Kepler-186f is the first earth-sized planet located in the habitable zone of another star that has been discovered. With this discovery, the search for life on other planets has entered into a new zone of discovery.
In some ways very significant, it may be the first one we have seen. In others not so. The universe is very big and there will be a lot of these out there.
The more we find the merrier we will be, however lets hope the first one that finds us either does not have the technology to get here or does not have the track record humans do when it comes to exploring.
Well, there a lot of red dwarf stars in the Milky Way, but unless Kepler-186f has a single, very large moon, I suspect it must wobble a lot - making its climate far more erratic than Earth's!
Barry,
We knew since thousand of years that the earth was round but in 1968 when we for the first time saw an image of our planet taken from the vincinity of the moon, it was significant and most of us can picture this image when thinking of our blue planet. Today is a day like that. We knew for a long time that such earth-sized planet in the habitable zone had to exist but now we directly detect the first one.
Dr. Seth Shostak, a senior astromer at SETI is convinced that we will scientifically discover intelligent alien life on other planets of this galaxie within the next 20 years (40 at most).
Dr. Shostak said in this task that in astronomy we are looking towards the past but when we will detect the first electromagnetic signals from an alien civilisation, we will detect something of our future. It will be the greatest experience of our species. Communication is totally another business since it requires to bypass the wall that general relativity but I am an optimist.
https://www.youtube.com/watch?v=IVV4zRuE1mw#aid=P-iCEBNiW98
For now we are developing the technology to detect the the chemical signatures in the atmosphere of life in those planets.
James,
I do not have the specific about the specifics.
Regards
Louis,
If we can be "convinced that we will scientifically discover intelligent alien life on other planets of this galax[y] within the next 20 years" then surely I can speculate that this and most other 'Earth-like' planets throughout the galaxy will _not_ have a single, large, stabilizing moon to regulate climatic conditions. I am willing to guess that (since we're trying so hard), we may discover evidence of simple extraterrestrial life forms before our time expires...
Best wishes
James,
Shostak estimations are based on the lastest data and he is convinced (I do not know if he is the only one being convinced, but assuming that is not a lunatic) that it is a sure shot to discover at least one alien civilisation most likely within 20 years. This estimation is based on what we know now and based on knowledge of the technological advances that are coming.
How did he do his estimation in the details and about the necessity to stabilize the planet with a moon or other means, I do not know.
Louis,
Please - certainly there are too many unknown variable factors involved in the development of intelligent life on yet unidentified planets to reliably make such a prediction! If one could have remotely observed the Earth at any time in the distant past they might have detected the presence of abundant, even complex, life forms - but how would one have predicted when intelligent life might be developed? I'm not here to disrespect anyone, but I find this prediction to be untenable!
There has only been remotely detectable intelligent life on the Earth for the past few hundred years, at best, out of 4.5 billion years... It remains to be seen how long we can persist! My best to all intelligent life forms - wherever and whenever they might be!
The presence of intelligent life on earth would have been detectable a lot earlier than a few hundred years ago. It would depend on what method the observer was using to do the detection. Forest clearance in large parts of Europe were completed in the Iron Age and any intelligent alien observer would have been able to detect that if they were close enough.
For at least 6000 years significant sized human settlements have been distributed all over the planets surface. Again depending on how sophisticated the alien observer was (or how close) they would have been able to see artificial structures in many parts of the world.
Probability suggests that any intelligent (in our terms) alien life form will originate on an Earth like planet in order that they can evolve from single celled animals, thorough multicellular organism, to those with a notochord and bilateral symmetry to something with an upright stance, stereoscopic vision, an opposing thumb, vocal chords and a sophisticated intelligence. Without those characteristics you cannot make a hand axe and if you did not start with a hand axe you will not have needed up with a sophisticated industrial society capable of broadcasting its presence.
There will have been many such evolutions in the history of the universe but whether any of them are in our neighbourhood and able to make us aware of them is a different matter.
James and Barry,
We can only observe life here and we know only one intelligent species and doing science with one sample is always difficult. Back to the time where we thought earth was the center of the universe, we then thought we were really unique and central in the then known cosmos. The copernitian revolution decentralized us as a planet, made our case a mediocal case with this respect. Life was still held as probably unique. But the more we are learning on life of this planet and the more we tries to imaginate what was the beginning of life and the more we tend to think that earthly life at the microbial level is a mediocal situation. Now the estimate is that 20% of stars have earth-sized planet in the habitable zone. How much of this real estate hold primitive form of life? Our current science is too primitive to make estimate on that. Observational astronomy may provide answers before biological sciences can answer this question. Our present biological knowledge is insufficient. The less we know in a domain and the more is attribute to contingency . Fourty years ago, the rare earth hypothesis was much more popular than the mediocrity hypothesis because a lot of what was attribute to freak accidents is now attribute to regularities. There will always be a mixed for order and contingency in biology but the mix will diminish on the side of contigency with advances in knowledge. To the ignorant, everything is a miracle.
Intelligent life on earth is just beginning and we already are in the beginning of a human induced meta biological extinction. We are politically and economically out of control and it is what is undermining the ecological foundation of our survival. I hope that we will overcome this and if we do then we have about 1 billion years ahead of us. Assuming that some other alien civilization strived for billion of years then the chance to detect them are higher than those that strive just a few thousand years. It is why if we detect an alien civilisation, it is likely one that is old and more advance than ours.
Louis, indeed if we were to encounter an advanced civilisation today or even in the next few hundred years it would almost certainly have to be much older than ours. The only likely encounter we will have is via an interception of a communication channel, as radio waves. That will have to have come from many light years away as we have detected no planetary systems within our close stelar neighbours capable of harbouring any intelligent life form.
We have had radio transmission for around 120 years and it is possible that signals transmitted by wire could have been broadcast for the last 160 odd years. Anyone picking up signals transmitted from Earth would have to be within a minimum of 150-200 light years.
The further away any star system capable of sustaining intelligent life the older it would have to be for us to detect it. It is safe to assume that there is no broadcasting civilisation within several hundred light years of Earth, it could be that they are thousands of light years away. A signal emanating from a star system 500 light years away that we detect would have to have been broadcast by a civilisation at least 350 years in advance of our technology.
There are almost inevitably life forms out there in the universe that build cities, have legal systems and watch TV. We are unlikely as things stand to ever be meeting them however. They like us will be organic. They like us will be constrained by physical laws, especially the speed of light so, unless we have got physics completely wrong they are not coming here in a starship.
Barry,
In the future we may discover new physics allowing to tune in a cosmic internet. But just detecting a few hundred or a few thousand year old radio broadcast not even intended for us to detect would be an incredible rosetta stone on our future. Imagine the challenge of decoding this broadcast. I think that all old civilisations have to mature into stellar being and that here on earth are rapidly converging towards it. Most of cosmic communications are probably in between stellar beings converging towards meta stellar beings. Someone should write a good science fiction book on how meta stellar beings trying to converge at the universe level to become God.
It is not specifically interesting. It is not because it has an Earth size that it has more chance to host life than a double-earth size planet. The fact that it is in a habitable zone is interesting, but it is not the only planet within a habitable zone.
In addition to this, M stars are known for their high activity and therefore strong stellar wind. How actually habitable are planets around such kind of stars, given the probable high radiation level?
Patrick,
You are most probably right. But it is interesting as the beginning of an era of discovery of planets in the habitable zone.
It is very interesting that there are planets in habitable zones around their stars. Providing the planets themselves have habitable characteristics there is every good reason to believe they will be inhabited by some form of life.
Any Earth sized rocky planet will almost certainly have vast amounts of water and if it is within a habitable zone this will most likely be in the form of liquid oceans (although Earth did go through a long period of total cover with ice in the Precambrian) It will also be more likely than not to contain the organic compounds necessary for life.
If we are talking about life similar to that on Earth there are a number of other requirements. The planet would be likely to need a large moon in relatively close orbit to provide gravitational energy to power tides and plate tectonics. The life forms at the origin of life would need to have evolved in an anoxic environment and produced the atmospheric oxygen by respiration. The planet would need an iron core of similar size to Earth's to generate an electromagnetic field.
Even with all these (and there are many more) conditions there will be huge numbers of planets out there with, not only life on them but life that speculates about the probability of life on other planets.
If we are very lucky and Einstein was wrong we might get to meet them some day.
How is it that the moon has a stabilizing effect here on earth? I would think it would do the opposite. I cite as evidence the tides.
I would think what IS interesting about this new planet is that it is a similar size to earth for this reason. It's likely to have a gravity that could foster intelligent life.
Edward,
Without the Moon, Would There Be Life on Earth?
Scientiic american, , Apr 21, 2009
http://www.scientificamerican.com/article/moon-life-tides/
Edward Kilson,
"How is it that the moon has a stabilizing effect here on earth? I would think it would do the opposite. I cite as evidence the tides."
Please note that simply mentioning the tides only provides evidence that the Moon imparts a significant gravitational influence on the Earth.
That the Moon imparts a stabilizing, rather large, proximal gravitational influence on the Earth should counteract destabilizing, periodic effects that passing planets may impart in a multiplanet system. See http://www.nature.com/news/earth-sized-exoplanet-spotted-in-star-s-habitable-zone-1.15066. The planets within the Solar system exhibit varying rotational axis alignment (i.e., obliquity) instabilities, depending on several factors discussed below.
When making my comment, I was recalling reports of a 1993 study - http://www.dx.doi.org/10.1038/361615a0 - http://www.imcce.fr/langues/fr/presentation/equipes/ASD/person/Laskar/misc_files/Laskar_Joutel_Robutel_1993.pdf - whose abstract concludes:
"... But if the Moon were not present, the torque exerted on the Earth would be smaller, and the chaotic zone would then extend from nearly 0° up to about 85°. Thus, had the planet not acquired the Moon, large variations in obliquity resulting from its chaotic behaviour might have driven dramatic changes in climate. In this sense one might consider the Moon to act as a potential climate regulator for the Earth."
IMO the most straightforward test should be to consider Mars, which is most representative of a moonless planet such as such as (presumedly) Kepler-186f in a multi-planetary system. See http://en.wikipedia.org/wiki/Axial_tilt#Other_objects_of_the_Solar_System
"All four of the innermost, rocky planets of the Solar System may have had large variations of their obliquity in the past. Like Earth, all of the rocky planets have a small precessional rotation of their spin axis. This rate varies due to, among other things, tidal dissipation and core-mantle interaction. When each planet reaches certain values of precession, orbital resonances may cause very large, chaotic changes in obliquity. Mercury and Venus have most likely been stabilized by the tidal dissipation of the Sun. The Earth was stabilized by the Moon, as above, but before its capture, the Earth, too, could have passed through times of instability. Mars' obliquity is currently in a chaotic state; it varies as much as 0° to 60° over some millions of years, depending on perturbations of the planets.[16][26] The obliquities of the outer planets are considered relatively stable. Some authors dispute that Mars' obliquity is chaotic, and show that tidal dissipation and viscous core-mantle coupling are adequate for it to have reached a fully damped state, similar to Mercury and Venus.[2][27]"
This has since become a disputed subject (perhaps because of it implications for extraterrestrial life among enthusiasts). See http://dx.doi.org/10.1016/j.icarus.2011.10.013 http://barnesos.net/publications/papers/2012.01.Icarus.Barnes.Moonless.Earth.pdf - IMO, however, this study does not adequately represent the perturbational effects of other planets in a system.
http://www.nature.com/polopoly_fs/7.16807.1397754651!/image/1.15066_Kepler186f_ComparisonGraphic.jpg_gen/derivatives/landscape_630/1.15066_Kepler186f_ComparisonGraphic.jpg
Confirmation of statistical expectations is always good. If a solar system forms N planets it seems likely that at least ONE of them ends up in a habitable zone. This discovery confirms that expectation and the associated expectation that organic molecules floating in planetary oceans is likely a common occurrence in the galaxy.
We know that intelligence life exists in the visible universe because we exist. But we do not know if we are a single case, a rare case (arbitrary definition of rarity could be 1 case per galaxy life time) , or common in the order of several million per galaxy at the current time. We will most probably be able to detect the presence of microbial life in most of the planets in our galactic neighborhood no so far in the future. We will also be able to detect directly the presence of forest on large land mass on exoplanet in our galactic neighborhood. This would provide a minimal information on similiraties between multiple cases of biological evolution and from there we might be able to estimate how special we are.
What are your thought on this. Are we alone and how will we proceed to answer this question? As long as we are not sure that we are not alone, we are a bit like in the pre-copernitian model of being at the center of the intelligent cosmos. Will we be push out of the center of the intelligent cosmos?
Intelligent life is likely to be rare in terms of the vast majority of star systems being unable to support such life but as Louis says we know there is intelligent life out there because we are here. Even if it were only one in 100 million stars that had intelligent life looking up at it there would be vast numbers of populations out there in varying states of social and scientific evolution. Even if is only one in a billion there will still be lots of them. They will be out there in different stages of social and scientific evolution because there is more than enough real estate and absolutely plenty of time for this to have happened millions of times.
We may by advances in technology even be able to detect some evidence of life and one day we may pick up a regular transmission from an exoplanet. What kind of creature will have sent it?
We can be sure that any extra-terrestrial capable of building a radio set or a skyscraper on their world will have evolved from a primeval life form in much the same way we have. No intelligent life form will have sprung fully formed into the universe. If they can build radio sets and skyscrapers they have a highly developed language. That means they stand upright and have a self awareness like we do. If they can build a radio set they have an opposing thumb and stereoscopic vision because any creature that builds a radio set is descended from one that made hand axes.
They will live in large urban communities supported by farms and a ruling class and a working class. They will have leaders and followers. They will be driven by curiosity and desire to explore. depending on how technologically sophisticated they are they may even already be looking at us.
All in all the intelligent life in the universe will have evolved much the same as we have and will be constrained by the same laws of physics that we are. That makes it most unlikely that we will ever be visiting each other, but looking on the bright side we may be better off without a visit. Our own history tells us that an encounter between a technologically advanced society and a much less technologically advanced society has rarely been of benefit to the less well developed.
Will this planet be tidally locked (in synchronous rotation about its parent star)? I had an analytic model to deal with stability of the climate in such situations in a highly simplified way (pages 7-9). I don't think it prevents the planet being habitable if it is tidally locked, but it would perhps affect how we look for life.
I think this planet will be considered quite significant in the long run, although it is difficult to appreciate this at the moment. The trick is finding such planets reliably, not just when they transit, so we can find one within 20 light years of home and do detailed follow up. The value of Kepler is in showing that such planets (terrestrial ones in the habitable zone) almost certainly exist within this radius of Earth.
FYI - see http://news.sciencemag.org/space/2014/04/false-signs-life-alien-worlds.
Kepler discovery about the new planet is very significant for exploration of life in cosmos . Also, if intelligent life is their, we can develop a new era of relations. It will help in understaning a lot the Physics of the Planets. So it is a very great discovery.
IMO, it's far too soon to be getting excited about the prospects for intelligent life - even here on Earth!
It has been mentioned that we might detect the lights from cities, but I think that would only come into play for Mars, for example... Meanwhile, long before any campfires might have been observed on Earth - its conditions that might favor the development of life would have been indicated by the frequent observation of lightning (from Mars, for example). See http://www.youtube.com/watch?v=i6RxE-f2iyQ.
Again, I wouldn't light any candles in the window to encourage alien visitations...
James, you are right they are likely to be like all visitors and stay rather longer than is comfortable.
James,
It is highly unlikely that an alien life form visiting earth could live outside of a air tight suit. The earth bacteria, the earth virus would probably be deadly. We are in symbiosis with the earth viruses and bacterias but it would very very unlikely that alien life form could be compatible with microscopic earthly life form. The only way for an alien life form to adapt to this planet would be for them to bio-engineer an earthly lifeform which would be able to learn their culture and become part of their culture here. Maybe we could be a candidate but it is not certain. Our biggest concern for now is to survive our own toxic mess long enough to evolve a way to govern ourself that is compatible with our environment.
It is a good question… A clear to the question response was given buy Giordano Bruno, when he claimed the universe contained an infinite number of inhabited worlds… The question is: how is it likes that worlds?… we also able to find easy question with a analogy of uniformity of Charles Lyell : "An attempt to explain the former changes of the Earth's surface by reference to causes now in operation"… from this we can assume that in a exoplanet with similar planetological condition like Earth exists same condition like in actual Earth… The next Lois Basard says: “We know that intelligence life exists in the visible universe because we exist”… We cannot be sure about the types of life because the actual knows life in Earth is connected to water, CaCO3, CH4, N2, we are not able to says that the actual life forms on Earth may be connected to an uncial apparition mode (monogenesis) or they was appeared in more ways (plurigenesis)… only one thing we can assume that life connected to water was appeared in only way, because it can be originated in simple chemical systems… from this can be concluded that exists possibility to find same forms of life into Mars and Moon… (The Mars is an older planet than Earth and behaves similar like Earth… When it was in a position like the actual Earth to the Sun.. with a younger core (with bigger gravity field) existed similar condition like in actual Earth… then is clear than the Earth type life connected to the water was able to appear onto Mars… Now the condition is different what we can observe onto Earth… from this assumption the Mars life may (have to) exist in subsurface condition… But for a better understanding we have to build a better geological model like plate tectonics (gave a better planet formation theory, because the actual data shows clear that our interpretation about gravity force is wrong, and the rocky planets was formed from Sun)…
love must be universal, not limited to this planet alone, will go for it, man need real exolove not just in movies alone, finding will attract more effort. Good to Dreamers and so I am happy.
In fact I did some preliminary calculations of the spin-orbit evolution for K186f and probably it is locked in a 1:1 resonace, but this depends on the age of the system, wish by the way is unknown.
The time to reach the 1:1 resonace is around 1.2 Gyr. If the system is younger, then there is a possibility to find something interesting.
Louis:
The interesting thing is not the fact to be in a 1:1 resonance. If the planet is already locked, its possibilities to be habitable are very low because the big difference between the temperature in both hemispheres and the low rotation that reduce the intensity of a probable planetary magnetic field.
Never the less, if the final resonace of the planet is 3:2, and there is a not negligible probability for this, then there is some possibility to be habitable. There are some works on locked planets habitability, you can chek the work on "Photosynthetic Potential of Planets in 3:2 Spin Orbit Resonances" by Brown et.al:
http://arxivweb3.library.cornell.edu/pdf/1402.5044.pdf.
I hope to have more information about the spin-orbit evolution of the planet soon.
Keep in touch.
FYI - see http://www.nature.com/news/wind-may-deflate-search-for-habitable-planets-1.15335 - another potentially limiting factor...
Hello James:
We know that... if you want, you can see our work in this matter:
iopscience.iop.org/0004-637X/770/1/23/
Hello Pablo,
That's great - good work, but I and other casual readers may not know.
I find your interesting preprint at http://arxiv.org/abs/1304.2909. The new study - http://arxiv.org/abs/1405.7707 - focuses on specific conditions produced by M-dwarf stars, which you do mention as being extreme.
Best wishes!
The work is good, but I wanted to find some explanation about Mars… but it’s not described it…
László-Attila,
Perhaps http://en.wikipedia.org/wiki/Mars#Atmosphere and http://en.wikipedia.org/wiki/Atmosphere_of_Mars#History - and their references - might help explain the conditions on Mars...
James Dwyyer,
The Mars-Earth has not Fi-Ni core (The Wikipedia describes of Mars’ inner structure is erroneous) … Their cores are similar… only differences: that: proportion of Earths’ core volume with Earth total volume is smaller than proportion of Mars’ core volume with Mars total volume… This reason makes me to take carefully Pablo’s work… Remarks: Wikipedia lot of time has good information, but their mainstreams’ science concepts interpretation does not reflect the reality!
László-Attila,
Well, this posting relates to Kepler-186f, not Mars, so I had to wonder why you thought there might be some discussion of Mars here. A more thorough read finds that the Mars Wikipedia entry does rely on references - http://dx.doi.org/10.1016%2Fj.icarus.2011.03.024 for example - and goes on to state:
"This iron sulfide core is partially fluid, and it has twice the concentration of the lighter elements that exist at Earth's core. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but it now appears to be dormant."
You did not provide any explanation much less any reference for your dismissive view - all sources of information should be considered analytically.
For a good reflect making would be needed lot of descriptions, because lot of new information won in last 20-30 years have being interpreted with a scientifical model which basics has 200-400 years, and for this it is not able to give an accurate interpretation… Example: “The iron sulfide core” interpretation was modelled into base of Newtonian gravity model and Goldschmidt geochemistry – immediately we are able to show a strong contradiction of this interpretation… That is why I am between those who do not accept this model… Erath structure (core: inner-core + outer core; rocky part: mantle and crust) rest: http://planeterosion.blogspot.hu/
… We know well that actually we do not have a well sustained gravitational model (but in few years we will have: 0-15 years)… As we know that Kepler-186f is a rocky planet like Mars… even if that from the position we can conclude that Kepler-186S is closer planet-evolutionary to Mercury… from the next actual data (distance Kepler-186f distance from it star is 0,36 AU, orbital period 129.9 days and its radius is 1,1 Earth radius; Mercury distance from Sun is 0,39 AU, orbital period 87.969, its radius is 0,383 Earths radius and their total and model used in Planet erosion the next assumption can be made: The Kepler186f is not so dens like Mercury, evolutionary their age is closest to the Mercury, actually if we take in consideration that their central star is a M1-type dwarf star sirface temperature is more smaller than our Sun… That means that Kepler-186S is a rocky planet (the question is that it has core like our Earth) its surface gravity has more less than the Earth’s gravity… perhaps is similar with our Moon…, exists possibility that it has very only weak atmosphere…. The Earth type life has no chance to evolve into this planet…. The question is that exist asteroid belts in the mentioned star? If they exist they are more closer like in case of our Earth… From their existence we can make assumptions about the nearby planets!
Three extremely large telescope project might be completed in the next 6 to 10 years:
The GMT, 22 m, 800 millions US$, 2020
http://en.wikipedia.org/wiki/Giant_Magellan_Telescope
The E-ELT, 39 m, the optical/near-infrared range, 1.2 billion US$, mid 2020s
http://en.wikipedia.org/wiki/European_Extremely_Large_Telescope
The TMT , 30 m, near-ultraviolet to the mid-infrared, 1.2 billion US $, mid 2020s
These plan instrument are intended among other purposes to study the presence of water and life in exoplanets at different stages of formation, exoplanet atmospheric chemistry etc.
My question is how likely will the exolife existence question be answered in 10 years if we assume that one of these projects will succeed to be built?
The question Louis relates to what sort of exolife existence you consider discovering. So far, would we talk civilizations not more advanced than us which does not seem to be an extraordinarily expectation, the blunt situation is that NO electromagnetic signal which could reveal such a presence in the entire universe probed so far has ever been observed. Our terrestrial signals (e.g. TV, etc.) extend now over kind of a 60 light years sphere which would make us easily detectable by anyone paying attention like we do. Are we the only civilization around ?
Patrice,
Since Copernicus we learned that we are not at the center of the physical cosmos and it would be extremely surprising that we are at the center of the intelligent life cosmos. That the cosmos think itself just here on this planet in that vast realestate!!! But like all the big questions experience is the only way to solve it. We seem to be made to search for our intelligent soul mate. Maybe, It is just that we are not enough intelligent yet to make this contact. That this contact is easily feasible as soon as you get to the basic minimal intelligence level. Sixty light years is almost nothing. Very soon we will have the instruments to detect primitive life. It will be a first step. These new instruments are the new telescope of Galileo that will make us reach the Copernicus revolution of life before the mega Copernicus revolution of intelligent life.
Louis,
60 light years is the small volume (still not negligible) in which the electromagnetic emissions we made betray our presence through a characteristic "noise", volume in which an alien civilization could easily detect us if they live in it. Reversely, it is hard to admit that as deep as we've scanned with large radio-telescopes we've not detected any such "structured" type of emission so far that would betray/reveal the existence of a long-lived ET civilization. But I like your sentence "We seem to be made to search for our intelligent soul mate"... perhaps we'll succeed, but I'm - for once - not that much optimistic... Hope to be wrong.
Our terrestrial radio signals now extend in fact to around 80/85 light years and the earliest over 100 light years (those however would be rare indeed) The problem is not whether intelligent life exists at that close proximity but at what stage its industrial evolution is.
If it was as little as 50 years behind us it would probably not have sufficiently sophisticated equipment to pick up our signals, let alone respond to them. For all we know there could be hundreds of industrialised civilisations within 80 light years of Earth and we might be the most advanced.
It is equally possible that there are none and that we are in fact the only intelligent life within 100 light years, I hope that is not the case.
I am confident that 'out there' is a sentient being with enough technology to be looking towards us and wondering if we are here. They will have an upright gait, an opposing thumb, stereoscopic vision and the ability to speak. In other words they will look something like us. These characteristics are essential for the development of technology. We can build spacecraft and telescopes because our distant ancestors picked up stones and shaped them into tools.
If there are any intelligent soul mates out there they will be like us, that should give us not only a sense of wonderment and desire to meet them but should also be tempered with just a little concern.
Barry,
I think that the process of the evolution of intelligence and civilisation on this planet is rapidly reaching a critical stage of our coming together which will be echo our initial evolution as a species at that point we will begin to be stellar being needing a stellar being interaction in the coming together at a higher level.
If we are ever likely to meet our galactic soul mates there will need to have been some remarkable coincidences in our evolution and theirs. It is one thing finding a planet in a habitable zone of its star but there is a spectacular difference between life starting there and evolving along the same lines as life on earth.
The star that the planet revolves around must be of type that will last at least 8 to 10 billion years such as the G2V main sequence star that we orbit. It will take at least 3.5 billion years for complex life to form to be able to produce a species that is sentient and capable of tool making.
The accretion nebula from which the planet formed will need to have had a very high concentration of water in its make up and this would have had to have rained down in the early stages of the planet to make oceans and an atmosphere. The planet will have to have the right mass to prevent that atmosphere from evaporating back into space.
The Earth very early in the Hadean was hit by a proto-planet which increased Earth's planetary mass and simultaneously created the moon. The moon’s influence right from the very beginning made life on earth more likely and certainly more likely to evolve beyond a primitive stage. The impact knocked Earth rotational axis over between 24 and 22 degrees resulting in seasons. The effect of seasonal weather greatly influenced the diversity of species on the planet.
The Moon causes tides and this too was crucial to the evolution of multicellular creatures in tidal lagoons in the Precambrian.
he Earth’s crust is formed of tectonic plates and the movement of these over the last 700 million years is also a major influence on the evolution of life on the planet. Vulcanism has been responsible for climate changes that gave life a boost at several occasions, even the mass extinctions resulted in life returning with more vigour and diversity.
It is not of course impossible that intelligent life could evolve on a planet without a moon and plate tectonics in a system with a different stellar classification but it is unlikely. It is relatively easy, in fact probably inevitable that life will start in some form or other on many kinds of planet. It is the sustaining of it and its evolution that is the difficult bit.
Barry,
The new instruments that will come into service in the next decades will certainly allow us to experimentally verify the existence of primitive life and complex life in exoplanet in our Galaxy. In our lifetime. Only that will be the biggest scientific discovery since Copernicus. When I was kid, there were plenty of Space alien TV shows. So living in the universe was part of the popular culture. But the data about life outside of earth were then inexistent. Since then the chemistry of life has been detected everywhere in space. In the sixties, there were no direct evidences that other stars had planets and now we found thousand. In the sixties we knew for thousand of years that the earth was a sphere but we saw it for the first time in 1968 from the moon. What a moment! The life discovery moment that is coming very soon will be very important. All my aesthetic sense of Nature point that not only intelligent life is all over but that stellar life is all over and that instantaneous communication accross the cosmos is scientifically possible.
Louis
I believe there are people out there and that is what they are, people. As it stands at the moment we may one day hear from them but because of the distances we may never meet them.
We can only hope that what we know about the laws of physics are wrong and that interstellar space flight is possible, its just we have not worked it out yet.
I think I will invite opinions on that in an RG question.
Barry, I read and appreciated you exchange with Louis. I'd like to add some points. First, there is no need of an impactor (like the moon) so that the Earth would lie at a 23° angle (or so) on the ecliptic. So does Mars and it was not impacted in its early life with a major body like the Earth was with the Moon. My point is that the impact might have contributed to (and probably did) but is not required per se. The second point is that you cannot hope to be wrong (about the laws of physics) to dream of a better world. The third and this is not a kind perspective, is that reversing your observation (that we have emitted to kind of a 85 light sphere so far) we have not even with the most sensitive radio-telescopes ever observed in the entire universe - ANY signal that we might consider artificially generated by some kind of intelligence. The universe is desperately devoid of the kind of signal that we've been emitting for the some decades. It simply means - given that the probability that we've missed so far such a signal is very low - that there is no alien civilization of our kind out there. I dislike it very much, but I will not go as far as hoping that we're wrong on everything to dream that we're not alone... We have to face the harsh reality, life might be in many places in various forms, but we might be the only civilization in this universe as surprisingly and improbable it might seem. I must confess that it challenges me also on my theological grounds...
Patrice
Your points are well taken. The impactor is probably responsible for the tectonic plates and Mars does not have these making it a much less active planet. The combination of seasons and tectonic activity are almost certainly a contributor not simply to life on Earth but its complexity.
The universe is of a size that, in spite of our great achievements in measuring it is inconceivable in human terms. Life will be rare within it undoubtedly, intelligent life even more so but probability suggests that it is there. We have not looked at the entire universe yet and because of its size probably never will. To date we have only seen a tiny fraction of it in detail, indeed we are still to see clear images of a body within our own solar system.
I agree with you that it is unlikely that we have, after so many centuries of studying them got the laws of physics wrong. That too is extremely improbable but not of course, impossible.
Intelligent life has been on Earth for upwards of 100,000 years. that is roughly how long it has taken Homo Sapien Sapien to travel from hand axe to supercomputer, from primitive animistic belief to sophisticated philosophy and science. There could be billions of intelligent life from out the who have yet to invent radio and who are still behind us on that journey.
The Search for Extraterrestrial Intelligence has, as you rightly say spent decades looking for an artificial signal in the universe. It is quite possible that even after hundreds of years we would still have missed it. The signals we send out are feeble in cosmic terms and even though they may still be detectable light years away it is highly unlikely they would be tens, hundreds or thousands of light years away. The sky may be teeming with radio traffic, we just have not tuned in yet.
I do not think hope is incompatible with science. My experience tells me that it is unlikely that we will ever conquer disease but, by making the effort, based on hope we can achieve great things.
We may never meet our distant neighbours but if exploration of the universe means anything we should really hope they are there.
Barry and Patrice,
We do not know the fundamental physics of the universe and it might be possible and conceivable into the future physics to communicate instantly. I will do my H.D. Wells and speculate of this future physics. Suppose that at much higher density energy level than we can reach in our particle accelerator that you can transmit in the fabric of spacetime at these energy levels. Suppose that the physics at these density level, a quantum gravity physics of the future, that we discover that if we impact any location is instantly impacting all other locations. Assuming we discover the technological way to impact and to sense impacts then we would automatically have access to a cosmic tranmission medium that if it exist is necessarily very busy and used by higher forms of life for their coming together. The whole scenario hinge on a number of big IF which are field of exploration of our imagination.
Louis
We do know the fundamental physics of the universe and they are fairly constant. It is the esoteric stuff we are unclear about and probably will always be. The basic problem is the speed of light. We cannot exceed this speed and even if we could travel at 90% of it it would be virtually impossible to navigate. Even interstellar space is not a perfect vacuum and impacts with even molecules of matter at that speed would expose any starship to unbelievably destructive forces.
The speculation of warping space has been around for many decades and if the Big bang theory is correct it is probably possible in theory but would require harnessing and directing energy on a literally cosmic scale.
I am unsure where the 'dilithium crystals' fit on the periodic table or what properties they possess that facilitate the contraction of space-time to allow travel through it. I am even more intrigued as to how the Romulans harnessed an artificial quantum singularity within a material space craft without it collapsing into a black hole.
I have been trying for years to get an explanation of how the Heisenberg Compensator or the Inertial dampers work but all I have ever been told is "very well!" (forgive the flippancy there but I love the science of Star Trek)
You are absolutely right about the big IF's but they conspire against interstellar travel rather than support its possibility.
I hope I am 100% wrong in the way I interpret physics and that the future holds a United Federation of Planets. I do have a few reservations though.
If any intelligent life is out there it will be like us. Upright gait, stereoscopic vision, opposing thumbs and an ability to communicate in abstract terminology. It will have evolved like we have starting with toolmaking, discovering fire, developing civilisations. It will have a long history of exploration as we do. Without those traits it would not be possible to build a spaceship and travel to the stars even if the physics allowed it.
We need to seriously consider the history of a technologically superior civilisation meeting one less so. Its not promising!
Barry,
I am not optimistic at all about travelling. I am optimistic about communication. General relativity cannot be true at very high energy levels. At these levels, a quantum gravity will be necessary. My speculation is that space as we conceive it in general relativity does not exist in the same manner at very high energy levels allowing for instant communication.
I am also of the opinion that intelligent life reaching the level where it can interact (communicate) at the galactic scale would have enough in common to be able to communicate. But I think that to reach this level, we will not exist at our current level. I think that human will reach a new level where individuals will become much more integrated into a collective. And I think that intergalactic communication/interaction is in between collective beings. Individual cells formed collective multicellular beings, and humans from the beginning have learned to integrated into societal beings which became through technologies more and more integrated and now we will reach a new level of integration. Our own identity is already a collective enculturation process but we just do it unconsciously. At the next level we will do it efficiently and I do not see that as a big brother scenario of centralized power but at exactly the opposite of decentralization participatory power.
Barry and Louis,
Good reading you. A couple of additional point with respect to what's required to host an aerial intelligent life (and submarine one as a starting point) able to later use radio-frequencies for interstellar communications.
Saying that you need water is not a fantastic assumption, a lot of water - perhaps not as much as we have, but a lot will help, otherwise get a ticket to any other body of the solar system and try to live there :-)
Having said that, if you expect some sort of life which is not strictly submarine (as you now have a lot of water which is getting somehow cumbersome !), then you need plate tectonics to create light - say calc-alcaline rocks - coming from the melting of the oceanic basaltic floor under hydrated conditions in the subduction zones, to create small cratonic-like formations of lower density that will stand above the oceans level due to their isostatic equilibrium (sound magic, but nearly is). Otherwise, no way, submarine life only will be possible. Hard to develop electromagnetic interstellar communications from under the oceans...
These small neo-cratons will wander around and collide over millions of years until they manage to create sizable continents able to host aerial life as we've been knowing it since say Devonian (400 million yrs). Finally, hundreds of millions of years later, primates or sorts of, will evolve to build sophisticated instruments to try to detect and why not attempt communicating with other alien civilizations...
Then, from time to time you get a comet, an asteroid or anything else that will re-initialize somehow the system, in the most brutal manner !
This is not fiction, it is the highly improbable sequence of events and conditions that have happened here, on Earth. Right size for the right gravity (otherwise no atmosphere or 100 times thicker as for Venus), a lot of water (not observed anywhere else), plate tectonics (not observed anywhere else), correct star, correct place, no dramatic impacting body for some time, etc.
I'm quite afraid that we should acknowledge the highly improbable sequence of events that has lead us to having this discussion :-)
Life might be frequent and occurrences of various types may well exist in many places, given that we have kind of 400 billions stars in our own galaxy. But evolved creatures typing on a keyboard and wondering whether they are lonesome in this huge universe might be extremely rare.
And I dislike it, but tend to accept it...
When Peter van de Kamp (1901-1995) did his best to try to discover dark companions with classical astrometric methods (and somehow succeeded to find some) I never though that during my life time we would have knowledge of bodies like Kepler-186f at 500 light-years. It is a fantastic news, but at the same time I doubt very much that we will ever find intelligent signals waiting for us to be deciphered to start our first interstellar discussion.
Hope I'll be wrong.
Patrice
You are correct in asserting the circumstances that lead to intelligent life on earth are highly improbable but it happened here! There is nothing special about our star or our position in the galaxy (also undoubtedly a factor in our evolution) billions and billions of stars of the same type and age are present in the universe, huge numbers of them in our own galaxy itself.
High improbability is relative to numbers of opportunities and there is no shortage of opportunities for life elsewhere in the universe. It will of course be very rare but rarity is also relative.
There may very well be civilisation out there far in advance of our technology. A most probable reason we have not yet met them is that it is indeed impossible to defeat the laws of physics that keep us imprisoned in our own solar system. We may not have heard from them because even if they are ten thousand years in advance of us their signals might still not have reached us because of the huge distances involved.
Simon Conway Morris in Life's Solution: Inevitable Humans in a Lonely Universe engages in some superb speculation on whether we are alone in the Cosmos. It is a superb book but I disagree with his conclusions. We deal with probabilities from a human perspective and that confuses us. Probability on a Cosmological scale is beyond our understanding.
I will never be able to empirically prove my own views and I engage the principal of doxasticism in making this conclusion but; somewhere 'out there' is a sentient being typing a similar message to this one on similar social network in a galaxy far, far away... as they say in the movies.
I remember to the probability discourse in the 1960's on the emergence of life elsewhere that was based on the science of the time and now there is almost no doubt that the probability of emergence of life are high and not even exclude in this solar system. For intelligence life, the probability discourse is pessimist now but It will change. When science does not know, it replaces God's miracle by probability's miracle but with ignorance dissipates a little bit than the probability's miracle evaporate as well.
Dear Barry and Louis,
I appreciated your answers and share your visions. At the same time I also wanted in my message(s) to underline just 1% of the odd circumstances that make us aware of what we are for some decades before we're gone as individuals (and perhaps as a civilization) on a time scale of 15 billions years. The 99 other % that make us here improbable would have made the messages too, way too long :-)
But having said that, I love Barry's view that somewhere in these billions of galaxies made of hundreds of billions of stars, some alien creature is typing a similar message as mine, with similar hope and similar despair...
I also like very much Louis's position as he is always positive with respect to life in general and science in particular and good things can only happen if you expect the best.
Question now: I consider an alien civilization having similar means as we have today (best radio-telescopes available - known signal/noise ratio) trying to detect intelligent signals in space. Given the signals we have emitted and their intensity, is there a model that would assess at which distance our own signals would vanish for them and would not be detectable any longer ? What is the sphere of detectability of our presence (now or in some decades - time to let the stronger and recent signals travel) for an alien civilization having comparable means ? At which maximum distance an alien civilization with same means as we have now would detect us (eventually in some decades) ?
PS1: sorry for rephrasing 3 times my question this morning, my brain is a bit frozen and I hope it makes the question clearer... does it ? :-)
PS2: I already listen to Louis' screaming about all my assumptions (same tech level, etc.) but let's make a start with that.
If we take a civilisation that is exactly as advanced as we are they will be broadcasting at the majority of frequencies across the radio band width and using powerful transmitters to do so. The problem with detecting those signals is that if this alien civilisation developed radio for the same purposes we did it was to transmit over very short distances. Thousands of miles, not hundreds of lightyears.
The strength of radio signals is governed by the inverse square law which severely attenuates them over distance. The vast majority of our past radio signals that will have emanated to a total distance of around 110 light years will be indistinguishable against the cosmic radio noise from sources immeasurable more powerful than own transmissions. Trying to detect the signals from a planet 100 light years away would be like trying to hear a firecracker exploding against the background noise of an H Bomb.
We will not find artificial radio signals in the cosmic background noise. We will have to target specific stars and they will need to be chosen not only from stars that are likely to have rocky planets in a habitable zone but ones that are not between us and a giant radio source. It could take several life times to locate such a signal at that pace and even though SETI is decades old now it is very early days.
Now it could be possible that 'out there' is a civilisation maybe two thousand years ahead of us technologically. Maybe they have picked up our signals. What will they know about us?
They will know we fight each other incessantly. They may even have the technology to decipher our TV signals to see constant war and even broadcasts of us conducting H Bomb tests. Maybe that is why they never bothered to send us a reply!
Eight new planets found in 'Goldilocks' zone: Two are most similar to Earth of any known exoplanets.
The two most Earth-like planets of the group are Kepler-438b and Kepler-442b. Both orbit red dwarf stars that are smaller and cooler than our Sun. Kepler-438b circles its star every 35 days, while Kepler-442b completes one orbit every 112 days.
http://www.sciencedaily.com/releases/2015/01/150106134633.htm
A Sun-like star named Kepler-444 with 5 orbiting planets, dating back to the dawn of the Galaxy, has been discovered by an international team of astronomers. At 11.2 billion years old, it is the oldest star with Earth-sized planets ever found and proves that such planets have formed throughout the history of the Universe.
http://www.sciencedaily.com/releases/2015/01/150127111418.htm
Thanks Louis for reporting these recent and extraordinary discoveries. Surprising that this thread does not interest more people ?
Louis
There is a good coverage of that story in the New Scientist last week. The planets are almost certainly rocky but are too close to the orange dwarf star to sustain life. One has an orbital period of 9.5 days.
Barry,
The significance of the Kepler-444 discovery is that it extend the time realelstate of life in the universe back to at least 11.2 billion years old. It is now certain that some of these 12.2 billion years old star system will have earth-like planets in the goldilock zone. If we assume that in this galaxy 12 billion year ago, one planet in the goldilocks zone took about 4 billion years to reach the state where one species became intelligent and survive the initial stage of civilized tribal state and continue evolving then it is now 8 billion years of evolution. We cannot even imagine the kind of culture there are in now.
Patrice,
The recent pace of the significant discoveries for finding places where life could potentially exist is amazing. This is because we have new instruments allowing us to do these discoveries. In the next 10 years, new instruments will allow us to analyse the chemical composition of exo-planet atmosphere in the galaxy and this will allow to detect with high probability the existence of life on these planets.
Louis
You are quite right that the formation of planets occurred very soon after the aggregation of galaxies and formation of stars and extends the possibility of life in the universe exponentially. This leads to the inescapable position that there may have been many millions of civilisations many billion years before the Solar System existed. The difficulty is that if there are indeed many civilisations hugely older that ours then they too have been unable to communicate and travel between the immense distances between stars.
If they are millions of years in advance of us in evolutionary terms them we can only conclude that interstellar travel is impossible or surely they would have found a way.
Barry,
Suppose that in a few million years we can send probe to billion of planets because we are curious about life and most particularly about intelligent life then maybe our policy would be one of none interference because as soon as we would contact and interfer then we would not be able to know about them without this interference. Another of my speculation that is close to Theilard's vision is that it is in the nature of life evolution to reach a stellar being level at which point all stellar being lifeform reach the knowledge and the technology to communicate and interact with other infant stellar being and start to merge at the next level. So maybe there is a huge hierarchy of higher and higher stellar beings jointing at the highest level into something that would amount to be a universal cosmic being. End of the sermon to the Universe.
Louis
We can send probes to almost anywhere already but the problem remains that we cannot communicate over these distances, within reasonable time under the current laws of physics.
Nothing travels faster than light and there is as yet no indication that this barrier can be broken. It would require a set of physical laws well beyond anything yet observed to achieve this and while we are handicapped by these laws any form of communication between, let alone travel to these distances is inconceivable.
We need to separate the two issues. There is no doubt in my opinion (supported by logic) that there will be countless civilisations out there some much more advanced that we are, just as there will be world at an earlier stage than we are. What seems inescapable is that they live by the same laws of physics as we do and we are all prevented by them from ever meeting.
We have no verifiable evidence of us ever being visited and there is no prospect in the distant, let alone foreseeable future of us ever doing any visiting.
I live in hope that there is yet to be born a Zephraim Cochrane and that we will one day travel the stars by warp drive. At the moment it is simply a dream, a very nice one but only a dream.
Barry,
The theoretical situation may change and the limitation of communication to the speed of light may have some loopholes. Do not forget that general relativity is surely wrong given that it is not compatible with quantum physics and the later is more certain. The next theory of quantum gravity may change the situation and may open a possibility of instantaneous communication accross the universe. I am not hopefull for spaceship traveling faster than the speed of light but I am hopefull for communication at very very high energy level, energy levels in the fabric of space itself. But in the near future the propect to detect microbial life in exo-planet are very high.
Louis
As you know I hope I am totally wrong in my pessimism about space travel or being able to communicate with other intelligent life forms. I am not however optimistic that the quantum world offers us much assistance since we do not actually live in it. You are quite right about general relativity and even Einstein accepted it was seriously flawed but we live in a universe of matter and energy for certain and it poses the problem.
One of the biggest problems with travelling through space is the fact that it is not empty. Since at present it is only feasible that humans would have to be in an energy propelled vessel to make a space voyage the presence of particles on matter in space would be a huge problem.
Any space ship travelling through interstellar space at the speed of light, were that possible would be destroyed by the huge energy released by collision with even a tiny particle. They would be unavoidable in a long space mission.
Similarly navigation would be impossible due to the relative position of interstellar bodies being shifted.
Warp drive is the only possible method by which we could travel these distances but the physics of that require energy levels similar to those emitted from a quasar. It is inconceivable that we could control let alone generate such forces.
As I say, I hope I am wrong and physics is due for an overhaul!
Discovery of KEPLER 452b
It is a planet a little more than one and a half times as big in radius as Earth. Known as Kepler452b, it circles a sunlike star in an orbit that takes 385 days, just slightly longer than our own year, putting it firmly in the “Goldilocks” habitable zone where the temperatures are lukewarm and suitable for liquid water on the surface — if it has a surface.
cording to studies of other such exoplanets. In an email, Jon Jenkinsof NASA’s Ames Research Center, home of the Kepler project, and lead author of a paper being published in The Astronomical Journal, said the likelihood of the planet’s being rocky was 50 percent to 62 percent, depending on uncertainties in the size of its home star. That would mean its mass is about five times that of Earth.
http://www.nytimes.com/2015/07/24/science/space/kepler-data-reveals-what-might-be-best-goldilocks-planet-yet.html?_r=0
I think the 5 earth masses is important as any substantial atmosphere that is in hydrostatic equilibrium would then have a much stronger necessary pressure gradient in that atmosphere (and of course, higher surface pressure). Plus initial atmospheric loss would be less due to higher gravity. I am sure lots of investigator will be running simulations of the atmospheric and geological properties of a 5 earth mass planet, as that is now a unique part of parameter space.
While it is likely that the atmospheric pressure on Kepler 452 is higher than that on Earth there is no direct relationship between planetary mass and density of atmosphere. The atmospheric pressure at the surface is determined by the density of the gasses and the depth of the atmosphere.
Venus is very close to the size of Earth but its atmosphere is 90 times more dense, causing temperatures at its surface far above that possible for life to form (even though Venus is in fact in the 'goldilocks zone' of our Sun)
It is quite possible that in spite of having a much stronger gravitational field that Kepler 452 has a habitable atmosphere. It is other factors that mitigate against it having complex or intelligent life.
We have yet to determine whether these rocky exoplanets have moons and this is important because without them there are negligible tides in any large areas of surface water, or oceans. Tectonic activity rather than simple volcanism is also reliant on large moons and both had fundamental influence on the evolution of life on earth.
It is tantalising to think that if the proto planet that struck Earth in the Hadean had hit squarely on, rather than with a glancing blow that Earth too would be about the size of Kepler 452b and without a moon. If that had happened it is unlikely we would be here today to discuss it.
One other fascinating observation made about the newly discovered planet is that it is probably 1 billion years older than Earth. Assuming that life could have formed at least hundreds of millions of years before it did on Earth and that similar evolutionary influences were present we should expect it to harbour intelligent life.
If they are still there (if they ever were) it raises two difficult conundrums. What is preventing a civilisation millions of years in advance of ours from interstellar travel?
Were they once there, but have now been extinct for millions of years?
Barry,
If highly advance technological civilisation evolved elsewhere in the Galaxy, I think that it is likely that they sent probes that are currently monitoring us without disturbing us. I think that the home planet is the only possible liveable place for any organism and that there is no need nor desire for advance civilisation to colonize other planets.
Louis
I am not sure that all civilisations that may have evolved elsewhere in the galaxy could be assumed to be so benign as to wish to avoid 'disturbing' us.
Science fiction has a lot to teach us in this respect. As a great fan of Star Trek (but not a Trekkie) I enjoy looking at all the possible sentient species that the crew of all the USS Enterprises encounter. Some are benign most are aggressive, many have developed the technology to travel the vast interstellar distances.
For all the differences in these species they all have very much in common. They are all humanoid, a physical format necessary if one is to build a starship. They are all either explorers or conquerors, just as we Homo Sapiens.
Any intelligent life form that builds space ships or space probes must have evolved in the same way we have both biologically and socially. Any being that builds space probes had ancestors that made stone tools. Any being that builds space ships lives in complex hierarchical societies involving thousands of beings with a common goal.
Living in societies and building tools are the building blocks for civilisation and for conflict. If there are complex societies out there they will be like us in many more ways than they are different.
When the European explorers from the 7th to the 19th century went about with their ships and probes they were looking for more than knowledge. When they encountered natives in the far flung lands they explored it was rarely to the natives advantage. An encounter with a 17th century technologically advanced civilisation was more often than not a disaster for the less advanced indigenous peoples.
If we ever experience the 'first contact' or 'close encounter' of science fiction fame let us hope that we have at least a similar level of technological evolution. We may not like the idea of being 'civilised' by our superior intellect galactic neighbours.
Barry,
Once upon a Time:
The history of domination and conquest and colonization and exploitation etc etc of well organized well armed and most aggressive group of humans being on other less well armed, less organized group of human beings has inspired most of the science fiction on aliens. We live in very aggressive societies are in young age are brain washed into thinking the way our societies maintain themself. There was no war on this planet before homo sapiens sapiens. Apparently there was no war for a long period of our first history when we were matriarchal, communal and had fertility goddest. Armement, the horse and the patriarchal hiearchical order change all this and the domination of the most aggressive , well armed and most organized and hiearchical began. WHAT IF our only way out of self-destruction is an obligatory return to the matriarchal, communal and mother earth respect? At the end of the 19th century the idea that the evolution of the social was moving towards the formation on this planet of a human super-organism that is one with the planet forming a stellar organism. I share this vision of homo sapiens being a eukariot cell of the social organism. Intelligent life has the potential to developed for 1 billion years on a typical planet where life is possible and we only have developed for 100 000 years. I am convinced that the mature stage is the stellar organism and the interstelllar stage of life only exist among these, not among independent cells of these beings.
End.
On the relation between planetary mass and atmospheric pressure.
1. Of course the dependence on temperature is more important. In the case of Venus, it was simply too hot to have oceans to mix out all of the Carbon Dioxide - early earth atmosphere had as much CO_2 as Venus still does - simply melt all the limestone on the ocean floor to recover that CO_2.
2. Mars doesn't have much of an atmosphere because of its low surface gravity - atmosphere simply diffuses away via the Maxwellian velocity distribution.
3. Uranus and Neptune have relatively thick atmospheres due to their many earth Masses.
In terms of probes - yes a simply statistical argument suggests that the Earth would have been visited several times by random probes over the last 4 billion years if say other civilizations launched one at the rate of 1 per year in some random direction.
On the "1 billion years" for life to develop - taking us as an example there are some real issues here:
1. How do we safe guard against the next large asteroid impact (100 million year timescale)
2. How do we deal with the next large Ice Age (100,000 year time scale)
3. What about the next possible large scale tectonic cycle of activity (again on the 100 million year time scale)
4. What about being near a spiral arm region in our galactic orbit and subject to very nearby stars going Supernova (100 million year time scale again).
Planets are not closed systems - on these timescale they are subject to significant external forces.
Planets are indeed open systems and life on earth was to a very large extent dependant upon that fact. The formation of the planetary body itself by accretion demonstrates that planets are open systems. The heavy elements in the material that made the Earth came from distant supernovas including all the carbon that forms the basic building block of life on Earth.
The concentration of water on the surface is largely due to the bombardment phase in the Hadean, again demonstrating that earth is an open system. The collision of the proto planet causing the earth to simultaneously increase in mass and creating a moon made gave the planet characteristics that would influence the evolution of life.
As to the mass of a planet affecting its ability to harbour life, it is likely that planets with multiple earth masses or fractions of them may contain rudimentary life forms such as prokaryotes. More complex life forms are much more influenced by gravity, especially multicellular forms of life. Large animals such as humans or animals of a similar body mass have skeletal structures that are evolved to operate in the optimal gravity of Earth. A plant with three time Earth's mass would require its animals to have far more massive skeletons, which would cause mechanical difficulties not conducive to the development of intelligent beings.
Louis
The oldest site found that indicates 'warfare' is on the border of Egypt and Sudan and dates from between 13,000 and 14,000 years ago. 59 (possibly 61) skeletons were discovered here all of whom died violent deaths inflicted by stone weapons, many still had flint arrowheads in their bones.
The bodies were men, women and children including infants indicating some form of internecine and organised killing. All had clearly died from their injuries as no signs of healing are present in the wounds.
What is startling about this is that it predates sedentary societies and as such lacks the usual reason for prehistoric warfare. Pre-sedentary groups rarely fought since most of the reasons for fighting were not present. It was when sedentary populations need to guard crops and livestock that territorial warfare per se was 'invented'.
We do not know if the victims found at what is known as Cemetery 117 lived in patriarchal or matriarchal societies. Men, women and children had all been killed with equal savagery. What we do know is that organised mass killing, whether you call it warfare or not has been with us for a very long time.
I made calculations in "Number of Galactic Civilizations" presented at the 2013 European Congress of Planetary Scientists which show that our Galaxy most likely has a number of habitable planets but very likely has no concurrent Advanced Civilizations. Please don't make a bet on Shostak's 20 years, you most likely would loose it.
Ivan,
Calculations can only be made when one make a number of assumptions and some of these are most likely false. I read articles where people calculate million of civilizations in our Galaxy. Probably using another set of assumptions. I trust the calculation but not so much the assumptions. I use one assumption without any real empirical support for it, that the evolution of life on this planet is more typical than exceptional. It is called the Copernican principle.
No objection, but my calculations give an overview of all possible galactic habitability scenarios based on non-controversial mathematical principles. My few basic assumptions try to help identify the high probability scenarios. The conclusion is straightforward. Existence of a substantial number of habitable planets with advanced civilizations most likely distributed over the Galaxy's habitable time span.
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