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Thread: We are not alone . . .

  1. #21
    Senior Member Rook's Avatar
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    Quote Originally Posted by Northumbrian View Post
    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.

    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?

    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.
    See, was any of that difficult? Why did we need to go through that back and forth in order to move the debate forward??

    Quote Originally Posted by Northumbrian View Post
    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).
    Sigh. It should be clear what I meant and I suspect you understood. Your links have made the subject mute now

    Quote Originally Posted by Northumbrian View Post
    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).
    You must surely agree that we are much more aware/caring about environmental issues now then we have ever been. Suggesting that this increased care will continue for many decades, is not such a controversial idea.

    Quote Originally Posted by Northumbrian View Post
    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.
    It depends on the objective of the mission. Colonisation in order to 'conquer' is unlikely except in the very unlikely event we've fucked up Earth to the extent it's uninhabitable. It's also unlikely it's mission will be to gain access to resources - it'd be 'easier' to mine asteroids and 'dead' planets than deal with alien life, especially with the distances involved). I think that by the time we progress to inter-stellar travel, we should have our populations under some control so as to not 'need' living space.

    Quote Originally Posted by Northumbrian View Post
    * 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.
    Inteligence creates technology, so unless we encounter them when they are at the 'hunter/gatherer' stage, we will be able to recognise their abilities.

  2. #22
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    This new discovery looks interesting.

    http://www.universetoday.com/103131/...g-gliese-667c/

    Gliese 667c has 6 or 7 planets, with 3 in the habitable zone, and its "only" 22 light years away (on our doorstep in cosmic terms).

  3. #23

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    Quote Originally Posted by Northumbrian View Post
    This new discovery looks interesting.

    http://www.universetoday.com/103131/...g-gliese-667c/

    Gliese 667c has 6 or 7 planets, with 3 in the habitable zone, and its "only" 22 light years away (on our doorstep in cosmic terms).

    Northumbrian..please stop it..there aren't any aliens..they would have been here by now..and as I know you lurrve blinding everyone with BS..and your alleged scientific ''knowledge''

    is hypothetical..

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    If there is a species out there that can be considered a viable life form, then we better hope it doesn,t find us, as against us finding it. Because for that to happen, it,s intelligence levels on a ratio with ours, could be measured in the light years that divide its planet from ours . Which rather implies that the best we could hope for would be a cage in one of their zoo,s.

  5. #25
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    Quote Originally Posted by wolfie View Post
    Northumbrian..please stop it..there aren't any aliens..they would have been here by now..and as I know you lurrve blinding everyone with BS..and your alleged scientific ''knowledge''

    is hypothetical..
    The bizarre notion that aliens don't exist is mathematically implausible (to put things mildly). Just within the observable Universe, there are something like a trillion trillion planets (thats 10 to the power of 24). A trillion trillion is more grains of sand than exist on every desert and every beach on this planet. Are you seriously suggesting that life only exists on one of these planets? Remember the same laws of physics and chemistry exist on every planet in the Universe. Its true that nobody can prove it explicitly, but it is logical to assume that wherever you have liquid water, Carbon, a source of heat and stable conditions you will get life ... and life inevitably evolves over time into more complex forms.

    There is no reason at all to assume that if aliens existed, they would have visited us. Intelligent, technological civilisations are likely to be hundreds, or thousands, of light-years apart at the best. The technology involved in travelling such distances is unimaginable, and given the restrictions placed on us by the laws of physics (relativity) may never be possible.

    Perhaps you could inform me which part of my "alleged" scientific knowledge you considered to be "BS". As I have a PhD in Astrophysics, I can claim to be talking with some authority on the subject. Where is your knowledge based? Please don't say the Bible, lol!

  6. #26
    Senior Member Rook's Avatar
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    Quote Originally Posted by Northumbrian View Post
    The bizarre notion that aliens don't exist is mathematically implausible (to put things mildly). Just within the observable Universe, there are something like a trillion trillion planets (thats 10 to the power of 24). A trillion trillion is more grains of sand than exist on every desert and every beach on this planet. Are you seriously suggesting that life only exists on one of these planets? Remember the same laws of physics and chemistry exist on every planet in the Universe. Its true that nobody can prove it explicitly, but it is logical to assume that wherever you have liquid water, Carbon, a source of heat and stable conditions you will get life ... and life inevitably evolves over time into more complex forms.

    There is no reason at all to assume that if aliens existed, they would have visited us. Intelligent, technological civilisations are likely to be hundreds, or thousands, of light-years apart at the best. The technology involved in travelling such distances is unimaginable, and given the restrictions placed on us by the laws of physics (relativity) may never be possible.
    Also, the fact that there are trillions of planets out there mean that the likelyhood of them picking our (not particularly remarkable) solar system to visit is quite low.

    Unless we happen to be the closest habitable planet to them, they are likely to only visit us when they have 'proof' of our intelligence - which I assume (but please correct me) will only really come from things like radio waves, which would take a bloddy long time to reach the nearest star, let alone the nearest habitable planet with intellignet life able to receive, deceipher and track it.

  7. #27
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    Quote Originally Posted by Rook View Post
    Also, the fact that there are trillions of planets out there mean that the likelyhood of them picking our (not particularly remarkable) solar system to visit is quite low.

    Unless we happen to be the closest habitable planet to them, they are likely to only visit us when they have 'proof' of our intelligence - which I assume (but please correct me) will only really come from things like radio waves, which would take a bloddy long time to reach the nearest star, let alone the nearest habitable planet with intellignet life able to receive, deceipher and track it.

    You are absolutely correct. An equivalent civilisation to our own would probably not notice us against the backdrop of millions of sun-type stars just in our region of the our own galaxy. If they had a space based interferometer (essentially two space telescopes operating in tandem with a large seperation between them) they might have surveyed our Sun and imaged eight little dots nearby. Recognising that the third dot would be in the habitable zone, it is just about possible that they might be able to take a spectrum of the third dot and recognise the signature of Oxygen and Methane in its atmosphere. These two gases, out of equilibrium with each other, in any atmosphere are a fairly clear sign of biological processes. Technologically, we are not at this level yet. NASA cancelled its plan for space-based interferometer a few years back, whilst its unlikely we will be able to take atmospheric spectra of nearby exoplanets for many decades (although it is feasible).

    Lets assume (rather optimistically I would say) that the closest hyper-civilisation lives only 200 light year away. It is just about possible that they might know of the Earth's existence and that it harbours biological life. Unfortunately, this is not going to make the Earth stand out that much. Within 200 light years of any star in the Milky Way, there are likely to be tens of thousands of Earth-type planets which support life. It doesn't mean that any have technologically advanced intelligent life, which is presumably incredibly rare. Take Earth for example. If an alien was to arrive here at random during any point of the last 4.6 billion years of the Earth's existence, there is about a 75% probability that he would find a planet that supported life. However, the chance of finding a planet that supported a technological civilisation (capable of broadcasting and receiving radio signals) would only be about 1 in 40 million. Thats not much better than the odds of winning the Euromillions jackpot!

    It is often cited that out TV or radio signals would give us away. Well in about the year 2136, our first high-powered TV carrier waves would reach our hypothetical civilisation. It is just about possible that if they had SETI-type radio receiving equipment far more sensitive than our own SETI technology and had been specifically pointing their radio telescopes towards Earth for many years (why would they?) they might just be able to recognise the incredibly weak signal of our carrier waves above the noise of nearby natural radio sources (such as the Sun and Jupiter). Note that we are only talking here about the carrier waves - they would recognise sinusoidal radio waves of a fixed frequency but wouldn't stand a cat in hells chance of seeing any amplitude or frequency modulation (which is how the data is encoded) above the noise. Even if they could, how would they even begin to decode it? To make things worse, the demise of analogue TV means that these carrier waves are now being switched off!

    Of course, if our hypothetical aliens recognised our TV carrier waves as a sign of intelligent life, we are not going to hear from them for another 200 years (around the year 2336!). As for them visiting us, well it would take 2,000 years at the mind-boggling speed of 10% of the speed of light. Would they really go to that much effort for a civilisation that might not even exist any more by the time they got here? The conclusion then is that we can't draw any conclusion from the fact that we've never been visited by aliens! They simply will be unaware of our existence, and in the unlikely circumstance of being aware of us would probably not go to the trouble of visiting us!
    Last edited by Northumbrian; 07-09-2013 at 05:21 PM.

  8. #28
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    Quote Originally Posted by Rook View Post
    Earth-size planets 'number 17 billion'



    17,000,000,000 Earth-sized planets . . . a fair few must have the right combination of factors which allow for life
    Nice round figure! Sounds like it's been plucked out of the air - which is probably has!

    There are only two things that mankind will never know the answers to - how the human brain works, and what lies beyond the universe. There are those making a good living by pretending they do know though.
    Last edited by Ollyof39; 08-27-2013 at 09:12 AM. Reason: afterthought!!

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    Quote Originally Posted by Ollyof39 View Post
    Nice round figure! Sounds like it's been plucked out of the air - which is probably has!
    Not so much plucked out of the air. Missions like Kepler are starting to give us some real statistics about the number of Earth-type planets in the galaxy. If there are 100 billion stars in the galaxy and 1 in 6 has an Earth-sized planet, hence 17 billion Earth-sized planets. In fact, this is only a lower estimate. Kepler can only detect Earth-sized planets in close orbits around very dim stars, so perhaps the true figure might be nearer 1 in 2 or even 75%. Given that the number of stars in the Milky Way could actually be as high as 500 billion, then its possible there could 250 to 400 billion Earth-sized planets in our galaxy. Then you consider that there are a trillion galaxies in the visible part of our Universe!

    Quote Originally Posted by Ollyof39 View Post
    There are only two things that mankind will never know the answers to - how the human brain works, and what lies beyond the universe. There are those making a good living by pretending they do know though.
    There are many things that mankind might never know, but I don't think those two would count. I believe we will understand how the human brain works - in fact, enormous strides have been taken in that direction. As for "what lies beyond the universe", I'm not sure that is even a meaningful question. Most serious cosmological models assume that the universe is infinite and therefore doesn't have a "beyond", although it is certainly the case that the part of the Universe which is visible to us has an "event horizon", beyond which we cannot directly see.
    Last edited by Northumbrian; 08-31-2013 at 06:23 PM.

  10. #30
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    So much speculation, so little proof!? As for:

    Most serious cosmological models assume that the universe is infinite and therefore doesn't have a "beyond", although it is certainly the case that the part of the Universe which is visible to us has an "event horizon", beyond which we cannot directly see.
    Well that's a nice 'pat' answer to satisfy a gullible public, and keep the cosmological show on the road isn't it? I could have said that!!

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