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dark energy ?

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    #32
    [-0-]
    Closed Accounts Posts: 3,981 ✭✭✭[-0-]


    Guys, I'm not qualified in this particular area by any means but I do have a question. Why will all suns burn out? Will new suns not be born?


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    #33
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    No, because only stars above the Chandrasekhar Limit will 'explode' as a supernova. However, as star systems are moving further and further away from each other, stars are gradually becoming smaller and smaller in size. Therefore, evntually, all stars will be below the Chandrasekhar Limit, and will just end up as white dwarf stars.

    Picture it like this: You have a 'humongous' star which goes supernova. It's remains then form a few smaller stars, which are constantly moving away from each other as the Universe expands. These then go supernova themselves, and the process continues, giving smaller star sizes.

    White Dwarves will eventually just give off all of the energy as light, and then appear as nothing more than a black rock of fused Iron (I think)??


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    #34
    [-0-]
    Closed Accounts Posts: 3,981 ✭✭✭[-0-]


    Awesome. Thank you Kevin!


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    #35
    Hoovers
    Closed Accounts Posts: 77 ✭✭Hoovers


    Kevster wrote: »
    White Dwarves will eventually just give off all of the energy as light, and then appear as nothing more than a black rock of fused Iron (I think)??

    White Dwarfs are just big balls of degenerate matter and they structurally resemble a huge spherical diamond, due to the crystallized lattice arrangement of the ionized carbon and oxygen inside.

    But not all White Dwarfs end their life in this slow, long way. If they are in a close binary system they can trigger a type Ia Supernova. Boom!


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    #36
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    Ah yes, that's true. Is it fused Iron that they are composed of though? Also, when a main sequence star (eg the Sun) runs out of Hydrogen, the Helium in the core fuses to Carbon (?), and then this fuses to Iron?


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    #37
    L_gaucho
    Closed Accounts Posts: 63 ✭✭L_gaucho


    usemyillusion12 wrote: »
    and when it comes to writting a programe for it , id go to a guy who knows how to , i wouldnt trust my basic knowledge of it , so in reality , it is totaly pointless

    Ah yes, but you've just added a variable into yur calculations. (you'd be sort of blindly trusting the programming guy).
    Einstein ran into this problem, he was frustrated with the Phyics, and found he needed to invest more time in mathematics to get his solutions. (as alot of his discoveries came from thought experiments)


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    #38
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    I'm more interested in dark matter, but that's not why I'm posting. I'm sure most will remember this recent story:

    NASA's Swift orbiting observatory spots oldest supernova yet

    Now at 13 billion light years away, the light from this far off supernova obviously did not have to travel 13 billion years in distance. Does expansion take care of this, or am I confused with this question that I'm sure has been asked umpteen times before?


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    #39
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Nevermind. I already got the answer by reading my own link - back to regular scheduled programming :confused:


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    #40
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    To be honest - ozhawk66 - I don't even know what your question was/is. Rephrase it, will you?


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    #41
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Kevster wrote: »
    To be honest - ozhawk66 - I don't even know what your question was/is. Rephrase it, will you?

    Well, when I first heard of the Supernova dated at 13 billion years, it finally occured to me that it obviously didn't travel 13 billion years in distance, or so it seemed to me.

    Do you know what I mean?, in the sense the Universe was obviously not as large 4, 8 or 10 billion years ago, as it is now.


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    #42
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Another thing, when we - humans - use the WMAP and look out to the far reaches of the universe, are we looking outward towards the edge, so to speak. Or are we looking back inward towards the "singularity"?


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    #43
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    Im' kind of understanding what you're talking about now, but I don't feel as if any answer I give you would be correct. Let's just wait until some other persson comes along and clears things up. Regarding the WMAP, the question you're asking is very good, and one that I have no idea of the answer!

    I'm only an amateur cosmologist:p


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    #44
    Thrill
    Registered Users Posts: 5,485 ✭✭✭Thrill


    Dark-energy particle spotted?

    http://www.nature.com/news/2009/090529/full/news.2009.531.html?s=news_rss


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    #45
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    That's a tough read. Are they saying that the expansion of the Universe can be explained by particles spreading/expanding their energy-range outwards to encompass a larger area? If all particles did this, then that would explain why the Universe expands.

    Like, a particle has an influence on the 4cm^3 of space around it one moment but then - in the next moment - it has an influence on the 16cm^3 (or some other higher amount) of space around it?


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    #46
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Kevster wrote: »
    Regarding the WMAP, the question you're asking is very good, and one that I have no idea of the answer!

    I'm only an amateur cosmologist:p


    I kind of have my own "answer", but I'll wait it out for someone on the know :cool:


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    #47
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Thrill wrote: »
    Dark-energy particle spotted?

    http://www.nature.com/news/2009/090529/full/news.2009.531.html?s=news_rss


    [QUOTE=and his colleagues have shown that if the photons convert into axion-like particles for part of their journey, they could reach Earth undisturbed6. [/QUOTE]

    Interesting.....:confused:


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    #48
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Maybe evidence of some "creation" going on after the bang? I've always wondered if that were the case, and maybe even still going on, albeit on a much smaller scale now.



    Astronomers revise galaxy-formation models with the discovery that early galaxies could have grown fat — fast.


    Slurping up cold streams of star fuel, some of the Universe's first galaxies got fat quickly, new observations suggest. The findings could overturn existing models for the formation and evolution of galaxies that predict their slow and steady growth through mergers.


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    #49
    Micky 32
    Registered Users Posts: 6,556 ✭✭✭Micky 32


    Kevster wrote: »
    Please be honest with me, Podge_irl: Where did you read about this before? I'm not attacking you here - just genuinely curious.

    Ah the big rip theory, apparenly it might just happen eventually :D

    Watch the last minute of this, 3 mins on

    http://www.youtube.com/watch?v=W2kvsUO-hdM&feature=PlayList&p=3CA191F154BAF046&playnext=1&playnext_from=PL&index=1


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    #50
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    Interesting, but it was made-out earlier in this thread that our atoms are drifting apart right now, ever so slowly (which is just not true I believe). I never discounted that they wouldn't eventually be 'broken' apart as the Universe' energy is dissipated so much. For the time being, however, the subatomic forces are quite capable of keeping atoms/matter together in us, plants, and for everything else on EArth and in the Solar Systems.


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    #51
    Podge_irl
    Moderators, Sports Moderators Posts: 25,589 Mod ✭✭✭✭Podge_irl


    ozhawk66 wrote: »
    Another thing, when we - humans - use the WMAP and look out to the far reaches of the universe, are we looking outward towards the edge, so to speak. Or are we looking back inward towards the "singularity"?

    I'm not sure you quite conceptually grasping what people mean by looking towards the beginnings of the universe. You are neither looking outward or looking inward, the concepts don't really make sense in this regard. There is no "edge" to look out towards (well, there are cosmic horizons and what not, but we have no reason to believe there is a physical edge to the universe). When we look into deep space we are receiving light that was transmitted billions of years ago, and so are seeing the universe at an earlier age.

    I realise that its easy to conceptualise the big bang and resulting expansion as the universe emanating from one point, but its not really what happened. There is no such thing as looking outwards or inwards.


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    #52
    Podge_irl
    Moderators, Sports Moderators Posts: 25,589 Mod ✭✭✭✭Podge_irl


    Kevster wrote: »
    Interesting, but it was made-out earlier in this thread that our atoms are drifting apart right now, ever so slowly (which is just not true I believe).

    Hmm...I'm not sure I explained what I meant properly. The model of expansion that we currently have dictates that the galaxies themselves aren't physically moving apart like billiards on a table (or at least not to any appreciable degree) but rather that space-time itself is expanding (which is more or less the only way to account for the super-luminal speeds at which it happens I think). If space-time is expanding it is doing so more or less homogeneously, and so it is going to affect everything in the universe. The distinction between bodies moving apart within our space and space expanding is an exceedingly important one. I think the phrase "drifting apart" gives the wrong impression.


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    #53
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    You know I respect you now dude (Podge_irl), but I want some clarity on this because I'm confused now. According to current theory, are atomic particles moving apart or not? I also said that it's daft to think that they are, but I never discounted that the Universe is expanding.

    I'm only an amateur dude! Be easy!:o


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    #54
    Podge_irl
    Moderators, Sports Moderators Posts: 25,589 Mod ✭✭✭✭Podge_irl


    Kevster wrote: »
    You know I respect you now dude (Podge_irl), but I want some clarity on this because I'm confused now. According to current theory, are atomic particles moving apart or not? I also said that it's daft to think that they are, but I never discounted that the Universe is expanding.

    I'm only an amateur dude! Be easy!:o

    The single most important distinction you need to understand is that there is a difference between moving within space and space itself expanding.

    Think of it this way - say you have a really really long piece of metal. The expansion that we speak of when referring to the galaxies moving apart would also cause that long piece of metal to grow longer. That's because the very space it inhabits is what is being stretched. This very same stretching cause distances between objects to increase - in that sense then yes atomic particles are moving further apart (though its such a small effect on that scale as to make it negligible). When we deal with expansion in cosmology (well, when cosmologists do it, I try to avoid that stuff!) the discussion largely centres around the spacetime geometry - i.e. the shape of the very fabric of spacetime itself. It doesn't really matter what objects are present in space - the expansion happens uniformly everywhere.

    The physical motion of the galaxies and stars within space is a very different issue. They are also moving in this regard, but the expansion of space is the more dominant effect. There is a whole other area of physics discussing this, but I know next to nothing about it. In this more classical sense though, the particles are not moving apart. For want of a better analogy - the distance you measure between two protons with a ruler is not changing, but the ruler itself is stretching along with the gap.


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    #55
    Kevster
    Closed Accounts Posts: 2,980 ✭✭✭Kevster


    I think that i'll just stick to my long-held opinion that the Universe is 'expanding' only in-so-far as the galaxies and superclusters are moving further apart because that is how they were set in motion in 'the beginning'. Also, I still believe that it will all collapse back upon itself some day. Yes, i'm ignoring the maths behind it all, but I think that it'd be arrogant of us to claim that we even know 1% of how the Universe operates.


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    #56
    ozhawk66
    Closed Accounts Posts: 99 ✭✭ozhawk66


    Podge_irl wrote: »
    I'm not sure you quite conceptually grasping what people mean by looking towards the beginnings of the universe. You are neither looking outward or looking inward, the concepts don't really make sense in this regard. There is no "edge" to look out towards (well, there are cosmic horizons and what not, but we have no reason to believe there is a physical edge to the universe). When we look into deep space we are receiving light that was transmitted billions of years ago, and so are seeing the universe at an earlier age.

    I realise that its easy to conceptualise the big bang and resulting expansion as the universe emanating from one point, but its not really what happened. There is no such thing as looking outwards or inwards.


    I personally don't think, or "visualize" the universe with an edge either. But the universe obviously has depth.

    But if we are looking closer to the beginnings of the universe, are we not looking "inwards"? TOO the singularity?


    * personally I have not read even close enough to give a legit opinion on the singularity concept, but I tend to think The Big Bang is one of those examples of yes, it happened. But not quite the way we think, or portray it? (hence, inflation, for example.)


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