Simultaneous events and Einstein's absolute time
in [Relativity]
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From: Ste on 3 Feb 2010 22:23 On 4 Feb, 01:59, artful <artful...(a)hotmail.com> wrote: > On Feb 4, 11:55 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > Ian Paisley's shown his face in another guise again: "No, no, no, > > no..." > > Perhaps you should stop saying so many things that are wrong. If you > understood the subject about which you were posting at such length, > you wouldn't waste so much of it with the nonsense that is incorrect. > Especially s what you have said has already been explained to you as > wrong. Its just a monumental waste of time on your behalf. > > Now .. if you are wanting to learn, now that you know what aspects of > what you have said are wrong, then perhaps you should begin be looking > the correct statements .. or asking what is correct. I am *often* asking for explanations. It's been like pulling teeth so far, particularly when it comes to discerning between real and apparent effects.
From: Ste on 3 Feb 2010 22:23 On 4 Feb, 02:04, artful <artful...(a)hotmail.com> wrote: > > To STE: Please note that it is not just the finiteness (as you were > implying) .. but ALSO that it is a (universal) CONSTANT that has the > consequent that time is absolute. > > Light could travel with a finite speed (but not a universally constant > one) as it does in (say) emission theory, and that would be compatible > with absolute time. The same is so for naive ether theories, where > the speed is finite, but not the same in all frames of reference. > However, those theories do not correctly model reality (ie they are > not valid models). > > Do you see the difference? Yes, the same point was raised elsewhere. I was already aware of it. Incidentally you don't need to shout my name with capitals.
From: PD on 4 Feb 2010 09:37 On Feb 3, 12:10 pm, Ste <ste_ro...(a)hotmail.com> wrote: > 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 does have a density: zero -- by definition. Density is a property that describes how much matter is contained per unit volume. "Empty space" is the end point of that spectrum. > It also seems to ignore that light does not > in fact travel through matter, it travels *around* matter and through > empty space. Interesting. Explain how this works through a pane of glass. > 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. No, it is not the reduced density of empty space which is said to be the cause of redshifting. You cannot reduce a density of zero any further. > > > > 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, One cannot increase or decrease the density of empty space. The density of empty space is by definition zero. > 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? Not at all. The first postulate of SR specifically makes a statement about the speed of light in empty space, not in matter. > 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". I don't think it's underestimated at all. It's perfectly clear to physicists what it means. The fact that SR's conclusions are different in the context of light's passage through matter may have been a sudden realization by you does not mean that it has been overlooked by others. > > > > > > > > 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. But they DO. Unfortunately, you haven't availed yourself of that. All you've looked at apparently, is material full of daunting equations, at which point you come to the conclusion that that's all it's about: equations.
From: Ste on 4 Feb 2010 18:16 On 4 Feb, 14:37, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 3, 12:10 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > 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 does have a density: zero -- by definition. Density is a property > that describes how much matter is contained per unit volume. "Empty > space" is the end point of that spectrum. Indeed, and as I say this presupposes that empty space does not also have some analogous property of "density". Indeed I thought that was the argument behind the expanding universe paradigm. > > It also seems to ignore that light does not > > in fact travel through matter, it travels *around* matter and through > > empty space. > > Interesting. Explain how this works through a pane of glass. Either the light is absorbed and retransmitted, or it is deflected, or it passes through the empty space between molecules. > > > 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? > > Not at all. The first postulate of SR specifically makes a statement > about the speed of light in empty space, not in matter. We weren't talking about matter. We were talking about light travelling through empty space! > > 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". > > I don't think it's underestimated at all. It's perfectly clear to > physicists what it means. The fact that SR's conclusions are different > in the context of light's passage through matter may have been a > sudden realization by you does not mean that it has been overlooked by > others. What are you talking about Paul? We were talking about if the value of 'c' changes for *empty space* - others seemed to express the view that it would be neither here nor there.
From: PD on 5 Feb 2010 09:58
On Feb 4, 5:16 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > What are you talking about Paul? We were talking about if the value of > 'c' changes for *empty space* - others seemed to express the view that > it would be neither here nor there. Alright, let's get the discussion back on track then. The light speed postulate is one about light's passage through space in the absence of matter. |