geordief

So is the 4D event that describes the Big Bang any different from the other 4D events we can describe mathematically ? Is it just an "unprivileged" member of the set with no way to differentiate it from any of the others? The manifold merely "catalogues" all the events without laying out any "qualitative" differences whatsoever? Is there no kind of kind of "ordering" at all...? (just relationships between arbitrary pairs of events) .

Thanks Is it possible to set the values of s1 x1 y1 z1 t1 to zero? Could those values represent an event at around the Big Bang? and allow us to find the 4D distance of any event with respect to it? Am I right that the set of 4D events is increasing or does the fact that the Manifold is described as "static" preclude that possibility? Did my OP "make sense" ? Was it shot through with misunderstandings ?

Preamble: I hope I can post here (in the homework sub forum) since I am trying to "catch up" ** with the subject of Relativity in a way. If the universe is represented by a model consisting of the set of events in a 4D manifold , are there points in this manifold that have particular characteristics (or properties?) For example ,what does it say if events are separated from each other by the same 4D distance? Secondly the event that represents the Big Bang , would that be the event with the greatest sum of distances from all the other events? Thirdly would this event (the Big Bang) be considered to be at the "centre" of the manifold? Fourthly: Is there a subset of events that have the same "distance" from the Big Bang and what can be said about them that might be interesting? Can anyone provide me with a link on the internet to where these kinds of questions are answered-or put me right as to whether my questions actually make sense....? Have I badly misunderstood how this manifold model is supposed to work? ** By "catch up" I mean I am trying to learn some of the standard theory and not to challenge it.

I think I have heard that that is one of the main areas of present enquiry.

I doubt that.Quantum theory doesn't seem to require "continuums" and that is how the smallest domains are explained at the moment

In order not to cross post ,you need to work with 2 pages . With the first you check for the freshest content and with the second you write your post. I do this some of the time, not always.

I think you may have edited out your answer to the question "Perhaps MSC will let us know if we are on the right lines regarding his MO." It was "perhaps" wasn't it ? -or was that a typo?

You have to convince your audience (and then judge that your audience is not gullible). Are Ophiolite and myself on the right lines as regards your perhaps "shoehorning" your perception of reality into what would be a more scientific method of learning things ( one big step rather than lots of little baby steps)?

Yes that is very close . I remember from the days I was interested in "alternative" philosophies there was something called Gestalt Therapy which seemed to be saying that depending on how you looked at something a hidden pattern would emerge .... Perhaps MSC will let us know if we are on the right lines regarding his MO. To follow on from Oph's post it might be that there are two processes ,one internal and subjective and the other external and objective that need to dovetail for new learning to be effective (statemement of the obvious perhaps)

Is MSC just making a general observation (using a perhaps poor example) that the obvious and everyday can be hiding its secrets in the open? Sometimes you may need to look at something with the eyes of a child.(I am no expert ) Perhaps , as the others are saying there is nothing to see here .(I crossed posted,Oph )

@robinpike thanks.I do need and did benefit from that resume but I kind of take it as a given that in your earth/moon /spacecraft scenario that the distance as agreed by the 3 observers in the 3 different frames of reference is a function of the speed of light (even if I still struggle with the actual mathematics involved). My question (if I can still summarize it) was whether this is universally the case. Strange has convinced me otherwise as he has pointed out that dark matter seems to exist in isolation from the effects of em radiation and so ,presumably we might need some other mechanism to define or measure distances in that context.. Hope that clarifies my question (which I think Strange did resolve for me in a way that was quite clear) and my understanding of the answers.

Poor Robin Williams seemed to have been dealt a terrible hand. Suicide perhaps seems more comprehensible in his case. His life seems to have been disintegrating according to the latest report.

Does robinpike's line of argument belong in the thread from which this was split off ? http://www.scienceforums.net/topic/91940-how-fundamental-is-light-to-the-physics-of-the-universe/ In post #5 of that thread Strange said "You seem to be saying that because we can use light to measure distance, that distance must be defined by light. This seems just as illogical as the claim that because we can use change to measure time, time is defined by change. It is refreshing to see someone apply the same logic to space as to time, even if it is equally wrong." Is robinpike's argument in line (or counter to ?) to that point? I cannot really contribute as my head is below the water line but maybe robinpike could make that same point in the earlier thread ?

Thanks. I will go away and try and work my way through that (eventually I hope).

Am I being facetious.? You press the button and that involves electro -magnetism(I am just trying to tag along) I think you are being facetious but maybe I deserve it for asking questions outside my remit.

How do you measure the time in that situation? How do you know what has occurred in the muon? Is it not by the use of a beam of light? (apologies if I am wrong -I am just prodding ) Are there any situations where time can be physically counted (not inferred) without a beam of light being used at some point in the process?

Ok I will counter that "even if" is actually ambiguous and can (also) be understood as accepting the truth of the phrase that follows. I am fairly sure I have heard it used that way but accept now that that is not how you used it.

Apologies for truncating your quote (for my benefit) .Still for my purposes I still think my interpretation was close to what you were saying (that is the majority view amongst physicists in your opinion, isn't it ?) I would guard against that "cherry picking" if I could but I am not so confident in my intellectual abilities (I am very indisciplined in that regard and there is really little hope for me) When I was younger ,my father gave me a copy of "How to think" by C.E.M. Joad which I was quick to dismiss. A lifetime of intellectual indiscipline has reinforced that decision and I have now come to the point where a change of heart would be ineffective By the way this is the 5th or 6 th draft (all very different) so I have attempted to (over-?) address your point. Edit :thanks for the editing Swansont -I am just getting used to the layout

Is light(em radiation) not the only method of measuring distance in a vacuum? Do distances (in the space-time sense) have any meaning if not measured in a vacuum?.

I of course accept your criticisms Ophiolite . Perhaps ,though you have answered my question in the main when you say "the majority of physicists doubt their reality, " Whatever about my own lack of rigour I am glad that this seems (if you are right) to be the prevailing view. I would find it unsettling otherwise. PS your "Do you know the equations well enough to say this is what happens?" was a rhetorical question perhaps , since I said towards the end of my post " do I simply have my lack of proper scientific/mathematic education to blame for my blinkered vision? " -which concedes that point , I think.(although that might have come across as false modesty instead of being ,perhaps an overestimation of my capabilities) The Mobius strip , yes I have heard of it. I don't follow what you mean by "what number comes after 12 ?". I am also unclear as to what would constitute "two separated parts of a mathematical object." but perhaps I understand your overall meaning.

(just as a warning all my ideas here are second hand in that I have mostly gleaned them from the internet and the likes of Scientific American over the years) I do have a fairly specific question (I hope) concerning the title of my thread . I have become accustomed to the idea that the "fabric of space-time" is a misnomer and that we are really talking about an analogy. Space-time ,as I think I have learned is a mathematical model of the universe and the universe itself is ..the universe. Anyway ,when I come across the idea that the "fabric of space-time" can be "torn" to the extent that even "wormholes" can (theoretically ) be formed my wish is to disbelieve this possibility as an example of the analogy being carried too far and ..........really this sounds only like science fiction to me. I prefer to believe that ,under those and like conditions what really happens is ...we don't know because the equations have run out. I very rarely seem to come across this view point (or bias?). Do I share a respected view with the scientific community or do these ideas of worholes and "tears in the fabric of space-time" actually have a "respected" following ( and do I simply have my lack of proper scientific/mathematic education to blame for my blinkered vision -which might not be a first ? ) Or have I just created a false dilemma somehow?

Thanks . Yes that is very easy for me to understand. I look forward to learning about dark matter in my lifetime

Well(hopefully to clarify) my inclination is to "believe" that light is not fundamental but everything I have read leads me to feel that a universe without light (em radiation) is is an absurdity. I would like this not to be the case (for the absurdity to hold water) but I know that what I like does not count.

Does that loosely fit in with my idea that , without light the space between "things" would no longer exist ?(so light would be entirely fundamental to our understanding of "separateness" (of course I do not follow your maths or even your follow up)

Is it as stark as that? After all have I not heard of scenarios close to what is termed the Big Bang where light had not formed ? ( or have I misheard /misunderstood and are they saying that light was simply trapped in the initial conditions that they think existed around then and so there was no time in the past yet theorised when light did not exist?)