at uni about this. He had just written an article on the probability of intelligent life forming in the universe, and came to the conclusion that it wasn't too unlikely. Can't remember the exact figures.

In it he used statistical analysis to arrive at his answer. He used the evolution of life here on Earth as his statistical sample. A smaple size of 1!

I argued with him for an entire leture about that. I tried to tell him that the sample size was 1, and he tried to use the fact that life on the separate continents had been evolving seperately for millions of years, and that on each continent there had evolved a relatively intelligent life form had evolved. And therefore it was a sample size of greater than 1. Further more that each continent had experienced differences and therefore the samples were independant.

To me that was a load of crap. The sample all came from the same blue green planet. That is a sample size of 1, with a few independant replicates. If he had provided evidence of evolution on Mars, perhaps I would have backed down.

I think it was Loren Booda who said earlier that a sample size of one tells you very little, and that I agree with.

Anyway. Basically all I'm saying is that life on Earth probably tells us very little aboutlife elsewhere. That being said I agree with CJames, in that if intelligent life exists in our galaxy and it is at all common, we would probably have seen it evidence of it by now.

 

[O Great One]

Intelligence responsible for life

Did the Intelligent Designer(s?) create life elsewhere?
Interesting thought...

 

[DrChinese]

Originally posted by Pauly Man
I remember having a huge debate with one of the Physicists at uni about this. He had just written an article on the probability of intelligent life forming in the universe, and came to the conclusion that it wasn't too unlikely. Can't remember the exact figures.

In it he used statistical analysis to arrive at his answer. He used the evolution of life here on Earth as his statistical sample. A smaple size of 1!

Where to start? Single positive indication of life in the universe, our own? So of course you are right to criticize that the sample size is way too small.

But I think it is even worse than that. It needs to be a random sample. Starting out with a positive that supports your position? I think that borders on scientific fraud. If, of course, it was about something other than intelligent life in the universe, for which this problem has long been recognized.

So I agree with you 200%.

 

[Rashid]

1962

In 1962 (forgot the exact date) an object was spotted over the Atlantic Ocean and traveled to Arizona in 16 minutes. This object was detected on 2 different types of RADAR systems and fighters scrambled after it. This is all documented and fact.
At first the Military claimed it was an asteroid. This would make sense since according to witnesses it was very bright. But 1,000s of other people in different cities saw it maneuver, stop occasionally, and travel back on its' path. This is why the Military scrambled fighters. Do you think they would be able to catch a meteorite that can travel from the Atlantic Ocean to Arizona in 16 minutes?
Apparently the object exploded over the Arizona desert for unknown reasons.
This object was no atmospheric phenomena since it was tracked on 2 Different RADAR systems. Not to mention if it was an atmospheric phenomena then why would the military scramble fighters over it?
The Military then said it was a jet exercise since those were highly popular in that era. They made a clever mistake when they said it happened over a period of hours. The Military used Zulu time and Pacific time in their report. When you calculate it out by witnesses and by their mistake it turns into 16 minutes. Not hours.
What man made object can travel from the Middle of the Atlantic Ocean to Arizona in 16 minutes making incredible maneuvers and hovering over cities? I just call it a UFO. Doesnt mean it's extraterrestrial though. But it sure makes you think about it.

 

[CJames]

Rashid, can you please provide a link to an article about that as I would really like to question its validity.

 

[Rashid]

History Channel

Actually without hype it was on I believe the Discovery Science 2 nights ago here in Seattle WA I believe. If it wasnt on Discovery Science it was on Sci-Fi or the History Channel. I always seem to catch those episodes. I usually don't listen to them since they are full of Hollywood hype and exageration but this show presented it's information without overexagerated voices or people. It simply stated the facts as if it was doing a presentation. I think I caught it on the TV at about 1-2:00am Pacific time.
Most of those TV shows that show UFO evidence don't hold much ground or seem overdramatic for me to watch. But this was a show that covered various topics so they couldn't stay on the UFO topic too long.
I did a quick Google search and here's what it yeilded. http://www.nicap.dabsol.co.uk/1962.htm This site just lists various UFO sightings on different dates.
http://www.ufo-ufo-ufo.com/53.htm This is a site I just found doing the same search. Seems kinda thrown together and thus might loose credibility. I know that what I see on the Television might be wrong information but the program I watched took the time to interview people who witnessed the sighting (could be actors) and provided Official government documents from the Freedom of Information Act about the problem. They even shown the news paper articles of the first and second Military explanations of the incident.
Sorry to not have the exact information the show presented available at this moment but this is what I watched and remembered about the show. I rarely forget such things. The only thing I seem to forget are womens names.

Rashid

 

[Rashid]

More Evidence and good Evidence

http://www.nicap.dabsol.co.uk/bigsur1.htm

It seems that this site is all about UFO's and doesn't really touch on Extraterrestrial activity. It talks about theories about UFO and the connection to "aliens" but really focus's on actual proof of UFO's.
I highly recommend checking it out.
http://www.nicap.dabsol.co.uk is the main page for the site. The other link above is an interesting event I never really knew about.

Rashid

 

[HazZy]

maybe if one day we can create life in a laboratory (come on now, it shouldn't be THAT difficult) i will consider the posibility of life being abundant in our universe, but until that day i'll consider it a very very rare gift.

 

[drag]

Greetings !

Welcome to PF HazZy !

Originally posted by HazZy
maybe if one day we can create life
in a laboratory

What do you mean ?
In many ways we have, already.
Do you mean watch it form from chemicals
into organic molecules and single-cells ?

Live long and prosper.

 

[HazZy]

thanks!

life from non-life hasn't been accomplished yet to my knowledge. in fact i believe the law of biogenesis is still alive and kicking. i may be wrong, but I'm pretty sure about this one, if you know otherwise please inform .

 

[Royce]

How do we know that they didn't? It's possible that we ourselves are a result of their seeding our planet with DNA. That would certainly be more plausable than making the trip with thousands of settlers over vast distances for long periods of time.
Another thought, maybe they did, toward the center of our galaxy where the stars are not so far apart and ingored the outskirts where the pickin's are so slim. It will be generation before we could ever know.

 

[drag]

Greetings !

I'd like to point out that we are living in
the most likely strip (about 10-15 phousand
light years across) of the galaxy in terms
of potential formation of life. The center of
the galaxy is too violent and the stars have
too much metalicity. The outskirts have stars
with low metalicity. The centers of the galactic
"arms" aren't very hospitable either. We're on
"prime" galactic realestate, you might say.

Live long and prosper.

 

[CJames]

Originally posted by Royce
How do we know that they didn't? It's possible that we ourselves are a result of their seeding our planet with DNA.

That is indeed a possibility. However as I said we would expect to see more evidence.

That would certainly be more plausable than making the trip with thousands of settlers over vast distances for long periods of time.

[??] What do you mean? In order to seed a planet you have to have been there...

Another thought, maybe they did, toward the center of our galaxy where the stars are not so far apart and ingored the outskirts where the pickin's are so slim. It will be generation before we could ever know.

The way life has spread so far on Earth has demonstrated that species don't move together in large groups. Instead, they simply expand outward, evolving along the edges of migration as conditions change. Even on the short time scale, a collony of bacteria doesn't move from area to area, it spreads.

It will be a very long time before we can know for sure that this galaxy is empty, and as a (future) scientist I don't wish to make assumptions. I'm simply stating that the most likely possibility seems to be that this galay is entirely or nearly devoid of intelligent life anywhere but on Earth.

 

[CJames]

We're on
"prime" galactic realestate, you might say.

Which is why we should expect to find extraterrestrial life right here if it is very common.

 

[pete1141]

extraterrestrial life

I think the notion of E.T life falls into the same category as believing in life after death. It's just wish fulfilment. There seem to be an almost infinite degree of variation in forms of cosmic bodies both inside and outside our own galaxy. So why would it be unthinkable that we were unique ? I am not a mathematician /statistician, but would love to know what the odds are or even if it is possible to work out the odds mathematically. My intuitive guess is that the odds for and against ,given present knowledge, are even. I personally think we are unique and all the UFO watchers and yearners for ET life are kidding themselves. I will donate a large summ of money to charity if you can prove me wrong.

 

[Stellar Tourist]

If life is found, one thing is certain they will be no where near our level of technology or civilisation. They will be either so far behind or way ahead of us.

"human beings do not carry civilisation in their genes"

M Mead NY

 

[Chronos]

Statistical treatments are interesting, though controversial. Even though this planet is a sample size of one, the fact that 'intelligent' life exists here does have certain implications. Given the sun is a very average main sequence star, it is reasonable to assume a probability that:

a] stars similar to our sun have companion planets
b] some such planets have chemical compositions similar to Earth.
c] some of these planets have orbits amenable to life.
d] life is likely to arise on such planets.
e] intelligent life will likely to evolve on such planets, given enough time.

Given the large number of stars similar to our sun, even assigning modest probabilities to each of these assumptions results in many planets inhabited by intelligent life forms within this galaxy.

It is, however, very improbable that any two planets, are sufficiently near in space, time and technological capability, to detect each other. We are not detectable by any other civilization, with technology similar to ours, at a distance of more than about 50 light years. Since we have not discovered super-luminal means to send messages, we are not detectable by any other civilization in the universe beyond this distance, unless they have super-luminal means of travel or detection.

The question then becomes why would such an advanced civilization need or wish to disturb one as primitive as ours [assuming they even considered us 'intelligent']? My guess is they would have laws forbidding tampering with us, or our habitat [prime directive thing]. We already know what happens on this planet when advanced societies collide with primitive societies. If technologically far advanced societies exist, and are aware of us, I suspect they would be very careful how they interact with us. Their scientists, most likely, would insist on it.

 

[pete1141]

Chronos . I think your argument is very well put together . However because of the extreme distances involved we ,in al likelyhood will never know the truth. I am a sceptic and am not convinced . I still say there is just as much possibility of there being no life elswhere as there is life. I think we are driven in these arguments as much by our human driven desires and emotions, as by cold logic. The universe contains vast areas about which we know nothing . Objects which defy physical description ,at least by our puny human brains , abound. Yet we are still convinced that there is a 99.99999% possibility that life exists elswhere. I say there is a counter argument that there is a 99.99999% possibility that life does not exist elswhere which people do not like to contemplate ,because of the dread of the possibility of our utter isolation in the universe.

 

[Nereid]

Statistical treatments are interesting, though controversial. Even though this planet is a sample size of one, the fact that 'intelligent' life exists here does have certain implications. Given the sun is a very average main sequence star, it is reasonable to assume a probability that:

a] stars similar to our sun have companion planets
b] some such planets have chemical compositions similar to Earth.
c] some of these planets have orbits amenable to life.
d] life is likely to arise on such planets.
e] intelligent life will likely to evolve on such planets, given enough time.

Given the large number of stars similar to our sun, even assigning modest probabilities to each of these assumptions results in many planets inhabited by intelligent life forms within this galaxy.

Some time ago I amused myself by making some estimates of probabilities like these. With a twist; instead of a single number, I made two guesses for each - 'seems very unlikely to be higher than this', and '(ditto) lower'.

First though, what is the current state of observational data, relevant to this question? Sun-type stars are reasonably easy to see, at least out to several thousand parsecs. While I doubt anyone is actually counting them, from sample, we could estimate there are ~100 million in the Milky Way (+/- 1 OOM).

Of the ~100 exoplanets detected so far around main sequence stars, none are of ~Earth mass. While most of the parent stars of these planets are ~Sun mass, IMHO, there's simply too little data to draw well-constrained conclusions about how common 'our' solar system is.

- - - - end of data, start of speculation (Milky Way) - - -
'Sun'-like stars: 1 billion (Hi); 10 million (Lo)
... with companion planets: 800 million; 100,000
... and chemical compositions similar to Earth: 300 million; 1,000
... with orbits amenable to life: 100 million; 10
... with life: 80 million; 1
... with intelligent life: 1,000; 1

In the next two decades I expect that the probability ranges for each of Chronos' steps will be better constrained, except for the last step. This improvement will come from programs to detect exo-planetary systems, and the finding of (extinct?) life on Mars and/or Europa (or not).

It's the last of Chronos' steps that I think is the most problematic. Making a probably unjustified generalisation, it seems that physics/astronomy folk believe intelligent life is pretty much inevitable, once life starts on a planet - as Chronos says, it's just a matter of time. OTOH, biology folk tend to believe intelligent life is pretty much a fluke; there's nothing in evolution or the geological history of the Earth that favours intelligence. Although it's somewhat dated now, the http://www.planetary.org/html/UPDATES/seti/Contact/debate/default.html gives a flavour of this difference.

Of course, the Milky Way is but one (spiral) galaxy among billions ...

 

[Chronos]

I try not to get philosophical about matters of science, but, I think it is just as arrogant for us to assume we are the center of the universe as it is to assume we are its most unique product... after thought. assuming life arises on any planet, evolution will compel it to become increasingly intelligent to compete. We have numerous intelligent species on this planet. Unfortunately, we fail to acknowledge the nature and level of that intelligence. One night I drank too much and slapped my dog upside the head for absolutely no reason. The next morning I woke up and the old pooch was laying there right beside me licking my hand. Who was more intelligent?

 

[Chronos]

Footnote: I am subscribing to the principle of mediocrity. There is a reasonable probability we are pretty average when it comes to sentient life forms that have ever evolved over the history of the universe. The premises I used [at least 1 thru 4] look fairly solid. The timeline [how many are within communication distance at any given time?] appears to be the main issue. That possibility appears to be the most remote. Perhaps the silence of the cosmos is testimony of how rare civilizations arise within communication distance of like civilizations at the same time. That premise is difficult to disprove given our current state of scientific knowledge.

After-after thought. So, write to your political representative [senator, or whatever you call them] and strike up this conversation:

Citizen: Hey Senator [minister or whatever], I just had a great idea, let's spend billions to build a beacon that will last for a billion years and advertise the fact we were once here.

Senator [minister or whatever]: I like your idea, but, since we will all be dead in a billion years and nobody will give a comets tail, I am going to raise your taxes to defray the cost of answering silly questions like yours.

 

[Nereid]

I try not to get philosophical about matters of science, but, I think it is just as arrogant for us to assume we are the center of the universe as it is to assume we are its most unique product... after thought.

For all we know, the most 'advanced' form of life in the universe is dark matter creatures who inhabit the halos of dwarf galaxies!

Surely it's more important to build from existing knowledge than to make assumptions of any kind?

assuming life arises on any planet, evolution will compel it to become increasingly intelligent to compete.

Yes, that's a common view of many physics and astronomy types, including Sagan. As I said earlier, biologists generally have a hard time with this line; there's precious little to show evolution produces direction of the kind you assert. Further, complex life is pretty recent - why did it take so long after life got going for it to show its face? And, talking of complex life, why not plants? After all, as complex life, plants were there way before animals!

 

[Nereid]

Footnote: I am subscribing to the principle of mediocrity. There is a reasonable probability we are pretty average when it comes to sentient life forms that have ever evolved over the history of the universe.

That's fine, except it doesn't address Fermi's question (Where are they?)

Assume it takes 5,000 years for a sentient life form to travel from one stellar system to another, once it reaches homo sap's current level of understanding of physics and astronomy. In much less than one galactic year (~200 million years) the whole Milky Way would be thoroughly colonised. If sentient life were reasonably probable, the Milky Way would've been colonised well before the Sun was formed.

The premises I used [at least 1 thru 4] look fairly solid.

Agreed, and once we've done some more digging on Mars, as well as Europa (and Ganymede and Callisto), we'll have much more to go on re these.

... including factors often missed in these kinds of discussions; e.g. probability of life on the moons of gas giants (most discussions quickly dive into estimates of 'Earth-like planets').

But how will we ever address the question of whether 'life not like us' exists?

 

[Chronos]

The issue, I think, is how probable that a civilization, such as ours, can find another civilization near enough, intelligent enough, and technologically able to communicate with us at any given time?

 

[Nereid]

How would you go about making an estimate of that probability?

 

[Chronos]

A rough, though reasonable [imo] way to estimate that probability is

http://www.pbs.org/lifebeyondearth/listening/drake.html

I do agree, however, that approach only considers the probability of how many other civilizations exist in the galaxy. It does not consider the likelihood that any other is sufficiently near and technologically compatible for us to communicate with. That probability, I think, is the one that best explains the Fermi objection.

 

[Pythagorean]

maybe we'll design a ship that hitches rides on planets and asteroids to conserve fuel.

furreal though:

in short:
we could establish stations on nearby planets and begin mining their resources.
-------------------------------------------------
in breaths:
If we started colonizing planets and establishing stations and finding ways to mine resources, we could eventually come to a situation where we're using say, Mars to produce and manufacture interstellar ships; and have drop ships from various planetary stations dropping the needed supplies on Mars that have been gathered from various planets where we've established resource-gathering stations.

It probably couldn't be established in our lifetime, but it seems like the only way to go about it if you want to be able to produce the resources required for something like planetary colonization.

----------------------------------------------

Also, whose to say we won't find an efficient way to manipulate atoms in such a way that we can turn any element into any element?

Basically, I refuse to be amung those whose ancestors didn't believe a TV or a satelite were ever possible.

The biggest problem would be waiting for the discovery that sparks the interest of an investor by implying that such technologies are actually persuable AND profitable.

edit: pursuable?

 

[xy]

the life that's out there might be what you all have least expected and all keep that one to myself