NASA: We'll find signs of alien life by 2025

[rollingstein]

How is that a conflict of interest? Everyone has the right to flog their own livelihood.

Yes. But I'd be very wary of believing that estimate.

 

[Astudious]

@Astudious Evolution is like a wheel on top of a very tall hill. It's difficult to get the wheel rolling, but once it does, it will definitely lead to more complex organisms over time (even though it's random). One of the "hiccups" to the evolution of intelligent species like us (other than the formation of primordial life itself) is the transition from unicellular prokaryotes to multicellular eukaryotes (if I remember correctly, it nearly took a billion years for this transition to occur, and life on Earth itself is just about 3.5 billion years old; the longer the transition period, the greater the probability that the transition was unlikely and rare). I guess I should clarify: by discovering complex organisms, I mean discovering a "composite" organism - a collective group of structures (cells) in which the chemistry of life occurs, functionally related to each other, but fundamentally distinct (or something along those lines; you get the idea). Now that would be proof that formation of life to that level of complexity is not rare, and we have extremely few likely candidates left for "The Great Filter" which would stop the wheel from rolling towards levels of intelligence comparable to humans, since we don't have any other period of evolutionary stagnation worth mentioning on this timescale. It would be a sign that the filter is ahead of us intead, and that wouldn't be a very pretty scenario.

I agree: this falls under, I suppose, the category "if we find traces of several civilizations as complex as ours" in my post, which must be extended to "if we find traces of several biological entities that would be foreseen by the standard procedure of evolution as we know it to proceed to the same degree of advancement or complexity as our civilization within a timescale of a few billion years at most".

Which, personally, I do not think probable.

 

[Chronos]

There are as many possible explanations for the Fermi paradox as odds against any particular one being true. It is ridiculously improbable that abiogenesis is a process unique to earth. Yes, we haven't duplicated it in the lab, but, that's not the first example of a natural process we struggle to reproduce. Life, and intelligent life, are two different questions. In a utopian environment, there is scarcely any point in intelligence. You need sustained selection pressure to elicit a learn or burn response from DNA, IMO. The nature and timing of events sufficient to prod intelligence without destroying it could be the 'great filter'. We humans spent most of our history closer to extinction than success, before we began to collectivize knowledge and create civilizations. Intelligent life like our own might truly be a statistical oddity that has only occurred a few handfuls of times over the history of this galaxy. However disappointing, it is not unreasonable to suspect we could currently be the most advanced inhabitants of our galaxy.

 

[mfb]

So ,even if we come across a solar system exactly identical to ours which 10 or 20 light years away ,we will not able to detect either the Earth-analog or the Jupiter-analog ?

Depends on how hard we look and how lucky we are with the orientation of the orbits, but it would be very challenging unless we are very lucky.

If gas giants as big as Jupiter can't be found because they are a little far away from their star ,then how did we find kepler planets or super Earth's ? these are quite small compared to the gas giants right? and they not very close to their star either.

Kepler needs at least three transits to find a planet. At about 4 years observation time in the primary mission, Kepler could not find planets with an orbital period of more than two years at all, and if you add the time of the first transit and various downtimes every observation with a period above one year is very lucky. Also, the planets have to transit the host star - this is becoming less likely for planets with a larger separation from the star. All that is independent of the size of the planet.
To find earth-sized planets you have to measure the luminosity very precisely, better than 1 part in 10000. That was not possible for all stars, but there are many stars where it was possible.

Us being the first and only intelligent organisms to develop in the galaxy does not seem very probable either.

Pure speculation from your side again. We don't know. If there is no great filter, it is likely. For your claim you would have to show the existence of such a filter, which would be a great publication on its own.

I mean only one planet with intelligent life in 40 billion?

Not one, just the first one. Also, where is your point?

And is it fair to rule out what can and cannot be achieved in thousands of years

To follow your argument, you have to do exactly that.

If we were to find traces of several civilizations as complex as ours that failed to make it further, that would corroborate your point.

That for sure.

Evolution is like a wheel on top of a very tall hill. It's difficult to get the wheel rolling, but once it does, it will definitely lead to more complex organisms over time (even though it's random).

If you can prove that, write a paper about it. If you cannot, please don't write speculations as facts.

 

[lpetrich]

I could not find out what Dr. Stofan expects to be detected in that time. I also think that that is very overoptimistic. Let's see what an organism needs to metabolize and grow:

1. Liquid water, to serve as a solvent and raw material: H2O
2. Several other elements: C, N, P, S, various metal ions (can be trace amounts)
3. Usable thermodynamic disequilibrium, like chemical disequilibrium or suitably-energetic photons

These are all extrapolated from the Earth's biota, but there are plausible arguments for the first two, and the third one is a necessity. It enables organisms to appear to violate the Second Law of Thermodynamics by metabolizing and growing and reproducing and moving and the like.

Organisms can alter their environments in various observable ways, sometimes massively, like photosynthesizers releasing large quantities of molecular oxygen into the atmosphere. This is in chemical disequilibrium with its producers and with the less-oxidized crustal rocks. Rocks with Fe++ instead of Fe+++. But there can be nonbiological processes that produce chemical disequilibria. Like serpentinization: FeO + (1/2)*H2O -> (1/2)*Fe2O3 + (1/2)*H2. FeO has Fe++ and Fe2O3 has Fe+++. The resulting hydrogen will be out of equilibrium with a neutral or oxidizing atmosphere. Neutral: lots of CO2 and/or N2. Oxidizing: lots of O2.

Mars

Its surface is borderline at best for liquid water, being cold with a thin atmosphere, though there is an abundance of evidence that it had oceans and rivers some 4 billion years ago.

However, a few km down may be more friendly to organisms, and there is possible evidence of their presence: methane. Tiny amounts of it have been detected in Mars's atmosphere. (Mars methane detection and variability at Gale crater: Science magazine) It's typically a part per billion by volume, though it is sometimes greater.

It could be produced by 4H2 + CO2 -> 2H2O + CH4, where the H2 comes from serpentinization. It could be some nonbiological reaction alongside the serpentinization, or it could be organisms like Earth's methanogens. These organisms get their energy from the aforementioned reaction, and are a major source of methane in the Earth's atmosphere.

It might be possible to go further by finding the isotopic composition of Martian methane and comparing it to that of Martian water and Martian CO2. As a check, this ought to be done on Earth methanogens to see if they produce any distinctive signatures of isotopes.

Interior oceans of large icy moons

Moons like Europa, Ganymede, Callisto, Enceladus, and maybe also Titan, Triton, and Ceres (not a moon, but it has a similar size). They have the first two ingredients, but there is a serious question of whether any of them have the third ingredient: some usable disequlibrium like chemical disequilibrium.

There is a possibility for that. Several of them have rocky interiors, and they may get heated enough from radioactivity or tides to cause serpentinization and its production of hydrogen. This would likely be in disequilibrium with some of the contents the interior ocean.

Titan's surface

That would require some rather exotic biochemistry, starting with having hydrocarbons as a solvent. It would be biochemistry with H, C, N, but not much O or others. It doesn't look like it could make the necessary amount of complexity.

Extrasolar planets

The best chance here is doing spectroscopy and looking for out-of-equilibrium atmosphere gases like O2. That's going to be VERY difficult. For starters, one would have to do it in the infrared to get away from the bulk of the planet's star's light.

 

[PWiz]

Pure speculation from your side again. We don't know.

You don't need to know the actual result to ascribe a probability to it (no one tosses a fair coin 1000 times to assign a probability, now do they?) . What is unlikely is unlikely, nothing more to it. I'm not claiming anything, just commenting on how probable it is. After looking at the numbers I posted in #46, one would require some serious convincing (looking at the size and age of the universe) to think we are the first one. A lot of evidence is required to believe what is not obvious at all.

Not one, just the first one. Also, where is your point?

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us. Also, the probability of being the first one is not very different from being the only one. I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

To follow your argument, you have to do exactly that.

I have - please read the last sentence of post #46.

If you can prove that, write a paper about it. If you cannot, please don't write speculations as facts.

I would like to see some figures here. Has any period of evolutionary stagnation exceeded the nuclear transition of cells? How many early eukaryotes do we see around us? How do their numbers compare to prokaryotes? The vast number of bacteria and archaea still present is staggering - the evolution step still hasn't managed to convert most prokaryotes. I thought that this was a well established fact.

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable. And I was unaware that assigning probabilities to events in large sample spaces after looking at some well known facts counted as speculation. However, I'll drop the argument here if you insist.

 

[mfb]

(no one tosses a fair coin 1000 times to assign a probability, now do they?)

We are not tossing a fair coin, we are tossing an object where we don't even know how many sides it has. Saying one side is unlikely is pure speculation.

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us.

Yes, if such a filter exists. And even then it is just a relative statement, not an absolute one.

Also, the probability of being the first one is not very different from being the only one.

It is a massive difference. There could be millions of planets with life where intelligent life like ours might evolve within the next billions of years.

I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

Which is pure speculation, yes.

I would like to see some figures here.

Why do I have to provide evidence for a claim you made?

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable.

I did not claim that.
I said "if there is no great filter and the probability that life eventually colonizes the galaxy is high, then it is likely that we are the first - based on the observation that we do not see evidence of alien life doing that before us.
Note that I did not assign any probability to this "if" condition.

I don't think this discussion is moving forwards, my last post on those probabilities.

 

[PWiz]

@mfb Alright, so in short, all of this is mostly dependant on the existence of a filter (for which we have no evidence yet, yes) in the first place, right?

 

[mfb]

That will certainly be relevant for probability estimates, sure.

 

[Astudious]

You don't need to know the actual result to ascribe a probability to it (no one tosses a fair coin 1000 times to assign a probability, now do they?) . What is unlikely is unlikely, nothing more to it. I'm not claiming anything, just commenting on how probable it is. After looking at the numbers I posted in #46, one would require some serious convincing (looking at the size and age of the universe) to think we are the first one. A lot of evidence is required to believe what is not obvious at all.

I had a look at Post 46. Doesn't convince (read on).

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us. Also, the probability of being the first one is not very different from being the only one. I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

Sure. If by "Great Filter" you mean to include potentially, abiogenesis itself.

I have - please read the last sentence of post #46.

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable. And I was unaware that assigning probabilities to events in large sample spaces after looking at some well known facts counted as speculation. However, I'll drop the argument here if you insist.

Unfortunately giving some number of "Earth-sizedplanets orbiting in the habitable zonesof Sun-like stars and red dwarfs in the Milky Way ...orbiting Sun-like stars" is deeply insufficient. Hell, every planet in the universe could meet these criteria without it necessarily proving your point.

The Goldilocks Zone is not considered a serious barrier in the question of whether there is extraterrestrial life, because, of course, there are billions (at least) of planets which would match this criterion. The real barrier must be in the biochemistry of abiogenesis. Whether or not that is a process of any reasonable repeatability is unknown. Perhaps it was a freak occurrence on the order of (pulling a number from nowhere) 1 in 10²⁰⁰ Goldilocks planets. We cannot know or say that this is improbable ^until we a) see life elsewhere having emerged independently or b) understand abiogenesis and its initiation pathways better. This is something humans have crucially not been able to kickstart in the lab. We don't know how it happens and it looks like a fairly rare event from all lab trials; the point is, it could be almost infinitesimally improbable (and thus the chance of it happening elsewhere in our same universe is practically 0, regardless of how many Goldilocks planets there are), because we are just here to talk about it as its product.

We can only suppose that, if it is more probable than this, there are not too many other filters before our stage of evolution. I am inclined to suggest that the only reasonable "Great Filter", besides the first generation of life, would be amalgamation into working complex life that we discussed before. I'd be surprised to learn the "Great Filter" is actually something that hits civilizations once already well-evolved.

 

[PWiz]

@Astudious But my entire hypothesis was based on NASA finding life in 2025. That result would confirm that life isn't a freak occurrence, and that abiogenesis is not what's rare. In any case, the coming years would certainly throw some light on whether the Great filter exists or not, and if it does, what its nature could be, such as what you have suggested about complex life evolution (as our scanning range increases). Better hold on to your ideas tightly until 2025!

 

[DennisN]

I'm getting some popcorn!
http://www.huffingtonpost.com/2015/04/08/nasa-alien-life_n_7023134.html

Interesting discussion to watch, I enjoyed it! I am also hopeful, but for some reason maybe not as hopeful as they are in the discussion, i.e. I think it may very well take longer time to find good evidence of life. But what do I know? They are professionals in this field, and I am not .

Note: I did not eat popcorn while watching it, I ate ice cream.

 

[mfb]

Just found a related article: Complex organic molecules discovered in infant star system: Hints that building blocks of chemistry of life are universal

 

[rootone]

I'm not very surprised to hear that C-N bonds can be formed naturally under conditions which might easily occur in protoplanetary nebulae.
From this it's not a great leap of imagination so speculate that given further ideal conditions, such as a watery planet, these cyanides and similar might get involved in reactions that produce some amino acids.
We know that amino acids play a significant role in the chemistry of life on Earth, but they are not self replicating molecules.
I think one of the big unknowns here is, what is the simplest self replicating molecule?, and what are there conceivable conditions in which it might naturally arise.
It sure won't be RNA, the chances of RNA spontaneously occurring seem to me unlikely in the extreme.
There has to be a precursor self producing molecule which could at least have the potential to produce a minimally functional string of RNA.

.. but then again just because RNA then DNA became the basis of Earth based life, we can't assume that is the only possible basis for it.
There could be entirely different complex self replicating chemistry arisen elsewhere, and we might not even recognise it as 'alive' until it's examined in depth,

 

[256bits]

Astro Chemistry has been studying interstellar chemicals. Finding organic molecules in the gas surrounding an infant star system was more proof confirmation of the models the scientists had/have been using.

Regarding gas-grain chemistry,

Aims.The production of saturated organic molecules in hot cores and corinos is not well understood. The standard approach is to assume that, as temperatures heat up during star formation, methanol and other species evaporate from grain surfaces and undergo a warm gas-phase chemistry at 100 K or greater to produce species such as methyl formate, dimethyl ether, and others. But a series of laboratory results shows that protonated ions, typical precursors to final products in ion-molecule schemes, tend to fragment upon dissociative recombination with electrons rather than just ejecting a hydrogen atom. Moreover, the specific proposed reaction to produce protonated methyl formate is now known not to occur at all.
Methods: .We utilize a gas-grain chemical network to probe the chemistry of the relatively ignored stage of hot core evolution during which the protostar switches on and the temperature of the surrounding gas and dust rises from 10 K to over 100 K. During this stage, surface chemistry involving heavy radicals becomes more important as surface hydrogen atoms tend to evaporate rather than react.
Results: .Our results show that complex species such as methyl formate, formic acid, and dimethyl ether can be produced in large abundance during the protostellar switch-on phase, but that both grain-surface and gas-phase processes help to produce most species. The longer the timescale for protostellar switch-on, the more important the surface processes.

http://adsabs.harvard.edu/abs/2006A&A...457..927G

Zeta Ophiuchi, runaway star from an extinct binary, heats up interstellar gas ( which can be studied ) as it plows through forming a bow.
http://apod.nasa.gov/apod/ap110204.html

 

[DennisN]

Just found a related article: Complex organic molecules discovered in infant star system: Hints that building blocks of chemistry of life are universal

I think this may deserve it's own thread, if there isn't one already (or what do you say, mfb?). I've also found the full report. But which forum does it fit in, I wonder? Edit: I guess Astronomy (Planetary Science)... I'll look for a thread, or start one, I think . Edit: I started a new thread here.

 

[Jimster41]

Sorry if it sounds like I'm shill for this guy. No agenda, I swear, though I have enjoyed his writing. I was looking for publications with his name in arxiv, found this, and thought of this thread.

http://arxiv.org/abs/1410.7374

Internalizing Null Extraterrestrial "Signals": An Astrobiological App for a Technological Society
Eric J. Chaisson
(Submitted on 27 Oct 2014)
One of the beneficial outcomes of searching for life in the Universe is that it grants greater awareness of our own problems here on Earth. Lack of contact with alien beings to date might actually comprise a null "signal" pointing humankind toward a viable future. Astrobiology has surprising practical applications to human society; within the larger cosmological context of cosmic evolution, astrobiology clarifies the energetic essence of complex systems throughout the Universe, including technological intelligence that is intimately dependent on energy and likely will be for as long as it endures. The "message" contained within the "signal" with which today's society needs to cope is reasonably this: Only solar energy can power our civilization going forward without soiling the environment with increased heat yet robustly driving the economy with increased per capita energy usage. The null "signals" from extraterrestrials also offer a rational solution to the Fermi paradox as a principle of cosmic selection likely limits galactic civilizations in time as well as in space: Those advanced life-forms anywhere in the Universe that wisely adopt, and quickly too, the energy of their parent star probably survive, and those that don't, don't.

 

[zanick]

I think its conservative to assume that there are several 1 in a million events or conditions that need to be possible. Just two of them, give odds of life happening once per solar system. three or 4 factors, make near once in our known universe. :) (not to mention trying to find it during that period that it exists as well . in 10 billion years, giving at least 4 billlion for life to form) that in itself might be more than one in million.)

 

[Snerdguy]

Life is inevitable. But detecting it many light years away in a manner that is irrefutable is far from our scientific abilities. Sure, we may find indicators such as methane and water and other chemical compounds that we associate with the existence of life. But, they can exist for other reasons. It might be safer to say that, in twenty five years, we may be able to guess with greater certainty that the conditions on a certain planet around a different star from our sun could be conducive to life. But, unless we can somehow go there and see life, it's just speculation.

The problem with detecting life anywhere is that it is fleeting. It starts at random and only lasts for a tiny fraction of the time that the universe exists. If you are looking for intelligent life, as we define it, its even more fleeting. Life starts when the conditions are appropriate and ENDS when those conditions can no longer support it. Stars and planets come and go, some form faster and others slower. But during the life of any star and it's planets, the portion of time when conditions support life is pretty narrow. Look at how many times our planet had abundant life, then lost almost all of it and then recovered only to almost loose it all again before we, the homo-sapiens became the dominant species.

Eventually, we and all life on our planet will cease to exist. But, the period of time this planet supports life is going to be very short in comparison to galactic time. So, "life" elsewhere has probably sparked and ended countless times before we even came to exist and that's why we may never encounter life outside of our solar system, let alone intelligent life. The environmental conditions and chemical reactions that bring about life happen frequently but for relatively short periods of time and space is vast. Life on our planet probably won't exist long enough and during the right period of galactic time for it to be detected by other life forms. Yes, I know. In our arrogance we think our species can go on forever. It's really just a delusion.

 

[rootone]

Sure, water, methane, amino acids, none of those are certain indicators of life.
If we were able to detect fluorocarbons, aromatic compounds, and stuff like that then some kind of life 'as we know it' might then look like the best explanation.

 

[mfb]

Life is inevitable. [...]The environmental conditions and chemical reactions that bring about life happen frequently

Please give a source for that claim.

But, the period of time this planet supports life is going to be very short in comparison to galactic time.

Life on Earth has been around for 1/3 of the age of the universe, and did not end yet. I would not call this "very short".

 

[Jimster41]

In my post 67, Chaisson, from Harvard Smithsonian Center for Astrophysics, who I believe was intimately involved with SETI - (in fact the paper referenced there was related to a talk he gave to SETI researchers) I'm pretty sure would agree that the physical conditions that drive the formation of complex biological systems are a direct result of the expansion of the universe and the 2nd Law, and as inevitable. It is the premise of much of his writing - and is outlined in the reference paper There are references in the paper that are likely relevant.

 

[Jimster41]

Here's figure from the paper, with caption:Figure 1 – Energy rate densities for a wide spectrum of systems observed throughout Nature display a clear trend across ∼14 billion years as simple primordial matter changed into increasingly intricate, complex systems. The solid black curve implies an exponential rise in system complexity as cultural evolution (steepest slope at upper right) acts faster than biological evolution (moderate slope in middle part of curve), which in turn surpasses physical evolution (smallest slope at lower left). The shaded area includes a huge ensemble of energy rate densities as many varied types of complex systems continued changing and complexifying since their origin; the several dotted black curves delineate notable evolutionary paths traversed by the major systems labeled. The energy-rate-density values and historical dates plotted here are estimates for specific systems along the evolutionary path from big bang to humankind, namely, our galaxy, star, planet, life, and society, as compiled in the bubble inserts (Chaisson 2014b). Similar graphs likely pertain to extraterrestrial life-forms, as all complex systems fundamentally hark back to the early Radiation Era, evolve throughout the Matter Era, and potentially enter the Life Era (left to right across top).

 

[mfb]

That does not look like mainstream science.

 

[Jimster41]

@mfb I'm genuinely interested that you would say that. But I'd be appreciate a more specific justification of that claim.

http://en.wikipedia.org/wiki/Eric_ChaissonIf projecting Evolution through "Society" is discomforting... I recommend this one:

https://www.amazon.com/dp/0262600692/?tag=pfamazon01-20

A link to more info about Prof Jablonka. I'm only about halfway through that one. It's quite dense. But very good.

http://en.wikipedia.org/wiki/Eva_Jablonka

 

[mfb]

@mfb I'm genuinely interested that you would say that. But I'd be interested in a more specific justification of that claim.

Which claim?
"Person A says X" means at least one person says X, but it does not make that idea mainstream.

You can make log-scale plots of everything, that does not mean there would be some deeper connection between the plotted curves. And it certainly does not mean all those curves would have to exist at all.
US funding of science correlates with deaths from hanging, strangulation and suffocation
Divorce rates are linked to margarine consumption?
Age of Miss America is linked to Murders by steam, hot vapours and hot objects?

Also, the plot is a completely arbitrary selection with questionable values. Supernovae do not fit in at all, stars are not represented accurately there, and various other objects would have curves that do not follow the plotted pattern at all.

 

[Jimster41]

Just in case you didn't drill through...

I just want to be clear. This is not mainstream...?

Eric Chaisson
From Wikipedia, the free encyclopedia

[...] (removed by mfb, see below)

 

[mfb]

Please do not copy Wikipedia articles like that, that violates copyright. I removed the 1:1 copy.
Mainstream researchers can hold views that are not shared by the majority. That does not mean those views have to be wrong, but it is good to be skeptical (and if the opinion is not mainstream, that's exactly what is happening).

 

[Jimster41]

Sorry for plagiarizing wiki.

 

[Almeisan]

Ugh, this went ugly.

Mainstream opinion is historically known to be wrong a lot of the time.
Disregarding science because it does not look 'mainstream' is wrong. Any new discovery is not going to be mainstream when it is first discovered/proposed.
Apparently that guy is a 'mainstream scientist', the work discussed is in his field, it is not like he is publishing in something he wasn't trained.
If his crazy idea is 'wrong', and most cracy ideas are, it should be pointed out in a scientific debate. Crazy ideas proposed by trained scientists putting out thorough new ideas being examined closely by peers is how science moves forward. If tomorrow everyone stopped proposing new ideas, science is dead.

And wikipedia articles are not copyrighted. All you need to do is put a link to wikipedia and indicate any changes you made.

 

[Jimster41]

Ugh, this went ugly.

Mainstream opinion is historically known to be wrong a lot of the time.
Disregarding science because it does not look 'mainstream' is wrong. Any new discovery is not going to be mainstream when it is first discovered/proposed.
Apparently that guy is a 'mainstream scientist', the work discussed is in his field, it is not like he is publishing in something he wasn't trained.
If his crazy idea is 'wrong', and most cracy ideas are, it should be pointed out in a scientific debate. Crazy ideas proposed by trained scientists putting out thorough new ideas being examined closely by peers is how science moves forward. If tomorrow everyone stopped proposing new ideas, science is dead.

I appreciate the job the moderators are trying to do. I can understand that PF has a pretty tough problem in trying to provide a stable lucid source of reference for participants, like me who are coming from all angles, bringing confusion, and being confusing. A conservative perspective is reasonable. And I'll own up to the fact I have been influenced by the writings of this guy (no-one to blame but myself). I've come to realize how much recently, largely due to conversations I've had here, and so I'm revisiting my understanding from as many angles as I can find. Frankly, I had sort of assumed his ideas were widely accepted. So I have to be open to the realization that may not be true.

That said, I like the way you put it... and so far his thinking seems particularly "right" in my travels... partly because it is so gestalt. And as I am reading his second book... I am finding it even more, interesting, and frankly, lucid. One thing I like about him, he's not afraid to ponder and talk about the squishy side of things, biology, history, society, culture etc. In other words he's a cross-disciplinarian , which is refreshing. Surely an understanding of the world must be consistent with their complex "facticity", if not explanatory.

 

[D H]

That does not look like mainstream science.

Just in case you didn't drill through...

I just want to be clear. This is not mainstream...?

Eric Chaisson
From Wikipedia, the free encyclopedia

mfb was a bit waffly in writing "That does not look like mainstream science". I'll be less waffly: That is not mainstream science.

Just because someone has a PhD does not make what they write mainstream science. Just because they get that writing published in a peer-reviewed journal does not make what they write mainstream science.

There oftentimes are large lags in science between when a concept is first introduced, then refined, and finally accepted as "mainstream". I'll use a specific example, dark matter, to illustrate. Jan Oort and Fritz Zwicky first puzzled over what appeared to be a missing mass problem in the 1930s. Vera Rubin used much better instrumentation in the 1960s and 1970s to show that there was indeed a missing mass problem. The concept of dark matter didn't become mainstream until the mid 1980s or so. A number of people have proposed various solutions regarding what dark matter actually is. While the concept of dark matter most certainly is mainstream science, not one of those proposed solutions is mainstream science.

 

[Jimster41]

I'm good with that Sir. Makes perfect sense.

Is there a policy here I may have missed regarding discussing non-mainstream science. Seriously. I didn't read all the FAQs and rules...

 

[Evo]

I'm good with that Sir. Makes perfect sense.

Is there a policy here I may have missed regarding discussing non-mainstream science. Seriously. I didn't read all the FAQs and rules...

It's at the beginning of our rules.

• We wish to discuss mainstream science.That means only topics that can be found in textbooks or that have been published in reputable journals.

https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/

 

[Jimster41]

I can imagine that the first paper which was based on a talk Chaisson gave to the founders of SETI, arguably doesn't qualify

How about this one... that describes in more detail the derivation of the plot.
https://www.cfa.harvard.edu/~ejchaisson/reprints/unifying_concept_for_astrobio.pdf

A unifying concept for astrobiology
E.J. Chaisson Wright Center, Tufts University, 4 Colby Street, Medford, MA 02155, USA e-mail : eric.chaisson@tufts.edu

Abstract: Evolution, broadly construed, has become a powerful unifying concept in much of science – not only in the biological evolution of plants and animals, but also in the physical evolution of stars and planets, and the cultural evolution of society and its many varied products. This paper (1) explores the bulk structure and functioning of open, non-equilibrium, thermodynamic systems relevant to the interdisciplinary field of astrobiology, (2) places the astrobiological landscape into an even larger, cosmological context, (3) defines life, complexity and evolution writ large, (4) claims that life depends ultimately on the expansion of the Universe and the flow of energy derived therefrom and (5) proposes a quantitative metric to characterize the rise of complexity throughout all of natural history. That metric is neither information nor negentropy, for these inveterate yet qualitative terms cannot be quantified, nor even defined, to everyone’s satisfaction in today’s scientific community. Rather, the newly proposed metric is normalized energy flow, a revision of a long-cherished term – energy – that is physically intuitive, well defined and readily measurable. All ordered systems – from rocky planets and shining stars, to buzzing bees and redwood trees – can be best judged empirically and uniformly by gauging the amount of energy acquired, stored and expressed by those systems. Appeals to anthropism are unnecessary to appreciate the impressive hierarchy of the cosmic evolutionary narrative, including a technological civilization that now embraces an energetic agenda designed to better understand, and perhaps to unify, all the natural sciences. Received 10 June 2003, accepted 24 June 2003Is the "International Journal of Astrobiology" Reputable...?

http://journals.cambridge.org/action/displayJournal?jid=IJA

 

[Evo]

The Journal has been declining since 2011, it's impact factor has dropped to 0.826.

 

[D H]

This is a bit out of order response; I want to address this first remark before I delve into the body of the discussion.

And wikipedia articles are not copyrighted. All you need to do is put a link to wikipedia and indicate any changes you made.

Wikipedia articles most certainly are copyrighted. From http://en.wikipedia.org/wiki/Wikipedia:Copyrights, "The text of Wikipedia is copyrighted (automatically, under the Berne Convention) by Wikipedia editors and contributors and is formally licensed to the public under one or several liberal licenses. "

PF doesn't comply with those licenses. For one thing, we serve ads. For another, when we find some unapproved PF mirror site, we don't approve. In fact, we strongly disapprove.

Our general response to anything that looks remotely like a copyright infringement is to apply surgery. That includes material from wikipedia.

Mainstream opinion is historically known to be wrong a lot of the time.
Disregarding science because it does not look 'mainstream' is wrong. Any new discovery is not going to be mainstream when it is first discovered/proposed.

PhysicsForums primary focus is mainstream science. That's who we are. We've tried, multiple times, to allow and even encourage speculative discussions. The general consensus was that we need a personal theory forum like we need a computer virus. See https://www.physicsforums.com/threa...y-forum-like-we-need-a-computer-virus.765736/.

There are plenty of sites on the internet that take alternate views. You are free to participate in them. You are free to participate both here and at those other sites. All we ask is that you obey our rules at our site, and don't insist we be just like those other sites.

Is there a policy here I may have missed regarding discussing non-mainstream science. Seriously. I didn't read all the FAQs and rules...

You can find the rules in a number of places. At the top right of every PF window, there's a link to "Terms and Rules" under INFO. At the bottom, you can click on ABOUT. Our ABOUT page contains a link to "Terms and Rules", and also other useful information. Finally, at the very bottom, there's a "Terms and Rules" button. We try to make it easy.
Now, back to the main subject.

I've come to realize how much recently, largely due to conversations I've had here, and so I'm revisiting my understanding from as many angles as I can find. Frankly, I had sort of assumed his ideas were widely accepted. So I have to be open to the realization that may not be true.

I would venture that very little of astrobiology has made its way to "mainstream science". Yet. There's too much extrapolating from a sample size of one from within another sample size of one. Only one of the eight planets appears to bear life, and of that life, only one species has developed the capability to escape the planet. There is so much we don't know (yet). What science does know is that what it thought it knew about planet formation 25 years ago has been turned topsy-turvy, and regarding life beyond the the, science knows that it's currently clueless. Most astrobiologists take the "we are clueless" perspective -- and they want to get out of that category.

Saying that "we'll find signs of alien life by 2025" is a bit of an aggressive claim given that cluelessness. Should they look? Absolutely. Will they find something by 2025? Who knows.

 

[mfb]

Mainstream opinion is historically known to be wrong a lot of the time.

Still much less frequent than non-mainstream options.

Disregarding science because it does not look 'mainstream' is wrong.

It is wrong if you do science. We do not do science here! We discuss science. See the forum rules.

And wikipedia articles are not copyrighted.

They are, they are published under the Creative Commons Attribution-ShareAlike 3.0 Unported License and (usually) the GNU Free Documentation License. See Wikipedia:Copyright and Wikipedia:Citing Wikipedia for details. Just adding a link to the article somewhere (which was not present) is not sufficient, and incorrect citations frequently lead to various legal issues (mainly for images).

Can we get back to the topic of extraterrestrial life?

Edit: D H was faster (and more detailed).

 

[D H]

@mfb Us being the first and only intelligent organisms to develop in the galaxy does not seem very probable either. Where are you getting at?

Doesn't seem far from speculation. I mean only one planet with intelligent life in 40 billion?

What makes you so quick to reject the null hypothesis? Everything we've seen so far (which admittedly isn't much) is consistent with the null hypothesis.

 

[PWiz]

What makes you so quick to reject the null hypothesis? Everything we've seen so far (which admittedly isn't much) is consistent with the null hypothesis.

I don't want to drag this too long, so I'll summarize it real quick.

I'm not jumping to any side. It's all "if this happens, then..." etc.
If we don't find life for a long time, the probability of abiogenesis being rare in the universe continues to grow. If we find traces of complex life which existed in the past (in the coming years), then the probability of some "Filter" existing in the universe grows (since its proves abiogenesis is common but complex life progressing to become an intergalactic species is not). If complex life still in existence is found (intelligent extraterrestrials), then the probability of other complex species existing who have not yet come into our contact grows.

Basically, we don't know how abiogenesis works, and we don't have enough evidence to comment on it right now. I'm keeping all my options open and playing in the probability playground, waiting for something to roll my way. And about the null hypothesis, I don't think our sample space is large enough as of yet to dismiss these things, so in other words, the stamp should read "No correlation observed (subject to change)."

 

[mheslep]

Life sprang up on Earth almost as soon as it became habitable - like a billion years after it formed.

But how common is a habitable planet? Stable star, small habitable zone from the star, water, big moon to stabilize rotation orientation, outer gas giants to collect space junk, outside of galaxy to avoid super energetic phenomenon. Who's to say these conditions can not be less than one in a hundred million stars, i.e. once per galaxy, perhaps once per universe.

 

[mfb]

Stable star, small planet in the habitable zone, in the right distance from the galactic center: that's still in range of a billion. We'll learn more about gas giants in the next 10 years, and hopefully more about water as well. Moon-sized moons are ... tricky.

 

[mheslep]

"I think we're going to have strong indications of life beyond Earth within a decade, and I think we're going to have definitive evidence within 20 to 30 years," NASA chief scientist Ellen Stofan said Tuesday during a panel event on water in the universe.

Not precursors, but life itself? Sounds hopelessly arrogant to make such a prediction.

 

[Chronos]

A planet virtually identical to Earth [same 'big' moon, iron core, water, gas giant buddies, etc.] could be exceedingly rare - possibly on the order of 1 per galaxy, although I view this as probably a bit pessimistic based on the principle of mediocrity.

 

[Snerdguy]

Please give a source for that claim.
Life on Earth has been around for 1/3 of the age of the universe, and did not end yet. I would not call this "very short".

"Life is inevitable." has been said by many people in many ways for quite some time now. But here is one detailed explanation:
https://www.quantamagazine.org/20140122-a-new-physics-theory-of-life/

Life on Earth has come and gone and come back again a few times but for a few simple organisms. It's still not that long relevant to the age of the universe. I suppose it will always be a subjective observation though.

 

[mfb]

But here is one detailed explanation:

See the article:

His idea, detailed in a recent paper and further elaborated in a talk he is delivering at universities around the world, has sparked controversy among his colleagues, who see it as either tenuous or a potential breakthrough, or both.
[...]
"Jeremy’s ideas are interesting and potentially promising, but at this point are extremely speculative, especially as applied to life phenomena"

... and so on.

Life on Earth has come and gone and come back again a few times but for a few simple organisms.

There is no evidence of multiple independent events where life emerged from non-living things. All known life on Earth has a common origin. To our knowledge it was never "gone", although it had some hard times in between.

 

[Jimster41]

I think the playah is right. But I'm looking forward to learning what the new part is, because these ideas have been around a good long time. I encountered them 15 years ago in Prigogine, Chassion, Dawkins, Schroedinger, and others.

Some others...
http://arxiv.org/abs/0907.0042
http://www.earth-syst-dynam.net/2/37/2011/esd-2-37-2011.html

 

[Torbjorn_L]

I guess this discussion is mostly over, but since I am intensely interested in astrobiology I will make some quick notes.

- NASA's intent.
NASA, together with astronomers, are pushing for a new generation of large telescopes, here space telescopes. The observational constraint is that if life is likely, they can observe it soon. If not, they can start to constrain its likelihood from above.

- Search for life.
Besides the search for inhabited planets in the radiative habitable zone, we will eventually need to investigate many or most of our system's tidal habitable zones (ice moons). Because a) they constitute the perhaps largest type of biosphere volume, and because b) we can't observe a frequency of biosignatures elsewhere.

- Likelihood for life.

But, what if life is not common? Some things only happen once, even in near-infinitely large universes.

Until we have expanded our knowledge of life beyond a sample size of one, such speculations are interesting, but barely constitute science.

Nothing happens 'only once' in a sufficiently large universe, because the permutations among a finite number of particles in a finite observable universe is finite, see e.g. Tegmark.

But that isn't interesting, because we are restricting severely as in everyday life, "if that hadn't happen I wouldn't have ...".

What is relevant here is that emergence of life is a result of a process. And processes that result on the order of one ( zero, one, a few) events would be very finetuned.

The statistics of emergence do constitute science (and shows that emergence is a process; but see also below). See e.g. Lineweaver on how to do statistics here. Loosely, the rapid emergence we observe allows us to claim that the process is likely on at least the order of ~ 10 %/billion years.- Fermi's Question and the Hart-Tipler Conjecture
When we read "Fermi's Paradox" we see the result of a political process. Fermi asked the question "where are they" and answered that space travel and habitability cartography is difficult. (Which they are.)

[ http://www.universetoday.com/119735/beyond-fermis-paradox-ii-questioning-the-hart-tipler-conjecture/ ]

- Emergence of life.

I don't think there is good evidence. We can't even get steps of abiogenesis to happen even in controlled lab experiments.

They offer plausible partial pathways, but there is nothing like a cohesive, demonstrable route from non-life to life.

We have no idea how abiogenesis happened. ... We struggle to deliberately make synthetic life de novo when we can do so much in both biochemistry and molecular biology.

Cosmologists have not demonstrated how to make a universe within a lifetime in a lab. Yet we study the emergence of the universe.

Evolutionists have not demonstrated how to make whales within the lifetime in a lab. Yet we study the emergence of whales from land living ancestors.

So what do we know, and what do we need to test?

- We know that there are a number of trait homologies between geophysical systems of Hadean and modern cells. So we know the generic phylogenetic tree as much as we know other generic trees of similar complexity. (We also know emergence is a result of a process, first growth of the geophysical systems that it happened in, then evolution after self-replicators emerged.)

- There were also obvious constraints that were in tension with those observations. But whether you adhere to the "pure" RNA world (RNA protocells) of Szostak et al or the "dirty" RNA world (RNA vents) of Russell et al, the last 5 roadblocks I know of fell in the last year. (I have a referenced write up, but it is too long for a PF comment.)

- What remains is to test the two main pathways sufficiently.* This has been ongoing for, oh, a decade now, and it seems astrobiologists expect it will take a few more decades. I'm frankly surprised that people persist in claiming that there are observational problems.

*Meanwhile, if you want to do research strategy, the bottom-up pathway of Szostak is as simple as possible while the top-down pathway of Russell is as complex as the phylogeny constraints makes it. Ironically, or rather consequentially, that translates to the largest prior for Szostak but the largest posterior for Russell. So if I was into betting...

 

[Torbjorn_L]

Also, re thermodynamics of England, I would rather look at Russell, Pascal and Pross here. Especially the former group that are ore empirically based, and locate some problems of the latter two. (They claim that a photophile "soup" is necessary for emergence of replication. That is likely wrong, as any PCR reaction - if it can use metal atoms - can tell us.)

But, yes, emergence of life is a thermodynamic opportunity as a terrestrial planet cools. It extends the conversion of CO2 into CH4 into lower temperatures, maximizing entropy production if it happens.

 

[Jimster41]

@Torbjorn_L I would be interested in links to the research you mention.

It sounds like you are coming from the biology side. There is a thread discussing the plausibility of the physics (thermodynamics of emergence, complexity) over in the cosmology forum (where some might argue it is out of place). As I mention in that thread this seems to be a particularly cross disciplinary topic. To my thinking the synthesis it proposes between the basic physics of matter and energy, and the "life sciences" is one of its explanatory strengths.

https://www.physicsforums.com/threads/why-are-there-heat-engines.809331/page-2#post-5082768