Warp speed space travel and GR:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Aug 19, 2015.

  1. paddoboy Valued Senior Member

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    I thought that point was evidently clear, although on the same issue, I still see the point as debatable.
    I prefer attaching some reality to space, time and spacetime, and doing that does not confuse me or has me extablishing other properties to spacetime, other than it can be bent, warped and twisted in the presence of matter and which we see as gravity...and of course the DE component whatever that may be.
    A mathematical tool or representation, can also be looked on as real.
    "The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality".
    Hermann Minkowski:


    Your posts do seem as a rant in quite a few cases, and in many cases similar in style to another called Rajesh Trivedi who did his own lot of ranting.
    Just an observation.
     
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  3. Daecon Kiwi fruit Valued Senior Member

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    What happened to that guy? Did he get banned or did he just leave?
     
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  5. paddoboy Valued Senior Member

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    Just left us...it actually brought a tear to my eye, and a lump to my throat.

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  7. OnlyMe Valued Senior Member

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    It is unclear how that quote applies to space-time in the context of GR. In that quote Minkowski was referring to a flat 4D geometry and special relativity. I believe it was in 1908/09? before GR was published.

    In SR you really can think of space and time as direct components of a 4D coordinate system. In GR it is not that simple. In some respects I believe it was and has been convenient and yet unfortunate that space-time as a label just carried over from SR to GR, when there are significant differences.
     
  8. The God Valued Senior Member

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    Apologies, if my post appeared to be personal, my thrust was on the contents only. I gathered an impression, you may call that as conclusion on my part, that there was a bit of uncertainty in your expression of spacetime. Above quote stands validated.
     
  9. The God Valued Senior Member

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    Paddoboy,

    You seem to patronize people here, in your earlier post you apologized to Prof Lewis on my behalf, earlier on behalf of Danshawen.

    Now in the current post, you again make it provocative, when 'Onlyme' has realized that his reference to 'rant' was not leading to any positive discussion, your reference to that again was unwarranted.

    Names do not matter on this board, all are under some kind of pseudonym, and my objective is to bring forward or contest the content not the individual. If someone praises you here, that could be a momentary high, on the other hand if some one rebukes you, you can shrug off and move ahead.

    Back to content, I am not able to figure out or ascertain the veracity of your below statement, can you help ?

     
  10. The God Valued Senior Member

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    I second that. The words like warping of spacetime, distortion of spacetime etc are part of GR jargon. Whether the term spacetime around SR (1905 or so) is same in meaning with the term 'spacetime' as used in GR, can be debated with positive conclusion.
     
  11. paddoboy Valued Senior Member

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    Ignoring the rest of your rant, I'm simply saying that something does not need to be physical to be real. Just because you can't touch it, smell it, does not mean that it is an illusion.
    Not only has spacetime warpage been shown to occur in the presence of mass/energy as per GR, but also the Lense Thirring effect has been verified. [GP-B]
    While gravitational radiation has not as yet been directly observed, we do have pretty substantial evidence as to that prediction of GR also. [ Hulse-Taylor Pulsar]
    The "Alcubierre drive" proposal more than a decade ago now, outlines that possibility.
    https://www.quora.com/Is-spacetime-a-real-thing-or-just-a-mere-concept
    "If yes, you should consider spacetime to be a real "thing" as well. Spacetime is not just a passive arena for light and matter. It has its own dynamics; it interacts"

    http://einstein.stanford.edu/content/relativity/q411.html

    In essence, the reality of space, time, spacetime is still hotly debated and most here, including me, are expressing there own take on that situation. I'm with the affirmative.
     
  12. paddoboy Valued Senior Member

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    Not that significant. One simply includes gravity.
    SR can be thought of as a subset of GR.
    GR gives us a geometric description of spacetime in the presence of mass/energy. This is the warping of spacetime we refer to as gravity.
    SR deals with flat spacetime....the same spacetime other than for the geometrical shape.
     
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  13. brucep Valued Senior Member

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    Deleted
     
    Last edited: Aug 29, 2015
  14. brucep Valued Senior Member

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    For doing the physics it's the Minkowski geometry for SR which, as you pointed out, is the special case of the general theory where infinitesimal effects of gravity can be empirically ignored and for the general theory the spacetime geometry is Riemannian. The amazing thing is the local proper frame physics is derived from the Minkowski metric unless the infinitesimal local space time curvature must be accounted for. Such as for the GPS.
     
    Last edited: Aug 30, 2015
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  15. The God Valued Senior Member

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    This is the right perspective rather than saying that SR is the sub set of GR.

    The postulates of SR cannot be derived from the GR, but yes, Minkowski Geometry (the domain for SR) is the special case of curved space time of GR (where Gravity is taken as zero or very weak or infinitesimally small local space time where curvature can be assumed to be zero.). The argument can be extended for free fall as well. The only problem posed is from Gravitational Waves, but thats a different thing altogether.
     
  16. paddoboy Valued Senior Member

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    As bruce agrees, its the same thing as saying that SR is a subset of GR.
    The postulates of SR are, [1] The laws of physics are the same in all inertial frames of reference. and [2]The speed of light is the same in all inertial frames of reference in a vacuum.
    GR adds the postulate that gravity is geometry.......or in the words of John Wheeler "spacetime tells matter/energy how to move: matter/energy tells spacetime how to curve.

    http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec07.html


    http://casa.colorado.edu/~ajsh/sr/postulate.html

    http://csep10.phys.utk.edu/astr161/lect/history/einstein.html

    http://www.astro.ucla.edu/~wright/relatvty.htm

    Again my mind goes back to the days not so long ago that rajesh had problems accepting some SR/GR knowledge as well as many problems that involved BHs.
    Many of his threads as expected of course ended up in the fringes sections of alternative hypothesis and pseudoscience.

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    Last edited: Aug 30, 2015
  17. The God Valued Senior Member

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    Paddoboy,

    Your harsh behavior with me probably is due to the fact that you feel I am rajesh, and you would have had some bitter experience with him. Rest assured I am not.

    So, if you have any issue with the content of my posts, you have all the rights to express your opinion without reference to anybody. Beyond a point bringing out personal preferences or hatred in public domain, become sickening.
     
  18. The God Valued Senior Member

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    On the content, Brucep has not stated that SR is the sub set of GR. What he has said that in a limiting case, when the curvature of spacetime can be taken as zero (absence of Gravity or weak Gravity), it becomes the minkowski geometry a domain for SR. You have to make distinction between the two.
     
  19. paddoboy Valued Senior Member

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    The distinction is obvious, and certainly does not change the "subset" premise that I stated rajesh.
     
  20. paddoboy Valued Senior Member

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  21. James R Just this guy, you know? Staff Member

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    paddoboy:

    Please refer to members by their screen names. That is, refer to "The God" as "The God" and not as "rajesh".

    If you have evidence that "The God" is a sock puppet, please contact me privately and I will investigate the matter. We have a "no sock puppets" policy on sciforums.
     
  22. paddoboy Valued Senior Member

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    In my mind I'm rather confident that I'm correct, but no real concrete evidence as yet other than similarities in style, vocabulary and opinion. But will adhere to your requests.
     
  23. paddoboy Valued Senior Member

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    Harsh behaviour?? Hatred?? Rajesh often expressed similar emotional exaggerations particularly with me. I don't believe your indignation to be genuine and of course I do not hate you or rajesh for that matter.
    He dug his own grave here many times over, with threads moved to the fringes without any of my help.
    But rest assured as I expressed to James, you will be referred to as "the god" until more concrete evidence does reveal itself.

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    Last edited: Aug 30, 2015

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