Why have aliens never visited Earth? Scientists have a disturbing answer

I wonder how many thousand alternative scenarios could also be argued?

If we, in our time, can see problems that need addressed, how much more will they see it?

The critically unique circumstances for life and the additional circumstances to allow space-faring intelligence may also be the answer.

Another answer, of course, is that they are looking for us orbiting a "yellow Sun". ;)
 

rod

Oct 22, 2019
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The assumption of alien life and civilizations in *science* is based upon belief in abiogenesis as the true explanation for the origin of life, thus abiogenesis can create life in many different locations. Given enough time, some type of biological life will evolve into intelligence and perhaps space travel and communication. Charles Darwin published his views on abiogenesis in letters along with his warm little pond in the early 1880s and nothing of worthwhile evidence was shown to demonstrate that non-living matter evolves into life but he hoped that someday science would confirm this belief about origins. Still pending here for abiogenesis and E.T. phoning home. Immanuel Kant had trouble here too. His nebular hypothesis for the solar system was rooted in viewing that show me matter and he can create things. However, showing how matter turned into life was another story.

“Are we in a position to say: Give me matter and I will show you how a caterpillar can be created? Do we not get stuck at the first step due to ignorance about the true inner nature of the object and the complexity of the diversity contained in it? It should therefore not be thought strange if I dare to say that we will understand the formation of all the heavenly bodies, the cause of their motion, in short, the origin of the whole present constitution of the universe sooner than the creation of a single plant or caterpillar becomes clearly and completely known on mechanical grounds."
 
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Going to the central hypothesis that a highly technological society is doomed - the authors are still not addressing the reason that "innovation no longer keeps up with the demand for energy". That reason can be population dynamics, here on Earth, at least. There are too many of us already and the in-bred response to the stresses from that is to breed more people faster so that there are more of "us" to fend off "them".

While some well-fed and highly-educated people may have the time to think of that, the vast majority of the population doesn't feel they have the luxury to think about how to save civilization while they are trying to save themselves and their progeny.

So, collapse due to "lack of energy" does not seem to require getting more highly advanced technologically than humans are today.
 

rod

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A simple answer to the Why question presented in the title, E.T. does not exist and science has not shown that abiogenesis is operating in the natural world, past or present creating life from non-living matter.
 
Rod, What you posted is only one of many plausible explanations.

I look at it from a probabilistic modeling background, expanding on Drake's Equation.

Drake's Equation is pretty simple in the form the he first presented it. But, his parameters can be expanded to include all of the science findings that influence the probabilities that his parameters have specific values. There is a lot of computerized computational methodology (developed for assessing nuclear reactor risk and space probe success probabilities) that could be used to address expanded versions of Drake's Equation.

I tend to think that way, but have not tried to actually write out a model for evaluation. At this point, there would be so much speculative assignment of values to the parameters that I don't think it would be useful.

But, I still look at new scientific findings with a thought about what that would mean for Drake's Equation. For instance, all the building blocks for DNA have been found in space, now. And a meteorite found decades ago has recently been loosely matched to the distribution of the chemical components expected for products of a type 1A supernova - which are substantially different from the distributions found on Earth.

And, then there are all the findings about how the moon has influenced the habitability of Earth, but we are not yet able to detect moons on exoplanets.

So, I see far too much that is unknown to have any confidence that a technological species we could detect has a specific probability of being within the rather small sphere of space in which we are currently able to detect them.
 
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rod

Oct 22, 2019
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Unclear Engineer, my note on your post #6. The Drake Equation is mentioned and we do not know if any exoplanets have moons because we cannot currently detect them like we see at Jupiter for example. My observation. The Drake Equation is rooted in the belief in abiogenesis as taking place in nature, past or present. Immanuel Kant never showed this concerning how matter forms the Sun and planets evolves into life, and neither did Charles Darwin in his warm little pond. Assumptions should be stated clearly and abiogenesis is what I would call the foundation in the Drake Equation, a critical assumption that must be true or the equation could fall apart.
 
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Catastrophe

"There never was a good war, or a bad peace."
There are volumes on Drake's Equation elsewhere. In my opinion, you get out what you put in. The whole output is governed by your individual guess ((apart from a couple of terms where your guess is somewhat prescribed). Totally useless waste of time IMHO.

Cat :)
 
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True that the Drake Equation puts out something that is almost completely dependent on what you put in. And we simply don't know enough to get a numerical result that means anything at this point in our learning process (also called "advancement of science"). Doing complex computations on a lot of assumptions only gives an assumed result.

But, thinking about what we want to know in order to change some of the most significant unknowns into knowns is a logical way to direct scientific effort toward getting a real answer. And thinking of the results of recent studies in the context of what they tell us about some of the parameters in an expanded Drake Equation is also useful.

As to Rod's post about abiogenesis: there is good, hard evidence that life has developed in some way in the past. That evidence is us and all the living things around us. So, clearly, the probability for life developing in one-or-more places in our detectable sphere of our universe is unity, and the probability of it developing in more-than-one place within that sphere of detectability is the real question.

A lot of our science efforts in space directly seek answers to whether there is any indication that life has developed in other places besides Earth. Finding all of the building blocks for DNA already assembled in space that has not been contaminated by life on Earth seems to me to indicate a higher probability that chemical conditions on other worlds could have produced reproducing chemical forms that sustain "life".

Our real problem is that we can't really define "life" at a chemical level. But, people in laboratories today are assembling larger and larger molecules that are essential to life. I would not be completely surprised if I live long enough to read a headline that some lab somewhere has assembled a group of molecules that autonomously perform the functions that we call "life".
 

Catastrophe

"There never was a good war, or a bad peace."
I have no doubt whatsoever, that simple life is widespread throughout the billions of galaxies, each containing billions or trillions of stars with (together) trillions of planets. You have only to look at the diversity of life on Earth to see the adaptability present in diverse circumstances. Of course, I am referring here to microbiological and other simple offshoots thereof.

From such a myriad of choice, intelligent life will have developed, though perhaps only in millions of systems in each galaxy. So next comes the problem of communication. We should be considering not only the possible locations of intelligent life (distance), but the time span of such life and and the timing. BTW, I am not putting numbers in a Drake Equation but just qualitative reflecting on the important factors.

The span of such intelligent communication possibility may be very limited. We have had the ability to send messages, or signals, for about 100 years. It is your guess how long or short, such a civilisation might last. There are other risks than self destruction which might operate, but the life expectation is going to be the flutter of a butterfly's wing in comparison to the (widely varying, perhaps 10 billion year) effective life of a star. This temporal separation of civilisations may be as, or more, important than spatial separation. Spatial separation is, of course, very important. Even if both spatial and temporal separations, and simultaneity, coincided (very improbable) for a star as close as Proxima Centauri, communication would be on an 8 year round basis. I am obviously referring only to electromagnetic communication. In practice, such a basis might exceed 100 years for an average star distance. Possibly longer than the life expectation of one or both participants. Failure by either party might be for many reasons including political or accidental influences.

Then, once communication is established, on a level of mutual recognition, there is the question of mutual understanding on a linguistic level.

I am not at all surprised that we have not entered into communication with an alien species, though we may even be receiving signals not understood by us, or possibly even originating from a long dead civilisation.

Cat :)
 
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I suspect that Cat is right about life at least initiating on many, many planets at some time since whatever "beginning" there was. But, that is speculation at this point.

I think that the probability of life sustaining/surviving long enough to become technological is rather low. For one thing, it seems that the problem-solving capabilities of life on Earth may have been driven by disasters that life needed to adapt to in order to survive. So, it is not even clear that a long-stable environment would produce the fastest rate of progress from single cell to technological being. It may be that life develops capabilities fastest when surfing on the waves of extinction events, with most failing to survive.

And, just because a species develops technologies does not necessarily mean that they are aware of the rest of the galaxy. What if they are limited to life in water because there is no dry land? What if the clouds are so dense that they never see a star? What if gravity is so high that they never can leave their atmosphere?

All of those questions can be added to the "What if they don't last long enough to be around while we are?"

Regarding the doomsday scenarios where at least the technological parts of human societies collapse and are lost, it is not so clear that they could not redevelop rather rapidly, again, provided humans survive in roughly the same biological form as we currently have. It only took several thousand years to go from hunter-gatherers to space travel newbies.

To me, the real question is whether we or other technological beings can learn to not do the things that can cause technological societies to crash. If not, then we may get oscillating technical capabilities, at least for a while until we wipe-out on surfing the waves of disaster and go extinct.
 
...But, thinking about what we want to know in order to change some of the most significant unknowns into knowns is a logical way to direct scientific effort toward getting a real answer. And thinking of the results of recent studies in the context of what they tell us about some of the parameters in an expanded Drake Equation is also useful.
Yes. His equation (1961) was far superior to frame the discussion scientifically versus those that used the SWAG method. For example, Shapley guessed (1957) that 1 in a million planets had life, ~ 40 years before we objectively knew exoplanets existed.

As to Rod's post about abiogenesis: there is good, hard evidence that life has developed in some way in the past. That evidence is us and all the living things around us. So, clearly, the probability for life developing in one-or-more places in our detectable sphere of our universe is unity, and the probability of it developing in more-than-one place within that sphere of detectability is the real question.
IMO, abiogenesis is almost axiomatic to powerful evolution models. There currently is no known testable model for abiogenesis. On the other hand, it’s principle is not purely subjective. There are many objective elements that give reasonable argument for its likelihood.

Our real problem is that we can't really define "life" at a chemical level. But, people in laboratories today are assembling larger and larger molecules that are essential to life. I would not be completely surprised if I live long enough to read a headline that some lab somewhere has assembled a group of molecules that autonomously perform the functions that we call "life".
Agreed. If we’re fortunate to find both life and some details for it on exoplanets, exomoons, then perhaps the broad path can be narrowed to discover one or more abiogenesis processes.

iPhone
 
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Here's a much more disturbing answer.
First let's be very clear,
Extraterrestrials have never Publicly visited Earth in current history.
Absence of evidence is not evidence of absence.
Setting aside our own 'center of all importance' narcissism,
why exactly wouldn't some strutting pompous aliens want to announce themselves & demand to be taken to our leaders?
Maybe the aliens have some experience where this is bad for them &/or us?
What's so great about a species that is peeing away its life & death primary asset of its planet's biosphere?
If 'the proof is in the pudding' we don't even measure up to pudding.
If you read so-called 'science journals', loaded with unreplicatible trash, opinions, and titles that overreach & sometimes contradict their own data,
why would you even bother with that incompetent, sociopathic, hyperbolic species?
The human brain is an organ largely aimed at social leverage.
Very long on sensation very short on substance.
There is a reasonable likelihood that is a biological default.
Why are we so excited about some speculative 'them'?
A loser species is hoping to win the technology lottery?
We're 'lonely'?
Or at least they can & will rescue us from ourselves?
When do the hard headed, commanding intellects show up?
Not holding MY breath.
When the pompous narcissistic 'smart' people are stupid there's not much to hope for in the public arena.
CYOA, first last & always, because that's all there really is.
There is good science out there, buried in noise & trash, but sane adults HAVE to do their own homework/dumpster-diving.

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rod

Oct 22, 2019
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Occam razor favors E.T. does not exist as the correct answer, not endless *plausible* answers. Abiogenesis *must be true* to discuss life around the universe and exoplanets (whether 1 exoplanet or 10^500 exist). Abiogenesis is the foundation just like Charles Darwin thinking I document in post #3 shows or Immanuel Kant struggle with the problem of converting non-living matter into life. At some point abiogenesis advocates must prove their case in science, just like the heliocentric solar system had to be shown true by observations in the real world and in nature to be accepted in astronomy.

Today we have microorganisms said to be 4.28 billion years old using zircons. There is no fossil record evidence that these microorganisms evolved from non-living matter as their common ancestor or meteorites helped to create them before they appear, fully alive and functional in the fossil record. During this time in the fossil record, we have intense catastrophic bombardment conditions operating on the early earth model in astronomy today, compared to Kant or Charles Darwin model about life coming from non-living matter. Intense catastrophism is not part of their paradigm for the origin of life from non-living matter. Example Charles Darwin warm little pond with chemicals that evolve into life. Reports I collected in my home database show intense catastrophic bombardments on the Moon and Earth extending from 4.5 to 3.5 billion years ago or even more recent in the Precambrian, perhaps 3.3 billion. Using the 4.28 billion year old date for microorganisms on earth, the Moon could still be in a magma ocean (most current giant impact modeling using Theia) moving around the early earth, very much closer and shorter orbital period than the we see today, glowing in the night sky, red hot. More bombardments to follow like the origin of the South Pole Aitkin and other intense bombardments continuing in the Precambrian age model for earth. There is the Faint Young Sun too.

As far as I know, lab experiments do not use catastrophic bombardments and Faint Young Sun in their experiments to create molecules said to evolve into life, yet still are not life today in the labs as Charles Darwin in his letters from 1882 hoped science would confirm someday (140 years later and still not confirmed and shown true like the heliocentric solar system). We have man-made traps in the experiments used to get rid of various toxic conditions created during the experiments that are destructive to continued chemical evolution turning into life. All man-made traps used should be clearly documented and shown to the public and what toxic conditions were removed by the man-made traps.

What does the *science of abiogenesis* lead me to conclude? The lab work is biased and does not represent nature that existed in the early Earth-Moon system model according to astronomy, intense bombardment and catastrophism is an example.
 

COLGeek

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...or our neighbors just don't find us all that interesting or happen to be in the neighborhood.

While I have no doubt of the existence of intelligent life elsewhere in the vastness of the Universe, I can't imagine how humanity will receive the word of such confirmation.

Also, we had better hope whoever finds us is benevolent towards us and doesn't simply consider our planet an ideal place for experimentation.
 
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I am not understanding why this debate over abiogenesis is relevant to the question of whether there is intelligent life elsewhere.

It is an indisputable fact that there is life on Earth. So, no matter how it developed here or arrived here, what seems to be the best guess is that the same thing could have happened elsewhere, too. It seems that the onus is on the side of those who think that it could only ever happen here to prove that it never has and never will happen anywhere else.

So, the best questions seem to be related to how probable is it that life forms and develops elsewhere into technological societies. There seem to be a lot of factors that have been involved in making Earth habitable and keeping it habitable for billions of years, and it is not yet known how many places those conditions have been replicated , much less being clear if all of those factors are necessary for all kinds of life that could become technologically capable.

We now know that planets are not unusual, but our sample of their distribution of properties is biased by our limited detection technologies, to date. Hopefully, the Webb Telescope will be able to tell us more about the atmospheres of the planets we can find in our local neighborhood. That, and searches of Mars, and maybe even our moon for biological materials can help with figuring out whether just getting life started or giving it enough time to develop technological capabilities is the dominant factor in making close neighbor ETs few or none.
 
Like the beginning of the Universe, abiogenesis is a “beginnings” question that, for many, is less as a “how” question (science & philosophy) and more of a “who” question (religion). Abiogenesis, its specifics, can be argued to be suppositional only, but the circumstantial objective evidence is strong enough to make the idea of it plausible.

When Ptolemy was asked why he placed the orbit of Venus inside the Sun’s orbit, he responded by asking why God would waste all that space otherwise. But that thinking stalled acceptance of Copernicus due to too much empty space to explain lack of parallax. We fell guilty of hubris by centering our tiny planet in the Universe due partly to our short-sightedness. If we chose to claim to be the only intelligent planetary beings in the universe, will we not be embracing hubris yet again?

We are now over 5k exoplanets in number, which suggests at least one planet per star on average. Further, there are two lines of evidence for a galaxy count of ~2 trillion observable galaxies. If this number increases slightly, then we may have close to 6x10^23 stars and....planets. Avogadro would be proud. ;)

Of those 5k exoplanets, I find only 9 candidates in the HZ of a reasonable radius, none of which may prove to host life. At best, it’s reasonable to think we are extremely rare, at least in our part of the galaxy. This suggests to me that ET folks, if found, are out of phone range, though given the number of exoplanets, how could they not be out there...somewhere?
 
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If you are interested, I would direct you to a series of YouTube videos from Isaac Arthur wherein he discusses every aspect of the Fermi Paradox in an educational and entertaining fashion.
 

rod

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Post #16 comments, "It seems that the onus is on the side of those who think that it could only ever happen here to prove that it never has and never will happen anywhere else."

This thinking works both ways. Those who point to Earth and argue that life is here, thus it could be somewhere else in the universe, evolving in the past or present, have not proven their case either. The heliocentric solar system required necessary demonstration in astronomy and nature to be accepted over the geocentric solar system.
 
Post #16 comments, "It seems that the onus is on the side of those who think that it could only ever happen here to prove that it never has and never will happen anywhere else."

This thinking works both ways. Those who point to Earth and argue that life is here, thus it could be somewhere else in the universe, evolving in the past or present, have not proven their case either. The heliocentric solar system required necessary demonstration in astronomy and nature to be accepted over the geocentric solar system.
As I posted elsewhere, I tend to think of questions like this probabilistically. I start with the data that is available, and look at how well it represents the issue in question.

In the case of life on Earth, I think the rational questions are related to how rare the conditions on Earth are in the rest of the Milky Way Galaxy. We do not know the answer to that, yet. But, so far, there does not seem to be much about the Earth that would be expected to be rare. My guess is that a large, stabilizing moon or binary planet system is one of the most infrequent situations, but we do not have data on the frequency of that, yet. Nor are we confident that we know how important it is.

So, yes, it works both ways. But, since we already have proof that life on a planet like Earth is not impossible, it seems highly unlikely that there will be no life whatsoever anywhere else in the universe. To convince me that life does not occur anywhere else, you would need some logic and data, not just "We haven't found any, yet."

So, what are the arguments that the Earth is unique enough that life could only have occurred here?
 
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rod

Oct 22, 2019
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"So, what are the arguments that the Earth is unique enough that life could only have occurred here?"

I would agree using the postulate of abiogenesis as true for the origin of life. However, what happens to the probability argument if special creation is the correct answer and abiogenesis never happened?

"To convince me that life does not occur anywhere else, you would need some logic and data, not just "We haven't found any, yet."

That is an interesting approach but examine the heliocentric solar system debates. What if we did not see Venus phases or other predicted (specific predictions) in astronomy for the heliocentric solar system? Folks easily see the Sun moving across the sky but showing the Earth is moving around the Sun requires specific measurements and verification to prove. That is the standard I use for E.T. phoning home before accepting as science.

"So, what are the arguments that the Earth is unique enough that life could only have occurred here?"

This view could work before more than 5,000 exoplanets confirmed now. However, none are shown to be like Earth and with life on them. So far, no other planets in our solar system are confirmed with life either, in the past or present. Consider the exoplanets, how many are confirmed with fossil records? None.
 
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This thinking works both ways. Those who point to Earth and argue that life is here, thus it could be somewhere else in the universe, evolving in the past or present, have not proven their case either.
Right, but no one here is suggesting proof exists. This is about probability, which is assisted by the Drake summary of variables in equation form.

The heliocentric solar system required necessary demonstration in astronomy and nature to be accepted over the geocentric solar system.
Agreed. “Necessary demonstration” is the phrase Bellarmine gave Galileo (1616) to get him to cool his jets when challenging the dogmatic and mainstream view. This goes to the heart of science, though we see it in objective evidence. But circumstantial evidence, if objective, shouldn’t be too quickly dismissed.
 
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rod

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Right, but no one here is suggesting proof exists. This is about probability, which is assisted by the Drake summary of variables in equation form.

Agreed. “Necessary demonstration” is the phrase Bellarmine gave Galileo (1616) to get him to cool his jets when challenging the dogmatic and mainstream view. This goes to the heart of science, though we see it in objective evidence. But circumstantial evidence, if objective, shouldn’t be too quickly dismissed.
Helio, the probability view only works if abiogenesis is true. No abiogenesis for the origin of life and special creation, probability view falls on difficult times. So the Drake Equation must assume abiogenesis as true to start the calculations.

My posts point out that abiogenesis is the foundation for all probability of life arguments found in other parts of the universe today, including our solar system. If abiogenesis never took place or does not take place in nature, things fall apart quickly.
 
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Helio, the probability view only works if abiogenesis is true. No abiogenesis for the origin of life and special creation, probability view falls on difficult times. So the Drake Equation must assume abiogenesis as true to start the calculations.
No doubt abiogenesis is the favored view, but, alternatively, if one owned a million acres and flush with incredible funds, would only one very tiny garden be the favored scenario?
 
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rod

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No doubt abiogenesis us the favored view, but, alternatively, if one owned a million acres and flush with incredible funds, would only one very tiny garden be the favored scenario?
Helio, whoever or whatever owns the acres, this postulate requires modification to Drake equation. Let me know when that is done :)
 

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