Preferred Frame Theory indistinguishable from SR
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From: Daryl McCullough on 5 Jul 2010 07:18 harald says... > >On Jul 5, 3:00=A0am, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: >> What do you consider to be the *real* twin paradox? >The one that Einstein was confronted with - the first "twin" or >"clock" paradox that we know of. I meant: what do you consider paradoxical about it? Can you say that in your own words? I don't want you to quote Einstein. I want you to describe the paradox and why in the world you consider it paradoxical. You complain that I miss your point, but it seems to me that you have scrupulously avoided making one with any clarity. If you want to make a point, lay it out in detail and give your arguments in your own words. -- Daryl McCullough Ithaca, NY
From: Daryl McCullough on 5 Jul 2010 08:46 harald says... >Acceleration effects are not identified as gravitational fields in >Newtonian physics (which, as you now know, you didn't know); and >neither is that the case in SRT. In those theories acceleration is >"absolute", and no gravitational fields are caused by acceleration. This is a topic for another discussion, but I'm talking about "pseudo-gravitational" fields, which crop up in both SR and Newtonian physics if you use accelerated coordinates. >> I think it is because you have not made it very well. I still >> have no idea what your point is. > >Just study Einstein's paper carefully, I want to know what *YOUR* point is. State it in your own words. >In this thread, you pretend no less than that: > >- Newton was mistaken with his Space postulate (while you evidently >didn't even bother to read his arguments) >- you know better than Einstein what his own theory is about (Cranky) That isn't cranky. 100 years of relativity development does give one a more complete perspective. I would say that a typical physics graduate student understands Newtonian physics better than Newton, and understands relativity better than Einstein. That doesn't mean that they are smarter than Newton or Einstein---it's a lot harder to invent a new theory than it is to understand or expand on an existing theory. Anyway, I don't care to argue with Newton or with Einstein. They are not around to argue with. If you have a point to make, make it yourself. Don't hide behind Newton or Einstein. -- Daryl McCullough Ithaca, NY
From: Daryl McCullough on 5 Jul 2010 09:42 Daryl McCullough says... >harald says... > >>Acceleration effects are not identified as gravitational fields in >>Newtonian physics (which, as you now know, you didn't know); and >>neither is that the case in SRT. In those theories acceleration is >>"absolute", and no gravitational fields are caused by acceleration. The idea that "gravitational fields are caused by acceleration" is, as I have pointed out many times, a very misleading way to describe the equivalence principle. It's not that acceleration effects are a kind of gravitational field, it's that gravitational fields are a kind of acceleration effect (they are an indication that you are accelerating relative to the local inertial frame). You don't need a theory of gravity in order to know what things "look like" in an accelerated coordinate system. You just take the description in inertial coordinates, and apply a coordinate transformation. It's just calculus. But if you do this for SR, you find some interesting things: 1. All objects accelerate downward (unless acted upon by a force) at a rate that is independent of the composition of the object. A thrown object will follow, not a straight line, but a parabola (roughly speaking). 2. Clocks that are "higher up" run faster than clocks that are "lower down". These are effects of acceleration that are derivable without any mention of any theory of gravity. The key observation behind the equivalence principle is that fact (1) is true (or approximately true) for objects in a uniform gravitational field. So perhaps it is possible to interpret *gravitational* fields as a kind of acceleration field due to the use of noninertial coordinates. If so, this identification makes a definite prediction, namely (2) that clocks that are higher up in the gravitational field should run faster. So the real insight in General Relativity is not that acceleration effects are gravitational fields, it's that gravitational fields are a kind of acceleration effect. To make this work, it is necessary to have curved spacetime, so that the notion of being unaccelerated can vary from place to place (to allow for nonuniform gravitational fields). The same insight could have been done with Newtonian physics, but historically it wasn't. Newtonian gravity can likewise be described in terms of curved spacetime, and under this description, the "force of gravity" becomes just an acceleration effect. -- Daryl McCullough Ithaca, NY
From: harald on 5 Jul 2010 13:00 On Jul 5, 2:46 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > harald says... > > >Acceleration effects are not identified as gravitational fields in > >Newtonian physics (which, as you now know, you didn't know); and > >neither is that the case in SRT. In those theories acceleration is > >"absolute", and no gravitational fields are caused by acceleration. > > This is a topic for another discussion, but I'm talking about > "pseudo-gravitational" fields, which crop up in both SR and Newtonian > physics if you use accelerated coordinates. We agree on "pseudo", while Einstein rejected that. > >> I think it is because you have not made it very well. I still > >> have no idea what your point is. > > >Just study Einstein's paper carefully, > > I want to know what *YOUR* point is. State it in your own words. I did, also in the part of my sentence that you exactly here snipped: *you'll know what theory the paradox challenges*. THAT (and only that) was my point: the clock paradox challenges the General PoR. You certainly are aware that, despite Einstein's *suggestion* to that effect in the introduction of his 1905 paper, SRT is *not* based on the General PoR. > >In this thread, you pretend no less than that: > > >- Newton was mistaken with his Space postulate (while you evidently > >didn't even bother to read his arguments) > >- you know better than Einstein what his own theory is about (Cranky) > > That isn't cranky. 100 years of relativity development does give > one a more complete perspective. I would say that a typical physics > graduate student understands Newtonian physics better than Newton, ?! You have just become aware (except if it hasn't sunk in yet) that a typical physics student is clueless about Newtonian mechanics, since he/she is taught something else instead. I find it a very illogical statement that such a student would know Newton's physics better than himself, after having been misinformed about it! > and understands relativity better than Einstein. That could very well be so (the word "relativity" isn't specifically Einstein's theory). Perhaps this is just about words? Do you call a plastic cup a "glass", while I insist that it is a plastic cup, after which you insist that plastic cups are much better glasses?! > That doesn't mean > that they are smarter than Newton or Einstein---it's a lot harder > to invent a new theory than it is to understand or expand on an > existing theory. Yes. > Anyway, I don't care to argue with Newton or with Einstein. > They are not around to argue with. > > If you have a point to make, make it yourself. Don't > hide behind Newton or Einstein. I made my point at the start (a factual statement) - and you jumped on it. ;-) Harald
From: Paul Stowe on 5 Jul 2010 14:26
On Jul 5, 10:00 am, harald <h...(a)swissonline.ch> wrote: > On Jul 5, 2:46 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > > > harald says... > > > >Acceleration effects are not identified as gravitational fields in > > >Newtonian physics (which, as you now know, you didn't know); and > > >neither is that the case in SRT. In those theories acceleration is > > >"absolute", and no gravitational fields are caused by acceleration. > > > This is a topic for another discussion, but I'm talking about > > "pseudo-gravitational" fields, which crop up in both SR and Newtonian > > physics if you use accelerated coordinates. > > We agree on "pseudo", while Einstein rejected that. > > > >> I think it is because you have not made it very well. I still > > >> have no idea what your point is. > > > >Just study Einstein's paper carefully, > > > I want to know what *YOUR* point is. State it in your own words. > > I did, also in the part of my sentence that you exactly here snipped: > > *you'll know what theory the paradox challenges*. > > THAT (and only that) was my point: the clock paradox challenges the > General PoR. > > You certainly are aware that, despite Einstein's *suggestion* to that > effect in the introduction of his 1905 paper, SRT is *not* based on > the General PoR. Strictly speaking the 'domain' of the 'special' theory of relativity is limited to inertial states. The original principle of relativity as expressed in Einstein's 1905 work covered only that domain. So Harald is correct, the paradox is confined to the situation where, you have identical twins one remain in the original inertial frame, the other accelerated rapidly (nearly instantaneously) to speed ~c travels for x time wrt the original FOR, reverses comes to an equally rapid stop (wrt the original FOR) then returns the same way. Since SRT is based upon v^2 effects (second order quantities) the directionality of any asymmetry is lost in the expressions that quantify changes. However, there is NO! paradox, either in nature, or SRT, once one understands that limitation. The traveling twin, not the stay at home twin will be physically younger. On a one-way trip however, we can't say which one would be for an equal physical duration. That would depend upon the speeds of both FOR relative to the CMBR... Directionality does matter. > > >In this thread, you pretend no less than that: > > > >- Newton was mistaken with his Space postulate (while you evidently > > >didn't even bother to read his arguments) > > >- you know better than Einstein what his own theory is about (Cranky) > > > That isn't cranky. 100 years of relativity development does give > > one a more complete perspective. I would say that a typical physics > > graduate student understands Newtonian physics better than Newton, > > ?! You have just become aware (except if it hasn't sunk in yet) that a > typical physics student is clueless about Newtonian mechanics, since > he/she is taught something else instead. I find it a very illogical > statement that such a student would know Newton's physics better than > himself, after having been misinformed about it! > > > and understands relativity better than Einstein. > > That could very well be so (the word "relativity" isn't specifically > Einstein's theory). > Perhaps this is just about words? Do you call a plastic cup a "glass", > while I insist that it is a plastic cup, after which you insist that > plastic cups are much better glasses?! > > > That doesn't mean > > that they are smarter than Newton or Einstein---it's a lot harder > > to invent a new theory than it is to understand or expand on an > > existing theory. > > Yes. > > > Anyway, I don't care to argue with Newton or with Einstein. > > They are not around to argue with. > > > If you have a point to make, make it yourself. Don't > > hide behind Newton or Einstein. > > I made my point at the start (a factual statement) - and you jumped on > it. ;-) > > Harald |