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    Quote Originally Posted by Rook View Post
    In practical terms, even traveling at 99% the speed of light, it would take you longer than that to reach Alpha Centauri - the human body can not tolerate accelerating that rapidly. I remember reading somewhere that it'd take years of steady acceleration to reach the speed of light, and then the same steady deceleration to slow down before we reach our target. So even if we could reach 99% speed of light in 60 seconds, our fragile bodies wouldn't survive such acceleration
    You are quite correct Rook. I think it would take about 12 months at 1g acceleration to reach relativistic speeds, and a corresponding 12 months to slow down again. I suppose what you would ideally want to have is continuous acceleration for the first half of the journey and continuous decelleration for the second half. This way there would be no health consequences on the astronauts resulting from long periods of weightlessness. Alternatively, you could shave off time by having a greater acceleration - say 3g - and having the astronauts in some form of stasis to protect them from it.

    Finding an energy source to provide such a continuous acceleration is another matter, of course. As is protecting the astronauts from interstellar gas molecules which would rip through their bodies like the deadliest cosmic rays when the ship is travelling at relativisitic speeds.

    Providing these engineering challenges could met, a journey lasting 2 and a bit years on ship time to Alpha Centauri could be on the cards. It may not be Star Trek, but neither does it sound completely unfeasible either.
    Last edited by Northumbrian; 01-27-2013 at 12:40 AM.

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    This discovery, announced last month, passed me by:

    http://en.wikipedia.org/wiki/Kepler-62

    It looks like the best Earth-analogue discovered to date. The star is a little dimmer than our own Sun, and is orbited by 5 terrestrial (rocky) planets. Two are in the habitable zone, and one - Kepler 62f - the outermost, looks particularly interesting. Its a little larger than Earth and receives about 50% of the sunlight that we do (not a problem if it has a thick atmosphere, which given its size it probably has).

    I reckon that we are only a year or so away from the discovery of an exact analogue of the Earth. The only trouble with these Kepler discoveries is that all the target stars are so far away. Kepler 62 is 1200 light years away!

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    Administrator Will's Avatar
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    Quote Originally Posted by Northumbrian View Post
    This discovery, announced last month, passed me by:

    http://en.wikipedia.org/wiki/Kepler-62

    It looks like the best Earth-analogue discovered to date. The star is a little dimmer than our own Sun, and is orbited by 5 terrestrial (rocky) planets. Two are in the habitable zone, and one - Kepler 62f - the outermost, looks particularly interesting. Its a little larger than Earth and receives about 50% of the sunlight that we do (not a problem if it has a thick atmosphere, which given its size it probably has).

    I reckon that we are only a year or so away from the discovery of an exact analogue of the Earth. The only trouble with these Kepler discoveries is that all the target stars are so far away. Kepler 62 is 1200 light years away!
    I've always wondered what would happen if there were two planets in a habitable zone both capable of supporting life, and they both produced sentient life at the same time. As highly improbably as that is, would they learn better understanding of each other and the universe in general, or would it make them more xenophobic? Most likely they would learn to communicate by radio long before they ever physically met. Would they become more tolerant of that which is different, or would they be firing missiles at each other at the first chance? Judging by human nature I'd be tempted to say the latter.

    Also, would it make them realise the folly of religion (I believe all sentient life must go through a stage of believing in religion) seeing as how they would most likely be completely different, or would they become more entrenched in their beliefs, believing that their god is the one true god?
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    Quote Originally Posted by Will View Post
    I've always wondered what would happen if there were two planets in a habitable zone both capable of supporting life, and they both produced sentient life at the same time. As highly improbably as that is, would they learn better understanding of each other and the universe in general, or would it make them more xenophobic?
    I think if you look at our own planet, the omens for the peaceful co-existence of two intelligent species are not very good. Since we are the only intelligent species living on Earth, it is hard for us to imagine a time when we shared the planet with another intelligent species. Nonetheless, incredibly it did happen.

    As recently as 30,000 years ago, two intelligent but seperate humanoid species lived in parallel across much of Europe and Western Asia - Homo Sapiens and Homo Neanderthalis. As we all know, it didn't turn out well for the Neanderthals. They had vanished within a few thousand years, perhaps leaving within the European consciousness folk-memories of trolls, goblins and "little-folk". Not everyone blames Sapiens for their demise, but it seems a curious coincidence that Neanderthals coped well on their own for 500,000 years in Europe through the worst of the Ice Ages, but then vanished quite quickly (along with many other species) when we arrived on the scene. DNA and genetics has proved one old theory wrong - they didn't vanish by interbreeding with our species as they were genetically incapable of doing so (not to mention the fact that we would have found each other sexually repulsive, unless enormous brow-ridges is your thing!).

    I suspect that any encounter between two intelligent species, even if (or perhaps especially if) both are technologically advanced, will probably always lead to conflict with one side prevailing over the other. Perhaps the movie "Avatar" isn't too far from the truth in its portrayal of what happens when two intelligent species meet. It certainly would be nice to know if ET is out there, but perhaps for either our sake or theirs lets hope he isn't too close!
    Last edited by Northumbrian; 05-25-2013 at 12:04 AM.

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    Senior Member Rook's Avatar
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    Quote Originally Posted by Northumbrian View Post
    DNA and genetics has proved one old theory wrong - they didn't vanish by interbreeding with our species as they were genetically incapable of doing so (not to mention the fact that we would have found each other sexually repulsive, unless enormous brow-ridges is your thing!).
    I thought we shared 4% of our DNA with Neanderthals? I don't know if that study has since been disproved, but it does show that we DID interbreed with the brutes . . . it also shows that black people do not have that inherited DNA, which poses distasteful questions in my mind . .

    The Neanderthal example is limited though, by our technological advancement (as you hint at). The more we progress, the less violent we become as a species. Perhaps by the time a speicies achieve inter-planetary flight, they'd be a bunch of mellowed out hippies? The other planet may be in the middle-ages still though, and highly exited by violence

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    Quote Originally Posted by Rook View Post
    I thought we shared 4% of our DNA with Neanderthals? I don't know if that study has since been disproved, but it does show that we DID interbreed with the brutes . . . it also shows that black people do not have that inherited DNA, which poses distasteful questions in my mind . .
    We actually share over 99% of our DNA with Neanderthals, but that is not saying much as we share over 98% with Chimpanzees and Bonobo's! It is always difficult to determine exactly the point where a "speciation" has occured, i.e. when interbreeding becomes impossible, but from what I have seen all recent genetic studies point to it having happened between ourselves and Neanderthals (which is hardly surprising as the populations had been geographically seperated for at least 300,000 years). Even if we could have produced an offspring with a Neanderthal it would have been infertile, much like the offspring of a horse and a donkey,

    Not sure where you are getting the idea from that European's are genetically distinct from black people, but this sort of "racial" theory of genetics is heavily discredited. There are nationalistic "scientists" in China who try to propose a similar origin for the Chinese race (by mixing Homo Sapiens with Homo Erectus rather than Neanderthals - Erectus still lived in eastern Asia when Sapiens moved in) and thus explaining the supposed "superiority" of the Chinese race. Utterly deluded and utterly wrong!

    Most people are surprised (possibly given their own prejudice) to learn that the major genetic dividing line within Homo Sapiens is actually between southern Africans and eastern Africans, though of course it is nowhere close to being a speciation. In fact, all non-Africans from Europeans to Chinese to Australian Aborigines to Polynesians to Native Americans are in fact eastern Africans, being entirely descended from a single east African population of no more than a few hundred individuals which 70,000 years ago managed to cross the straits of Yemen to become stranded in Arabia. All the slight cosmetic differences which have occurred since then (from skin/hair colour to eye shape and height variation) have been the result of selection due to environmental factors, and not interbreeding with other homonids!

    Quote Originally Posted by Rook View Post
    The Neanderthal example is limited though, by our technological advancement (as you hint at). The more we progress, the less violent we become as a species. Perhaps by the time a speicies achieve inter-planetary flight, they'd be a bunch of mellowed out hippies? The other planet may be in the middle-ages still though, and highly exited by violence
    I'm not sure about that. As we become more technologically advanced our ability to destroy our own environment and wipe out other species becomes ever more efficient. I suppose it isn't malicious violence, but that might seem a moot point to a species which is becoming extinct on our account. One imagines that in our travels around the cosmos we might encounter a species as intelligent as our own, but in a less technologically advanced state. As civilised as we are, an Earth-type planet would be a rare and valuable resource indeed in a galaxy largely hostile to life. I don't doubt that we would find excuses to sideline or even eliminate these people if they stood in the way of what we wanted. On the other hand, if the species encountered was more advanced than us, would we not expect them to treat us in the same way?
    Last edited by Northumbrian; 05-28-2013 at 02:24 PM.

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    Senior Member Rook's Avatar
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    Quote Originally Posted by Northumbrian View Post
    We actually share over 99% of our DNA with Neanderthals, but that is not saying much as we share over 98% with Chimpanzees and Bonobo's! It is always difficult to determine exactly the point where a "speciation" has occured, i.e. when interbreeding becomes impossible, but from what I have seen all recent genetic studies point to it having happened between ourselves and Neanderthals (which is hardly surprising as the populations had been geographically seperated for at least 300,000 years). Even if we could have produced an offspring with a Neanderthal it would have been infertile, much like the offspring of a horse and a donkey,

    Not sure where you are getting the idea from that European's are genetically distinct from black people, but this sort of "racial" theory of genetics is heavily discredited. There are nationalistic "scientists" in China who try to propose a similar origin for the Chinese race (by mixing Homo Sapiens with Homo Erectus rather than Neanderthals - Erectus still lived in eastern Asia when Sapiens moved in) and thus explaining the supposed "superiority" of the Chinese race. Utterly deluded and utterly wrong!

    Most people are surprised (possibly given their own prejudice) to learn that the major genetic dividing line within Homo Sapiens is actually between southern Africans and eastern Africans, though of course it is nowhere close to being a speciation. In fact, all non-Africans from Europeans to Chinese to Australian Aborigines to Polynesians to Native Americans are in fact eastern Africans, being entirely descended from a single east African population of no more than a few hundred individuals which 70,000 years ago managed to cross the straits of Yemen to become stranded in Arabia. All the slight cosmetic differences which have occurred since then (from skin/hair colour to eye shape and height variation) have been the result of selection due to environmental factors, and not interbreeding with other homonids!
    The link clearly states that we did interbreed with Neanderthals. If that study has since been discredited, then please provide me with a link.

    My previous comment was badly worded perhaps, so I will instead quote directly from the article: Most people living outside Africa can trace up to 4% of their DNA to a Neanderthal origin, a consequence of interbreeding between the two groups after the great migration from the contintent.

    To me, that sounds like a small but significant difference between Africans and non-Africans. Not enough for speciation of course, but still different, distinct perhaps?

    Quote Originally Posted by Northumbrian View Post
    I'm not sure about that. As we become more technologically advanced our ability to destroy our own environment and wipe out other species becomes ever more efficient. I suppose it isn't malicious violence, but that might seem a moot point to a species which is becoming extinct on our account. One imagines that in our travels around the cosmos we might encounter a species as intelligent as our own, but in a less technologically advanced state. As civilised as we are, an Earth-type planet would be a rare and valuable resource indeed in a galaxy largely hostile to life. I don't doubt that we would find excuses to sideline or even eliminate these people if they stood in the way of what we wanted. On the other hand, if the species encountered was more advanced than us, would we not expect them to treat us in the same way?
    Our ability for greater destruction increases with tech, but our desire for destruction decreases with time and civility (it would seem). We are less violent today than we have ever been, yet our ability to destroy has never been greater. By the time we advance to inter-stellar travel, it's probable that we will see the destruction of other beings as utterly repugnent and unacceptable.

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    Quote Originally Posted by Rook View Post
    The link clearly states that we did interbreed with Neanderthals. If that study has since been discredited, then please provide me with a link.

    My previous comment was badly worded perhaps, so I will instead quote directly from the article: Most people living outside Africa can trace up to 4% of their DNA to a Neanderthal origin, a consequence of interbreeding between the two groups after the great migration from the contintent.
    Just because you found a review of a single paper in the Guardian that proves absolutely nothing. There are dozens of other papers which prove the opposite, and if you are too lazy to do the research yourself I'm not going to do it for you. The overwhelming opinion of scientists in the field is that Humans and Neanderthals were not closely enough related to interbreed, and I'm not going to argue with them (and neither should you). Of course, the ancestors of Sapiens who lived in the Horn of Africa 0.5My ago probably would have encountered the Homo Heidelbergensis who left Africa to spawn the population of Neanderthals in the Middle East and Europe. At this time the genetic differences would have been less and a limited amount of interbreeding may have taken place prior to the migration of the first group out of Africa, which is ACKNOWLEDGED by the authors of the paper you quoted. Even so, the genome has only been constructed from nuclear DNA - other studies have found no link between human and Neanderthal mitochondrial DNA, which proves that interbreeding between Neanderthal females and Human males could not have taken place. It would be odd then that interbreeding between Human females and Neanderthal males happened but not the reverse. The obvious conclusion is that it didn't.

    There have also been suggestions that the 2010 reconstructed Neanderthal DNA genome is severely contaminated with human DNA - hardly suprising as it was constructed from fragments only a few genes long.

    Quote Originally Posted by Rook View Post
    To me, that sounds like a small but significant difference between Africans and non-Africans. Not enough for speciation of course, but still different, distinct perhaps?
    There is no such thing as an African. All non-Africans are East African and the major genetic divide within Homo Sapiens is between Southern Africans and East Africans (which includes us).

    Quote Originally Posted by Rook View Post
    Our ability for greater destruction increases with tech, but our desire for destruction decreases with time and civility (it would seem). We are less violent today than we have ever been, yet our ability to destroy has never been greater. By the time we advance to inter-stellar travel, it's probable that we will see the destruction of other beings as utterly repugnent and unacceptable.
    Then why is the rate of species extinction increasing exponentionally? It may not be malicious violence, but every time a couple have more than two children or a tree is chopped down in the Amazon forest, an act of violence is being committed against the other species with which we share this planet.

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    Senior Member Rook's Avatar
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    Quote Originally Posted by Northumbrian View Post
    Just because you found a review of a single paper in the Guardian that proves absolutely nothing. There are dozens of other papers which prove the opposite, and if you are too lazy to do the research yourself I'm not going to do it for you. The overwhelming opinion of scientists in the field is that Humans and Neanderthals were not closely enough related to interbreed, and I'm not going to argue with them (and neither should you).
    I am not arguing with those (unstated) experts of yours, the experts in my link are. I am completely open to the idea that they may be wrong, but as a scientific man, you must surely recognise that as knowledge grows, old assumptions are reassessed in the light of new evidence. With this in mind, I would appreciate it if you could indeed link me to a more recent study than I have linked to, which supports your argument. Thanks


    Quote Originally Posted by Northumbrian View Post
    There have also been suggestions that the 2010 reconstructed Neanderthal DNA genome is severely contaminated with human DNA - hardly suprising as it was constructed from fragments only a few genes long.
    Link?

    Quote Originally Posted by Northumbrian View Post
    There is no such thing as an African. All non-Africans are East African and the major genetic divide within Homo Sapiens is between Southern Africans and East Africans (which includes us).
    You know what I mean. The East Africans who remained in Africa are different from the East Africans who left. For the purposes of easy discourse, I will refer to the East Africans who remained in Africa as Africans, and those East Africans who left as non-Africans.

    Quote Originally Posted by Northumbrian View Post
    Then why is the rate of species extinction increasing exponentionally? It may not be malicious violence, but every time a couple have more than two children or a tree is chopped down in the Amazon forest, an act of violence is being committed against the other species with which we share this planet.
    It's a bit of a stretch to say cutting a tree down is an act of violence - far too hippy like for my tastes. Species are dying off, yes, but that doesn't really counter my point. Never before in human history have humans cared so much about other animals and the environment. We are not yet at the point where all of us care so deeply that we temper our behaviour, but we are slowly getting there imho

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    Quote Originally Posted by Rook View Post
    I am not arguing with those (unstated) experts of yours, the experts in my link are. I am completely open to the idea that they may be wrong, but as a scientific man, you must surely recognise that as knowledge grows, old assumptions are reassessed in the light of new evidence.
    The old assumption WAS that humans and Neanderthals interbred, or perhaps even further that Neanderthals were the ancestors of White Causasian people and Erectus were the ancestors of East Asian/Mongoloid people (the so-called Multi-regional theory). It is this theory (which had rather unpleasant racial undertones) which has been swept away by the genetic research. Humans (Homo Sapiens) evolved in Africa and then (from 70,000 years ago) migrated out of Africa displacing earlier hominids which they did not and could not interbreed with.

    Quote Originally Posted by Rook View Post
    With this in mind, I would appreciate it if you could indeed link me to a more recent study than I have linked to, which supports your argument. Thanks
    Your wish is my command:
    http://www.pnas.org/content/109/35/1...d-16f033ef7090

    For a more readable summary of the Eriksson and Manica (2012) paper:
    http://www.telegraph.co.uk/science/s...ists-find.html

    Took me 2 minutes to find on Google. Don't you know how to use google?

    Quote Originally Posted by Rook View Post
    Link?
    You want a paper pointing to contamination issues in the Green et al genome reconstruction?

    http://www.plosgenetics.org/article/...l.pgen.0030175

    Sorted I would say.

    Quote Originally Posted by Rook View Post
    You know what I mean. The East Africans who remained in Africa are different from the East Africans who left. For the purposes of easy discourse, I will refer to the East Africans who remained in Africa as Africans, and those East Africans who left as non-Africans.
    No I don't know what you mean. The East Africans who remained in Africa are the same as the East Africans who left Africa (and became our ancestors). At the very least, the differences are very much smaller than those between East Africans and South Africans. So your use of term "African" is meaningless, at least in a genetic sense (though I don't disagree that there are historical and cultural connections linking different regions of Africa).

    Quote Originally Posted by Rook View Post
    It's a bit of a stretch to say cutting a tree down is an act of violence - far too hippy like for my tastes. Species are dying off, yes, but that doesn't really counter my point. Never before in human history have humans cared so much about other animals and the environment. We are not yet at the point where all of us care so deeply that we temper our behaviour, but we are slowly getting there imho
    Yes it did sound somewhat hippyish but I was trying to present things from the point-of-view of a non-human species. If somebody bulldozed your home and your neighbourhood you would probably consider it a violent act. Yet this is exactly what we do to an area of the Amazon forest the size of Belgium every year. Concern for animals and the environment is all very well in prosperous Western countries, but I don't see that concern shared in the developing world (which after all is the bulk of humanity).

    Whenever there is a conflict of interest between humans and other species, we always put ourselves first. Hence we have lost countless species from this planet - our cousins the Neanderthals being just one of the first species we apparently made extinct (despite their intelligence and close relationship to us). Getting back to the original topic, I don't see this changing if we encounter another intelligent* species on a different planet. Earth-like planets are probably very rare in the Universe, and if we ever developed interstellar travel, any habitable planet would be prime real-estate for human colonisation (especially the way that we breed). I can't see why other civilisations wouldn't see our planet in the same light.

    * whether a species is "intelligent" or not is perhaps another whole saga of debate. The idea of intelligence which we have is defined very much by our own species and is probably not applicable when dealing with other forms of life.
    Last edited by Northumbrian; 06-03-2013 at 05:52 PM.

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