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Life in the Universe
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| HarbingerDawn | Date: Thursday, 30.08.2012, 11:46 | Message # 31 |
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haha perfect 
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| neutronium76 | Date: Monday, 10.09.2012, 10:08 | Message # 32 |
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Quote (LevArris) And if they really need resources or a new place to live, well - we know how many "Terras with life" are out there . They can settle down on any of them without superior intelligence species.
You mean in SE. Not in reality  . Because in reality we only know of one solar system with one terra with (intelligent) life. The rest is pure speculation. We don't have the means to detect extrasolar planets smaller than gas or ice giants. And I really don't believe in the latest discoveries of highly likely possible earth-like planets in nearby systems. At distances above 1LY, detection of such planets is just impossible (or highly unreliable) with current technology. Ok I know this is off-topic but the reason I am writing this is because earth-like terras are probably very very rare in the universe and in the galaxy: http://en.wikipedia.org/wiki/Rare_Earth_hypothesis . So if there is a more advanced civil. out there it will be literally hunting for planets like ours. Especially if they have consumed their resources. So all these ideas about an advance civil. being mature enough and ethical enough is very naive thinking: The more advanced they are, the more energy and resources they will need. I bet they are like locusts aka independence day and they go from earth to earth and suck every single drop of resource they can possibly get. Destroying of course all life in the process. So the very very few earth-oasis in the desolation of space, will turn into deserts and all universe will be sterilized in the billions of years to come. A ''happy'' ending...
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Edited by neutronium76 - Monday, 10.09.2012, 11:21 |
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| HarbingerDawn | Date: Monday, 10.09.2012, 11:28 | Message # 33 |
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| Quote (neutronium76) http://en.wikipedia.org/wiki/Rare_Earth_hypothesis
I generally disagree with the Rare Earth Hypothesis. It seems to me to just be another attempt at the age-old tradition of making humanity and Earth seem somehow exceptional and unique in the cosmos, that there is nothing else like us and that we should consider ourselves some sort of superior creation.
That is not my only reason for disagreeing with it, of course, and I don't dispute that complex life and civilizations might be extremely rare. It is the reasoning that is typically presented that I find non-compelling.
The idea of a "galactic habitable zone" doesn't seem very likely to me. Yes, maybe there are some places in the galaxy that would not be likely to support life, but I think that those places are the exception rather than the rule. It seems probable that more than 90% of the galaxy has conditions suitable for the development of life. It would be more appropriate to talk of "galactic death zones" as these places that are hostile to life are probably less common.
The idea that life can only arise and evolve to complexity around Sun-like stars is also not well supported. There is certainly an upper limit to how massive a star can be, since it must exist in a stable state for long enough for life to evolve high intelligence, which would almost certainly take a few billion years or more. But there is no clear lower limit. Rare-Earthers like to say that most K and M class main sequence stars cannot support life, largely because of tidal locking. But it is entirely possible for a tidally-locked planet to have conditions suitable for the development of life.
There is also no compelling evidence to suggest that only planetary systems with a specific configuration are suitable for life. On the contrary, many of the systems being discovered lend support to the opposite view, that worlds on which life could develop can exist in many kinds of planetary systems.
One of the strongest cases that Rare Earthers make against Earth-like planets being common is that a large moon may be required, and the formation of such objects is exceedingly unlikely. On the surface, this is a good argument. But in the development of planetary systems there are many protoplanets that are orbiting the star that could collide in such a way as to produce a large moon around a planet (it would take the collision and merger of 10 Mars-sized worlds to create the Earth). Recent observational evidence suggests that these types of collisions are common in developing planetary systems, so large moons produced in impact events are probably not as uncommon as it would first seem.
The only argument of the Rare Earth Hypothesis that may be difficult to dispute (and that I see no obvious shortcomings with) is that the development of complex life from simple life (eukaryotes from prokaryotes) is an unlikely or difficult occurrence. It may be that it is uncommon for complex life to arise on a living world. But it otherwise seems that life itself may not be uncommon in the universe, it certainly is becoming clear that environments capable of supporting life are very common. If these environments can also create life, then life may be on billions of worlds in the galaxy, and so even if only one biosphere in a thousand produces complex life, there may still be millions of worlds with that complex life, and therefore I think many thousands of worlds with large multicellular creatures and perhaps intelligence. The only thing that seems likely to be truly rare to me is technological civilization.
My thoughts exactly
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Edited by HarbingerDawn - Monday, 10.09.2012, 12:14 |
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| neutronium76 | Date: Monday, 10.09.2012, 11:33 | Message # 34 |
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| Quote (DoctorOfSpace) I still think in the spirit of exploration we should allow them on the international space station.
Actually at least one out of six members of the ISS should be Chinese in order for the ISS crue composition to accurately represent the earth's human race distribution. So that if aliens come aboard they see an accurate representation of our species  !. But then you will need 1 African, 1 Australian/Oceanian, 1 American, 1 Caucasian (CentralEuropean) and 1 empty (probably another Asian due to Asia's large population )
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Edited by neutronium76 - Monday, 10.09.2012, 11:35 |
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| neutronium76 | Date: Monday, 10.09.2012, 17:04 | Message # 35 |
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| Quote (HarbingerDawn) I generally disagree with the Rare Earth Hypothesis. It seems to me to just be another attempt at the age-old tradition of making humanity and Earth seem somehow exceptional and unique in the cosmos, that there is nothing else like us and that we should consider ourselves some sort of superior creation.
Although on the surface that is what it seems like with the Rare Earth Hypothesis (REH from now on ) the hypothesis itself doesn't mention or even suggests the slightest hint for such a thought. It clearly stipulates a series of logical thoughts and tries to use scientific evidence in order to support its argument.
Now lets take your points of disagreement (or doubt I should say better - sorry about my english, its not my mother language  _ and analyze them a bit further:
Quote (HarbingerDawn) The idea of a "galactic habitable zone" doesn't seem very likely to me
Ok. So you propose something like the vice versa of Wikipedia's article. That the habitable zone is the norm and the death zone is actually the exception. But the article clearly describes the properties of this zone and why it is a zone, actually a ring of certain thickness around the galaxy. There are certain factors such as the 1.Star metallicity, 2.The X-ray and gamma ray radiation from the black hole at the galactic center, and from nearby neutron stars and 3.Gravitational perturbation of planets and planetesimals as a function of distance from the galac. core. All these are very important scientific data that can not be disregarded. Also another interesting observation as I read this part of the article is that this hab.zone is not a static ring! it has a wave-like pattern as it is disrupted by the galactic arms!
Quote (HarbingerDawn) The idea that life can only arise and evolve to complexity around Sun-like stars is also not well supported
Ok I am not an expert on this as I don't know much about star classification but I suppose there could be a habitable zone theoritically around any star. However sun-like stars give a planet (provided it has size, density(i.e gravity) and rotaion within certain ranges) that orbits within the habzone, the time required to develop more complex life forms, and also are more energetically stable than other star types. Also regarding tidal locked planets around main sequence stars (or any stars), they would probably (if not certainly) have extreme climate conditions: http://www.youtube.com/watch?v=T-9h2DRykYU (Ok this is not exactly the same as tidal locking but is close to that ) . Also the artcle sais: The habitable zone for a main sequence star very gradually moves out over time until the star becomes a white dwarf, at which time the habitable zone vanishes.
Quote (HarbingerDawn) There is also no compelling evidence to suggest that only planetary systems with a specific configuration are suitable for life. On the contrary, many of the systems being discovered lend support to the opposite view, that worlds on which life could develop can exist in many kinds of planetary systems.
Really? Any such worlds?
It has been suggested that the presence of large gas giants close to or even inside the rocky planet formation zone will destabilize the orbits of such planets. This can be illustrated uzing the Universe Sandbox gravity simulator software. The absence of gas giants however may live the inner rocky planets unprotected from asteroid impacts.
Quote (HarbingerDawn) One of the strongest cases that Rare Earthers make against Earth-like planets being common is that a large moon may be required, and the formation of such objects is exceedingly unlikely
Even if the formation of an appropriate size moon is common, that does not guarantee the planet-moon system will be suitable for life. Because this planet-moon must possess all other properties. If the moon orbits the planet at a highly retrograde, elliptical orbit or if the orbital plane is 90 degrees vertical to the planets orbit plane around the star, then conditions will not be ideal for life to develop.
Quote (HarbingerDawn) The only argument of the Rare Earth Hypothesis that may be difficult to dispute (and that I see no obvious shortcomings with) is that the development of complex life from simple life (eukaryotes from prokaryotes) is an unlikely or difficult occurrence.
Well that is probably true. Simple bacteria, unicellulars or amoebaes is one story, but multicellular is another. And all these is because the more complex the life form, the more narrow the range of all these planetary parameters must be. In fact if tolerance for unicellulars is 10%+- ideal values, the tolerance for simple multicellulars goes down to 0.01% and if we go to more complex life forms, tolerance deviation approaches practically zero.
And finally there is also another argument that is in favour of the REHers: It is one explanation of the Fermi Paradox. And a strong one IMHO. Or to reverse it: The fermi paradox is another strong evidence in favour of the REH.
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Edited by neutronium76 - Monday, 10.09.2012, 17:09 |
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| DevonX | Date: Monday, 10.09.2012, 17:07 | Message # 36 |
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| Aerospacefag | Date: Monday, 10.09.2012, 17:20 | Message # 37 |
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| DevonX, at least, on our planet.
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| DoctorOfSpace | Date: Monday, 10.09.2012, 17:20 | Message # 38 |
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| Quote (Aerospacefag) at least, on our planet.
I disagree
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| HarbingerDawn | Date: Monday, 10.09.2012, 17:23 | Message # 39 |
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| Quote (DoctorOfSpace) I disagree
You disagree that there is life on our planet? 
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| DoctorOfSpace | Date: Monday, 10.09.2012, 17:25 | Message # 40 |
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| Quote (HarbingerDawn) You disagree that there is life on our planet?
Are we ready to get all existential in here?
I just realized this may go off topic very fast
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Edited by DoctorOfSpace - Monday, 10.09.2012, 17:28 |
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| Talisman | Date: Monday, 10.09.2012, 17:48 | Message # 41 |
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| Quote (DoctorOfSpace) Are we ready to get all existential in here?
I just realized this may go off topic very fast
Do you want to disagree that there is life on Earth just to be different or is that a serious view you have?
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| DoctorOfSpace | Date: Monday, 10.09.2012, 17:52 | Message # 42 |
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| Quote (Talisman) Do you want to disagree that there is life on Earth just to be different or is that a serious view you have?
It was a joke, an unfunny one at that but one to goad a response/discussion. Then I realized that such a joke would be in poor taste to the discussion of this thread.
Nah but srs there is no life on Earth.
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| HarbingerDawn | Date: Monday, 10.09.2012, 18:29 | Message # 43 |
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| Quote (neutronium76) the hypothesis itself doesn't mention or even suggests the slightest hint for such a thought. It clearly stipulates a series of logical thoughts and tries to use scientific evidence in order to support its argument.
I know that it doesn't say that these things are true, but I wonder if that way of thinking may have contributed to the development of the hypothesis. The idea that we're somehow of cosmic significance just never seems to die. But it doesn't matter as the REH is a valid scientific hypothesis, and should be addressed as such.
Quote (neutronium76) All these are very important scientific data that can not be disregarded
I don't dispute that. But I have seen no compelling evidence that any of these factors would greatly bias against life nearly every part of the galaxy. They merely mention bad things that can hinder life's development, but they have not demonstrated that these unfavorable conditions truly exist across most of the galaxy. That is the part that I doubt. Stars of sufficient metalicities can be found in almost all regions of the galactic disc, as can supernovae which could be harmful. And it has also been recently discovered that small worlds like Earth actually do form around stars with much lower metal content; it is gas giants that seem to require more heavy elements to form. There are several stars in the neighborhood of the Sun that could explode as supernovae in a short time, and probably something like ½ to ¾ of the galactic disc has a roughly similar distribution of massive stars. Obviously this has not posed a problem for life on Earth. Also, the Sun has been passing in and out of the galactic arms throughout its life, with no obvious ill-effect. In any case, no objects exist within the arms for billions of years, since their orbits take them out of the arms. The arms themselves are therefore not really a factor. As for the galactic core, I don't think it has been demonstrated that its environment would be very disruptive. I'm sure many hypothetical/theoretical calculations have been done, but probably very few based on real data. I would be surprised if such a study concluded that the entirety of the galactic core region was completely unsuitable for life. More likely it is just region very close to the galactic center, a region that probably contains less than 2% of our galaxy's stars.
Quote (neutronium76) The habitable zone for a main sequence star very gradually moves out over time until the star becomes a white dwarf, at which time the habitable zone vanishes.
Very true. This actually lends even more support to lower-mass stars being well suited for the development of life. A star of 1 Solar mass exists on the main sequence for about 10 billion years; the Sun is already almost too hot for Earth to be habitable. But lower mass stars exist in that stage for very much longer. The smallest stars exist on the main sequence for trillions of years. Even a star that is 0.8 solar masses will live more than twice as long as the Sun. This gives life all the time it needs to develop.
Quote (neutronium76) Also regarding tidal locked planets around main sequence stars (or any stars), they would probably (if not certainly) have extreme climate conditions
That can be true, but this greatly depends on the planet's atmosphere. If it has a thick atmosphere with a lot of cloud cover, it will have a very stable climate and temperature all over its surface (like Venus). But this is not necessary, nor is it desirable if you want civilizations (being able to see the stars is a good thing ). If the planet is towards the outer part of its star's habitable zone, and if it has an atmosphere with a moderately strong greenhouse effect (stronger than Earth's) then it will not have very severe conditions.
Quote (neutronium76) Really? Any such worlds?
Many of the multiple-planet systems we have discovered have more- and less-massive planets mixed together, often in close proximity, and these can be stable. Kepler-11, Gliese 581, and HD 10180 are all examples.
Quote (neutronium76) The absence of gas giants however may live the inner rocky planets unprotected from asteroid impacts.
It is almost certain that the gas giants in our Solar system have caused more impacts on Earth than they have prevented. Long-period comets become short-period comets (and therefore spend much more time in proximity to Earth) because of close encounters with the gas giants. Also, the best current model for the formation and evolution of our Solar system (the Nice model) suggests that the migration of the gas giants was responsible for the Late Heavy Bombardment. If this migration had happened later in the Solar system's development, life on Earth would have been destroyed. Large planets can be a very destabilizing influence on a system.
Quote (neutronium76) If the moon orbits the planet at a highly retrograde, elliptical orbit or if the orbital plane is 90 degrees vertical to the planets orbit plane around the star, then conditions will not be ideal for life to develop.
Because of the formation process, highly eccentric and highly inclined orbits are unlikely. That only leaves retrograde as a concern, which at most decreases the odds of an Earth-like world by half.
Quote (neutronium76) The fermi paradox is another strong evidence in favour of the REH.
There are many possible explanations of the Fermi paradox. Personally, I think that it is simply that technological civilizations do not commonly arise, and fairly often destroy themselves. Or perhaps there are millions of civilizations out there. But why should we know about it? Radio communication may be as obsolete to most of them as smoke signals are to us. Even now most of our most easily detectable radio broadcast methods have been replaced. What is easiest to detect is very high power, analog encoded signals. We started using these in the 1930's. Less than 50 years later, satellite communications, cable television, and digital encoding began making this type of broadcast obsolete. Any aliens that listen to Earth today would notice very much less radio noise. Our world only announced its presence to the cosmos for less than a century. The only way that we will ever hear from other civilizations is if they are actively trying to communicate with us. Most of them probably would not, for various reasons. Even if they are doing this it's possible that they are not using radio. There are many reasons for why we haven't detected alien life, none of which require Earth-like planets to be rare.
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Edited by HarbingerDawn - Tuesday, 11.09.2012, 01:08 |
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| werdnaforever | Date: Friday, 14.09.2012, 04:43 | Message # 44 |
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| About that joke... of course life exists on Earth. The real question: is there intelligent life on Earth?
Back on topic: The possibility that there's no other life in the universe is so remote it's practically infinitesimal. Sure, an overwhelming majority of the universe is no doubt lifeless, but it is so gigantic that the miniscule fraction of it that could harbor life is itself enormous. This is logic I'm sure many of us may have heard before.
Life isn't necessarily restricted to Earth-like, DNA carrying cellular creatures. From what I've seen, most people are often too Earth-centric when it comes to the possibility of alien life. If we ever discover extraterrestrial life ourselves*, the odds are it will be unlike anything we've ever seen- different chemicals, different structure (who's to say life has to be made of cells as we know them?), etc. Consider the complex organic molecules in Earth's life, and imagine molecules equal only in complexity. There's room for diversity, and the more diverse the possibilities are, the more worlds are likely to have conditions and materials ideal for life of some kind. Don't get me wrong: there might be different groups of chemicals and environments that are more likely to support life than others. Chemistry is what it is despite whether you're on Earth or a planet a terraparsec away.
Thus, there should be billions, maybe trillions of worlds with life of all kinds within the observable universe (and beyond). It's really not a matter of opinion.
As for intelligent life; you could say it's as rare to the rest of life as life is to the universe. We don't really know how common it could be- it all depends on evolution, and we can only speculate on the evolution of alien life. Many know of the Drake equation, and we could extend that to different levels of intelligence if we want. A few lucky civilizations may evolve into become superintelligent beings far beyond human understanding- perhaps that is the rarest type of life.
*Europa doesn't count; if it has a liquid water ocean under the ice, life there could be similar to our own.
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| Jakman217 | Date: Sunday, 14.10.2012, 06:45 | Message # 45 |
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| I wasn't able to fit the whole question in the name. Anyway, given a planet with life coming into intelligence / sentience, where would be the best place for it to grow and learn. Ignore the likelihood of whether it would even be there and plop the solar system down where ever with the first fledgling societies. Where do you think it would learn the best and develop the quickest?
The places I think for it would be either neat the galactic core, assuming it could survive the almost constant daylight from the stars and radiation from the black hole. That would give it only a (relatively) short distance to a black hole and many secrets of the universe. Or it could be in the galactic halo, with an epic view of the galaxy. Along with that a (possibly) better view of gravity at its most impressive. Or right where it is, in the uncharted backwaters of the unfashionable end of the western spiral arm.
You can take anything into account, or ignore it with an infinite improbability drive that is space. My personal favourite is the second because of the epic view.
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