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General Chat Thread, BBC News - Black Hole's 'Big Meal' Could Spark Fireworks in General; Originally Posted by jinnantonnixx Only a conscious observer can perceive the flow of time. A clock doesn't measure time's flow ...
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    Quote Originally Posted by jinnantonnixx View Post
    Only a conscious observer can perceive the flow of time. A clock doesn't measure time's flow any more than a ruler measures distances between points.
    A clock will run slow moving at speed. This has been observed in the GPS satellites. In fact, the US Airforce were unsure at to whether to believe Einstein, and insisted on a "switch" to enable or disable compensation for the time dilation effect. They haven't switched it off!


    I'm surprised that the "Drake Equation" hasn't come up yet. Personally, I find it a bit simplistic, but as a starting point:-

    Last edited by Andrew_C; 13th January 2014 at 05:14 PM.

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    Quote Originally Posted by Andrew_C View Post
    A clock will run slow moving at speed. This has been observed in the GPS satellites. In fact, the US Airforce were unsure at to whether to believe Einstein, and insisted on a "switch" to enable or disable compensation for the time dilation effect. They haven't switched it off!
    +1 for this! It made me chuckle when I read that story!

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    Quote Originally Posted by ICTDirect_Dave View Post
    Of course all of these figures and stats are only in relation to the Observable Universe (100Bn Galaxies etc...) when we take into account that this is just a tiny part of the actual universe (best guess so far is anywhere from 250 x bigger to infinitely bigger (big margin of error there))
    Wooa. The 'observable' universe is everything we can see and everything we can infer from what we see. I'd assume you are referring to "Dark Matter" and "Dark Energy" as being the rest of the universe?
    it seems rather hard to belive that we're the only life (intelligent or otherwise) We might well be the only life in our observable section of the universe (although I doubt it) but the odds of there being life must surely fall dramatically if what we can currently observer is less than 1% of everything that is actually out there right now.
    Scale has nothing to do with probability. The set of even integers is infinite, but the probability of finding an odd number in it is precisely zero. Even if the universe has 250 times more 'stuff' than we can actually see, that may make no difference to the probabilities of life.

  4. #64

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    Quote Originally Posted by pcstru View Post
    Wooa. The 'observable' universe is everything we can see and everything we can infer from what we see. I'd assume you are referring to "Dark Matter" and "Dark Energy" as being the rest of the universe?


    Scale has nothing to do with probability. The set of even integers is infinite, but the probability of finding an odd number in it is precisely zero. Even if the universe has 250 times more 'stuff' than we can actually see, that may make no difference to the probabilities of life.

    Nope dark matter and dark energy (if proven) are just as common in this part of the universe. I mean the amount of universe that we can observe. We can only see so far in a sphere with us at the centre but we're we to travel to the edge of that sphere there would be another sphere equally large around whatever point we were located. Its perfectly possible to be somewhere in the universe and be so far away that you cant see any of the stars or galaxies that we can see feon where we are! Just because the universe is 13.8bn years old doesn't mean its only 13.8bn lightyears across.

    And of course scale improves the odds in this case. Life happened here on earth and if that's the case and even if it is a very lucky roll of the dice, adding 250 or more times the stuff in the universe only gives you more dice rolls! The more rolls the better the chance of your number coming u!.
    Unless by your evens and odds statement you're saying we didn't get here by chance (what do you know that I don't?). But that's a wholly different debate

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    Quote Originally Posted by ICTDirect_Dave View Post
    Nope dark matter and dark energy (if proven) are just as common in this part of the universe. I mean the amount of universe that we can observe. We can only see so far in a sphere with us at the centre but we're we to travel to the edge of that sphere there would be another sphere equally large around whatever point we were located. Its perfectly possible to be somewhere in the universe and be so far away that you cant see any of the stars or galaxies that we can see feon where we are! Just because the universe is 13.8bn years old doesn't mean its only 13.8bn lightyears across.
    The evidence for this is what? I mean it might be after 13.8 billion years it's all invisible pink flying unicorns, but unlike the universe being 13.8 billion light years old, there is no evidence at all that I can point to to support that. If you want to say the universe is 250 times as big as currently 'observed' (and that 'unobserved' is not DM or DE), do please point me toward some evidence. It would be new to me and I'd love to see it. Seems to me that would have to be something beyond the cosmic background radiation.

    And of course scale improves the odds in this case. Life happened here on earth and if that's the case and even if it is a very lucky roll of the dice, adding 250 or more times the stuff in the universe only gives you more dice rolls! The more rolls the better the chance of your number coming u!.
    Unless by your evens and odds statement you're saying we didn't get here by chance (what do you know that I don't?). But that's a wholly different debate
    No, I'm saying that in some cases more 'stuff' simply makes no difference to the odds. We have no evidence of life anywhere else. Belief in life elsewhere is like belief in god or invisible pink flying unicorns, it is not based on any evidence. I think "there life intelligent elsewhere" is an OK theory, but the fermi paradox is actually a strong argument that, in this case absence of evidence may well be evidence of absence.

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    Quote Originally Posted by pcstru View Post
    ...it's all invisible pink flying unicorns, but unlike the universe being 13.8 billion light years old, there is no evidence at all that I can...
    A couple of small points to make here:

    1. These Unicorns are all the more remarkable for being both pink and invisible.

    2. A light year is a measure of distance not time: It is the distance that light travels in one year.

    [/Pedantic mode]


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    Quote Originally Posted by DaveP View Post

    2. A light year is a measure of distance not time: It is the distance that light travels in one year.
    True dat.

    (ETA - I occasionally think "light year ago" is appropriate as a nod to the inseparability of space and time, but strictly speaking a light year is a measure of distance).
    Last edited by pcstru; 14th January 2014 at 07:47 AM.

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    Quote Originally Posted by pcstru View Post
    The evidence for this is what? I mean it might be after 13.8 billion years it's all invisible pink flying unicorns, but unlike the universe being 13.8 billion light years old, there is no evidence at all that I can point to to support that. If you want to say the universe is 250 times as big as currently 'observed' (and that 'unobserved' is not DM or DE), do please point me toward some evidence. It would be new to me and I'd love to see it. Seems to me that would have to be something beyond the cosmic background radiation.
    There's plenty of evidence & maths out there to look at. For starters the universe that we can theoretically observe has a radius of 45-47 billion lightyears depending on what you define as observable. (How Big is Our Observable Universe? Starts With A Bang - some maths and graphs to explain this). This next link explains how we can work out that the actual universe is much bigger still (How Big is the Entire Universe? Starts With A Bang). We can basically see less than 1% of everything that is out there.

    A quick note on the CMB also. It isn't some wall beyond which there is nothing, the CMB is the background temperature of the whole Universe everywhere, it's the afterglow of the Big Bang and as such permeates through the entire universe.


    No, I'm saying that in some cases more 'stuff' simply makes no difference to the odds. We have no evidence of life anywhere else. Belief in life elsewhere is like belief in god or invisible pink flying unicorns, it is not based on any evidence. I think "there life intelligent elsewhere" is an OK theory, but the fermi paradox is actually a strong argument that, in this case absence of evidence may well be evidence of absence.
    I don't like the Fermi paradox, it's a bit too sweeping, who is to say that civilizations would colonize the whole galaxy or that they would even choose to encounter us should they have travelled this far. Not to mention that maintaining a civilization for the tens of millions of years required to travel to every point in the galaxy would be unlikely in it's own right. we still don't know if our planet is the only place life can be found in our own solar system, there's still the water moons of Jupiter and Saturn and the odd methane emissions from deep underground during the martian summertime that we haven't explained and won't likely be able to do until we've spent a fair amount of time actually visiting these places.

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    Scale vs Odds: careful not to get muddled between relative and absolute numbers. If there is a 0.0001% chance of life evolving on a planet, there is a 0.0001% chance of life evolving no matter how many planets you have. But if you talk in absolute numbers, a million planets would produce one suitable to life, whereas a billion would produce a thousand. Same probability, different absolute amounts. The issue then becomes distribution - we might all be too far apart.

    I think the problem is inherently depressing, because either:
    a) We're the only intelligent life, and the Universe is aiming low
    b) Civilisations destroy themselves before they have the chance to make sufficient headway into the Universe - which is therefore likely the fate that awaits us.

    I say either or, there's hundreds of possibilities, but looking at human history the latter does seem likely (and assuming evolution is universal, any sentient species is likely to have got where it is by selecting for aggression in the early days in order to out-compete other predators).

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    Quote Originally Posted by sonofsanta View Post
    b) Civilisations destroy themselves before they have the chance to make sufficient headway into the Universe - which is therefore likely the fate that awaits us.
    Yeah, we're gonna do that whether we're alone in the universe or not..

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    Quote Originally Posted by ICTDirect_Dave View Post
    A quick note on the CMB also. It isn't some wall beyond which there is nothing, the CMB is the background temperature of the whole Universe everywhere, it's the afterglow of the Big Bang and as such permeates through the entire universe.
    Actually, I believe the CMB is the first light that was able to move unimpeded across vast distances, which occurred during the last major phase transition that the universe passed through whereby it had cooled sufficiently that atoms could form. Prior to that the universe was a plasma of ionic protons and alpha particles, free roaming electrons, photons and other more exotic particles (neutrinos etc.). The protons and electrons impeded the photons' ability to propagate right up to the point where they phase transitioned to atoms, freeing the photon residues from the big bang and allowing them to propagate. At the point this would have happened the universe would have still been extremely hot, but the further stretching of the universe and corresponding cooling means that these photons, which would have originally been at much higher frequencies, have now "cooled" to the microwave range.

    I guess this could be interpreted as the afterglow of the big bang (these photons were mostly created in that event or a phase transition that occurred afterwards), but the glow itself is more indicative of the universe at the time of the atom phase transition.

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    We're still in a position where we're not sure exactly what lives in our own oceans, so our current chances of finding life (intelligent or otherwise) elsewhere seems slim...

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    Quote Originally Posted by SkywOrca View Post
    Actually, I believe the CMB is the first light that was able to move unimpeded across vast distances, which occurred during the last major phase transition that the universe passed through whereby it had cooled sufficiently that atoms could form. Prior to that the universe was a plasma of ionic protons and alpha particles, free roaming electrons, photons and other more exotic particles (neutrinos etc.). The protons and electrons impeded the photons' ability to propagate right up to the point where they phase transitioned to atoms, freeing the photon residues from the big bang and allowing them to propagate. At the point this would have happened the universe would have still been extremely hot, but the further stretching of the universe and corresponding cooling means that these photons, which would have originally been at much higher frequencies, have now "cooled" to the microwave range.

    I guess this could be interpreted as the afterglow of the big bang (these photons were mostly created in that event or a phase transition that occurred afterwards), but the glow itself is more indicative of the universe at the time of the atom phase transition.
    Afterglow is so much more poetic though and to be honest I think it's a fair description to give it. True there were a few stages between actual big bang and original light (not to mention nearly 400,000 years), but I think it's an excellent way of summing up into one sentence what you just said

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    Quote Originally Posted by ICTDirect_Dave View Post
    Afterglow is so much more poetic though and to be honest I think it's a fair description to give it. True there were a few stages between actual big bang and original light (not to mention nearly 400,000 years), but I think it's an excellent way of summing up into one sentence what you just said
    Bleh, poetic schmoetic! But yes, I guess it does make a more succinct summary of the actual physics.

    I do find the various phase transitions that have occurred in the evolution of our cosmos intrinsically fascinating, however. If you really want to blow your mind watch some of the sixty symbols interviews with Ed Copeland on his work on cosmic strings and the large scale after effects of phase transitions that occurred during the "Higgs Era" of the universe (some incomprehensibly small fraction of a second after the big bang!) to see how odd things really could get if you can wrap your head around the crazy maths.

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    Quote Originally Posted by ICTDirect_Dave View Post
    There's plenty of evidence & maths out there to look at. For starters the universe that we can theoretically observe has a radius of 45-47 billion lightyears depending on what you define as observable. (How Big is Our Observable Universe? Starts With A Bang - some maths and graphs to explain this). This next link explains how we can work out that the actual universe is much bigger still (How Big is the Entire Universe? Starts With A Bang). We can basically see less than 1% of everything that is out there.
    Thank you. I learned a lot from that.
    A quick note on the CMB also. It isn't some wall beyond which there is nothing, the CMB is the background temperature of the whole Universe everywhere, it's the afterglow of the Big Bang and as such permeates through the entire universe.
    It is a wall in that, it is the first EM radiation. You can't 'see' beyond it because it is the first thing to see.
    I don't like the Fermi paradox, it's a bit too sweeping, who is to say that civilizations would colonize the whole galaxy or that they would even choose to encounter us should they have travelled this far. Not to mention that maintaining a civilization for the tens of millions of years required to travel to every point in the galaxy would be unlikely in it's own right.
    The problem is if life is reasonably common, then some should and it should only take one to fill a galaxy in fairly short order. I think it's not a matter of contact (per se), but signs - radio chatter, cherenkov radiation ... astronomical 'anomalies'. I'm not a huge fan of it myself but it is an interesting counter theory to the "other life must exist just on the numbers". And I think it should be compelling if we continue to look with ever better instruments etc, yet keep turning up nothing.
    we still don't know if our planet is the only place life can be found in our own solar system, there's still the water moons of Jupiter and Saturn and the odd methane emissions from deep underground during the martian summertime that we haven't explained and won't likely be able to do until we've spent a fair amount of time actually visiting these places.
    Sure but right now there is no real evidence for life in those places and occams razor is an unforgiving blade. If I posit the existence of fairies the the bottom of gardens, I need some evidence for that. Saying, "well, we've not looked in all the gardens yet" isn't evidence in support of the theory. We know what 'life' does if it gets established - it runs rampant. Even planet wide disasters don't wipe it out and it permeates from the top of the atmosphere to surprisingly deep into the planet. I'd be quite shocked to find only a few hardy specimens eeking out a minimalist existence on Mars or Europa. That seems to me to go against evolutionary ontology, which is something we do have huge amounts of evidence for.

    On balance I probably believe more that there is other life, even intelligent life out there somewhere. But it's belief and I can't honestly say I have any good evidence on which to base it. I've nothing against belief (hell, I've just been ordained), I just like to recognise it for what it is (whatever that might be! :-) ).

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