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Thread: cosmological constant w

  1. #1 cosmological constant w 
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    I was doing some reading and I came across the cosmological constant w. It was new to me so I decided to investigate and learn what it is. I did some googling and wikiing and all I could find was that it had something to do with equation of state, but I couldn't figure out what it is. Could someone please either point me in the direction of an article that explains it or explain to me what w is?


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  3. #2  
    Forum Professor river_rat's Avatar
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    I would battle to explain it better then Wikipedia:

    http://en.wikipedia.org/wiki/Shape_of_the_universe


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  4. #3  
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    care to explain what that has to do with w? They use omega to describe the shape of the universe, is that the same as w?
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  5. #4  
    Forum Professor river_rat's Avatar
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    ah i thought you meant a lower case omega.

    w in the equation of state just gives you the relationship between the "pressure" driving the expansion of the universe and the energy density of the universe.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  6. #5  
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    ya, the equation is P = wpc^2
    P is pressure
    p is energy density
    From what I read w is generally thought to be -1 but it is possibly >-1. It obviously helps describe the relationship between pressure and energy density, but all it is is the relationship?
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  7. #6  
    Forum Professor river_rat's Avatar
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    yep, its just a parameter in the equation of state that tells you how the "dark energy" is affecting the expansion of the universe.

    It might mean more to a cosmologist but to me that's all i see.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  8. #7  
    Forum Ph.D. Steve Miller's Avatar
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    The cosmological constant goes back to Einstein if I'm right here. It says basically, the cosmos would
    not expand and not shrink, either.

    If this was you are searching for?

    It's pretty wired to work on some issue in terms of mathematic missing the physical relation, isn't it?
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  9. #8  
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    wow... That could be the simpilist concept in the history of science... So basically w = -1 means the universe is expanding, w = 0 means it is not expanding or shrinking, and w = 1 means it is shrinking. That's really all it is?
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  10. #9  
    Forum Ph.D. Steve Miller's Avatar
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    I don't think in mathematical terms, at least I try to avoid them. The outcome of mathematics at best was 0
    if there is a result to the particular equation at all. +/- 0 is same. Never mind! That's pretty cool for a whole
    lot of science occurring in other fields of science again and again, but to me it's not an answer on questions
    I have.

    For what I think, the cosmological constant was surly a fact in certain regions of the universe. The universe
    will be 'stable' at the moment in a certain region. It might as well but expand and inflate in other regions.

    Or in the same region at an other point in time (how to measure otherwise? ).

    I find it an interesting delivery over times the universe was seen as a whole and the cosmological
    constant as well as other, you know, not have taken place thinking, were applied to the whole universe
    and not just to a certain region. That's what I think was a major failure about the cosmological constant or
    a weakness of it, as you like.

    A twisting space time was also something Einstein 'invented' and which he hold responsible for gravity on
    earth.

    Space time might be space itself solely, and as it is twisting there are belts of space-time (or space itself )
    that will bend, expand, even kind of compress, all of this as it was twisting.

    Applied to the whole universe, Einstein himself described the cosmological constant as , how he said, I
    forgot, but he found it was wrong what surely was applied to the whole universe the same regions same
    moment.

    He has rejected later on again. Please, read the article on Wikipedia as you have not done yet. A.Einstein
    was a person, who was back over and over again. You can not dodge him nor his work anyways. So I
    would recommend to read about him n Wikipedia as well as on other sources.
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  11. #10  
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    I had a lot of trouble understanding what you were saying there. Are you saying that you think there is a flaw in the cosmological constant because it is cosmological, whereas you think it should be more local? And that I should read about Einstein?
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  12. #11  
    Forum Ph.D. Steve Miller's Avatar
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    I think he has been the greatest physicist of all times but what he did was all wrong. Not being
    worth the paper he used.

    He tried to se the universe as a whole. Whereas, we not even today have information about the
    universe as a whole, and btw. we will never have this info, I think.

    I think he can not see the universe as a whole in terms of motion in some way. The universe
    will, as you said, be still, not moving.

    Planets for example do move all the tome so does the moon, comets whatever there was. As
    planets move like our does space will not stand still. Instead space has to make space as
    earth passes. Einstein will ever remain in history. you will have to deal with what was left
    about him if you are concerned about science, physics, history, all. And, you will have to
    have a sight about him in some was which was yours clearly.
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  13. #12  
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    I think what you're looking at has different answers depending on the scale you apply that thinking to.

    In the field of probability there is a concept called the "law of large numbers". Basically, you could roll 100 dice and get 30 6's. But you could never roll 1,000,000 dice and get 300,000 6's.

    If the constant is more or less true, then very small portions of the universe might not obey it, but very large chunks always will.
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  14. #13  
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    Basically, you could roll 100 dice and get 30 6's. But you could never roll 1,000,000 dice and get 300,000 6's.
    ummm... i dont know what to say to this...
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  15. #14  
    Forum Ph.D. Steve Miller's Avatar
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    I don't either...
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  16. #15  
    Forum Professor river_rat's Avatar
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    How about "prove it"

    Shawngoldw : you are confusing omega and w as i did
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  17. #16  
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    lol. So omega = -1 or 0 or 1 says whether it will collapse or expand or stay static while w = -1 is just... -1?

    Prove it
    uhh ya I guess that works...
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  18. #17  
    Forum Professor river_rat's Avatar
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    Omega tells you if the universe is open (< 0), closed (> 0) or flat (= 0) in the large. The data seems to point towards Omega = 0. If Omega <= 0 then the universe is expanding.

    w tells you how dark energy effects the expansion, if w < -1/3 then the universe is accelerating, if w = -1 then the acceleration is exponential and if w < -1 then the expansion is so fast that it will eventually rip the universe into pieces (i.e. the big rip).
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  19. #18  
    Forum Ph.D. Steve Miller's Avatar
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    lol ... big rip
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  20. #19  
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    river_rat, does w tell the net expansion of the universe, or the expansion only based on dark energy?

    as for...
    Quote Originally Posted by Steve Miller
    lol ... big rip
    I didn't find big rip funny until you said that, it kinda reminds me of a buddy of mine who someone would surely slap for a comment like that!
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  21. #20  
    Forum Ph.D. Steve Miller's Avatar
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    Sure. Yes you're right. Think again and you will see who was on the flag actually. Big bang is yet funny.
    Do not have to wait for your big rip.
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  22. #21  
    Time Lord
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    Quote Originally Posted by ShawnW
    Quote:
    Basically, you could roll 100 dice and get 30 6's. But you could never roll 1,000,000 dice and get 300,000 6's.
    ummm... i dont know what to say to this...]
    This effect has actually been proven again and again in tests where they roll millions of dice and tally the results.

    The theory of large numbers is in fact the cornerstone of the entire insurance industry. It's why they're able to calculate rates the way they do, and end up being being able to estimate them closely enough to set their prices competitively.

    Basically, an insurance company with low prices is one that has a better team of actuaries, because it means that they can be more sure of their estimates. When in doubt, you always price high, because if you set your price low you can kill your company off very quickly.

    (I happen to know this because I interned in an insurance company's actuarial department. I'm not making it up.)
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  23. #22  
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    they can test it over and over again, that doesn't mean that it is true. There is an extremely low chance that it will happen, and you may as well say it won't if your using it for practical purposes. But it is possible...
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  24. #23  
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    Yeah, I don't mean that it's impossible. It's like winning the lottery in two states on the same day, but technically it's possible.

    I mean that the odds of getting 30 out of 100 vs. the odds of getting 300,000 out of 1,000,000 are staggeringly different.

    Still, if the success of casinos around the nation tells you anything, it's that the odds usually bear out.
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  25. #24  
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    Quote Originally Posted by kojax
    Yeah, I don't mean that it's impossible. It's like winning the lottery in two states on the same day, but technically it's possible.
    K, I'm glad we're on the same page here it's just that your first statement:
    Quote Originally Posted by kojax
    But you could never roll 1,000,000 dice and get 300,000 6's.
    Well, That statement sends a different message by using the word "never".
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