Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Updated Drake Equation

  • Please log in to reply
97 replies to this topic

#26 rekokich

rekokich

    Viking 1

  • *****
  • Posts: 856
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 31 October 2019 - 03:36 AM

Bill,

The Oxford model, based on the Monte Carlo simulation, is an alternative statistical method to the Drake equation, which attempts to quantify the unknown based on no data points.

The Oxford model yielded 53% - 99.6% probability that we are the only technological civilization in our galaxy, and 39% - 85% probability that we are alone in the observable universe. I find a simple mathematical inconsistency in their results.

Assuming the”worst case” scenario, the probability that we are NOT alone in our galaxy is
100% - 99.6% = 0.4%.

Then, in a universe of 200 billion galaxies ( 2E11 ), the probability that we are NOT alone would be:
1 - ( 1- 0.004 )^2E11 = 1, or 100%,
not 15%.as suggested by the Oxford model.


Edited by rekokich, 31 October 2019 - 11:55 AM.


#27 Sleep Deprived

Sleep Deprived

    Mariner 2

  • *****
  • Posts: 220
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 31 October 2019 - 04:32 AM

Rekokich, you have an interesting approach to extrapolating the Milky Way's likelihood of tech civilizations to that of the universe.  The Milky Way is larger than the average galaxy, so should have a higher than average chance of tech civilizations.  Also, a large number of the 200 billion galaxies would be over, say, 5 billion light years away.  Because they are that distant, they would also be made up of earlier-generation stars and tend to be metal-poorer than our galaxy.  I would expect metallicity would have a great effect on the likelihood of life, and civilized life, too.  I am not versed in the Oxford model, so I don't know what assumptions went into it.  I don't know if that model takes into account the factors I have mentioned, but I would think these factors would have a great effect on the likelihood of life (and especially intelligent life) in the broader universe.  These effects would tend to lower the probability that we are NOT alone, in the worst case scenario in the visible universe.  Your point is well taken, but needs a little work.



#28 rekokich

rekokich

    Viking 1

  • *****
  • Posts: 856
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 31 October 2019 - 01:28 PM

Sleep Deprived,

Thank you for your comment.

While an average galaxy is smaller than the Milky Way, the latest NASA estimate for the number of galaxies in the observable universe is two trillion - ten times more than the previous estimate of 200 billion in my calculation. So the result is still as close to 100% as you can imagine.
https://www.nasa.gov...viously-thought

With some exceptions, the vast majority of galaxies arise from primordial intergalactic matter containing mostly hydrogen, some helium, and trace lithium. So, most young galaxies have low metallicity and, as you mentioned, low probability of advanced life. Further nucleosynthesis occurs within stars, during supernovae, and during neutron star collisions. These processes result in increasing metallicity as galaxies age.

The Milky Way is about 13.5 billion years old - just as old as any distant galaxy visible within the lookback time distance of 13.5 billion years. We presently SEE them in the early stages of evolution (with low metallicity), just as they presently SEE us in the early stage of evolution (with low metallicity), although we are all in reality develped and enriched with metals at the present cosmological time.

Considering that light travels at a fixed speed against expanding space, it is important to remember that any information (e.g. metallicity) we receive from distant galaxies is billions of years old.



#29 Sleep Deprived

Sleep Deprived

    Mariner 2

  • *****
  • Posts: 220
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 31 October 2019 - 03:17 PM

All true, rekokich.  This is one arena where we could get into a debate over what the mean of 'is' is.  In my mind, when we talk about the visible universe, we are talking about what we can see - when we look at a galaxy 10B LY away, we are looking at a young galaxy.  o me, it 'is' a young galaxy with all the attributes of such a galaxy.  Short of a massive break in the accepted current laws of physics, there's no way to know what that galaxy would be like if we could travel there faster  than the speed of light - instantaneously going there to observe.  It's not a matter of technology, it's a matter of the laws of physics.

 

Having said all that, I get your point.  If we could view the universe, as it is today but not be sidled by the speed of light (so EVERYTHING we see is as it would be if it were 13.7-ish B years old), the inconsistency you spotted could very well hold.  Bear in mind, if we ignore the speed of light, the universe is infinitely large.  We would see what the current Big Bang background radiation has turned into in the intervening 13.7 B years.  Would there be an infinite # of galaxies in the infinitely large universe?  Or would all the galaxies occupy a sphere of a certain size in an infinite of nothingness?  I see your POV, I just have a different one.



#30 DaveC2042

DaveC2042

    Mariner 2

  • -----
  • Posts: 228
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 31 October 2019 - 03:56 PM

Dave,

You are correct. The single lineage argument is unconvincing because it is yet another example of false inference.

The LUCA study showed that currently known terrestrial life forms have a common origin in a hydrothermal vent prokaryote. But, prokaryotic cells already manifest very substantial structural complexity in the form of double plasma membranes, cell walls, pilli, flagella, cytoskeletons, nucleoids (self-replicating DNA), ribosomes (self-replicating RNA), plasmids (self-replicating rings of DNA). These cells communicate environmental conditions to each other via chemical mediators (quorum sensing), and exchange genetic information with adjacent cells through the pilli (e.g. antibiotic resistance).

Numerous structural elements, dual genetic composition, regulated gene expression, and behavioral sophistication indicate that LUCA itself was not a primordial life form, but rather a merger product of MULTIPLE precursors.

The single lineage argument is easily refuted by:
- Incomplete investigation of all terrestrial life forms,
- Extinction of selected lineages caused by interspecies competition or environmental factors, and
- Merger of multiple primordial lineages into more complex biological


I think this is really overstating the case.

None of your bullets are definitive evidence of multiple starts, just evidence it's possible and plausible.

In reality, this is just something no one is sure of.

On the face of it, there is one form of life today, so it is reasonable to think there was one start. This is also supported by the manifest unlikeliness of it happening.

However, the speculation that it could have started more than once, and one form won out, is legitimate. Certainly there is no evidence this is not the case.

In between, there is the idea that current life is an amalgam of multiple starts. This has a good deal of circumstantial support. The issue for this debate is what do you mean by the start of life?

At one end, you have some separate chemical paths that are clearly not life, fusing into a single life form. That sounds implausible to me.

At the other, you have multiple distinct life forms fusing into a symbiote which wipes out its antecedents. That also sounds implausible to me.

In between is a vast, much more plausible, spectrum of possibilities where it is not necessarily obvious exactly where the moment life starts. In this area, you are arguing about semantics as much as science.

And, as I said above, we simply don't know at the moment.
  • llanitedave, russell23 and Sleep Deprived like this

#31 russell23

russell23

    Voyager 1

  • *****
  • Posts: 10,187
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 31 October 2019 - 04:25 PM

I'm in the "rare Earth" camp where I'm defining "Earth" as a long term stable habitable planet with complex multi-cellular land and ocean ecosystems

 

And I don't care about estimates based upon other galaxies.  I prefer to focus on the Milky Way in order to keep the numbers in a context that is more relatable.   So in our galaxy, right now, I would not be shocked (assuming we had the means to determine for certain) if we learned that we are living on the only "Earth" in the Milky Way.   I also would not be shocked to learn that the number of "Earths" is dozens or hundreds, or even thousands. 

 

But based upon our knowledge of planetary science, the Earth's history (geological & biological), stellar life cycles, extra-planetary threats to ecosystems, and so on, I just don't think it is very likely that our galaxy is teaming with "Earths".  And when the longevity of a civilization is factored in we may very well be "alone" as a technological species at this moment in our galaxy's history. 


Edited by russell23, 31 October 2019 - 04:27 PM.

  • astroneil likes this

#32 DaveC2042

DaveC2042

    Mariner 2

  • -----
  • Posts: 228
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 31 October 2019 - 04:40 PM

Another thought, which I and others may have mentioned before.

Skipping over some relativistic technicalities, in a universe with multiple lifes, one of them will arise first. Possibly by a substantial margin.

They would look out and find themselves alone.

This could be us.
  • russell23 likes this

#33 Sleep Deprived

Sleep Deprived

    Mariner 2

  • *****
  • Posts: 220
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 31 October 2019 - 04:43 PM

I suspect I'll get flak for this, but maybe there is only one way to make life.  I don't believe it myself, but it is certainly possible.  In that case, maybe life DID spontaneously start in multiple places/times on Earth and because there's only one way for it to happen, the various 'lines' are indistinguishable from each other.  Who knows, maybe single cell life is being spontaneously formed right now, but it just looks like all the other single-cell life forms out there.  Or perhaps the conditions that allow the formation of 'our' type of life are completely incompatible with other types of life, so ONLY one type of life was ever really possible on Earth.  Obviously, all conjecture.  Until we find ET, I suppose, we may never know.

 

Wouldn't it be a kick if we traveled untold light years to find an inhabited planet, landed on it, and it only looked like we landed on some unknown continent on Earth, with trees and 'grass' and animals with molars and hooves, etc.????  The animals may be as different from what we know in North America as the animals in, say, Australia.  Imagine the surprise of the first European that laid eyes on a kangaroo.  Maybe that's about as different  as is possible.  I'd like to think lots of other things are possible, but who knows????


Edited by Sleep Deprived, 31 October 2019 - 04:50 PM.

  • russell23 likes this

#34 sg6

sg6

    Fly Me to the Moon

  • *****
  • Posts: 6,908
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 31 October 2019 - 05:38 PM

The Drake equation was somewhat simplistic. Also it was produced basically by people that wanted there to be other life so was a little bias. It lacked detail in many ways - how important is the moon we have? Was never a factor. Metallicity of the star forming region. Also since it was produced we have found the planetry arrangement in our solar system is unusual it seems. Don't think we have yet found one like ours, equally will agree we need better resolution.

 

One talk I attended about this, was presented I suspect more realistically and they had a balloon for each identifiable requirement they had made, if I recall they had 22 balloons. I did get a copy of the presentation but the software I have fails to open the file - MS changed the Powerpoint software at some time. Mine is old.

 

What the big question is what is the probability of the various conditions being true and what does that mean/imply.

 

Often comment there is one answer to why have we not heard from another - We are the first to crawl up out of the primordial slime and build a radio. Someone has to be first. Trouble is universal and evolution timescales are large, the next might be a million years behind. It has taken us mammels 64 million years to get here since a lump of rock removed the opposition called Dinosaurs.

 

Expect a "Drake Equation" to be almost impossible. Too many inputs, some may be almost irrelevant, others highly relevant - who decides the weighing.



#35 Sleep Deprived

Sleep Deprived

    Mariner 2

  • *****
  • Posts: 220
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 31 October 2019 - 05:49 PM

 

Expect a "Drake Equation" to be almost impossible. Too many inputs, some may be almost irrelevant, others highly relevant - who decides the weighing.

Not to mention possible missing inputs.  Or relationships between various factors that are important to the outcome.  The Drake Equation is a great place to start in our search for ET, but it is only a start.  Newton's Equations of motion were a great start, too, until the 20th century scientists 'improved' upon them with relativity.



#36 InterStellarGuy

InterStellarGuy

    Viking 1

  • *****
  • Posts: 620
  • Joined: 25 Jun 2008
  • Loc: Overland Park, KS

Posted 01 November 2019 - 12:50 AM

As far as everything being speculation, well that is true, even within the link you provided (I would not consider the initial premise valid that indirect evidence allows any hypothesizing, instead it only allows more non-evidentiary speculating).  Nothing relative to there being life present elsewhere in the universe at all is evidenced based.  So any discussion of possible life in the universe is 100% speculation.  No one even knows what is necessary for abiogensis for goodness sake.  So one saying we are unique or are not unique, well both are speculative although it can be said so far, after many decades of searching, only life on Earth is evidenced.  But even here, no evidence on how it started, which would be critical to speculate with any degree of confidence if those abiogenisis conditions might exist elsewhere.

 

Btw, at the end of the section of the link you provided discussing the Oxford Model it is mentioned that in a universe of 200B galaxies the likelihood of ETI would be 1.  Not sure that is relevant to the Drake Equation as that was only meant to model our galaxy.  Tempting to try to extend to the entire universe, but not relevant IMO and opens new cans of worms.  Best to stay within scope.  Actually, any non-zero probability for anything, given an infinite universe, will always be one so the numbers game becomes a problem when infinity is in the room and you really then need to nail down whether any of the prior assumptions in you equation can indeed be possible.  So as example, will technological civilizations ever last long enough to be meaningful for detecting any of their radiations?  Is it possible for a civilized species to exist for more than a few thousand or million years?  It indeed may not be.  So when you factor things like that, then presuming that the time for life to get to civilization takes eons  longer than that civilization can hope to survive, affects the 200B case cited.  I think it was quite wise of Drake to keep the argument framed to our galaxy as all the variables are unknowns really.  Extending the argument further is just folly.

 

I also do not think that statement in the link you provided that says the Fermi Paradox "infers that ETI do not exist because we have no evidence of them" is a valid point.  The paradox does not infer that so the argument that follows is moot.  Fermi's paradox simply states there appears to be a paradox -- if there are potentially so many, why not detectable?  Many have forwarded plausible rationales for this, including the Oxford folks in their discussion.  

 

As far as everything being speculation, well that is true, even within the link you provided (I would not consider the initial premise valid that indirect evidence allows any hypothesizing, instead it only allows more non-evidentiary speculating).  Nothing relative to there being life present elsewhere in the universe at all is evidenced based.  So any discussion of possible life in the universe is 100% speculation.  No one even knows what is necessary for abiogensis for goodness sake.  So one saying we are unique or are not unique, well both are speculative although it can be said so far, after many decades of searching, only life on Earth is evidenced.  But even here, no evidence on how it started, which would be critical to speculate with any degree of confidence if those abiogenisis conditions might exist elsewhere.

 

Btw, at the end of the section of the link you provided discussing the Oxford Model it is mentioned that in a universe of 200B galaxies the likelihood of ETI would be 1.  Not sure that is relevant to the Drake Equation as that was only meant to model our galaxy.  Tempting to try to extend to the entire universe, but not relevant IMO and opens new cans of worms.  Best to stay within scope.  Actually, any non-zero probability for anything, given an infinite universe, will always be one so the numbers game becomes a problem when infinity is in the room and you really then need to nail down whether any of the prior assumptions in you equation can indeed be possible.  So as example, will technological civilizations ever last long enough to be meaningful for detecting any of their radiations?  Is it possible for a civilized species to exist for more than a few thousand or million years?  It indeed may not be.  So when you factor things like that, then presuming that the time for life to get to civilization takes eons  longer than that civilization can hope to survive, affects the 200B case cited.  I think it was quite wise of Drake to keep the argument framed to our galaxy as all the variables are unknowns really.  Extending the argument further is just folly.

 

I also do not think that statement in the link you provided that says the Fermi Paradox "infers that ETI do not exist because we have no evidence of them" is a valid point.  The paradox does not infer that so the argument that follows is moot.  Fermi's paradox simply states there appears to be a paradox -- if there are potentially so many, why not detcteable?  Many have forwarded plausible rationales for this, including the Oxford folks in their discussion.  

 

 

Is the fermi paradox really even valid? As you stated: "if there are potentially so many, why not detcteable?" This assumes the technology for detection is there, which it isn't. We have no way of doing so.

 

SETI for example can only detect a civilization if we receive a narrow high power signal at a specific frequency (1420 Hz ) pretty much aimed for us, and we have to be listening to that star at that point in time. It doesnt detect radio leakage, and even positive hits are difficult to verify ( the wow signal for instance )

 

We still have no telescope capable of detecting bio or techno signatures in an exoplanet's atmosphere. And in our own solar system we can't even agree on what constitutes a detection of life ( see the viking lander thread ).

 

So given that, how is our lack of detection a paradox? It seems to me, that hypothetically speaking, if the closest 10 star systems all had life bearing worlds populated by civilizations at or beyond our technology, with our current technology, we would be unable to detect, yet alone verify that, short of anything less than one of them sending an interstellar vehicle, manned or unmanned, to visit us.


  • DaveC2042 likes this

#37 DaveC2042

DaveC2042

    Mariner 2

  • -----
  • Posts: 228
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 01 November 2019 - 02:08 AM

Is the fermi paradox really even valid? As you stated: "if there are potentially so many, why not detcteable?" This assumes the technology for detection is there, which it isn't. We have no way of doing so.

 

SETI for example can only detect a civilization if we receive a narrow high power signal at a specific frequency (1420 Hz ) pretty much aimed for us, and we have to be listening to that star at that point in time. It doesnt detect radio leakage, and even positive hits are difficult to verify ( the wow signal for instance )

 

We still have no telescope capable of detecting bio or techno signatures in an exoplanet's atmosphere. And in our own solar system we can't even agree on what constitutes a detection of life ( see the viking lander thread ).

 

So given that, how is our lack of detection a paradox? It seems to me, that hypothetically speaking, if the closest 10 star systems all had life bearing worlds populated by civilizations at or beyond our technology, with our current technology, we would be unable to detect, yet alone verify that, short of anything less than one of them sending an interstellar vehicle, manned or unmanned, to visit us.

I've always thought we are being either a little unfair, or a little too deferential to Fermi about this.  In context, it's pretty clear it was a  bit of a throwaway comment, and not a deep insight based on a whole lot of work.

 

At the time, I think it was a reasonable thing to wonder, given what we knew, and didn't know.

 

But when you get into the nuts and bolts of both the astrophysics and the biochemistry now, it's very clear that there is no paradox.  It is entirely plausible that life is very rare, and when you factor in the distances involved, it is not surprising that we haven't met anyone.



#38 Sleep Deprived

Sleep Deprived

    Mariner 2

  • *****
  • Posts: 220
  • Joined: 17 Apr 2019
  • Loc: Seattle Area

Posted 01 November 2019 - 02:19 AM

Good point, InterStellarGuy.  So, if we've been pumping out electromagnetic signals (radio, TV, even lasers - although I don't know if they've ever been DIRECTED to another star system) for, say, 125 years, only receivers within 125 LY could possibly have detected them.  For curiosity's sake, though, if a receiver were at, say Alpha Centauri, or Sirius, and passively listening to anything going on around the sun, could they even detect our noise, assuming a technology level similar to our's?  Or could they only detect something that is directed at them?  If they COULD detect radio or TV from us, I would expect it would be a cacophony of signal to the point that it would be JUST noise.  They might wonder what it is about the Sun that makes it so radio/TV noisy, but everything might be so jumbled together that it is like white noise.  If they are looking in whatever wavelength turns out to be Channel 4, they would be receiving EVERY Channel 4 on that side of Earth.  It would be like trying to make out language in a room of 1000 people, all speaking at the same time and volume.  Just white noise.

 

If we DIRECTED a high-power signal, then I can imagine that coming through loud and clear above the din.  But, I don't know.  Anybody ever look into how detectible we would be with our non-directed EM activity??


Edited by Sleep Deprived, 01 November 2019 - 02:23 AM.

  • Dynan likes this

#39 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 12:33 PM

Most probably we will never get to any of these 'colonizable' planets. The distances are too vast. The technology needed will probably never materialize before we wipe the planet clean ecologically.

 

Even if a 'generational starship' launched, and lasted eons, Earth would never see or hear from them again. We'd never know the fate of space-born humanity.

 

Arthur C. Clarke's adage holds in this situation: "Don't commute. Communicate." So unless someone/something out there shoots out an intelligible signal, we're alone.

Sadly, you're probably right, we're in the middle of a mass extinction event right now and most people dont even know it.

 

Even the Proxima Centauri system is thousands of years away based on current technology.  To send an uncrewed probe might be as short as 50 years.



#40 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 12:35 PM

I'm in the "rare Earth" camp where I'm defining "Earth" as a long term stable habitable planet with complex multi-cellular land and ocean ecosystems

 

And I don't care about estimates based upon other galaxies.  I prefer to focus on the Milky Way in order to keep the numbers in a context that is more relatable.   So in our galaxy, right now, I would not be shocked (assuming we had the means to determine for certain) if we learned that we are living on the only "Earth" in the Milky Way.   I also would not be shocked to learn that the number of "Earths" is dozens or hundreds, or even thousands. 

 

But based upon our knowledge of planetary science, the Earth's history (geological & biological), stellar life cycles, extra-planetary threats to ecosystems, and so on, I just don't think it is very likely that our galaxy is teaming with "Earths".  And when the longevity of a civilization is factored in we may very well be "alone" as a technological species at this moment in our galaxy's history. 

But do you think others existed before us and went extinct?  As perhaps we will too- our Greatest Filter may lie ahead of us (it may be upon us sooner than some think.)  Perhaps most/all sentient species go extinct because the very things that caused their rise also cause their fall?


  • llanitedave and mountain monk like this

#41 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 12:42 PM

Dave,

The best evidence for our uniqueness is that, based on genetic studies, all life on Earth evolved from a last universal common ancestor (LUCA), a single cell hydrothermal vent prokaryote, which appeared more than 3.9 billion years ago.

https://phys.org/new...ed-earlier.html

There is no other lineage of life on Earth so far detected.

If appearance of life were a common occurrence, a number of different genetic lineages should have developed in addition to LUCA. During the billions of years since, only viruses and prions evolved, which do not really qualify as independent life forms. These agents do not form cells, cannot produce their own energy, do not grow, and can not propagate outside a host cell.

The single origin of all life on Earth is a serious problem for the hypothesis that alien life must be common because life appeared so early in Earth's history.

In the end, ignorance can not be illuminated with any statistical model based on a single data point. But, if we were to discover other lineages of life on Earth or elsewhere in the Solar System, no matter how simple - that would be truly monumental. Recent studies have shown evidence of organic molecules in salty water expelled by Enceladus's geysers, suggesting the possibility of a hydrothermal vent biosphere. Magnetic field data from Europa indicate that it also has a subsurface salty liquid ocean. Another course of investigation would be to search for biomarkers in exoplanet atmospheres.

More WILL be revealed. Patience is a virtue; and virtue is its own reward.

Rudy

If we were to find evidence of ancient life having existed on Mars, that would also be monumental.

 

What about panspermia- the idea that life on Earth originated from elsewhere?



#42 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 12:44 PM

I don’t see the single lineage argument as compelling.  After all, there is only one surviving lineage in the genus Homo, even though we know that hominids were once far more diverse, and in several other evolutionary lineages groups that were once diverse have since gone through major choke points.  We don’t know whether there was a single origin of life on Earth, but a single surviving lineage is compatible with both single and multiple origin hypotheses.  A multiple origin model would still have set all the lineages in competition against one another, with the likelihood that one eventually came to dominate, and then overwhelm, the others.  A single origin model might imply not rarity of origin but rapidity of spread, such that the first life form to appear would occupy all available niches to the point that there would be no opportunities for a second origin to become established.

 

 I can see the possibility of both models being valid in different circumstances—on some worlds life would all be descendants of a LUCA, on others there might be two or more independent lineages coexisting.  

 

Like planet formation itself, biological evolution is chaotic, dynamic, unpredictable, yet ultimately tractable.  The possibilities are not infinite, but they are vast.  That’s part of the reason I think it might be a mistake to assume either that we’re alone in the galaxy, or that others would be essentially similar to us.

 

 I agree that patience will likely be rewarded.  I suspect those rewards will include a number of surprises.

We've also gone through several mass extinction events in this planet's history.  What would be the dominant species on our planet right now if the K-T event hadn't occurred?  Has anyone modeled that on a computer yet?



#43 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 12:46 PM

I've always thought we are being either a little unfair, or a little too deferential to Fermi about this.  In context, it's pretty clear it was a  bit of a throwaway comment, and not a deep insight based on a whole lot of work.

 

At the time, I think it was a reasonable thing to wonder, given what we knew, and didn't know.

 

But when you get into the nuts and bolts of both the astrophysics and the biochemistry now, it's very clear that there is no paradox.  It is entirely plausible that life is very rare, and when you factor in the distances involved, it is not surprising that we haven't met anyone.

It's quite possible that life itself is quite common, however technological life is very rare, maybe because it is self destructive and only exists for a very short period of time.


  • mountain monk and Dynan like this

#44 Dynan

Dynan

    Soyuz

  • *****
  • Posts: 3,611
  • Joined: 11 Mar 2018
  • Loc: NOLA

Posted 01 November 2019 - 01:12 PM

If we were to find evidence of ancient life having existed on Mars, that would also be monumental.

 

What about panspermia- the idea that life on Earth originated from elsewhere?

"How did Life start 'Elsewhere'" would be my question.



#45 City Kid

City Kid

    Gemini

  • *****
  • Posts: 3,383
  • Joined: 06 May 2009
  • Loc: Northern Indiana

Posted 01 November 2019 - 01:36 PM

It's quite possible that life itself is quite common, however technological life is very rare, maybe because it is self destructive and only exists for a very short period of time.

It's also quite possible that intelligent is quite common but the universe is so vast, the distances so great, we will never know. I see no paradox whatsoever just because of how far away everything is. The question, if intelligent life is everywhere, where is it, is easily answered by it's all too far away if it exists. I'm betting that no amount of technological advancement can overcome the huge distances between solar systems. 



#46 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 01:48 PM

It's also quite possible that intelligent is quite common but the universe is so vast, the distances so great, we will never know. I see no paradox whatsoever just because of how far away everything is. The question, if intelligent life is everywhere, where is it, is easily answered by it's all too far away if it exists. I'm betting that no amount of technological advancement can overcome the huge distances between solar systems. 

What about between here and the closest stars?  The breakthrough project funded by NASA seems to think we could reach the closest stellar systems in 100 years or so.

 

This was my line of reasoning (I recognize having a sample size of one makes it somewhat flawed, but it's all we have tongue2.gif)

 

We have had five mass extinctions in the history of this planet (that we know of) and are currently in the middle of the sixth (this one is human-induced.)  Let's say the K-T object hadn't crashed into the planet, would we have evolved more quickly and reached a much higher technological level than what we have now?  Or would some other species have done so and replaced us and if so would they have gotten to the stars by now because of this 65 million year head start (even a 1000 year head start would be enormous in technological terms!)

 

Now imagine some other advanced species on another planet that was older and/or had less mass extinctions than what we had on Earth- would they be much more advanced than us and what would they have accomplished by now?  Is a metallic body necessary for a space-faring species and if so would replacing our organic forms with metallic bodies make the passage of time meaningless to us, thus we could explore the whole universe, given enough time?  Could a species with a few thousand years head start on us (which is an insignificant amount geologically and biologically but enormous technologically) have reached this higher level of technology in order to do it or do most/all technological species go extinct because of their own flaws?  Lots to think about- and imagine!


Edited by Ring_Singularity, 01 November 2019 - 01:49 PM.


#47 Ring_Singularity

Ring_Singularity

    Messenger

  • ****-
  • Posts: 488
  • Joined: 27 Aug 2014

Posted 01 November 2019 - 01:51 PM

"How did Life start 'Elsewhere'" would be my question.

Indeed- it's almost like the idea of creating our universe from within another universe.  You just move the question elsewhere.

 

Microbes can travel on tektites between planets' perhaps long ago when Mars was more hospitable to life than the Earth was, life began there and was carried on a tektite to Earth as microbes?


Edited by Ring_Singularity, 01 November 2019 - 01:52 PM.


#48 llanitedave

llanitedave

    Humble Megalomaniac

  • *****
  • Posts: 29,985
  • Joined: 25 Sep 2005
  • Loc: Amargosa Valley, NV, USA

Posted 01 November 2019 - 11:24 PM

We've also gone through several mass extinction events in this planet's history.  What would be the dominant species on our planet right now if the K-T event hadn't occurred?  Has anyone modeled that on a computer yet?

I doubt that such a model is possible.  The process is far too chaotic, far too unpredictable.  Even with the K-T event, you could re-run the evolutionary clock endlessly and still not end up with anything looking like the current biological populations.


  • mountain monk likes this

#49 DaveC2042

DaveC2042

    Mariner 2

  • -----
  • Posts: 228
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 02 November 2019 - 02:17 AM

I doubt that such a model is possible. The process is far too chaotic, far too unpredictable. Even with the K-T event, you could re-run the evolutionary clock endlessly and still not end up with anything looking like the current biological populations.


Dawkins considers this in The Ancestor's Tale (which I cannot recommend highly enough).

He proposes it as a worthwhile high level thought experiment, rather than as a serious modelling exercise.

How likely is flight? How likely is a segmented body plan? How likely is intelligence? How likely is multicellularity?

All these things have evolved multiple times, though some of them not a lot. You'd probably expect them in a rerun, though maybe not flight every time (only happened 4 times so far).
  • llanitedave and Ring_Singularity like this

#50 russell23

russell23

    Voyager 1

  • *****
  • Posts: 10,187
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 02 November 2019 - 12:21 PM

Dawkins considers this in The Ancestor's Tale (which I cannot recommend highly enough).

He proposes it as a worthwhile high level thought experiment, rather than as a serious modelling exercise.

How likely is flight? How likely is a segmented body plan? How likely is intelligence? How likely is multicellularity?

All these things have evolved multiple times, though some of them not a lot. You'd probably expect them in a rerun, though maybe not flight every time (only happened 4 times so far).

This was also the primary theme of Stephen J. Gould's 1992 book "Wonderful Life".   Gould argued that if you could rewind the tape of life's history the small contingencies of history would result in a different outcome.


  • llanitedave and Ring_Singularity like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics