geordief

How is that different from the "outer universe" ? Does your "universe" have a boundary?

Strange's link in the above post#16 seems to deal with this issue(not that I could follow the discussion). I think my idea was ,kind of "out of sight out of existence" (to paraphrase) but it seemed to have been taken on board and dismissed there.

So not a subject for scientific study as such? (if we cannot relate to it then we cannot make measurements that describe it) By the way this "ultimate expanse of Nothingness" sounds suspiciously like we are cling filming our ether and maybe double wrapping again to be sure

If there is an ether that contains all the matter in the universe, what is the ether in?

Pretty sure I have heard that. In Special Relativity observers in mutually moving (at relativistic speeds) frames of reference both see each other slowed down but with time dilation due to gravity wells it is as you described and one will see the other speeded up. (must update my diary ) Do you think we can extrapolate from that that a singularity never happens and so cannot represent a problem in GR? I mean we cannot change our FOR qualitatively in this regard and do all our theories have to take account of that fact? Is that just playing with words?

Isn't that what the "expansion of the universe" is supposed to do?

I think I may have another couple of different questions/observations about black holes that maybe I can ask here. 1: Is it possible to say that from the point of view of an outside observer the black hole never actually reaches any supposed "singularity ? Does the process slow down at an exponentially increasing rate and does the BH simply keep approaching the singularity without ever reaching it (from the observer's pov) ? 2:There seems to be a major distinction between a small BH and a large BH..Is it possible to imagine that ,as a BH grows we can say it approaches an effective diappearance? BH> infinity = no BH?

I am only "fishing" but (perhaps I am asking the same question) is there ever a physical situation where the same circumstance can be exactly described by either a linear or a non-linear equation? I appreciate(I think) that the equations are perhaps by definition approximations to the physical reality in the first place (unless it is the other way round and the physical reality is an approximation to the equations )

Is that a principle that stretches right across mathematics? Is there ever a situation where non-linear equations can ever be translated into linear equations? (if I am making sense)

Is it possible (in theory) to "subtract" one geometry from another (the changed from the pre-existing) and arrive at those diagrams that showed the signature of the BH merger that we all saw recently? Am I even close?

thanks. It is way above my pay grade. Hopefully your answer will be helpful to someone else

Mathematically are these gravitational waves caused by changes in a gravitational field modeled by using differential /integral calculus? Are the local tensors differentiated wrt to some property of spacetime and does that produce a picture of a gravitational wave?

I have just a small ( theoretical) question on the side that may be relevant. Is there a logical impediment on attempting to model the universe as a whole by making a model of part of it? There are always ,inevitably loose ends?(just part of the deal) Is that perhaps a reframing of a question that has already been asked /anwered in different ways? Btw my last post went unchallenged . So I was right? There are no "waves of gravity" emanating from objects:it is only changes in gravitational fields that produce these effects.? The universal gravity field is ,so to speak "in place" and has been caused by the accumulation of countless small and large changes over time. PS would that mean that the recent gravitational waves detected from the binary black hole merger caused a vanishingly minute but permanent change in the gravitational field that exists in our own little solar system?

I do not think that "gravity waves" as you describe them exist. When I looked up "gravity waves" the term is used to describe (for example) waves caused by the moon on the oceans of the earth. https://en.wikipedia.org/wiki/Gravity_wave I don't think that is what you meant by that. Gravitational waves are seemingly caused by changes in a gravitational field and are apparently much less energetic than you would imagine. I read that (perhaps I was told) even the double black hole that was recently detected was not particularly energetic even at quite a close distance.to the event If you are looking up and imagining a black hole I suspect it would not be emitting much radiation at all unless it was gobbling up a large star or another black hole at the time. If it was quiescent (between meals) I imagine it would be all quiet on the Western Front.

More or less as I thought then . The only(respectable) idea I have come across that seems to parallel this effect may be "extremal aging" but iI have not been able to grasp the idea very well.

One of those questions in the post you directly answered (in the preceeding post)was What property of matter **causes geodesics to curve near them?"I thought this was a question that had not been answered. I thought Einstein had somehow figured out that if the spacetime model was curved in the presence of mass then it would correctly predict physical phenomena to an extraordinary degree of accuracy but that the actual rationale was lacking. After all nearly everyone disbelieved Einstein at first and it was only his correct predictions that got his theory respectability. I do not doubt there is a reason why mass causes spacetime to curve but I thought I had picked up that this was not yet known -and I have yet to come across any theory as to why it does that. Now I accept I may have badly misunderstood and would love to be disabused of that understanding if that is the case.. ** should be mass-energy ,I think.

Yes but that "something that can be considered at rest" can be as large as you like can't it? It can be ,for example the solar system . We could map the solar system and say A is more stationary wrt to its centre than B and so ,by that definition B is moving wrt A rather than vice versa. And we can expand beyond the solar system provided that the "locality" is well defined (has an outer border) .

Can we say ,generally that ,if we ascribe a locality(that can be as large as we like) to be our FOR then movement within that locality can be assigned non relatively? If so does the universe need to be infinite or perfectly symmetrical (which it isn't) for relativity to hold ?

Suppose we are an eye in the sky and we look down to the ground and see two objects which are moving relative to the other . We can see that one is stationary (or more stationary ,perhaps?) wrt to the landscape and one is not.So clearly if the two objects are moving wrt each other it is the former that is moving. wrt to the latter and not vice versa. Is there anything at all to this argument? Does the "all motion is relative" position rely upon the background being entirely free of sources of acceleration? I am not espousing this position as it would break with my lifelong understanding but I would like to see it dismantled (if it is not too obvious to need dismantling)

Is a Cauchy surface what you get when you set t=constant in the spacetime manifold?

Am I going too far to say that gravity seems as intrinsically non deterministic as quantum theory? Is it also inherently statistical? Would "chaotic" describe it better? (is that the same as "non-linear" ?)

Is there such a thing as a "unit" gravitational field ? Is it possible to model how one object with unit characteristics interacts with another object (again with unit characteristics) at a unit distance and ignoring external objects? If this was possible could one build upon that ? Does everything get too complex practically immediately and so the task is handed over to computers? I remember before the advent of supercomputers ,weather forecasters did their best nonetheless and I think it was said the skill was something of an "art"

I have heard that this is "notoriously difficult" and I think it must be done by computers (perhaps in the way that weather forecaster make millions of parallel calculations on ideally very small cells and ties them together) I also imagine (from what I have learned so far) that it may be that it is the spacetime tensors that could be summed in order to produce the resulting global field. Are there any alternative ways to do this process.?

Does the use of the word "why" anthropicise" events in nature? Does the basic meaning of "why" down the years apply to human intentions(I am speculating linguistically) and not to how events in nature are connected? One event is a precursor to another but there is no mentation involved (and mentation is a complex process whereas events are connected in a direct automatic way without intermediary. Can that be the (another) reason that it is not a valid word to use for objective understanding ? Of course "why" is used loosely to mean but "how" but that covers over its specific implication of a human agency. I know this why/how subject comes up a lot and I have seen the Feynman take on it.

Personally I think of space as the gaps between all those ingredients you have listed(although I won't stand by that). You seem to have populated interstellar space with "comments" . The internet and its various forums has a lot to answer for