Is there life in the universe, and if so has it visited Earth?

[Schrodinger's Dog]

http://personalgrowthcourses.net/video/ufo_videos [Edit by Ivan: link updated]

Bearing in mind this post by Ivan in the UFO stickied thread.

10,000,000,000,000,000,000,000 stars in the universe, a very conservative estimate but let's assume it's correct.

And the Drake equation is possible given the criteria and confirms there must be intelligent life: maybe in the galaxy, but definitely in the universe by the laws of probability.

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

And apply this to the universe, in a sort of what if way assuming this is fairly typical.

My question is two fold, we're fairly certain that probability indicates there must be life elsewhere in the universe, and assuming evolution works in simiilar if not the same ways elsewhere: it's fair to claim that their is intelligent life, so we accept life is out there? Yes/no?

Now given the conclusion is yes, do you think the intelligent life has visited Earth?

 

[DaveC426913]

"...we're fairly certain that probability indicates there must be life elsewhere in the universe..."
This is highly refutable.

However, I am personally fairly confident that hydrocarbons will do that crazy thing they do under the right conditions elsewhere. It's a question of how many factors have to be stacked in the favour of nurturing their evolution.

But no, I just don't think intelligent life has visited us.

 

[Schrodinger's Dog]

"...we're fairly certain that probability indicates there must be life elsewhere in the universe..."
This is highly refutable.

Agreed but this is what if and of course using logic it's fairly certain given the criteria, not absolute but fairly probable.

However, I am personally fairly confident that hydrocarbons will do that crazy thing they do under the right conditions elsewhere. It's a question of how many factors have to be stacked in the favour of nurturing their evolution.

But no, I just don't think intelligent life has visited us.

I think you're right. but I think given 4.7 billion years or so, it will happen eventually, but of course that is speculatory and assumes of course we may find intelligent life first. Of course if we conclude that we may travel to the stars then the probability wise it is much more certain.

 

[Ivan Seeking]

We can hardly address this issue without considering the following; also from the Napster:

INFLATION-THEORY IMPLICATIONS FOR EXTRATERRESTRIAL VISITATION
J. Deardorff, B. Haisch, B. Maccabee and H.E. Puthoff
Journal of the British Interplanetary Society, Vol 58, pp. 43-50, 2005.
http://www.ufoskeptic.org/JBIS.pdf

If the speed of light is the ultimate limit for speed as is suggested by Special Relativity, then depending on how common intelligent life may be, it might not be practical for any beings from one world to travel and meet beings from another. The distances and energy requirements may simply be too large for any race; anywhere or in any time. Depending on the chance of where life might arise, obviously there is always the possibility of having neighbors a light year or two away, which might be a practical distance to traverse. However, if some of exotic concepts from physics should pan out, or if we were to discover some other physics that allows us to somehow bypass Einstein's suggested limit, and again depending on how common intelligent life may be, and depending on how common the discovery of a means to interstellar travel may be, the chance of an encounter, or even of many encounters with many different beings from around the galaxy, may range from infinitely small, to nearly one, over some interval of time.

Consider that when I started here at PF, the argument was made that ETs could likely never find us; that it would be like finding a particular grain of sand at the beach. Now, even we are discovering ways to identify earth-like planets.

It always comes down to what might be possible given another race of beings who are a million, or even a billion years ahead of us. So I refuse to vote in your poll since I don't know what might be possible if ET has a billion years headstart; or even what might be possible here on earth, tomorrow.

 

[Ivan Seeking]

I will say this: If I knew that interstellar travel were possible and practical by some physics that we have yet to understand, I would probably believe that any number of the most impressive UFO cases were in fact encounters with ET without even batting an eye.

 

[Bradracer18]

You guys are talking waay over my head here, but if something came in through the atmosphere, wouldn't we see it coming(in space), and definitely when it came into the "sky"? I'm talking about like the military, not us as regular "joes".

 

[Ivan Seeking]

Given a million years more advanced technology than we have, how could we know? We would have to know how they could get here in order to know if we would detect them.

Presently there is a movement to identify all potential earth-crossing asteroids and comets. If we can't even do that yet, how would we spot something even as plain as an approaching space capsule? As for being in the atmosphere, have you heard of stealth technology[ had already by those clothed apes on the third planet?]

 

[radou]

If intelligent life ever visited us, we wouldn't know, since it is not likely that it would be interested in us at all.

 

[George Jones]

If intelligent life ever visited us, we wouldn't know, since it is not likely that it would be interested in us at all.

The ending of http://www.youtube.com/watch?v=9JSR_6qfXTg" seems appropriate.

 

[Schrodinger's Dog]

The ending of http://www.youtube.com/watch?v=9JSR_6qfXTg" seems appropriate.

Many a true word spoken in jest

There really is bugger all down here on Earth

Just so we can apply the drake equation and get some numbers? What do you all think are reasonable values for

See link for options, but any value can be chosen, there are plenty of links that have more options.

N* = the number of stars in the Milky Way galaxy:100 billion

fp = fraction of stars with planets around them:5%

ne = number of planets per star ecologically able to sustain life:.33%

fl = fraction of those planets where life actually evolves:2%

fi = the fraction of fl that evolves intelligent life:40%

fc = the fraction of fi that communicates:25%

fL = the fraction of the planet's life during which the communicating civilizations survives:I'd estimate going on us about a billion years, if I'm optimistic? But this question is unanswerable.

Reasonable figures what would you chose?

 

[radou]

The ending of http://www.youtube.com/watch?v=9JSR_6qfXTg" seems appropriate.

Hits the spot.

 

[SGT]

Many a true word spoken in jest

There really is bugger all down here on Earth

Just so we can apply the drake equation and get some numbers? What do you all think are reasonable values for

See link for options, but any value can be chosen, there are plenty of links that have more options.

N* = the number of stars in the Milky Way galaxy:100 billion

fp = fraction of stars with planets around them:5%

ne = number of planets per star ecologically able to sustain life:.33%

fl = fraction of those planets where life actually evolves:2%

fi = the fraction of fl that evolves intelligent life:40%

fc = the fraction of fi that communicates:25%

fL = the fraction of the planet's life during which the communicating civilizations survives:I'd estimate going on us about a billion years, if I'm optimistic? But this question is unanswerable.

Reasonable figures what would you chose?

Using your figures and supposing Earth like planets last for 10 billion years, we arrive at 330 technological civilizations simultaneously in the Galaxy at any moment.
I think your estimate of one billion years for the survival of a communicating civilization is very optimistic. Ours has less than 100 years and we have risked to destroy it in a nuclear war and are now trying to destroy it by changing the ecosystem. A pessimistic estimate would be 100 years.
Using the geometrical mean between the two estimates, we arrive at around 300000 years. This brings the number of communicating civilizations to 1.
Hey, it´s us !

 

[Schrodinger's Dog]

Using your figures and supposing Earth like planets last for 10 billion years, we arrive at 330 technological civilizations simultaneously in the Galaxy at any moment.
I think your estimate of one billion years for the survival of a communicating civilization is very optimistic. Ours has less than 100 years and we have risked to destroy it in a nuclear war and are now trying to destroy it by changing the ecosystem. A pessimistic estimate would be 100 years.
Using the geometrical mean between the two estimates, we arrive at around 300000 years. This brings the number of communicating civilizations to 1.
Hey, it´s us !

Seems a bit pessimistic but I'll go with it, anyone else want to chip in some more accurate if you can call it that: guesstimates to the other variables?

 

[danscope]

You guys are talking waay over my head here, but if something came in through the atmosphere, wouldn't we see it coming(in space), and definitely when it came into the "sky"? I'm talking about like the military, not us as regular "joes".

Hi, We get little snowballs from space all the time. We occasionally get bigger ones. Earth , long ago...long long ago may have acquired it's oceans from a
comet impact...or even several comets. When you are talking about billions of years, anything is possible. It is also quite plausible. An ice comet impacting after our oceans had arrived would welcome frozen microbial life from another comet impact...a cosmic refrigerator so to speak. Just a theory.
Dan

 

[DaveC426913]

... are now trying to destroy it by changing the ecosystem...

It is not our ecosystem donig the signalling. We could live on a concrete ball, eat protein paste made in factories and still keep up interstellar communications. The ecosystem just serves to make for a pretty view.

 

[SGT]

It is not our ecosystem donig the signalling. We could live on a concrete ball, eat protein paste made in factories and still keep up interstellar communications. The ecosystem just serves to make for a pretty view.

I am not so sure. Vegetable life and the green algae in the ocean provide us with oxygen from the carbon dioxide responsible by the major part of the greenhouse effect. The growing temperature is in the origin of phenomena like El Niño, that cause droughts and inundations all over the world.
Changing to an artificial nutrition would only add to the greenhouse effect. And from where would the oxygen come?

 

[DaveC426913]

I am not so sure. Vegetable life and the green algae in the ocean provide us with oxygen from the carbon dioxide responsible by the major part of the greenhouse effect. The growing temperature is in the origin of phenomena like El Niño, that cause droughts and inundations all over the world.
Changing to an artificial nutrition would only add to the greenhouse effect. And from where would the oxygen come?

We would have to use more energy to extract it from existing oxides. (It's not like the oxygen is actually going anywhere, it's just getting bound up.) Of course, this would create more waste heat, but there's no lack of the raw elements and there's no lack of energy to process them as long as the sun shines.

In the near future, while we may wipe out much of our existing ecosystem, I seriously doubt that we could damage the Earth so badly, so rapidly that we would kill ourselves off b efore we could react. Even if it only took a blink of an eye, like centuries or millenia, we would turn our resources towards survival.

And of course, during all this, our efforts to find other habitable planets, far from being extinguished, would be doubled*.



*(not "redoubled". Man, I hate that word.)

 

[SGT]

We would have to use more energy to extract it from existing oxides. (It's not like the oxygen is actually going anywhere, it's just getting bound up.) Of course, this would create more waste heat, but there's no lack of the raw elements and there's no lack of energy to process them as long as the sun shines.

In the near future, while we may wipe out much of our existing ecosystem, I seriously doubt that we could damage the Earth so badly, so rapidly that we would kill ourselves off b efore we could react. Even if it only took a blink of an eye, like centuries or millenia, we would turn our resources towards survival.

And of course, during all this, our efforts to find other habitable planets, far from being extinguished, would be doubled*.
*(not "redoubled". Man, I hate that word.)

I am sure that we can´t destroy entirely the ecosystem. But we can damage it so badly that the lack of resources can make it difficult to keep the waste civilization.
Nature can´t defend itself, but it can avenge.
My point is: our civilization has a self destructive tendency. Perhaps this is a common trait of all technological civilizations. If this is true, the medium estimate of 300000 years for the life of a civilization does not seem so pessimistic.
Of course, since ours is the only civilization we know, we cannot extrapolate its traits to any other with certainty, but it is our best guess.

 

[Schrodinger's Dog]

I am sure that we can´t destroy entirely the ecosystem. But we can damage it so badly that the lack of resources can make it difficult to keep the waste civilization.
Nature can´t defend itself, but it can avenge.
My point is: our civilization has a self destructive tendency. Perhaps this is a common trait of all technological civilizations. If this is true, the medium estimate of 300000 years for the life of a civilization does not seem so pessimistic.
Of course, since ours is the only civilization we know, we cannot extrapolate its traits to any other with certainty, but it is our best guess.

Actually I disagree were still here, and so 300,000 would be logical if you see what I mean if we'd destroyed ourselves but we haven't so, it's a bit pessemistic, it's as if your saying right we're all going to die soon so 300,000. but I'm ok with it, however I think about 10 million might be a compromise.

with ten million and 20% instead of 25% for the value of communicating civs, doesn't allow that but anyway. 2640

even with original stats and 100,000 years it comes out at 26.400000000000002

 

[SGT]

Actually I disagree were still here, and so 300,000 would be logical if you see what I mean if we'd destroyed ourselves but we haven't so, it's a bit pessemistic, it's as if your saying right we're all going to die soo so 300,000. but I'm ok with it, however I think about 10 million might be a compromise.

with ten million and 20% instead of 25% for the value of communicating civs, doesn't allow that but anyway. 2640

even with original stats and 100,000 years it comes out at 26.400000000000002

Of course we have not destroyed our civilization, or we wold not be in this forum.
What I mean is that we have the power to do so and there are people wo would be happy with the end of civilization.
How much fissile material is there in the former soviet republics? How well guarded is it?
With a few kg of Pu a terrorist group can make enough dirty bombs to wipe a good part of our civilization. The same can be accomplished with germs.
And for what we see, there are fanatics enough who would be happy to make civilization retrograde a thousand years.
We must not dismiss rogue countries, like Iran and North Korea, that are pursuing nuclear expertise and even in the democratic countries there are enough politicians that would gladly launch us in a destructive war.
And, as I said, our communicating civilization has not completed its first century. Will the next generations be wiser? I don't know.

 

[arildno]

aah yes. Yet again that useless&pointless Drake equation.

 

[Schrodinger's Dog]

aah yes. Yet again that useless&pointless Drake equation.

You have a better guestimate equation, as the equation notes, it's only meant to spur people to ask questions about what sort of values they would apply and why, not to be 100% accurate, so it's never intended to be really applicable anyway as the variables are unkowable.

 

[russ_watters]

Using your figures and supposing Earth like planets last for 10 billion years, we arrive at 330 technological civilizations simultaneously in the Galaxy at any moment.
I think your estimate of one billion years for the survival of a communicating civilization is very optimistic. Ours has less than 100 years and we have risked to destroy it in a nuclear war and are now trying to destroy it by changing the ecosystem. A pessimistic estimate would be 100 years.
Using the geometrical mean between the two estimates, we arrive at around 300000 years. This brings the number of communicating civilizations to 1.
Hey, it´s us !

Whether or not we are capable of destroying our civilization completely with nuclear weapons, right now we are nowhere close to being able to destroy it ecologically. If the most dire predictions of global warming prove accurate, we should start noticing some economic and social effects of it (not economic and social effects of the predictions but economic and social effects of global warming itself) in a hundred years or so. Things like New Orleans and some parts of Florida becoming uninhabitable would be the first effect and on the grand scheme not that big a deal. It is certainly not possible for us to destroy ourselves via global warming in the next 100 years.

In 1000 years, ehh, maybe, but we'll run out of fossil fuels and have converted to something else long before that. And since historically speaking it looks like we are nearing the end of an interglacial period, unless we've broken the cycle we may soon (in the next few thousand years) have to deal with a ten degree C drop in global temperatures lasting a hundred thousand years. Now that isn't even enough to wipe us out, but it will make Europe, most of North America and most of Australia uninhabitable.

Longer term than that but less predictable is the occasional continent-killer asteroid.

Humans are unique in the animal kingdom in their ability to adapt quickly to their environment through technology instead of evolution. That makes us very hard to wipe out completely.

The point: though again it is difficult to tell due to lack of information, it is not unreasonable to believe humans could be around for thousands more years, possibly even millions. The absolute limit for life on Earth is 3-4 billion more years, after which the sun's output will change significantly enough to make the planet unable to sustain life of any kind we are familiar with.

 

[DaveC426913]

aah yes. Yet again that useless&pointless Drake equation.

Aah yes. Yet again a useless and pointless comment.

 

[Ivan Seeking]

Of course we have not destroyed our civilization, or we wold not be in this forum.

What I mean is that we have the power to do so and there are people wo would be happy with the end of civilization.

This doesn't automatically suggest that all or any civilizations are doomed to self destruction. At this point, the only hard evidence that we have suggests that the chance of finding intelligent life on all earth-like planets is 100%.

 

[PIT2]

Im in no way sure or convinced, but my bet is yes. I think technical limits of travel can be broken, and i think ufo sightings on Earth suggest an advanced unknown intelligence. Not all of course, but there are some bizarre cases.

 

[DaveC426913]

...i think ufo sightings on Earth suggest an advanced unknown intelligence. Not all of course, but there are some bizarre cases.

Thing about this stance is that there isn't really much of an in-between - it's a pretty black and white issue - or might as well be.

If you grant that even one single account is bona fide, then you grant that an advanced alien civilisation is, in fact, visiting us. Once you grant that - there's no reason not go on to conclude that most otherwise unexplainable sightings are legit alien craft.

You see, this "fact" of advanced civilisations visiting us becomes the de facto simplest and most likely explanation for many otherwise very mysterious sightings. Occam's razor will be satisfied by "those alien craft".

I put to you PIT2 to ask yourself if your "not all but some" stance has less to do with how many sightings are legit, than it does with your willingness to commit to the 'believer' stance i.e. you're hedging your bets.

But I could be wrong.

 

[Ivan Seeking]

Thing about this stance is that there isn't really much of an in-between - it's a pretty black and white issue - or might as well be.

If you grant that even one single account is bona fide, then you grant that an advanced alien civilisation is, in fact, visiting us. Once you grant that - there's no reason not go on to conclude that most otherwise unexplainable sightings are legit alien craft.

You see, this "fact" of advanced civilisations visiting us becomes the de facto simplest and most likely explanation for many otherwise very mysterious sightings. Occam's razor will be satisfied by "those alien craft".

I put to you PIT2 to ask yourself if your "not all but some" stance has less to do with how many sightings are legit, than it does with your willingness to commit to the 'believer' stance i.e. you're hedging your bets.

But I could be wrong.

I think at issue is the idea of "unexplainable". Since most UFO sightings are explainable, you may both be saying the same thing. The other issue is that of potentially unrecognized phenomena. If we have no other guesses as to what some reports might be, and even if ET does drop in once in a while, it could be that legitimate ET reports get mixed in with the other phenomena.

 

[Ivan Seeking]

Oh yes, as for hedging bets, isn't that the only logical position to assume? Why should we assume what is or is not possible given our limited knowledge of the facts and an incomplete physics? It seems to me that any "belief" in this regard is a statement of faith that is not based on logic or science. Of course, this wouldn't apply to anyone who has had a so called "close encounter". They would be the only ones [assuming that they exist] here who have a justified belief. Ironically perhaps, anyone who makes such a claim is often treated as a crackpot by those who cling to a faith.

Now what does that remind me of...religion?

 

[PIT2]

I put to you PIT2 to ask yourself if your "not all but some" stance has less to do with how many sightings are legit, than it does with your willingness to commit to the 'believer' stance i.e. you're hedging your bets.

This is what i said:

i think ufo sightings on Earth suggest an advanced unknown intelligence. Not all of course, but there are some bizarre cases.

In other words, i think the bizarre cases are suggestive of an advanced unknown intelligence.

I think a lasershooting large triangular object - that is seen by dozens of police at the same time, while being tracked on 4 different radars and locked on by f16's (the belgian triangle)- is more suggestive of an advanced unknown intelligence, than say... a group of orange lights floating through the air near a party where skylanterns are released.

Btw i really don't care if I am called a believer. If i did, i wouldn't openly admit that i think alien visitations are more likely to have occurred than not, would i?

 

[arildno]

Aah yes. Yet again a useless and pointless comment.

And the Drake equation remains worthless all the same.

 

[DaveC426913]

Oh yes, as for hedging bets, isn't that the only logical position to assume? Why should we assume what is or is not possible given our limited knowledge of the facts and an incomplete physics?

But he wasn't hedging like this: "I believe that there are likely alien craft, but I'm open to the possibility that there are not."

He was hedging like this: "I believe that there are definitely alien craft, but I'm going to say they only explain a few of the juiciest sightings."

The latter is making a commitment but then trying to backpedal.

It's sort of the difference between:
"In a boxing match, I will bet on the winner AND make a side bet on the loser." (perfectly acceptable)
and
"I will bet on the winner but afterward I may claim I wasn't serious." (if you're going to bet you'd better have the courage of your convictions).


Anyway, this is a totally academic sidebar discussion...

 

[PIT2]

The latter is making a commitment but then trying to backpedal.

Actually, i was admitting that I am in no way sure or convinced that alien visitations occur.

"I will bet on the winner but afterward I may claim I wasn't serious." (if you're going to bet you'd better have the courage of your convictions).

After what? After we have colonised the entire universe and completely dug up and inspected the soil on all planets and proven that no aliens visited us? Oh and it would have to happen in my lifetime or i wouldn't be able to feel the shame of being proven wrong and thus claim that i wasnt serious...
It makes no sense.

 

[setAI]

I voted yes- but I do not believe in little grey men-

we have probably been 'visited' by every form of intelligence in every universe that has achieved universal quantum computing or classical hypercomputing: through physically equivalent quantum simulations of our universe- the foamy quantum spaces between the atoms of our world and bodies likey contains a vast zoo of sub-femtotechnological computation interfaces emerging out of the quantum multiverse from more forms of intelligence than their are atoms in our observable universe- but of course there is no way to find any evidence yet- [soon]

which means that there aren't any silver saucers or skinny grey aliens running around- we are more likely just one of an infintude of reality shows- [but who/what- if anyone- is watching? and is our 'show' interactive?]- it is naive to think that technology would remain stuck in the industiral paradigm- industry is merely a brief ignition where intelligence evolves toward total integration/access with all information- SETI needs to stop scanning the heavens and start scanning the Planck scale

 

[PIT2]

we have probably been 'visited' by every form of intelligence in every universe that has achieved universal quantum computing or classical hypercomputing

Does that mean we are a simulation?

 

[setAI]

Does that mean we are a simulation?

the Simulation argument is very compelling- but I think ultimately moot becasue of the superposition principle: every possible process that could generate our world exists in superposition and our world is the sum-over-histories- some of those histories started as a simulation and some as a natural physical process- and some arise randomly- but it is the total of these in superposition that allowed our world to exist as it does- thanks to unitary quantum mechanics

which also means that every possible intelligence that has acheived/obtained the necissary computing or physical resources to simulate a world like ours is capible of interfacing with it at a fundamental level- perhaps some can only watch and others can interact- who knows? the point of this idea though is that industrial age flying vehicles with intelligent animals on them soaring through vast interstellar space is unrealistic- real aliens would be much more intimate and subtle

 

[PIT2]

the point of this idea though is that industrial age flying vehicles with intelligent animals on them soaring through vast interstellar space is unrealistic- real aliens would be much more intimate and subtle

What kind of travel would it be, in what kind of devices?

 

[vanesch]

In as much as the universe is much bigger than just the simple "visible universe" in physically different ways (bubbles in inflation, MWI style situations or other), and in as much that the anthropic principle plays a role (which is debatable, but is nevertheless an argument), I think the probability of intelligent life might be way way way lower than we would simply (Drake-style) estimate it on some naive considerations. After all, the simple fact that we are here, in as much as this is biased by the anthropic principle, might only mean that there could be some other intelligent lifeforms in *the entire universe*, but given that that is way way bigger than the visible universe, we might still be very alone in our visible universe!

 

[DaveC426913]

Btw i really don't care if I am called a believer. If i did, i wouldn't openly admit that i think alien visitations are more likely to have occurred than not, would i?

That was not meant as a sleight. I'm just trying to determine if you do think we have indeed been visited. i.e. if you had to bet your life on it, on which side would you bet?

 

[DaveC426913]

And the Drake equation remains worthless all the same.

Are you hoping someone will beg you to share your wisdom? Or do you just have a whim to poop on an otherwise perfectly good discussion?

 

[Ivan Seeking]

In as much as the universe is much bigger than just the simple "visible universe" in physically different ways (bubbles in inflation, MWI style situations or other), and in as much that the anthropic principle plays a role (which is debatable, but is nevertheless an argument), I think the probability of intelligent life might be way way way lower than we would simply (Drake-style) estimate it on some naive considerations. After all, the simple fact that we are here, in as much as this is biased by the anthropic principle, might only mean that there could be some other intelligent lifeforms in *the entire universe*, but given that that is way way bigger than the visible universe, we might still be very alone in our visible universe!

Note that even a much smaller Drake result is still a very large number if considering the visible universe and not just our galaxy.

I tend to expect that Drake errored on the safe side [results too small] due to our naive and anthropic view of what life is and where it might be possible for intelligent life to exist, and for that matter, our anthropic view what makes intelligence possible.

Correction: I guess it could be that I really mean the application of Drake's equation. I don't recall how specific some of his language was. For example, does intelligent life require an earth-like planet in order to evolve?

 

[HallsofIvy]

http://video.google.com/videoplay?docid=-5594744703753734741

Bearing in mind this post by Ivan in the UFO stickied thread.

10,000,000,000,000,000,000,000 stars in the universe, a very conservative estimate but let's assume it's correct.

And the Drake equation is possible given the criteria and confirms there must be intelligent life: maybe in the galaxy, but definitely in the universe by the laws of probability.

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

The Drake equation does not confirm anything. I notice that at the sight you cite, the note that each coefficient could be "from 0 to 100%" but then allow you to enter no value less that 0.0001%. Is there any reason to think that the real values are not far less than that? I don't think there is any reason expect any range of values! We just don't have the information.

And apply this to the universe, in a sort of what if way assuming this is fairly typical.

My question is two fold, we're fairly certain that probability indicates there must be life elsewhere in the universe, and assuming evolution works in simiilar if not the same ways elsewhere: it's fair to claim that their is intelligent life, so we accept life is out there? Yes/no?

Now given the conclusion is yes, do you think the intelligent life has visited Earth?

Since we have no reason whatever to assign even approximate values in the Drake equation, we certainly have no reason to "accept life is out there".

 

[DaveC426913]

each coefficient could be "from 0 to 100%" but then allow you to enter no value less that 0.0001%. Is there any reason to think that the real values are not far less than that?

No, but there's no point in calculating the results with those numbers. The chances come out < 1 : 10^-20.

 

[vanesch]

I tend to expect that Drake errored on the safe side [results too small] due to our naive and anthropic view of what life is and where it might be possible for intelligent life to exist, and for that matter, our anthropic view what makes intelligence possible.

Correction: I guess it could be that I really mean the application of Drake's equation. I don't recall how specific some of his language was. For example, does intelligent life require an earth-like planet in order to evolve?

Yes, but there are numbers in there which are totally out of the blue. For instance, "the probability to devellop microbial life on an earth-like planet". What if it is 10^(-30) ? Also, the "probability for intelligent life to devellop on an earth-like planet where microbial life develloped"... what if that equals 10^(-200) ?

Again, the fact that it happened on OUR planet shouldn't be factored in, because OF COURSE it happened on our planet. Each being wondering about it will be living on a planet where intelligent life devellopped. That says NOTHING about the probability for such an event to occur. So if we take that single and biased event out of our bag of observations, we have no indication at all that such a thing happens. The only thing we know is that it is physically possible for it to happen. But even if the probability for intelligent life to devellop equals 10^(-30000), there wouldn't be any problem for us to be here.

 

[Schrodinger's Dog]

The Drake equation does not confirm anything. I notice that at the sight you cite, the note that each coefficient could be "from 0 to 100%" but then allow you to enter no value less that 0.0001%. Is there any reason to think that the real values are not far less than that? I don't think there is any reason expect any range of values! We just don't have the information. Since we have no reason whatever to assign even approximate values in the Drake equation, we certainly have no reason to "accept life is out there".

Well for a start I'm clearly asking you to make the asumption that it does, in order to encourage debate, if we accept that it may provide an answer x.

Also I have clearly said that if you want to assign values to it that are other than the x on this site, you can there are plenty of sites out there, now taking x, do you think y?

http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=179074

Knock yourself out

It was meant to stimulate debate, not to be picked apart, it is if we assume x then y?

OK have I clarified?

I have already sated quite clearly that Drake equations only use is in prompting the asking of questions, I asked a question? I'm not sure what that guy's going on about with it being useful, no it's not meant to be useful in a real scientific sense it's meant to be abstract by definition, but that doesn't make it of no use in a philosophical sense. Therefore given that can we move on now, no it is of no scientific value exactly, we know.

Since no one here knows the answer for sure, then that's pretty much what the discussion is about, what do you believe the likelihood is of meeting alien life given x or whatever you like really but given x as starter, now in the future or wherever you want to take the OP.

 

[PIT2]

That was not meant as a sleight. I'm just trying to determine if you do think we have indeed been visited. i.e. if you had to bet your life on it, on which side would you bet?

My bet would be on the visiting aliens.

 

[DaveC426913]

My bet would be on the visiting aliens.

OK. What fraction of current unexplained sightings would you attribute to bona fide alien craft encounters?

We can probably categorize unexplained encounter in broad groups (I'm sure they already are), from "lights in the sky" all the way up to "extensive video footage of craft in flight" and beyond.

How would you (if you had to bet) divide them up?

 

[PIT2]

OK. What fraction of current unexplained sightings would you attribute to bona fide alien craft encounters?

We can probably categorize unexplained encounter in broad groups (I'm sure they already are), from "lights in the sky" all the way up to "extensive video footage of craft in flight" and beyond.

How would you (if you had to bet) divide them up?

I don't know the numbers, so a fraction is hard to guess. The group that makes me bet on aliens is the one where there are multiple witnesses(which can be judged according to various criteria), as well as physical evidence(which can also be judged). Obviously the less criteria a sighting satisfies, the less convincing i find it. I guess we can also safely say that, if the upperclass sightings are aliens, then some percentage of the sightings in lower classes would be aliens also.

 

[Ivan Seeking]

Yes, but there are numbers in there which are totally out of the blue. For instance, "the probability to devellop microbial life on an earth-like planet". What if it is 10^(-30) ? Also, the "probability for intelligent life to devellop on an earth-like planet where microbial life develloped"... what if that equals 10^(-200) ?

Again, the fact that it happened on OUR planet shouldn't be factored in, because OF COURSE it happened on our planet. Each being wondering about it will be living on a planet where intelligent life devellopped. That says NOTHING about the probability for such an event to occur. So if we take that single and biased event out of our bag of observations, we have no indication at all that such a thing happens. The only thing we know is that it is physically possible for it to happen. But even if the probability for intelligent life to devellop equals 10^(-30000), there wouldn't be any problem for us to be here.

I agree; our existence might be against all odds, however there is no evidence to suggest that this is true. Also, since there is no reason to believe that we are special, it is entirely possible that intelligent life is nearly as common as planets.

If we randomly select a grain of sand on the beach, is it more logical to expect that grain of sand to be unique, or typical. Does our observation of that grain change the odds? Were the odds for intelligent life on Earth different before we [humans] came to be? Unless we can cite reasons why we are unique, it seems to me that our very existence is evidence that life is common. Again, the only hard evidence for the odds is measured as 1:1, for intelligent life on earth-like planets.

 

[Ivan Seeking]

The ending of http://www.youtube.com/watch?v=9JSR_6qfXTg" seems appropriate.

Most excellent!

Note however the contradiction with inflation theory when citing the expansion rate limit. Dont we need to make a small change - the speed of light is not the fastest speed there is?