What do you think is the most likely explanation for the Fermi paradox?

[swampyankee]

Scientists can err, witness Lord Kelvin’s 1895 quote, and Felisa Wolf-Simon’s arsenic-using life. It’s certainly possible there will be both false positives (these have happened) and false negatives.

[Selfsim]

Scientists can err, witness Lord Kelvin’s 1895 quote, and Felisa Wolf-Simon’s arsenic-using life. It’s certainly possible there will be both false positives (these have happened) and false negatives.

Sure.
So the Fermi Paradox is just another false one then, eh? (Humour intended here).

[Van Rijn]

I don't remember it like that at all. I recall President Clinton announcing the discovery of life on Mars. And he was put up there at the request of NASA.

Whilst I go along with what you say about publicity, the later backtracking must've been embarrassing for all concerned.

Memory is far from perfect, and if I recall correctly, many news reports at the time missed important details.

Here is a transcript of his statement:

https://www2.jpl.nasa.gov/snc/clinton.html

Some key bits:

This is the product of years of exploration and months of intensive study by some of the world's most distinguished scientists. Like all discoveries, this one will and should continue to be reviewed, examined and scrutinized.
[...]
First, I have asked Administrator Goldin to ensure that this finding is subject to a methodical process of further peer review and validation.
[...]
Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered. Its implications are as far-reaching and awe-inspiring as can be imagined. Even as it promises answers to some of our oldest questions, it poses still others even more fundamental.

It was definitely an optimistic statement, but they were careful to include qualifiers.

[Van Rijn]

Let's also not forget about the notorious Richard Hoover episode who, in 2011, published a 'paper' in the crank Journal of Cosmology, wherein he claimed evidence in meteorites that life on Earth came from space, in this case, in the form of comet debris. (He's apparently made similar claims six times to date!)

Then again in the same crank Journal, a 'Rhawn Joseph' published an article in January 2014, concluding that the martian (in situ) rock, dubbed 'Pinnacle Island', was in fact, a living organism.

The pattern seems clear ... the fixation with 'life must be out there', (which of course provokes the Fermi Paradox), when combined with marginal scientific qualifications, (a BSc in Hoover's case), leads towards pareidolia driven delusions, a life of pseudoscientific crankdom, which then serves to perpetuate the accompanying fixation with the Paradox too (ie: Fermi's) ... which really never was one at all anyway(?)

The pattern seems clear . . . if we're just discussing the nonsense published in a crank journal. That's no reason to condemn serious research (like that on ALH84001, which has been extensively peer reviewed), or serious discussion about issues like the Fermi paradox.

Incidentally, we had an extensive discussion about the Journal of Cosmology on this board, and at one point one of their key editors popped in here with a negative comment (they were doing that a lot around the internet, see David Brin's experience with the Journal, for instance, where he tried to peer review a Rhawn Joseph article at their request). My recollection is that JoC initially got some publicity with a mention of one or another of their articles in some major newspapers. But it quickly became known as a crank journal and they later stopped getting mentions from serious news organizations.

I did a bit of research myself, and it was clear that Rhawn Joseph played a major part in the site. The website formatting was essentially the same as a personal site he had built earlier. He had a lot of ATM science claims. If I recall, he had some steady state eternal universe idea, argued modern evolution was wrong, abiogenesis was impossible, and insisted on panspermia.

Hoover's claims were very quickly criticized by the science community, and NASA made it clear he wasn't speaking for them. (I think also that he was retired at the time when the JoC article flap happened?)

[Selfsim]

The pattern seems clear . . . if we're just discussing the nonsense published in a crank journal. That's no reason to condemn serious research (like that on ALH84001, which has been extensively peer reviewed), or serious discussion about issues like the Fermi paradox.

Somewhat agreed .. I'm obviously challenging the 'seriousness' of FP discussions about so-called 'issues' though. The FP is only a paradox for philosophical thinkers .. its largely irrelevant for scientific thinkers (the latter of which, includes the proper Astrobiology researchers I've encountered, who are doing great work).
(Ie: one can't test against a believed-in standard .. so move on testing against one that isn't).

Incidentally, we had an extensive discussion about the Journal of Cosmology on this board, and at one point one of their key editors popped in here with a negative comment (they were doing that a lot around the internet, see David Brin's experience with the Journal, for instance, where he tried to peer review a Rhawn Joseph article at their request). My recollection is that JoC initially got some publicity with a mention of one or another of their articles in some major newspapers. But it quickly became known as a crank journal and they later stopped getting mentions from serious news organizations.

I did a bit of research myself, and it was clear that Rhawn Joseph played a major part in the site. The website formatting was essentially the same as a personal site he had built earlier. He had a lot of ATM science claims. If I recall, he had some steady state eternal universe idea, argued modern evolution was wrong, abiogenesis was impossible, and insisted on panspermia.

Hoover's claims were very quickly criticized by the science community, and NASA made it clear he wasn't speaking for them. (I think also that he was retired at the time when the JoC article flap happened?)

Yar .. it pops up occasionally elsewhere in my web forum travels .. and always gets the treatment it deserves. Its 'going-in' position/purpose is just outright anti-science (IMO).

[Gomar]

Aliens became too smart, developed nukes, waged wars, alien life was extinguished. As per main plot theme of 'Battlestar Galactica', it has all happened before, and it will happen again. Intelligent life in the universe will develop robots, weapons, so on that will either turn against them, or destroy them.
Perhaps, Gods, angels, demons were in fact aliens. Why did angels and Nephilim exist at all? Were Adam&Eve from another planet or dimension? Was Jesus a human?

Or... intelligent aliens are just too far from Earth.

[Gomar]

From:
https://www.realclearscience.com/blo...nd_aliens.html

"12. Aliens are already here and we just don't realize it. "

[Noclevername]

From:
https://www.realclearscience.com/blo...nd_aliens.html

"12. Aliens are already here and we just don't realize it. "

"6. Space is big."

[Selfsim]

0. We don't have a clue that what we're looking for, is actually alien life.

[Noclevername]

0. We don't have a clue that what we're looking for, is actually alien life.

You mean that "life signs" would not be immediately obvious and recognizable to us over a distance that even the fastest thing possible takes many years to cross?

What a concept!

[marsbug]

I rather like the analogy of pacific islanders looking past their islands bay at the open ocean and asking 'is there anything but storms and sea out there?'... while five minutes sailing and a dive would bring them to a coral reef teeming with colour, variety, and life. IMHO we'd be better off simply exploring without fixating on such a narrow thing as our current understanding of life... but perhaps that is too big an ask, and as a people we truly do need a goal to aim at.

[Spyrith]

I rather like the analogy of pacific islanders looking past their islands bay at the open ocean and asking 'is there anything but storms and sea out there?'... while five minutes sailing and a dive would bring them to a coral reef teeming with colour, variety, and life. IMHO we'd be better off simply exploring without fixating on such a narrow thing as our current understanding of life... but perhaps that is too big an ask, and as a people we truly do need a goal to aim at.

I always liked this quote from Arthur C. Clarke: “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

I think the question of whether we are alone or not is important to us on a philosophical level. If we are indeed alone, then that means we're special somehow. If we are the only intelligent species in the Universe then that means it's just us and this unimaginably gigantic sandbox we can do anything we want with it.

If we aren't alone, that too has meaning. On one hand, it means we aren't special and that there are others like us (meaning intelligent). Then there's the huge amount of questions that come up: what's the other species like? what do they eat? what was their history? what do they believe in? what do they eat for breakfast? what do they think of Seinfeld?

To go back to the OT. I think we're alone, at least in this galaxy. I think the conditions required to sustain intelligent life are very restrictive, and we here on Earth just got unimaginably lucky to exist. Also, I think we're one of the very species to exist, simply because the Universe is so incredibly young at this point. I read that the Universe will continue to generate stars for trillions of years, and we're only 13.7 billions years in.

[Barabino]

a few novels tried to imagine a human civilization accostumed to the huge expanse of time and space of a galaxy-wide civilization... that's nonsense: even if such a galactic civilization could cope with interstellar travel of a few people per century, it exhausted its own energy sources much sooner than contacting another earth... same same as living on a remote south pacific island and expecting to buy cigarettes one 20-pack each time...

[kzb]

I always liked this quote from Arthur C. Clarke: “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

I think the question of whether we are alone or not is important to us on a philosophical level. If we are indeed alone, then that means we're special somehow. If we are the only intelligent species in the Universe then that means it's just us and this unimaginably gigantic sandbox we can do anything we want with it.

If we aren't alone, that too has meaning. On one hand, it means we aren't special and that there are others like us (meaning intelligent). Then there's the huge amount of questions that come up: what's the other species like? what do they eat? what was their history? what do they believe in? what do they eat for breakfast? what do they think of Seinfeld?

To go back to the OT. I think we're alone, at least in this galaxy. I think the conditions required to sustain intelligent life are very restrictive, and we here on Earth just got unimaginably lucky to exist. Also, I think we're one of the very species to exist, simply because the Universe is so incredibly young at this point. I read that the Universe will continue to generate stars for trillions of years, and we're only 13.7 billions years in.

Not so sure about this. Current ideas imply there are rather special conditions for evolving and sustaining intelligent life.

Firstly, it needs a large spiral galaxy. All systems in a dwarf galaxy are subject to periodic extinctions due to GRBs.

Then, there is the level of metallicity. This needs to be within a certain range, not too low and not too high, but metallicity is increasing as the universe ages. This means the rate of formation of suitable systems will start to decline and more or less stop at a certain age. It's nowhere near that age yet, in fact the "productivity" of our own galaxy is still increasing, but at some point in the far future it will.

[Tom Mazanec]

All systems in a dwarf galaxy are subject to periodic extinctions due to GRBs.


Do you have a reference to that? It seems counterintuitive. It's not like life can spread away from a GRB that happens to be nearby. And if the dwarf is one thousandth the size of the giant, GRBs should be one thousandth as frequent.

[kzb]

All systems in a dwarf galaxy are subject to periodic extinctions due to GRBs.


Do you have a reference to that? It seems counterintuitive. It's not like life can spread away from a GRB that happens to be nearby. And if the dwarf is one thousandth the size of the giant, GRBs should be one thousandth as frequent.

There was a paper on arxiv a few years back which argued this.

In a dwarf galaxy, all locations are within range of a GRB. In a large galaxy, as time goes on, regions evolve which are outside the range of GRBs. Thinking about this now, I am not sure if this really holds together though !

[Tom Mazanec]

Seems unlikely. Why would, say, the Orion Arm be immune to GRBs? They can happen just about anywhere.

[kzb]

Seems unlikely. Why would, say, the Orion Arm be immune to GRBs? They can happen just about anywhere.

The incidence of GRBs is inversely related to metallicity. As a spiral galaxy evolves, the metallicity increases first in the inner region and spreads outwards. There is a metallicity gradient in the MW from centre to edge of disk.

There are also considerations of stellar density and supernova frequency affecting habitability, and those also have a correlation with galactic radius.

So maybe it is some kind of balance with GRB frequency (correlates with inversely with metallicity) and other factors all contributing.

[Spyrith]

Then, there is the level of metallicity. This needs to be within a certain range, not too low and not too high, but metallicity is increasing as the universe ages. This means the rate of formation of suitable systems will start to decline and more or less stop at a certain age. It's nowhere near that age yet, in fact the "productivity" of our own galaxy is still increasing, but at some point in the far future it will.

Out of curiosity, when will this metallicity threshold be reached? I know the Universe will keep producing stars for trillions of years but judging from your comment it likely isn't possible life will also be produced for trillions of years.

[kzb]

Out of curiosity, when will this metallicity threshold be reached? I know the Universe will keep producing stars for trillions of years but judging from your comment it likely isn't possible life will also be produced for trillions of years.

I don't know to be honest !

Also note the metallicity limit comes from the likelyhood of producing migrating Jupiters in the system. If this turns out to be wrong then it does not apply, or at least pushes it much further into the future.

[Dave241]

a few novels tried to imagine a human civilization accostumed to the huge expanse of time and space of a galaxy-wide civilization... that's nonsense: even if such a galactic civilization could cope with interstellar travel of a few people per century, it exhausted its own energy sources much sooner than contacting another earth... same same as living on a remote south pacific island and expecting to buy cigarettes one 20-pack each time...

Bolded mine. I don't see why this conclusion is valid. Was it part of the story you mentioned? Why would the author think that interstellar travel would exhaust anyones energy resources? Our star produces many orders of magnitude more energy each second then would be required to send a colony ship to a nearby star. Even without bothering with the sun at all we humans are able to envision several projects that would get a spacecraft to a nearby star system (granted only small robot spaceships, but that's still impressive), and we aren't using even a fraction of a percent of only the tiny bit of the suns energy that falls directly on our planet. Any alien civilization that has started harnessing it's own stars power output would have vastly more energy then what they need for interstellar travel.

For example, the sun produces 4*10^26 Joules/second and to accelerate a spacecraft the mass of the ISS up to 10% the speed of light would require 2*10^20 joules, or less then 1 millionth the power output of the sun in one second. So if you wanted to build a colony ship that is 1,000 times the mass of the ISS, and launch in on a 100 year journey to a star 10 light years away, that would only require the power the sun produces in 1/1000th of a second and that will power the craft for it's entire journey.

I've seen this argument before, that interstellar travel is so taxing that this is the reason aliens don't spread out into the stars, and it simply makes no sense to me. The barriers to interstellar travel are many, but having enough energy isn't one of them.

[Dave241]

Then, there is the level of metallicity. This needs to be within a certain range, not too low and not too high, but metallicity is increasing as the universe ages. This means the rate of formation of suitable systems will start to decline and more or less stop at a certain age. It's nowhere near that age yet, in fact the "productivity" of our own galaxy is still increasing, but at some point in the far future it will.

Could you explain this a bit more? Why would having higher metallicity stop star systems from forming? I'd think having more material to make planets out of besides hydrogen would only increase the number of planets. Or are you referring to the star having so much metal that it can't undergo fusion properly anymore? Thanks.

[Delvo]

the Universe will keep producing stars for trillions of years

Where does that quantity come from?

[Tom Mazanec]

https://en.wikipedia.org/wiki/Future...elliferous_Era
Stelliferous Era
From the present to about 1014 (100 trillion) years after the Big Bang

[eburacum45]

Could you explain this a bit more? Why would having higher metallicity stop star systems from forming? I'd think having more material to make planets out of besides hydrogen would only increase the number of planets. Or are you referring to the star having so much metal that it can't undergo fusion properly anymore? Thanks.

The problem with a high-metallicity system is often supposed to be that too many large planets form, which eject smaller Earth-like terrestrials, or otherwise crowd them out.

Solar systems that resemble our own are quite rare.

[Dave241]

The problem with a high-metallicity system is often supposed to be that too many large planets form, which eject smaller Earth-like terrestrials, or otherwise crowd them out.

Solar systems that resemble our own are quite rare.

Huh. Honestly that doesn't seem like very much of a barrier to life to me, and in fact could actually help it out. Put Jupiter or Saturn in Earth's orbit and several of their moons could be habitable, which would increase the number of potential habitable worlds, not decrease it.

But either way this does sound like the incredibly distant future, so by the time this becomes an issue we will be terraforming solar systems with ease anyway, right?

[eburacum45]

Habitable moons of gas giants would be quite unlike Earth in many ways, such as their rotation characteristics, tides, and high radiation levels in space around the primary. That might not make the emergence of life impossible, but the resulting species might be very different to the species that have evolved on Earth. At the very least these moon-dwelling aliens might avoid systems like ours because they find them inhospitable.

[Grant Hatch]

Let's also not forget about the notorious Richard Hoover episode who, in 2011, published a 'paper' in the crank Journal of Cosmology, wherein he claimed evidence in meteorites that life on Earth came from space, in this case, in the form of comet debris. (He's apparently made similar claims six times to date!)

Then again in the same crank Journal, a 'Rhawn Joseph' published an article in January 2014, concluding that the martian (in situ) rock, dubbed 'Pinnacle Island', was in fact, a living organism.

The pattern seems clear ... the fixation with 'life must be out there', (which of course provokes the Fermi Paradox), when combined with marginal scientific qualifications, (a BSc in Hoover's case), leads towards pareidolia driven delusions, a life of pseudoscientific crankdom, which then serves to perpetuate the accompanying fixation with the Paradox too (ie: Fermi's) ... which really never was one at all anyway(?)

Really... delusions, pseudoscientific crankdom? Seems your mind is made up.... you are cavalierly dismissing both people you call "cranks", as well as a thoughtful response to the question of the OP .... Why not simply say you think we are the only intelligent life in the universe? I think that statistics alone lends credence to the notion that intelligent life besides our own is out there....especially given our relatively late appearance on the scene. Why "we" haven't found evidence of it yet is a far more interesting subject..... clouded by inherent and palpable prejudices in part.....
My answer to his question is "it's simple", either we aren't looking for ET properly given the vastness of the field and the limits placed on the search, or they aren't ready for "us" to find them.... Or Both... far and near....

[kzb]

Huh. Honestly that doesn't seem like very much of a barrier to life to me, and in fact could actually help it out. Put Jupiter or Saturn in Earth's orbit and several of their moons could be habitable, which would increase the number of potential habitable worlds, not decrease it.

But either way this does sound like the incredibly distant future, so by the time this becomes an issue we will be terraforming solar systems with ease anyway, right?

Well hang on no-one has proven that intelligent life can arise on a Jovian moon.

The only system known to have evolved intelligent life is a possibly atypical planetary system around a relatively uncommon type of star.

[kzb]

https://en.wikipedia.org/wiki/Future...elliferous_Era
Stelliferous Era
From the present to about 1014 (100 trillion) years after the Big Bang

Yes but the formation of suitable planetary systems might tail off long before then. The stelliferous era lasts as long as the smallest stars continue to shine, which is not the same thing.