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

Has alien life visited Earth?

  • Yes

    Votes: 81 14.4%
  • no

    Votes: 201 35.8%
  • no: but it's only a matter of time

    Votes: 64 11.4%
  • Yes: but there is a conspiracy to hide this from us

    Votes: 48 8.6%
  • maybe maybe not?

    Votes: 138 24.6%
  • I just bit my tongue and it hurts, what was the question again? Er no comment

    Votes: 29 5.2%

  • Total voters
    561

Main Question or Discussion Point

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?
 
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Answers and Replies

DaveC426913
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"...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.
 
"...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.
 
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Ivan Seeking
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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.
 
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Ivan Seeking
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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.
 
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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
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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?]
 
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radou
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If intelligent life ever visited us, we wouldn't know, since it is not likely that it would be interested in us at all. :rolleyes:
 
George Jones
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The ending of http://www.youtube.com/watch?v=9JSR_6qfXTg" seems appropriate.
Many a true word spoken in jest :wink:

There really is bugger all down here on Earth:smile:

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?
 
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SGT
Many a true word spoken in jest :wink:

There really is bugger all down here on Earth:smile:

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 !!!
 
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?
 
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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.
Best regards, Dan
 
DaveC426913
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... 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
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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.)
 
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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.
 
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
 
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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
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aah yes. Yet again that useless&pointless Drake equation.
 
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
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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.
 
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DaveC426913
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aah yes. Yet again that useless&pointless Drake equation.
Aah yes. Yet again a useless and pointless comment. :biggrin:
 
Ivan Seeking
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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%.
 
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