geordief

Well what I am getting at is that your examples seem a bit like the clock that is right twice a day. I f you attempt to use the correlation between the two processes to estimate what the correlation would be a second time around ,then errors would enter the scenario as the setup could not be repeated exactly. To address Markus' point a little more directly (well tangentially) if anyone were to show how time based processes emerged fro timeless processes this would be an amazing achievement but I haven't heard that this has been done (or even attempted?)

What about repeatable accurate predictions?

Does that still allow one to make predictions? (I am guessing no ) If not is this method of measuring change only trivially rigorous?

Any specific examples? A is a function of B. What might that function look like? Would B be the inverse function of A?

OK,thanks.

Yes, apologies I should have realized that .And thanks for your patience. As an after thought I notice that you have included internal stresses as an element. Can that be broadly understood as reflective of physical non uniformity **of the small region? *perhaps non homogeneity is the correct term?

I see. So, as per Swansont asked earlier ,what do the elements of the momentum-energy tensor contain? Equivalently (I hope) what actual physical measurements would be required of an observer approaching (or at a constant distance from) one of your atmosphere free planets in order to determine the precise spacetime curvature at a point on, or at any distance from the surface? Speed of rotation,temperature,electric and other charges?Radiation? Anything else?

Very much. It is helping me to familiarize myself with the model although there can surely be no substitute for eventually familiarizing myself with some of the mathematics (even unrealistic goals can be a help ) I am taking it now that "energy-momentum" as a phrase only needs to be understood as a mathematical definition in a mathematical framework... Is it a fair comment that spacetime curvature is actually not an absolute "thing" but has to be defined relative to an observer?

Oops,I need to rephrase that (too late to edit) .I think I know that nobody actually knows that (the "how"") . I just meant to say "then perhaps there might be a little extra you could say as to what is "energy-momentum" as a physical phenomenon in the context of curving spacetime. How would you go about measuring it (or perhaps its components ) at any specific region ?

I said "physically or mathematically". Does "physically"necessarily have to mean "ontologically" ? Although mathematically seems to be the key to the lock in this case ,I think I was also asking for any possible physical flesh on the bone in the way you were using the term in your example .if you were just using the term in the context of the energy -momentum tensor then that is fine . But if you were using it in the sense of a physical " source of gravity" (your quote) then perhaps there might be a little extra you could say as to how it (presumably) causes space time to curve. If one is calculating the curved coordinates in the vicinity of a massive object am I to expect that we have also to take into account that massive object's velocity wrt the particular point on the coordinate map? Is that what this "energy-momentum tensor" provides for?

Be proud https://en.wikipedia.org/wiki/Ken_Dodd

Thanks. As I my level of understanding chemistry is so rudimentary ,I will leave it there.(although ,ambitiously/embarassingly my thoughts were how the situation might be viewed at the finer levels of detail in physical processes. Probably beyond all our kens*** ) **ken? kens?

Are both aspects to the chemical reaction equally "fundamental" ? One cannot be said to "pull rank" on the other?(I have very little chemistry) It doesn't depend on the level of the analytical approach as to whether the statistical or the deterministic outcome follows?

Is there a sense in which it might be expected that one or the other process is fundamental to the ways events unfold (not in our subjective lives but purely on a physical level **) ? Is there also perhaps a meeting ground somewhere where it can be said that both happen? I am curious as to whether ,if it is is posited that the universe is ,by its nature (or on the level we observe it) probabilistic a question could be asked if there could be any mechanism that lies behind this and whether that itself might be subject to examination in an experimental way. **perhaps a false distinction.

Could I ask you to say briefly what "energy-momentum" is,physically or mathematically in the example you have just used ? (or just a link as there seemed to be one or two uses for the term when I googled it) Does the dash (-) mean anything specifically? Not a ratio ,is it? Or does it just mean "a combination of the two"?

The model is a field?The likelihoods of the particle being found or experiencing a scattering event are mapped as a field? (in 4D?)

So the particle is a probability based field (existing between two points on its worldline,perhaps). The field that describes to the environment that the particle operates in is simply an aggregation of all the particles' fields,is it? Or is there a distinction to be drawn? Is the overall field subject to probability in the same way? Afterthought:the particles' probability field takes into account the zero probability of causality being broken.does it? (not all outcomes are possible)

Yes ,thanks. It is a great help ,though (as is often the case with me) it feels like a guide rather than an answer(for the reason you gave ,no doubt). I think I may have understood your ". In QFT the fields are probabilistic oriented. It represents the likely hood of a particle being created at one coordinate and annihilated at another coordinate" and it feels like an important element. s.

When the field is mapped and there is a particle embedded(?**)Is there any (mathematical) discontinuity between areas of the map (that of the particle and that of the underlying field)? Is there a smooth join? Is the particle wave overlayed onto the field or does it "rise from" the field (you might have to run my post through a gobbledegook checker ) **if that is correct or applicable terminology

I have been wondering what does "an excitation of a field" mean? Is the field not simply a set of readings taken at points on a co-ordinate map (not a "thing"as such) Is something causing the "excitation" or is the excitation just an unusual reading on the mathematical object which is the field? Is an "excitation " perhaps a state rather than something that has been "excited"?

The meaning of life can be seen as a joke (a bit like the propagating EM wave ,feeding on itself) Maybe though a genuine meaning of life could be to approach an understanding of this particular question.The answer has to include one's final dissolution and progress towards it (and also an appreciation that any judgement upon it is a work in progress,like poor old Beethoven and his unfinished symphony )

Is the (hypothesized) graviton expected to be an excitation of a gravity field? Were there any gravitons involved in the gravitational waves that have been detected over the past few years?

Thanks (I missed your post at the time) What chapter did they discussion the relationship between causality and c in? Chapter 2: The speed of Light? I can get some of the book online and may be able to find the relevant pages in Google Books https://books.google.ie/books?id=XChKDgAAQBAJ&pg=PT42&dq=Why+Does+E%3Dmc2+causality&hl=en&sa=X&ved=0ahUKEwiYuoD0jv7bAhWICsAKHW6uBiIQ6AEIKTAA#v=onepage&q=Why Does E%3Dmc2 causality&f=false although it would not be expensive to buy the book itself...

Probably to much for me to understand or research but I was basing my suggestion on the assertion that I have heard (on the BBC) that ,as expansion continues ,eventually (on a cosmic timescale) our presently observable universe will vanish and our stars/galaxies will switch off one by one as their speed of recession exceeds that of light. It is just fortuitous that we can now see the rest of the (gravity unbound) universe as later it will all be dark. Is not the corollary of this that ,in the past more was visible to us than is now and that it might be the case (if the universe was finite) that all ofit may have been visible to an earlier inhabitant of the Universe?

Can there be any possible relationship between the size of the unobservable universe to that of the entire universe with the possible curvature of the observable universe that may apparently (within the margin of error) have been measured? Is it believed there was ever a time that the entire universe may have been observable ?(when expansion was occurring at sub liminal speeds )