Is there any experimental or observational confirmation of curvature of spacetime?

Discussion in 'Physics & Math' started by Ultron, May 31, 2016.

  1. Ultron Registered Senior Member

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    I can prove that you are wrong

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    If you CAREFULLY read my post number 24 it is obvious that Im writing about PhysBang, that he has insight in physics and Im QUOTING his post from other thread, where he writes that he has studied cosmology. I havent written that I have studied cosmology or that Im scientist.

    So it seems that you have a problem with reading with comprehension.
    I would suggest that you read the OP and my later responses again more carefully and maybe you will get the main point what Im trying to discuss here.
     
    Last edited: Jun 1, 2016
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  3. Ultron Registered Senior Member

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    I would like to additionaly clarify the topic Im trying to discuss on example:

    GR covers many physical phenomenas.

    For example there is a special part of GR equation for Lambda / Cosmological constant, which is covering effects of Dark energy. When we ask what is causing Dark energy, the honest answer would be "We dont know".

    Relativity effects are also covered by GR equations. When we ask what is causing relativity, you could get many "philosophical" answers, but the honest answer would be "We dont know".

    Gravity is also covered by GR equations. But there is different situation than by previous two examples. When we ask what is causing gravity, the answer is that gravity is caused by curvature of spacetime. And Im asking, is this opinion supported by some experiments or observations? There are two possible approaches to this question. One easy approach is followed by most people participating in this thread and their solution is that every experiment confirming GR is confirming curvature of spacetime. But that was not that what I was asking for. I was asking if there is some experiment which specifically confirms curvature.
     
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  5. origin Trump is the best argument against a democracy. Valued Senior Member

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    Your continued trolling is getting old..
    No kidding. Physicist clearly state that 'we don't know'. We do not know what dark energy is we can only see it's effects

    Yes, relativity is covered in General relativity, not terribly surprising. What do you mean 'we don't know' what causes relativity? That doesn't even make sense. Maybe you do not know what relativity means?

    The question has been answered multiple times and the answer is yes. Why do you continue to ask the question?

    The question has been answered multiple times and the answer is yes. Why do you continue to ask the question?

    I guess it has not been answered to you satisfaction. I am afraid it will never be answered to your satisfaction since you are trolling and not looking for answers. Observations have confirmed that you are here to troll and annoy.
     
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  7. The God Valued Senior Member

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    You are right...

    1. We do not know what causes Dark Energy or for that matter where this energy comes from.
    2. We do not know how mass curves the space or spacetime.
    3. We do not know how this curved spacetime makes the mass move.

    Even if it is curved, for motion to take place some action is required, and we do not know what this action is ?

    No supporter of GR can come forward and say what is this spacetime in reality. They conveniently use space or spacetime to suit themselves.
     
  8. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    I had an idea about dark energy. I wont say a theory as no one can prove it. Anyway, I was thinking of creationism and the lottery... How creationists say that the universe was just right (intelligent design). And I was thinking the universe underwent a big crunch like a trillion trillion times before it got just right and dark energy is diffusion so to say of a universe catching up to itself from previous big bangs.

    Maybe I am too bored that I posted that.
     
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  9. geordief Registered Senior Member

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    592
    I hope I am not too off topic.I often like to piggyback on threads as they can bring up questions in my mind.
    Is your answer perhaps confusing the physical reality with the GR model?

    I am just talking about the model.It has not existed from time immemorial and requires an observer (FoR) at all times I think.

    So does the curvature of the same region of spacetime as measured by different "observers" vary ?

    Thanks
    I will bow out if I am off topic (or incomprehensible

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  10. PhysBang Valued Senior Member

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    Your question is based on a mistaken premise. In GR, gravity is not caused by the curvature of spacetime, gravity is the curvature of spacetime. You don't find GR somehow mysteriously causing a force, you find GR removing gravity entirely by changing the kinematics of the world such that bodies follow trajectories that are determined by the distribution of mass-energy.

    In one sense, what you are asking for is not possible, since it is deeply theoretical and cannot be entangled from the question of whether GR is correct or not. On the other hand, you have been given two clear examples: 1) the effect of gravity in cosmology can be clearly tied to both spatial effects and the temporal effects predicted by GR and 2) the effects of gravitational lensing introduces the temporal effects predicted by GR. This is as close as one could get to direct evidence that GR, and thus the curvature of spacetime, is responsible for the gravitational effects on the spatial changes in light.
     
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  11. Ultron Registered Senior Member

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    182
    Thanks for respones, it has really helped me. Especially I would like to thank DaveC and PhysBang for valuable insights.
     
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  12. DaveC426913 Valued Senior Member

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    Not all common sense is equal.

    You travel fastest in time (per an external observer) by having the minimum relative velocity (i.e. being in the same frame of reference).

    TG: the time dilatory effects of both SR and GR are extant to every person who owns a GPS device, such as a smart phone.
    The GPS software that tracks your location must (and do) take into account the time dilation, or it would not work - your apparent location would drift by metres each day.

    We know time dilation dues to both SR and GR is fact - it is easily demonstrable.

    We have one one model for time dilation, and that is cureved spacetime. There might be a better model out there someday, but until then, this is it.
     
  13. rpenner Fully Wired Staff Member

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    4,833
    Demonstration of curved space time:

    If space-time is flat (meaning uncurved), then it obeys the parallelogram law for composition of vectors and thus relative displacements in space-time.
    Thus if I have a vertical separation between two clocks with no net acceleration between them, those are parallel trajectories through space-time.
    And if I have two pulses of light from the lower clock to the upper, then those pulses are congruent and one see that in the limit of short time interval between pulses that they are parallel.
    Therefore, the sequence of flash + wait one second at high altitude and wait one second at low altitude + flash are expected in flat space-time to arrive at the same total differential.

    But, because of the experimentally verified phenomena of gravitational time dilation, we know the first composite displacement fails to complete the parallelogram by a time-like displacement which is (to first order) proportional to both the interval between flashes and the spatial separation between clocks. This is impossible for flat Minkowski space-time and exactly the prediction of curved space-time.

    This argument is a bit of a cheat since it hides some coordinate dependence. But if we do the same logic in free-fall rather that in Schwarzschild or ground-based coordinates, we avoid the cheat. But one the other hand, the time-dilation relation for clocks in nearby orbits is a bit trickier.
     
    Last edited: Jun 1, 2016
  14. paddoboy Valued Senior Member

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    The only proof I see is your own obfuscation.
    Obviously you are not a scientist, and btw, neither am I...difference being of course is that I do not presume to invalidate 100 years of evidenced based cosmology.
    On your claims re what you say you do not claim......

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    On your "god given scripture" remark, there is a difference. Science/cosmology is based on experimental results and observational data.
    These results are further tested and researched by other scientists continually. eg: Gravitational waves, and BH's have just been recently confirmed with the aLIGO experiment. Sure lay people like you and me need to take that on as "faith"as obviously we have no access to the state of the art equipment, not that we would understand it anyway.
    Point being is that the experiment can be and eventually will be repeated, and repeated again and again.
    To class accepting such results without direct access as "god like scriptures" is akin to the conspiracy nonsense that would like to tell us that the Moon landings were faked, and that 9/11 was an inside job. Do you also accept such nonsense? Or you catch a bus every morning to work...you have faith that the bus will on most occasions be on time and traverse the correct route.
    To doubt such findings validating GR and spacetime curvature, is simply the argument our fanatical god bothering friends like to use as their excuse for trying to deride the science that has removed their deity of choice into near oblivion and irrelevancy.
    Oh and also your statement thus.....
     
  15. paddoboy Valued Senior Member

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    21,647
    There is observational support for the bending of light, which certainly is because light follows geodesic paths in curved spacetime. And obviously the GP-B experimental results among many other experimental and observational results, support such reality.
     
    Last edited: Jun 1, 2016
  16. Confused2 Registered Senior Member

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    443
    Then you say
    What is the cheat? The challenge is to establish the existence of curvature not the magnitude of it.

    I suspect you need some concept of 'space-time' before the concept of 'curved space-time' can be meaningful.

    I tried (but failed) to show 'all is not as simple as it appears' here:-
    Mainstream GR versus Farsight, mote in their eye or beam in his?
     
  17. paddoboy Valued Senior Member

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    21,647
    He [ultron] is wrong in presuming there is no direct evidence for spacetime curvature, and that has been supported in this thread by many examples and scientific papers.
    Whether you are alone or not, whether the likes of Farsight support you or ultron supports you, or any one of the other possible anti cosmology posters support you, is irrelevant.
    As I keep telling you, you, as a lay person posting on a remote science forum, open to any Tom, Dick and Harry, occupying a sliver of cyber space, carries no weight on the actual validity of SR/GR and other aspects of cosmology that you like to pretend you know something about.

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  18. paddoboy Valued Senior Member

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    At this time that is also the scientific answer. Or didn't you know that? Or are you obfuscating again? Well may you talk of honesty.

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    The rest of your post and questions have all been answered.
     
  19. Write4U Valued Senior Member

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    Is there a philosophical answer required?
    The term Relativity (SR) is well defined. Einstein just expanded the simple mathematical equation to a more inclusive mathematical constant.
     
  20. Spellbound Banned Valued Senior Member

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    Actually, it's only irrelevant to your tiny little atheistic "mind". Go crawl back under the rock you were let out from.

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  21. Dr_Toad It's green! Valued Senior Member

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    That's your sole contribution to the thread? What a dick you are.
     
  22. The God Valued Senior Member

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    What is this ?? You certainly are not in Paddoboy's league, please be more clear and precise.

    I am not getting into gravitational time dilation aspect, this is a killer even for GR, simply because things get out of control beyond EH due to this GR time dilation math.....It gives rise to funny stuff like WH. You did not notice both BH and WH are the products of maths failure....so if BH exists, then WH too...time travel too. But you know they don't in reality.

    Now coming to spacetime curvature, a BH is supposed to have very large (I am not using infinity) curvature, what is the resultant curvature of 2 binary BHs ?

    Forget BH, lets talk about binary Neutron Stars orbits....We are able to approximate down the GR in case of Sun - Planet system by making the planet as point as compared to Sun, ok fine...but in case of binary NSs...we can't do that. So how do you get elliptical or circular orbits...we don't know. I do not think, you can counter me, that there exists a clear GR maths which can establish stable orbit for two NS. But yes, Despite multiple mathematical juggleries, but yes Newtonian-Keplerian maths can do that....
     
  23. paddoboy Valued Senior Member

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    The usual unsupported unevidenced nonsense by the usual.
    No one really needs countering you, as you put it. You have nothing of any substance to counter, and zero credibility if other threads of yours are taken as examples.
    GR stands as near certain having passed every test thrown its way, most recently the confirmation of gravitational waves and BH's.
    Your continued ranting, and flaying of arms about will not change that.
    Cosmology my dear friend is the domain of expert professionals, while you play with words and pedant on this forum.

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