I'm literally crying having only you to read... why ???? Le mer. 1 janv. 2025, 01:55, Alan Grayson <[email protected]> a écrit :
> > > On Tuesday, December 31, 2024 at 6:44:17 PM UTC-7 Alan Grayson wrote: > > On Tuesday, December 31, 2024 at 3:31:33 PM UTC-7 Jesse Mazer wrote: > > On Tue, Dec 31, 2024 at 12:57 AM Alan Grayson <[email protected]> wrote: > > On Monday, December 30, 2024 at 1:03:20 PM UTC-7 Jesse Mazer wrote: > > On Sat, Dec 28, 2024 at 1:51 AM Alan Grayson <[email protected]> wrote: > > On Friday, December 27, 2024 at 10:05:51 PM UTC-7 Jesse Mazer wrote: > > On Friday, December 27, 2024, Alan Grayson <[email protected]> wrote: > > On Friday, December 27, 2024 at 6:48:56 PM UTC-7 Jesse Mazer wrote: > > On Fri, Dec 27, 2024 at 4:58 PM Alan Grayson <[email protected]> wrote: > > On Friday, December 27, 2024 at 9:16:39 AM UTC-7 Jesse Mazer wrote: > > On Friday, December 27, 2024, Alan Grayson <[email protected]> wrote: > > On Thursday, December 26, 2024 at 9:39:41 PM UTC-7 Jesse Mazer wrote: > > On Thursday, December 26, 2024, Alan Grayson <[email protected]> wrote: > > On Thursday, December 26, 2024 at 2:56:04 PM UTC-7 Jesse Mazer wrote: > > On Thursday, December 26, 2024, Alan Grayson <[email protected]> wrote: > > On Thursday, December 26, 2024 at 3:26:41 AM UTC-7 Alan Grayson wrote: > > On Thursday, December 26, 2024 at 12:12:43 AM UTC-7 Jesse Mazer wrote: > > On Wednesday, December 25, 2024, Alan Grayson <[email protected]> wrote: > > On Wednesday, December 25, 2024 at 5:14:21 PM UTC-7 Jesse Mazer > wrote: > > On Wednesday, December 25, 2024, Alan Grayson <[email protected]> wrote: > > *Why do refer to transformations that don't preserve time ordering? IIUC, > such transformations only occur when assuming motion faster than light. * > > > No, that’s not correct. Motion faster than light would be required if > there was a claim of causal influence between events with a spacelike > separation; but there’s no such claim here; in both Brent’s example and > mine, if we consider the event A of the back of the car passing the front > of the garage and the event B of the front of the car reaching the back of > the garage, there is a spacelike separation between those events, and > neither event has a causal influence on the other. > > > *I'm asking a general question. Why do you refer to failure of time > ordering? What was the point you thought you were making? AG* > > > Because as you previously agreed, the question of whether the car fits > reduces to the question of whether the event A = back of car passes front > of garage happens before, after, or simultaneously with the event B = front > of car reaches back of garage. Since these events have a spacelike > separation in both Brent’s and my numerical examples, in relativity > different frames can disagree on their order, that’s the whole reason we > say frames disagree on whether the car fits. > > > *As I recall, you were writing about the failure of TIME ordering, and > this would mean violation of causality, not what we're discussing on this > thread. AG * > > > You either recall incorrectly or misunderstood at the time, but > disagreement about the time ordering of two events A and B does NOT imply > any violation of causality; it just implies the spacetime interval between > A and B is spacelike, but normally this is combined with the assumption > that there are no causal influences between events with a spacelike > separation. > > Do you understand what the spacetime interval is? If I gave you the > difference in time coordinates T = tB - tA for the two events along with > the difference in position coordinates X = xB - xA, would you know how to > calculate the spacetime interval and judge whether it is timelike, > spacelike or lightlike? > > > > > *But if so, you're not within the postulates of SR, which is what this > discussion is about. So what point do you think you're making? AG* > > *Re: paradox: Assume there's an observer located in the garage. This > observer is in the garage frame. This observer sees the car easily fit in > the garage. Imagine another observer riding in the car. This observer is in > the car frame and observes being in the garage but never fitting in the > garage. What are the observations when the two observers pass each other, > in juxtaposed positions?* > > > I’ve asked this before, but by “see” do you mean in terms of when the > light from different events reaches their eyes, or something more abstract > like a computer animation they create of when events occur in their frame, > once they have measured the time and position coordinates of all events > using local readings on rulers and clocks at rest relative to themselves? > > > *Nothing more abstract. One observer sees the car sticking outside the > back of garage, the other sees it inside, when both are juxtaposed. * > > > You didn’t quite answer my question—you are just talking about what they > see with their eyes, right? > > > *I used the word "see". Is this not clear enough? AG* > > > > Not entirely, since it’s routine in relativity problems to use words > differently from everyday speech, for example in ordinary speech when you > talk about “observing” some event we are usually talking about visual > sight, but in relativity talking about what someone “observes” always > refers to how things happen in the coordinates of their frame, not to > visual sight. > > > > If so, there is no disagreement between observers passing through the same > point in spacetime about whether the car fits in a visual sense. > > > *Really? So if the garage is 10' long in rest frame, * > > > Do you mean 10’ in the garage’s rest frame? As I said before, just using > “rest frame” without specifying a particular object is unclear. > > > *I appreciate your thoroughness but here I just left out "its", as in "... > 10' long in its rest frame", and I think you should have easily inferred my > meaning. AG * > > > Given that you had recently objected to my use of the phrases “car’s rest > frame” and “garage’s rest frame” and hadn’t acknowledged my response about > how this is a standard way of speaking in relativity, I didn’t think it was > safe to assume that. It would help if you would acknowledge when something > I’ve said has led you to revise a view, even on something minor like > terminology, otherwise I don’t know when a given point needs to be > re-litigated. The recent discussion about how we can talk about events that > are spacelike separated without implying any faster than light causal > influence is another example; do I need to keep arguing that or does the > fact that you dropped that discussion mean you concede the point? > > > Could you please address my comment above so I know if we’re in > disagreement on these points? > > > *I don't object to your terminology. As I stated, if I had included "its" > in my statement, there would have been no ambiguity about terminology. And > as far as I can recall, I never objected to the use of your quoted > statements about rest frames. AG* > > > You objected multiple times in the last few days to my terminology where > "car's rest frame" refers to the frame where the car is at rest (i.e. it > has position coordinates that don't change with time) and the garage is > moving (so the garage is Lorentz-contracted in the car's rest frame), while > "garage's rest frame" symmetrically refers to the frame where the garage is > at rest and the car is moving (so the car is Lorentz-contracted in the > garage's rest frame). For example in the post at > https://groups.google.com/g/everything-list/c/vcrAzg4HSSc/m/XZrHB-IdAwAJ > I said: > > "In garage rest frame, garage has length 20 and car has length 25/1.25 = > 20. In the car rest frame, the garage has length 20/1.25 = 16 and the car > has length 25.” > > And you responded: > > "OK, assuming car is moving, but I wouldn't call that "in the car rest > frame" since you have garage length as contracted. AG" > > Then at > https://groups.google.com/g/everything-list/c/vcrAzg4HSSc/m/mFVsDGUtAwAJ > you responded by imagining “the rest frame” referred to some imaginary > initial conditions that were never part of the problem I described, > conditions where both the car and garage were at rest relative to each > other: > > “IMO, the rest frame is defined as the initial conditions in this problem > when the car isn't moving, and is longer than the garage. When the car is > moving, we have been calling the other two frames, simply the car frame and > the garage frame.” > > Then at > https://groups.google.com/g/everything-list/c/vcrAzg4HSSc/m/1AWAOHA4AwAJ > you again objected to the standard terminology in which “car’s rest frame” > just refers to the frame where the car is at rest in the sense of having a > fixed position coordinate, even if it is moving relative to the garage: > > “No one uses "rest frame" when describing the results in either frame when > the car is moving. You introduced that terminology recently, claiming it is > standard. AG” > > Then just yesterday at > https://groups.google.com/g/everything-list/c/vcrAzg4HSSc/m/O12FCXvmAwAJ > you again objected to this standard terminology: > > “What could be the meaning of "rest frame" associated with "garage"? I > don't have a clue. Shall we consult Webster's Dictionary?” > > > *I was being sarcastic. Not to be taken at face value. AG * > > > The Webster’s dictionary comment was sarcastic, but ‘What could be the > meaning of “rest frame” associated with “garage”?’ didn’t seem to be a > sarcastic question, especially since it echoed your confusion in the other > comments I quoted. > > > > > > So it would be helpful to know if you're willing to accept that my use of > "car's rest frame" and "garage's rest frame" is the standard way of talking > among physicists, or if you still object. > > > *Instead of haggling over this issue, and possibly taking some of my > comments out of context, we agree that when using the LT from either frame, > the car or garage length in that frame has not changed from its initial > condition, 12' or 10', respectively.* > > > I don’t know what you mean by “its initial condition.” Do you just mean > its length its own rest frame? Or do you think it’s essential to the > problem that we imagine some initial condition where both are at rest > relative to each other, and then the car is accelerated? If so I would > definitely object to that, the term “car’s rest frame” has no such > implications, it would have exactly the same meaning if we assumed the car > and garage have had a fixed relative velocity for an infinite time prior to > the car passing through the garage. > > > * At that point it was agreed that car cannot fit in garage because of > length considerations. Consequently, following that agreement, I calculated > using the LT, that the car fits or not -- fits in garage frame, doesn't fit > in **car frame -- based solely on length considerations. **If the car > can't fit from its frame when v = 0, it can't fit for any v > 0, since the > garage gets even shorter. I think you and Brent believe it can't fit in car > frame due to disagreement about simultaneity, whereas I use length > contraction to reach the same conclusion. * > > > I didn’t use any word like “because” or talk about the best conceptual > explanation, I just said that the question of whether the car fits in some > frame is *equivalent* to the question of the order of the events A and B in > that frame. It is of course also equivalent to the question of whether the > length of the car is shorter, greater, or equal to the length of the garage > in that frame. Equivalent here just means logical equivalence, ie the truth > value of the statement “the car doesn’t fit in this frame” is guaranteed to > be the same as the truth-value of “B happens before A in this frame” and > *also* the same as the truth-value of “the car is longer than the garage in > this frame”; it’s impossible in either relativity or classical physics for > one of these statements to be true while another one is false, or vice > versa. Do you agree they are equivalent in that sense? > > > Could you address my question here about whether you agree that, given the > clarification that I am talking about logical equivalence in the sense I > discussed above, the question of whether the car fits is completely > equivalent to question of the order of the events A="back of car passes > front of garage" and B="front of car reaches back of garage"? > > > *I apologize for being so dumb, but whereas I'm comfortable using relative > lengths of car and garage to determine fitting or not, I don't really > understand that the reversal of time order, of event B preceding event A, > is equivalent to car not fitting in garage.* > > > OK, but are you making an effort to understand? In general do you > actually want to understand what relativity says about these matters, or do > you just want to score a rhetorical "win" for your own arguments? If you're > interested in understanding rather than winning then you can't just stick > by whatever way of thinking is most comfortable for you, or most conducive > to your argument. > > > *All I want is to make some rhetorical points. What else could possibly > matter? And NO, I am definitely NOT making any effort to understand. Why > should I? After all, I am just a troll and this is what trolls do. AG* > > *This problem arose as an apparent paradox because two frames give > diametrically opposite conclusions in a particular situation. My result > using length contraction showed the same opposite conclusions. So, in an > effort to resolve the paradox, I consulted many sources, and it seems they > all reached the same conclusion as I did, but through different routes. > That's why Brent posted there's no objective result. Moreover, the videos > do not prove, despite what some of them claim, that the car fits in the > garage from the pov of the car frame. If the foregoing is correct, I don't > believe these various path resolve the paradox. Rather, they're just > re-stating it under different conditions. Correct me if I am wrong. AG * > > > *Concerning those videos, two which were reviewed on this MB, one by Brent > and one by you, they falsely claim to show that from the car frame, the car > really does fit in the garage.* > > > I watched the video and I never saw him make the false claim that the pole > (which takes the place of a car in that video) fits in the garage in the > pole's own frame. If you disagree, can you point to a time index in the > video where he says this, or a time index in the first video where he says > the car fits in the garage in the car's frame? > > > * This is what one expect to show if the disagreement of the frames is the > cause of the paradox, but apparently it isn't, and the disagreement about > simultaneity alone is sufficient to resolve the paradox. This is what I am > trying now to understand. AG* > > > *And we agree it can fit from the pov of the garage frame, since the car's > length contracts. So what are we arguing about is this; does the > disagreement about fit constitute an objective fact and thus a paradox? AG* > > > > *What could be the meaning of "rest frame" associated with "garage"? I > don't have a clue. Shall we consult Webster's Dictionary? As for my > numerical example, I suggest you do the arithmetic, and if you don't get my > prediction, I will concede the argument. AG * > > > *Yeah, use 12' and 10' for the lengths of the car and garage respectively > when at rest (which means no motion of car). Then using the LT determine > how fast the car must be moving to contract the car's rest length to > .000001' from the pov of the garage frame. Then place the car in the center > of garage, and recognize how easily it fits (by any method of your choice). > Now, from the pov of the car frame, and the speed of the car previously > calculated, calculate the contracted length of the garage, and place the > car at the center of the garage. Does the front of the car extend beyond > the rear of the garage, whereas previously it did not? No need to worry > about what "seeing" means in this comparison.* > > > It’s critical that you specify if by “see” you are talking about what > light signals are reaching their eyes at that point, or if you are talking > about the coordinates they assign to front and back of car and garage at > simultaneous moments in their own frames; the answer will be completely > different depending on what you mean. If you are just talking about visual > seeing, I can do that, but just be aware that most of the usual textbook > equations of relativity including length contraction are *not* intended to > address visual appearances. > > Jesse > > > *Let's forget about "seeing" in these scenarios since I agree it > unnecessarily complicates the analyses. I will go back to your post with my > question marks and try to resolve as much as possible. However, I don't > think we can resolve anything in these discussions, for this reasonaaaaa. I > proposed a scenario where from the garage frame the car fits with ease, > whereas from the car frame it fails to fit and in fact easily extends > beyond the rear end of garage. I conjecture that your response will be that > different frames give different measurements, so there's nothing > particularly noteworthy about this situation, and it certainly doesn't > amount to a paradox. This result concerning fitting or not can easily be > concluded without any arithmetic. Is my conjecture about your response > correct? AG* > > > Sure, if we are talking about local measurements in each frame rather than > visual seeing, I see no paradox in the fact that they disagree on the time > order of the spacelike separated events A=“back of car passes front of > garage” and B=“front of car passes back of garage” and therefore disagree > on fitting. > > > *In the example I posted, the frames disagree on fitting, and AFAICT > there's nothing to suggest a disagreement on the time order of events. In > fact, what you claim doesn't seem physically impossible in either frame. > Can you show me EXACTLY how you reached this conclusion, without referring > to one of your other posts? It seems that you pulled that conclusion out of > the preverbial hat. AG* > > > You can easily just look at the times of events in either Brent’s > numerical example or mine to see the two frames disagree on the order of > the two events I keep bringing up, A=“back of car passes front of garage” > and B=“front of car reaches back of garage”. In my example, A and B happen > simultaneously at t = 0 in the garage frame, while in the car frame B > happens at t’ = -15, which is before the time when A happens in the car > frame at t’ = 0. > > And isn’t it obvious that if some frame says that B happens before A, > meaning the front of the car reaches the back of the garage before the back > of the car has yet entered the front of the garage, then that’s equivalent > to the statement that in that frame the car doesn’t fit, whereas in a frame > where A happens before B or simultaneously with it, the car does fit in > that frame? > > This is one of the most basic aspects of analyzing the problem that we’ve > talked about over and over, and you’ve previously agreed to, I don’t > understand why there’s be any confusion here. > > > *Your memory is in error. I never agreed to that. * > > > Yes you did! See our discussion at > https://groups.google.com/g/everything-list/c/gbOE5B-7a6g/m/B15IG50SAQAJ > where I was responding to your previous comment at "I haven't thought about > ordering", and I said the following: > > "You haven't thought about it?? Disagreement about the ordering of these > two specific events (due to differences in simultaneity) is what Brent and > I have both been emphasizing as the fundamental resolution of the paradox, > have you not even understood that this is central to what we are arguing, > and considered in an open-minded way whether or not it makes sense? > > > *As I think I posted, I don't understand the argument that disagreement > about simultaneity resolves the paradox. This is surely the standard > alleged solution, but using the LT and length contraction, I seem to get a > paradox if we assume disagreement about fitting is the cause of the > paradox. You claim time-ordering shows the car can't fit. This is my > conclusion using length contraction, whiich seems simpler. So, our > disagreement of the resolution apparently has nothing to do with whether > the car fits from its frame, since we're in agreement that it does not. AG * > > > No, I wasn’t talking about the best way to understand or explain why the > car doesn’t fit, I was just talking about logical equivalence. But as I > have said elsewhere, an analysis of relativity of simultaneity is needed > conceptually if you want to answer the *separate* question “given that > different frames disagree about whether the car fits, how can we avoid the > conclusion that they must disagree in their predictions about local > physical facts?” > > > If you don't see why the ordering of these two events is considered > equivalent to the question of fitting, consider a simpler classical > scenario where everyone agrees about simultaneity and length. A car is > passing through a covered bridge, and we are observing it in a side view > with the car driving from left to right, so the front of the car begins to > disappear from view under the bridge as soon as it passes the left end of > the bridge, and begins to re-emerge into view as soon as it passes the > right end of the bridge. Would you agree in *this* scenario, if the back of > the car disappears from view on the left end before the front of the car > emerges into view on the right end, that means for some time the car was > fully hidden under the covered bridge, meaning it "fit" inside? And would > you likewise agree that if the front of the car starts to emerge from view > on the right end before the back of the car has disappeared from view on > the left end (say it's a very short covered bridge and the car is a stretch > limo), so there was never a time when the car was fully obscured from view > by the covered bridge, that means the car did *not* fit inside?" > > > > *I'm not sure. I have to think about this some more. Why can't we just > stick to lengths? AG * > > > You could at least ask some questions about whatever is puzzling you > rather than just avoiding the subject by switching to exclusive talk about > length. Remember, this is a purely classical scenario, no tricky issues of > length contraction or simultaneity. Classically, if we have an 18-foot long > limousine driving through a covered bridge that's only 6 feet wide, and > you're watching from the side with the limousine moving left to right, are > you genuinely unsure about whether you'll see the front of the limousine > poke out of the right side of the covered bridge BEFORE or AFTER the back > of the limousine first disappears behind the left side of the covered > bridge? If the front didn't poke out from behind the right side of the > covered bridge until AFTER the back disappeared behind the left side, that > would mean there was some period of time where the 18-foot limousine was > wholly obscured from view behind the 6-foot covered bridge, which doesn't > make a lot of sense geometrically. > > 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 [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/70c747d3-517b-416d-9bbe-353f77cadacdn%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/70c747d3-517b-416d-9bbe-353f77cadacdn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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