geordief

My OP is only concerned with processes that occur in nature and not with mathematical abstractions which attempt to model them ** The equation y = A sin(bx) does not describe any such process ,does it ? Is it not necessary to introduce the time parameter in order to model something which actually exists in nature.? Facetiously we cannot feed our bodies with mathematical equations. In post #10 I wondered if "stationaryism" was an idealized concept at odds with the way the universe actually works (continuous motion). . If we accept this concept then does this continuous motion imply time ? (locally ,globally?) As I said I am excluding purely mathematical representations which do not model anything existing as we observe them externally to our thought processes.(which is how I am seeing this y = A sin(bx) equation) A standing wave is not described by this equation because a standing wave is time limited (the string will eventually dissipate and the "standing" wave will move since ,in the "real" world it is not stationary but moving wrt any observer ) **I hope this is a valid distinction or do we have to say that mathematical models are a subset of the set of natural processes we observe around us?.

So as not to unintentionally confuse you, I replied to the first part of your post (you added the second part with the equation a few minutes later) I have not studied tensors yet and that equation is actually too hard for me too attempt to understand at this stage (maybe ever ) So the first part of your post did not confuse ,but the second would confuse me if I attempted to understand it properly...

No it didn't confuse . I manage that well on my own

Is this semantics.?I thought I had learned that GR incorporated Newtonian Gravity theory (you only do not use GR for most cases because the differences are normally zero to negligible and the computational effort is so extreme.) In the same way I anticipate that any new theory of Quantum Gravity that succeeds will incorporate both GR and Newtonian gravity in a Russian Doll-like way. Is my pov badly wrong? Is the Russian Doll analogy wrong headed? I had previously asked a question whether Newtonian Gravity was "something of a "special case" of General Relativity?" http://www.scienceforums.net/topic/94702-why-is-newtonian-gravity-so-accurate/page-1#entry917866 and was not disabused of the notion then.

Not a problem with that . What reality is is a question in its own right and the one (circular) answer might well be along the lines of "Reality is what may not be defined" Or less seriously "Reality ,like the poor will always be with us"

But doesn't the spacetime theory have the Newtonian theory "in its back pocket". Why bring up the mass attracting mass notion if it has been superseded? There is no going back to Newtonian force attraction is there except as a shorthand in special circumstances? People looking for a quantum gravity theory are surely not trying to incorporate Newtonian gravity into their new theory are they?

Well my knowledge is more holes than substance but I am thinking lately that motion is the "natural" order of things for objects in the the universe and so we are looking for the direction these objects will take anyway . There is no such thing as a stationary object.Everything is moving in its direction. Apparently this "natural" direction is along a geodesic in spacetime. Btw,I am not sure you can use the term "gravitational field" in the same way as as "EM field" (You know I am just parroting what I have heard so I can't back this up with the experience of a proper education) Maybe both are referred to as "fields" but I think them properties of the two fields are completely different.

I keep hearing (I think) it is the geometry of spacetime that causes this movement. I am not clear what role gravitons (they are only theoretical aren't they ) would play. Do they just mediate changes in the gravity field -not cause the gravitational effects of the gravity field "as is" ?

No but the distribution of the matter is being rapidly changed.,isn't it? Does that scenario allow us to ask the question whether or not the object would notice it was being accelerated.? Is it wrong to describe that scenario as "free fall" if the thing that the object is supposedly "free falling" to is itself rapidly changing ? Edit: hope I am not going too off topic Mike.

Is my Binary Black Hole merger environment a realistic scenario? Would it be complicated by the presence of gravitational waves? Or would the gravitational waves be a /the central part of the experiment? Actually I am not clear how long these gravitational waves last for . Are they just created "at the death" or would they be an important factor in the extremely close spacetime environment in a longer period leading up to the merger?

Can I take it ,though that the thought experiment is entirely impossible?(and so nothing can be inferred from it really) ? Or might something free falling towards and in close enough proximity to a merging Binary Black Hole be a good test object ?

If ,as a thought experiment the mass of the earth was to change noticeably ,would an observer in another frame of reference ,say something free falling from the moon towards the centre of the Earth notice no acceleration? So that (if I am right) from the FOR of the Earth ,the body approaching it - that body's acceleration **- would appear to vary with every change in mass (no idea how such a thing could be accomplished,if at all) but from the FOR of the infalling object or observer it would appear as if there was no acceleratiion "onboard" but the Earth would appear to be accelerating towards the observer or object.... **Edited to improve some clumsy language

As it is my OP perhaps I can go a bit "off piste" ? (thanks for the Rovelli reference-i will try and give it a look). I was wondering is there any significance to the observation that motion is actually the natural prevailing order of things and that "stationaryism" can be viewed as a limit ? (an idealized state ?) I feel clearly it justifies ** the use of a Minkowski geometry rather than a Euclidean. Are there any other fundamental consequences that might flow from an acceptance that a stationary frame of reference is an idealized concept? **I realize that it is also justified by experimental verification....

If we accept the concept of a time without motion does that mean we must disregard (as inconsistent) the idea that time can "stop" as is claimed in various scenarios (I think heat death is one)? Actually I may need to apologize to Strange as I see I may be just going over old recent ground on another forum where I asked almost the same question (my memory is to blame ) I think the process of decay in an atomic clock was there adduced as an instance of time passing without motion.

A very simple question but one that is quite likely the product of a garbled thought process (so apologies in advance): Is it possible to conceive of motion without the concept of time (either time per se or time as measured by a clock and a signal) ? Are Motion and Time joined at the hip? PS I am only posting in Philosophy because I fear my question may be too insubstantial for the Relativity Forum where I intended to put it

I would rather it went up in history but I fear it will indeed go down

Well I wouldn't be competent to say whether it would be misleading to use the term "arena" in anything like a scientific way. But ,as I was imagining it ,it would be completely unbounded in the sense that as events occurred it would accommodate them . So if the set of events was finite , then so would the "arena" they played out in and if it was infinite the "arena" would also " be there." But I doubt very much if it could be called a scientific description in any way . The most I could hope for is that it would be neutral and not misleading. But if it was that , then it would be a term that would appeal to me. as it embodies this notion of activity (events) , observation and space in the one term (as well as being a Latin word for the pleasure of using it )

Well I "failed" on several occasions. The mental trick I used to get over it was to promise myself to do better next time. So ,to put myself in your shoes I would consider it a success if my next (if there was to be a "next") "relapse" was to follow a longer period of abstinence. This method has the merit of making a virtue of failure. As I think I said before my final relapse came after 3 years of abstinence and was preceded by shorter periods varying between weeks and months .. Each period that ended with a "failure" was followed by a longer period of abstinence and there was a logic that it would become easier to completely break the habit at the end of the process. I have not smoked now for over 30 years . The urge went completely but it is always possible revisit the scenario. I can imagine that if I was involved in a car accident and in great pain I might accept a cigarette if I thought it might alleviate great pain but I doubt I would accept it if I thought I was dying as I would associate it with weakness and a kind of self injury.

Thanks for pointing out that the word "arena" is just an analogy. I like it (sadly not a Greek word -just Latin). Hopefully ,though it may be a closeish analogy and so more helpful to those of us who struggle with metal imagery. I feel that some may feel (and GR may assume ) that "events" is all there is and so this "arena" analogy is a sign post to to ....nothing So long as that (nothing) concept works I am happy to go along with it. Perhaps it It has the very great merit of simplicity.

Does the description "empty medium" have any meaning? Or an "arena" ,which is a space where things takes place but is not required to actually be a building or enclosed in any way. You can say that national shame and anger was the arena in which Nazism gained a foothold after the settlement at the end of WW1 The arena is filled with things and events , is defined by them but has no existence separate from them.

My understanding is at a very low level but are you not trying to perform a physical test on the geometry itself ? It is as if your architect gave you a plan for your new house and you tried to do a physical test on his plans. It would be nonsensical

I think the spacetime model is curved by the presence of mass-energy and light (along with everything else ) moves along the geodesic. The actual theory of GR doesn't consider (or at least doesn't address the question ) spacetime to be a "thing" that can be curved. If I have been paying attention

according to the expressions which are above, presumably it has been understood incorrectly (I have told incorrect! , ok ,this is my own incorrectness and of course I apologise) I attempt to paraphrase this as "Judging from the above comments, my meaning was misunderstood (Actually I accept it was my own lack of clarity for which I apologize ) Any help Oph? (Do you think I am right?)

Good luck and fair weather I see they are thinking of bringing back prohibition in India http://www.bbc.com/news/world-asia-india-37230259

If you are right that is a very good argument. and perhaps it gives a method for boosting one's chances of success in quitting. Give yourself extra opportunities for exercising your (depleted?) pleasure muscles over the hard period of weaning yourself off the weed. Get a new hobby perhaps . Take up painting? Writing a diary might be doubly useful .... .