What is Spacetime?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Nobody, Oct 22, 2011.

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  1. Reiku

    Reiku Banned Banned

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    What do you mean it, works well with the local universe? The background temperatures are pretty much homogeneous in every direction of spacetime we look, with about 10,000th of a degree of error.

    The bolded part: It stands to reason that the radiation is everywhere because it is a leftover of the big bang and that inflation pretty much smoothed this out. This is the theory, stop trying to modify it with concepts like ''maybe the big bang happened on a larger arena,'' because this does not work mathematically, which I have been trying to tell you now for three posts.

    And I am not short of admitting the Big Bang has problems, but your case posits more problems than what BB solves.
     
    Reiku, Nov 30, 2011
    #81

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  3. OnlyMe

    OnlyMe Valued Senior Member

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    You see what happens when you begin using descriptive words like "rubbish" when referring to a post?

    People stop reading and thinking, even you!

    You must have missed the disclaimer and made some misplaced leap to a steady state model. There was nothing steady state about my post. Though I did not spend a great deal of time putting it together, there would be no way for "us" to detect "now" any difference between what I presented and the idea of a big bang beginning form some point like beginning.

    All we can say is that what we call and know of as space, space and time or spacetime, is defined by the relationship between objects we can observe now, and a projection of what we believe into the past.

    The fact that we require objects to define space and motion, does not mean that "space" does not or did not exist in the abscence of objects. The Big Bang is a model representing the origin of "objects". It involves the origin of space only to the extent that we project observational limitations, into the discussion.

    Personnally, Mister.., I have no real opinions on the origins of the universe. Big bang, steady state, big bounce or otherwise. It has always been a mystery to me, how scientists studying, things like life here on earth and geological history have a great deal of uncertainty in how and when events have unfolded, while cosmologists and some physicists seem to be so certain of the details of what happened, when the universe began.

    EDIT: I should add that by setting space up as an perfect fluid of virtual particles, the fanciful model I presented joined GR and QM, by defining the space of GR, as having a fundamental virtual quantum structure... From which everything began. And I still am not promoting anything as a description of "the beginning".
     
    Last edited: Nov 30, 2011
    OnlyMe, Nov 30, 2011
    #82

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  5. hansda

    hansda Valued Senior Member

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    My understanding is as follows :

    Now we know that our universe is expanding (though total mass and energy of our universe is constant ) . That means space of our universe is expanding . But where this space is expanding into ? or , From where this additional space is being created ? They must be created from no-space .

    So if we consider , at big-bang space was created from no-space ; small-bangs are still happening at the frontiers of our universe to create space from no-space .
    Before big-bang , time must have existed but not space .
     
    hansda, Nov 30, 2011
    #83

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  7. Fraggle Rocker

    Fraggle Rocker Staff Member

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    Since we have so much trouble figuring out what happened at t=0, which may in fact need to be analyzed as a singularity or a discontinuity, I have often suggested graphing time on a log scale instead of a linear scale. This would give time an absolute zero like temperature, so the question, "what existed before the Big Bang," would be as meaningless as, "how does matter behave when its temperature drops below absolute zero?" It also naturally drags those first few yoctoseconds into much larger scale, perhaps making them easier to analyze. Besides, for all we know this may be a more accurate representation of the way the universe works. The fact that we experience time passing at a linear rate today could simply be due to the fact that thirteen billion years have passed and the second derivative is so close to zero that we can't sense it. Or... it could be that our biology is simply built that way, so we can't observe the slowing down of the passage of time.
    That's the same question I asked, and it's a meaningful one. Is it defined spatially as our Hubble Volume and temporally as the last thirteen billion years during which this Hubble Volume existed? That's an anthropocentric view of reality: Everything that we can see and infer is all that there is or ever was. If we've learned anything over the eons it's that an anthropocentric view of reality is often wrong!
    Regardless of how much thought you put into typing "a universe" instead of "the universe," it suggests that somewhere in the back of your mind you too are grappling with the anthropocentricity of our models and wondering if we're overlooking something else just because we haven't yet designed the instruments that can see it.
    For all we know we may be experiencing time backwards and the universe is rushing toward a Big Crunch. In that case the big question is about how it came into existence as... whatever it was. Since we're still not sure about all that dark matter and energy, we don'e know whether it means there is a Big Bang at one end of the continuum and a Big Crunch at the other, or if time is indeed logarithmic and expands to infinity at the opposite end. Reversing the passage of time and trying to analyze the beginning of a universe of infinite size and total entropy would be quite a challenge.
    But that's only in the physical universe. We have no trouble conceiving of an empty space-time continuum with distance- and time-markers postulated by us with no physical manifestations.
    That's very similar to my question. If there are no intelligent organisms to ask these questions, to attempt to measure distances with no milestones to bracket them, do the questions matter?
    We've certainly been hit over the head with that one before. Newtonian physics describes our tiny fragment of the universe perfectly. But the universe runs on Einsteinian physcis. Or perhaps something beyond that which we haven't quite grokked yet.
    This seems like an much more erudite elaboration of my oft-stated assertion that the Big Bang can be seen as nothing more than a temporally local reversal of entropy, which is allowed by the Second Law. Perhaps all we have to postulate is that the Laws of Thermodynamics have "always" and "everywhere" been in effect. I'm not enough of a physicist to walk on your exalted plane, but it seems like this isn't much different from your scenario of a soup of virtual particles--which, if I understand you at all, are always and everywhere constrained by the Three Laws, even when "always" and "everywhere" refer to a virtual universe.
    I keep coming back to the basic meaning of the word "space": nothing.
    That would be a sort-of space-time continuum with time but no space: a one-dimensional continuum.
     
    Fraggle Rocker, Nov 30, 2011
    #84
  8. NietzscheHimself

    NietzscheHimself Banned Banned

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    These two are the same thing...

    Before the BB, there was no "matter".

    Without anything to move there is no time. When all of what doesn't exist yet is in a singular place. There is no "space" either.
     
    NietzscheHimself, Nov 30, 2011
    #85
  9. Fraggle Rocker

    Fraggle Rocker Staff Member

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    So time and space are nothing more than attributes of matter? Like mass and charge? How does this fit into the boson-lepton-quark paradigm? Each particle has a mass and a charge (which, IIRC, may be zero). How do those attributes elaborate into distances and durations?

    Or is this just one more of the many Big Questions that we can't understand until we finally integrate gravity with the other three fundamental forces?
     
    Fraggle Rocker, Nov 30, 2011
    #86
  10. NietzscheHimself

    NietzscheHimself Banned Banned

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    Um... no. Matter is an attribute of time-space. The two terms are interchangable depending on perspective (All matter and All time-space).

    Matter is just a generic word for the smallest building block. I'm leaving the least defined aspect as the cause, but the two go hand in hand.

    The universe contains the same amount of "space" as it does "time" and in reality if the two are combined we end up with zero energy.

    Most people invision an object when you say matter, and nothingness when you invision time or space. This is an error. Every area is all made of some material, with a calcable amount of energy, unless it doesn't physically exist.
     
    NietzscheHimself, Nov 30, 2011
    #87
  11. hansda

    hansda Valued Senior Member

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    Do you mean to say that 'time' and 'space' are same thing . Then , why their units are different ? ... In that case 'speed' would be unitless .
    Does it mean that , before BB ; there was no "energy" ? ... Is it that , at the BB total mass and energy of our universe was created out of nothing ?
     
    hansda, Dec 1, 2011
    #88
  12. NietzscheHimself

    NietzscheHimself Banned Banned

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    They aren't. A lightyear is a measure of distance. It it the closest unit we have able to describe both space and time simultaneously.


    Before the BB growing fluctuations between matter and antimatter eventually built up enough energy to collapse together into a singular body which continued to radiate and expand its influence further into the unknown.

    So yes. Nothing... Or everything.
     
    NietzscheHimself, Dec 1, 2011
    #89
  13. AlexG

    AlexG Like nailing Jello to a tree Valued Senior Member

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    Before the BB, there was no matter or antimatter.

    This is a novel hypothesis.
     
    AlexG, Dec 1, 2011
    #90
  14. Aqueous Id

    Aqueous Id flat Earth skeptic Valued Senior Member

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    To which I am reminded of that pithy trove of yore: what existed before time?
     
    Aqueous Id, Dec 1, 2011
    #91
  15. NietzscheHimself

    NietzscheHimself Banned Banned

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    Thank you.

    I would say there was no mass before the BB.
     
    NietzscheHimself, Dec 1, 2011
    #92
  16. KilljoyKlown

    KilljoyKlown Whatever Valued Senior Member

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    You two sound very positive about something you couldn't possibly know about. But then taking the popular view does feel good and who am I to deny you that good feeling.

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    KilljoyKlown, Dec 1, 2011
    #93
  17. NietzscheHimself

    NietzscheHimself Banned Banned

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    I'm glad you know the feeling

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    NietzscheHimself, Dec 2, 2011
    #94
  18. arfa brane

    arfa brane call me arf Valued Senior Member

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    Don't forget: spacetime contains only time and distance, there is no matter.

    So to "add" material objects, we need to be able to measure their extent; objects with material extent have three dimensions. Thus, material objects are like a knot in the 'string' of spacetime where each of the three spatial (i.e. colored) threads intersect (that is, they 'tangle' together).

    So if that's all true, and it's true that you as an observer are a material object, then you're just a tangle of three one-dimensional threads; the 'tangling' occurs in the fourth dimension.

    Bwaa hah hah!
     
    arfa brane, Dec 2, 2011
    #95
  19. KilljoyKlown

    KilljoyKlown Whatever Valued Senior Member

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    Did anyone watch NOVA last night? Was all about this topic with a pretty interesting perspective.
     
    KilljoyKlown, Dec 2, 2011
    #96
  20. AlexG

    AlexG Like nailing Jello to a tree Valued Senior Member

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    Well KK, it does help if you've actually studied the subject at all.

    But then, they say ignorance is bliss, so who am I to deny you that good feeling.

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    AlexG, Dec 2, 2011
    #97
  21. Robittybob1

    Robittybob1 Banned Banned

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    For you are enjoying it too?

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    Robittybob1, Dec 2, 2011
    #98
  22. KilljoyKlown

    KilljoyKlown Whatever Valued Senior Member

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    But I do know about the current accepted theory. I just don't agree with the current best guesses. I think there's a great deal more to understand before we get it right. But your a consensus sort of guy, and that's okay, I always know where you stand.
     
    KilljoyKlown, Dec 2, 2011
    #99
  23. AlexG

    AlexG Like nailing Jello to a tree Valued Senior Member

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    Yeah, I like evidence. It makes me feel all warm and tingly when theoretical predictions match experimental and observational data. :yay:
     
    AlexG, Dec 2, 2011
    #100
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