Simultaneous events and Einstein's absolute time
in [Relativity]
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From: Ste on 3 Feb 2010 13:10 On 3 Feb, 15:08, Igor <thoov...(a)excite.com> wrote: > On Feb 2, 10:51 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > There exists a demonstrable maximum possible speed of > > > > > communications, designated "c". > > > > > You mean the maximum speed of communications using matter? Somewhat > > > > like how there is a maximum speed of communications using sound waves? > > > > But there's not a maximum speed of communications using sound waves. > > > Speed of sound is proportional to the density of the medium and has no > > > theoretical upper bound. > > > If you hold the expanding universe hypothesis to be true, then I > > believe the same argument about density applies to light. > > Except that light travels perfectly well through regions of zero > density. When it does travel through matter, it actually slows down. This seems to presuppose that "empty space" is not a thing with properties like "density". It also seems to ignore that light does not in fact travel through matter, it travels *around* matter and through empty space. After all, sound does not travel through a vacuum, which is a place where, by definition, its medium is rarefied. If we put lots of "vacuum bubbles" into the air (obviously, assuming that such an undertaking was possible and that the bubbles retained their shape), I'm sure you'd find the speed of sound would drop dramatically with the increasing density of these vacuum bubbles (just as the speed of light drops with an increasing density of matter). I personally reserve judgment on the issue for now. > And I don't understand what the expanding universe has to do with any > of this. Because, at least as I have understood the argument, it is the expansion (and therefore reduced density) of space which is said to be the cause of the redshifting observed of light from distant galaxies. > > And in any event, the point is that if the density of the medium *is* > > held constant, then the speed of propagation is constant and finite. > > That's true, but light and sound behave oppositely in regards to > that. Sound speeds up in higher density media, whereas light slows > down. So your analogy fails. It doesn't fail because it was *only* supposed to be an analogy. The fact that the medium of sound is matter, and the medium of light is space, and so therefore an increase in the density of one decreases the density of the other, does not seem to me to have any obvious implications that would justify saying that a finite speed of light proves something that a finite speed of sound does not. > > > > > Should the speed of light ever be discovered not to precisely > > > > > equal "c" (and there is some controversial evidence that this > > > > > may be the case for high energy gamma rays), this will have NO > > > > > CONSEQUENCE WHATSOEVER in regards to the validity of relativity, > > > > > since the "c" which is the speed of light is not the same "c" > > > > > which determines the properties of spacetime. > > > > > Which is the most absurd drivel I've ever heard. What you're basically > > > > saying is that the validity of relativity is independent of any > > > > measurement of the validity of its terms. > > > > No, relativity is based on a constant c which may or may not represent > > > the speed of actual radiation in vacuum. All that's sufficient to > > > state is that c is the maximal attainable speed possible. That's what > > > leads to the predictions of SR, not necessarily that c must be the > > > actual speed of electromagnetic radiation in vacuum, although for the > > > most part, it still holds up. But it really doesn't have to. They're > > > two entirely different issues. > > > Then how could you possibly establish a value for 'c', if not by > > measuring the speed of light? > > There are many quantities in physics that depend on c. So determining > c is not necessarily a question of measuring the actual speed of > light. And so far, we have no reason to doubt that the vacuum speed > of light is c, but it's not actually necessary. Maybe you need to > research how physical constants are measured. So if light travels slower than 'c', then wouldn't the predictions of, say, SR, become inaccurate? I think you underestimate the consequences of finding out that the speed of light is not constant - it would relegate relativity to the same position as classical mechanics, namely "a generally adequate approximation". > > > > It's this arrogance and loss of touch with reality that explains why > > > > we're up to 20-odd "hidden dimensions", because the loss of touch with > > > > reality has left scientists out in the wilderness, with neither the > > > > inspiration nor the intuitive guidance that comes with a connection to > > > > the material world. > > > > Well even Einstein said that our understanding of the universe should > > > be "as simple as possible, but no simpler". If it requires 20 hidden > > > curled up dimensions, so be it. But I think we've just begun to > > > scratch the surface on this stuff. > > > I agree, but whatever we find underneath, I don't expect it to be > > additional dimensions. > > The main problem is that, without additional dimensions, whether they > be metric spaces, fiber spaces, or whatever, GR is essentially a dead > end in explaining the bases of the other forces of nature. But this > is the conundrum we find ourselves in right now. Maybe there is > another way to approach this, but I have no idea what it would be. Indeed. I personally think the problem lies in the philosophical malaise that science finds itself in. What I would say is that physicists would do well to start taking an approach to relativity that is inspirational and heuristic, instead of a black-letter approach that holds the mathematical basis of relativity to be a fundamental truth. That is, they need to stop trying to advance science by deriving simplistic mathematical truths from relativity, and instead focus on what relativity tells us about the nature of the physical world.
From: Ste on 3 Feb 2010 13:39 On 3 Feb, 17:03, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 2, 9:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 2 Feb, 19:07, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 2, 10:51 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > On 2 Feb, 13:15, Igor <thoov...(a)excite.com> wrote: > > > > > > On Feb 1, 10:29 pm, artful <artful...(a)hotmail.com> wrote: > > > > > > > On Feb 2, 10:44 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > On 1 Feb, 18:27, Igor <thoov...(a)excite.com> wrote: > > > > > > > > > Absolute time and a finite speed of light are contradictory concepts. > > > > > > > > Therefore, since it's easy to demonstrate that light has a finite > > > > > > > > speed, absolute time cannot exist. > > > > > > > > The same arguments (whether true or not) can also be made from the > > > > > > > existence of a finite speed of sound. > > > > > > > Nope .. because the speed of sound is frame dependant > > > > > > And sound requires a medium. > > > > > And light requires a medium - we call it "empty space". > > > > And if this is how you want to define "medium" -- anything that > > > carries a transmission of any description -- then there is no > > > argument. But once again, this is not the connotation that physicists > > > had associated with "medium" when there was much fuss about whether > > > light was carried in a medium. > > > As far as I'm concerned, space is to light what air is to sound. > > In a very simplified and overly vague sense, this is certainly true. > The problem then comes in assuming that because the statement is true > in the vague sense, then it is true in the detailed sense. This is, of > course, where it breaks down. > > The statement is similar to saying that mammals are just like > reptiles. When asked to defend the statement, one could say "They are > both vertebrates. They both are tetrapods." Those statements are > undeniably true, and yet it is just as undeniably false that mammals > are just like reptiles. I agree. There is a difference between recognising the common or analogous properties of two things, and going too far and being unable to see or accept any differences. The important thing here is simply that both light and sound have finite propagation times, and if that finite propagation time is used as the basis of saying that simultaneity is relative and there is no absolute timeframe, then it seems to me that the finite speed of sound provides the same basis for that hypothesis. The reason I compare the two however is because, in fact, the finite speed of sound was *never* used as a basis for that argument, partly because it is possible to see something before you hear it, and so that is the necessary common sense proof that events *really do* happen before they are heard with the ears. The problem with light is that, as yet, there is nothing that goes faster, and so it's very difficult to employ evidence against the reasoning that events happen no sooner than they are detected (which is relative to perspective). However, I like to go around this by saying *let us suppose* that there is something that goes faster than light, and this once again allows us to suppose that events happen in an absolute timeframe and that events 'actually happen' at a time interval that is different from when they are detected by way of light. As I believe you said on a previous occasion, "that is not science", because it supposes a mechanism of transmitting information which does not exist in the real world, but it is my view that this dogmatic and minimalist approach to science that is actually hindering progress, because it locks people into thinking that "nothing happens until you observe it", when in fact this was precisely the view that Einstein strongly argued *against*.
From: artful on 3 Feb 2010 17:25 On Feb 4, 5:39 am, Ste <ste_ro...(a)hotmail.com> wrote: > The important thing here is simply that both light and sound have > finite propagation times, and if that finite propagation time is used > as the basis of saying that simultaneity is relative That is not the basis > and there is no > absolute timeframe, then it seems to me that the finite speed of sound > provides the same basis for that hypothesis. No .. because the speed being finite is not the basis > The reason I compare the two however is because, in fact, the finite > speed of sound was *never* used as a basis for that argument, partly > because it is possible to see something before you hear it, and so > that is the necessary common sense proof that events *really do* > happen before they are heard with the ears. No .. nothing to do with that at all > The problem with light is that, as yet, there is nothing that goes > faster, and so it's very difficult to employ evidence against the > reasoning that events happen no sooner than they are detected (which > is relative to perspective). You are confused about what RoS means. It is not (just) about visual appearance. > However, I like to go around this by saying *let us suppose* that > there is something that goes faster than light, and this once again > allows us to suppose that events happen in an absolute timeframe It wouldn't > and > that events 'actually happen' at a time interval that is different > from when they are detected by way of light. It has nothing to do with detecting with light > As I believe you said on a previous occasion, "that is not science", > because it supposes a mechanism of transmitting information which does > not exist in the real world, but it is my view that this dogmatic and > minimalist approach to science that is actually hindering progress, > because it locks people into thinking that "nothing happens until you > observe it", when in fact this was precisely the view that Einstein > strongly argued *against*. its not that its not science .. its that you have no idea what you are talking about and it is unrelated to the physics of SR
From: Jerry on 3 Feb 2010 18:50 On Feb 3, 6:04 am, artful <artful...(a)hotmail.com> wrote: > A beautiful analogy. Very nicely put. Did you come up with it > yourself, or was it something you read somewhere (just interested in > the source). Thanks for the compliment! How do you trace the genealogy of an idea? I picked up the analogy from my brother, who posted here in the "good old days" before these newsgroups became completely overrun with cranks (i.e. the good guys to crackpot ratio was still above 20%). He was a contemporary of Stephen Speicher, Franz Heymann, Bilge, Mati Meron, Timo Nieminen and others long gone whom we miss very much. Where he got the idea from I dunno... maybe it was original, maybe not. But I know for sure that he never dressed up the analogy in a story about Flatland. So is the idea original with me? It sorta depends... ;-) Jerry
From: Ste on 3 Feb 2010 19:55
On 3 Feb, 22:25, artful <artful...(a)hotmail.com> wrote: > On Feb 4, 5:39 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > The important thing here is simply that both light and sound have > > finite propagation times, and if that finite propagation time is used > > as the basis of saying that simultaneity is relative > > That is not the basis > > > and there is no > > absolute timeframe, then it seems to me that the finite speed of sound > > provides the same basis for that hypothesis. > > No .. because the speed being finite is not the basis > > > The reason I compare the two however is because, in fact, the finite > > speed of sound was *never* used as a basis for that argument, partly > > because it is possible to see something before you hear it, and so > > that is the necessary common sense proof that events *really do* > > happen before they are heard with the ears. > > No .. nothing to do with that at all > > > The problem with light is that, as yet, there is nothing that goes > > faster, and so it's very difficult to employ evidence against the > > reasoning that events happen no sooner than they are detected (which > > is relative to perspective). > > You are confused about what RoS means. It is not (just) about visual > appearance. > > > However, I like to go around this by saying *let us suppose* that > > there is something that goes faster than light, and this once again > > allows us to suppose that events happen in an absolute timeframe > > It wouldn't > > > and > > that events 'actually happen' at a time interval that is different > > from when they are detected by way of light. > > It has nothing to do with detecting with light > > > As I believe you said on a previous occasion, "that is not science", > > because it supposes a mechanism of transmitting information which does > > not exist in the real world, but it is my view that this dogmatic and > > minimalist approach to science that is actually hindering progress, > > because it locks people into thinking that "nothing happens until you > > observe it", when in fact this was precisely the view that Einstein > > strongly argued *against*. > > its not that its not science .. its that you have no idea what you are > talking about and it is unrelated to the physics of SR Ian Paisley's shown his face in another guise again: "No, no, no, no..." |