On Sat, Mar 1, 2014 at 9:55 AM, Edgar L. Owen <edgaro...@att.net> wrote:
> Jesse, > > Of course there is a rational justification for selecting one frame over > another in many cases. All frames are NOT equal when it comes to > representing ACTUAL physical facts. > > E.g. we can choose various frames to make someone's age pretty much any > number we like but nevertheless they are still actually the age they think > they are. If Alice is really 30 we can choose a frame in which she is all > sorts of different ages > I've already told you that proper time at an event on Alice's worldline is frame-independent, did you forget already? If one frame says Alice is 30 at a particular event in her worldline, like the event of her passing a particular object or observer (or her age when she reunites with her twin), then ALL frames say this, there is no need to use her comoving frame to get the correct answer. Different frames may disagree about simultaneity--what Alice's age is at the "same moment" that Bob turns 40, at a distant spatial location--but this is precisely why physicists don't believe there is any "actual physical fact" about simultaneity in relativity (this doesn't rule out presentism since there could still be a "metaphysical fact" about simultaneity, but no physical experiment would be able to determine it if there was, unless relativity turns out to be incorrect in its physical predictions). > but she is still actually 30. Different VIEWS of her age don't change her > actual age. Isn't that obvious, and don't you agree with this? > "Don't change her actual age" WHEN? Doesn't change her age at some specific event on her worldline, or doesn't change what her age is "now" at the same moment that some distant observer like Bob reaches a particular age, say 40? If the first I agree that she has an actual age at any given event on her wrodline, but there ARE no different "views" of this since all frames agree on her proper age at any specific event on her worldline. If the latter I don't agree there is any physical basis for saying she has a unique "actual age" when Bob is 40, since relativity doesn't give any physical basis for a preferred definition of simultaneity. > > Your expertise in relativity is clear but you don't seem to understand > that all frames are NOT equal when it comes to representing actual physical > fact. You don't understand the fundamental notion in relativity that some > frames represent actual physical fact, but others represent only HOW OTHER > OBSERVERS VIEW those physical facts. > Not a physicist in the world would agree with you that there is a "fundamental notion in relativity that some frames represent actual physical facts", you appear to be completely confused about the difference between your own p-time views and mainstream relativity. In special relativity there can NEVER be a basis for considering one inertial frame more "correct" than any other. There are only two kinds of facts in relativity: 1. Facts about frame-independent matters like the proper time of an observer at a particular event on their worldline; all frames agree in their predictions about these, so they don't give any reason to prefer one frame over another. 2. Facts about frame-dependent matters like the coordinate velocity of an object at a particular event on its worldline, or the question of which point on worldline B is simultaneous with a particular point on worldline A; different frames disagree on these matters, and in relativity NO FRAME'S STATEMENTS ABOUT FRAME-DEPENDENT MATTERS ARE CONSIDERED MORE VALID THAN ANY OTHER FRAME'S. If you don't believe me that it's a basic principle of relativity that all frames are considered equally valid and none are preferred over others, here are some quotes from books written by physicists that I found on google books: "If one reference frame moves uniformly relative to another, then the two are equally good frames for observing nature, and two identical experiments performed in the two frames will give identical results." --From "Relativity for the Questioning Mind" by Daniel Styer, at http://books.google.com/books?id=Ebr7YhJcUd0C&lpg=PP1&pg=PA13 "The descriptions of the two sets of observers are equally real and equally valid, each within their own frame of reference. Since no preferred frame exists, there is no objective basis for ascribing any more reality to one description than the other." --From "Understanding Relativity: A Simplified Approach to Einstein's Theories" by Leo Sartori, at http://books.google.com/books?id=gV6kgxrZjL8C&lpg=PP1&pg=PA173 "If Albert and Betty clap nearly simultaneously, one observer may report that Albert clapped first, whereas a second observer, in motion with respect to the first, may report that Betty clapped first. It makes no sense to ask, 'Who really clapped first?' The question assumes that one viewpoint, one reference frame, is valid or 'real' and the other is not. But time is not absolute; it is a property of a particular frame of reference. Both observers' viewpoints are equally valid." --From "The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics" by Robert Oerter, at http://books.google.com/books?id=KAMlsa8jjt4C&lpg=PP1&pg=PT35 General relativity goes even further and says that the laws of GR hold equally well in *all* smooth coordinate systems, here is Einstein himself on the subject, from "Fundamental Considerations of the Postulate of Relativity": "there is nothing for it but to regard all imaginable systems of co-ordinates, on principle, as equally suitable for the description of nature" You can see this quote at http://books.google.com/books?id=QE-fMnpR8hAC&lpg=PR1&pg=PA39 > > This is quite obvious from the age example above, but it also applies to > the actual relationship BETWEEN TWINS in my examples. The relationship > between twins is exactly that, it is a RELATIONSHIP BETWEEN ONLY THOSE > TWINS. Of course you can come up with frames in which that relationship is > VIEWED differently, but that DOES NOT CHANGE the actual relationship > between the twins TO THEMSELVES which is what my theory is based on because > that is the ACTUAL REALITY of that physical situation. It is not just some > arbitrary VIEW of that reality, it is the REALITY ITSELF. My theory > recognizes the need to concentrate on actual physical fact as opposed to > VIEWS of physical facts. > > There is a simple CRITERION to determine whether we are talking about > PHYSICAL FACT or a VIEW of a physical fact. If the parties TO THE FACT > AGREE on their views of the fact then that agreed view probably represents > the actual physical fact. If they DO NOT agree then this disagreement > represents VIEWS of physical facts rather than the FACTS THEMSELVES. I can > perhaps think of a few explainable exceptions but this is the generally > applicable criterion. > > For example the different ages of the twins when they meet is AGREED by > both twins. Thus it is a physical fact. But the different ages of twins in > relative motion is NOT AGREED by both twins. Thus those are VIEWS OF FACTS, > RATHER THAN THE FACTS THEMSELVES. An absolutely crucial distinction in > understanding what relativity is all about. > Wait, if you say "the different ages of twins in relative motion" are not agreed and therefore are "views of facts, rather than facts", wouldn't that mean you have to acknowledge there is no "fact" about what age of twin B corresponds to what age of twin A when they are in relative motion, and therefore there is NOT any "fact" about a 1:1 correlation between their ages during the relative motion phase? > > If we can agree on this obvious point, and that we CAN establish a 1:1 > proper time correlation on this basis, then I look forward to considering > your example which you claim PROVES this 1:1 proper time correlation is not > transitive. I'm pretty sure it is transitive when properly understood but > am certainly willing to consider your 'proof'. > It's not that I claim it proves p-time simultaneity is not transitive; rather, I claim that if you start from the 3 premises I mentioned that I thought you would agree with, one of which says that p-time simultaneity IS transitive, you reach a contradiction where you find that two different ages of the same observer would have to be simultaneous in p-time. If you wanted to avoid that contradiction, you could discard ANY of the 3 premises, you wouldn't necessarily have to discard the premise of transitivity. Again, the 3 premises are: 1. If a pair of inertial observers are at rest relative to one another, then events (like clock readings) that are simultaneous in their comoving frame are also simultaneous in p-time 2. Any two events that happen at precisely the same position and time coordinate in a particular inertial frame must be simultaneous in p-time 3. p-time simultaneity is transitive So to start with, please just tell me if you do agree with all these premises, or if there is one or more you disagree with or aren't sure about and require clarification on. And if you disagree with or are not sure about #2, this is the "same point in spacetime" issue we had been discussing earlier before you stopped responding, so in this case please go back to my last post on the subject at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/dM2tcGYspfMJand respond to that. Jesse -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. 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