On Sunday, February 2, 2014 9:16:09 PM UTC, Brent wrote: > > On 2/2/2014 12:44 PM, [email protected] <javascript:> wrote: > > > On Sunday, February 2, 2014 3:45:24 PM UTC, jessem wrote: >> >> >> >> >> On Sun, Feb 2, 2014 at 7:13 AM, <[email protected]> wrote: >> >>> >>> Jesse - if the assumption is a fundamental geometry akin to the surface >>> of a world, and if the speed of light is constant, then you could draw dots >>> around that world for exact intervals of the speed of light, in which case >>> the light arrives at each point from each other point at exactly the same >>> moment....isn't that saying edgar's p-time? >>> >> >> >> I don't understand what you mean by "dots around the world for exact >> intervals of the speed of light"--in terms of a standard spacetime diagram >> from SR, what would the dots be? Different events along the path of a >> single light ray, or events along the paths of multiple light rays >> radiating from some other event, or something else? It is true that the >> spacetime "distance" between any two points along a light-like path is >> zero, if that's what you mean, but I don't see the connection between this >> observation and the idea that the light arrives "at exactly the same >> moment", I'm not sure how you're defining that phrase. "Same moment" >> normally suggests a judgment about simultaneity, not a judgment about the >> proper time along a particular path between events. Also, note that by >> means of a zig-zag lightlike path (like that of a light ray bouncing >> repeatedly between mirrors), you can connect *any* two points in spacetime >> that are within one another's light cones by a path of zero proper >> time--for example, there is a path of zero proper time between the >> assassination of Julius Caesar and me sitting here typing this. So if you >> were to define events "at exactly the same moment" in terms of the >> existence of a path of zero proper time connecting the events, you'd have >> to say that all events throughout history occurred "at exactly the same >> moment" which is pretty clearly not how it works with Edgar's p-time. >> >> Jesse >> > > Hi Jess/Brent - thanks for getting back, > Perhaps I should backtrack to my first reaction reading your post. First > off, I definitely am not at your level on relativity so get ready for one > big pile of steaming ...misconception. I'll do the right thing, and keep it > short. > > I thought that one of the big themes from the principle of equivalence and > relativity via frames, was that there wasn't a complete resolution to the > absolute, non-relativistic conception of what the whole universe is like., > That you can't necessarily talk about a landscape in absolute terms at all. > > I read liz's thread on block time (very helpful thanks Liz) and will be > rephrasing this issue over there at some point too. > > It's funny because this came up for me first because I speculated with > some guys (and dolls) a lot nearer your level than mine - maybe 3/4 years > back - that spacetime had a definite geometry. They came back very firm it > did not. That even between the Earth and the Sun you couldn't look at it > that way. I must say I couldn't accept what they were saying and said so, > because for me, the geometry would be very clear that there was this huge > gravity well oneside, and this relativily tiny one the other (earth). > > > Dunno what was meant by "geometry". Einstein's equations relate the > metric of spacetime to the location of stress energy. That seems plenty > definite to me. Of course in application it's just a model and one > neglects various effects thought to be small, e.g. gravity waves coming in > from far away. > ok maybe we can bridge this. I'm naively taking the most popularized visual metaphor of Einstein's theory. The mattress as it were, with the steel ball laying upon it as it were, and the indentation that ball puts in the mattress as it were, and then the little animation that often comes next, of the mattress now a plane represented by two sets of respectively parallel lines, each set normal to the other resulting in little squares, the indentation now the distortion of those squares and the animated part the much littler ball rolling around the indented section. if that's good enough that you can do the bridging work from where I am to where things need to be for you to provide an answer that is within the limits of what you're prepared to give in this sort of situation, then, fabulous :o)
> > > But they maintained it wasn't legitimate to think that way and then when I > wouldn't buy but didn't have the expertise to make a case from relativity > knowledge, got the usual dressing down about intuition and how the world > isn't intuitive and all the rest. > > So where do we actually stand? Was their point legitimate but subtly > different to yours - and it's a case of I don't have the knowledge to tell > them apart? > > Or has this been a kind of furious debate within the field, or was a > furious debate? Is the matter now resolved for blocktime, or is it still > controversial, as say, MWI is in the quantum field? > > Could we start there? I'll obviously understand if your response is along > the lines, you've been able to deduce my level from my words, and > explaining this isn't going to work in a post, and I need to bugger off and > read a text book. Of course. However...I would settle for a roughie, and > the text book ain't likely to go down at the moment. > > > First read Lewis Carroll Epstein's nice little book "Relativity > Visualized" which has essentially no equations and yet manages to be pretty > rigorously correct. > actually I'll take action on this halfway with immediate effect by online ordering the book, with my thanks. But since I do contribute sometimes, I feel I ought, perhaps irrelevantly, mention I'm reasonable on the maths front, and I know more about relativity than the mattress thing. On the maths side....I have a pretty good first in engineering from a top band university...that was about 80 percent maths. albeit it was applied maths, albeit an undergrad degree is probably at least one maybe two major levels beneath the spitline minimum in a place like this. But.... still. It c'ain't be NUTHIN' :O) -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
