On Tuesday, January 28, 2025 at 7:28:08 AM UTC-7 Jesse Mazer wrote:
On Tue, Jan 28, 2025 at 12:52 AM Alan Grayson <[email protected]> wrote: On Monday, January 27, 2025 at 10:24:41 PM UTC-7 Alan Grayson wrote: On Monday, January 27, 2025 at 8:45:32 PM UTC-7 Jesse Mazer wrote: On Mon, Jan 27, 2025 at 8:24 PM Alan Grayson <[email protected]> wrote: On Monday, January 27, 2025 at 4:46:07 PM UTC-7 Alan Grayson wrote: On Monday, January 27, 2025 at 1:15:05 PM UTC-7 Jesse Mazer wrote: On Mon, Jan 27, 2025 at 3:01 PM Alan Grayson <[email protected]> wrote: On Monday, January 27, 2025 at 12:54:57 PM UTC-7 Jesse Mazer wrote: On Mon, Jan 27, 2025 at 8:32 AM Alan Grayson <[email protected]> wrote: On Sunday, January 26, 2025 at 9:02:01 PM UTC-7 Jesse Mazer wrote: On Sun, Jan 26, 2025 at 10:23 PM Alan Grayson <[email protected]> wrote: On Sunday, January 26, 2025 at 9:13:54 AM UTC-7 Jesse Mazer wrote: On Sun, Jan 26, 2025 at 1:54 AM Alan Grayson <[email protected]> wrote: On Saturday, January 25, 2025 at 11:25:53 PM UTC-7 Brent Meeker wrote: On 1/25/2025 10:13 PM, Alan Grayson wrote: On Saturday, January 25, 2025 at 9:06:18 PM UTC-7 Brent Meeker wrote: On 1/25/2025 6:34 PM, Alan Grayson wrote: On Saturday, January 25, 2025 at 6:47:22 PM UTC-7 Jesse Mazer wrote: On Sat, Jan 25, 2025 at 8:07 PM Alan Grayson <[email protected]> wrote: On Monday, December 9, 2024 at 2:01:28 PM UTC-7 Brent Meeker wrote: > > Nothing odd about dilation and contraction when you know its cause. > But what is odd is the fact that each frame sees the result > differently -- that the car fits in one frame, but not in the other -- > and you see nothing odd about that, that there's no objective reality > despite the symmetry. AG The facts are events in spacetime. There's an event F at which the front of the car is even with the exit of the garage and there's an event R at which the rear of the car is even with the entrance to the garage. If R is before F we say the car fitted in the garage. If R is after F we say the car did not fit. But if F and R are spacelike, then there is no fact of the matter about their time order. The time order will depend on the state of motion. Brent Jesse; it's the last two of Brent's sentences that I find ambiguous. What does he mean? What about them do you find ambiguous? He's just saying that if there's a spacelike separation between the events F and R (as there was in his numerical example), then you can find a frame where R happens after F (as is true in the car frame where the car doesn't fit), and another frame where F happens after R (as is true in the garage frame where the car does fit). *What does he mean by "But if F and R are spacelike, then there is no fact of the matter about their time order."? (What you wrote above?) * Brent writes > Yes. Just what Jesse wrote above. It means the two events were so close together in time and distant in space that something would have to travel faster than light to be at both of them. *More important I just realized that in the frame of car fitting, the events F and R aren't simultaneous, so how does one apply disagreement on simultaneity when one starts with two events which are NOT simultaneous? AG* Brent writes > That's why you should talk about events being spacelike...the relativistic analogue of simultaneous. *I'd like to do that. BUT if the Parking Paradox is allegedly solved by star**ting in the garage frame where the car fits, the pair of events which define fitting are not spacelike since they occur at different times! * You didn't read the definition of "spacelike" that I wrote above. You want everything fed to you in tiny bites of knowledge which you forget eight lines later, so the questions start all over again. Brent *I read it, but didn't like it. Big difference. Maybe you should stop trying to read my intentions. You may be smart, but reading my intentions is way above your pay grade. How could two events with the same time coordinate be referred as "so close together". Moreover, in all discussions of solutions to the paradox, events that are simultaneous in one frame, are shown not simultaneous in another frame. This being the case, the two events of the car fitting in garage frame are simply NOT simultaneous! Also, Jesse seems to be referring to different events than the ones you refer to. So there's a muddle IMO. As a teacher, your preferred method is to intimidate students. Grade now D+. AG * Why do you think I am referring to different events? I referred to the same events F and R that Brent did (F is the event of the front of the car coinciding with the garage exit, R is the event of the rear of the car coinciding with the garage entrance). If you don't like Brent's verbal explanation, I also gave you a mathematical definition of "spacelike separation" in two recent posts on the "Brent on Parking Paradox" thread at https://groups.google.com/g/everything-list/c/QgVdhXi3Hdc/m/KC2lIKyrDQAJ and https://groups.google.com/g/everything-list/c/QgVdhXi3Hdc/m/FF7TpbG-DQAJ -- "If you know the distance x and time interval t between the two points/events in the coordinates of any inertial frame, to say they are spacelike separated just means that x > ct (and an equivalent definition is that neither point is in the past or future light cone of the other one)". Since I explicitly referred to a time interval t between the two events, if you had paid attention to that you would have known not to say "the pair of events which define fitting are not spacelike since they occur at different times". Jesse *Yes, you defined spacelike separation, but without specific numbers for events, one cannot automatically claim two events are spacelike separated. Same goes for fitting in garage frame. I wasn't sure that all pairs of events in garage where car fits are spacelike separated. And sometimes I haven't caught up with your posts so I seem like I can't remember. And occasionally I do forget what someone posted. AG* I was responding to your statement "the pair of events which define fitting are not spacelike since they occur at different times", one doesn't need any specific coordinates to see that this statement is wrong because it suggests spacelike separated events can't occur at different times. If you hadn't read my definition or didn't remember it, fine. *I meant above that I needed all the coordinate values to determine if two events are spacelike separated; the time coordinates are not enough. AG * I gave you both x and t coordinates for F and R in my last message, see below. Or when you say "I meant above that I needed all the coordinate values", is "above" referring to your original comment "the pair of events which define fitting are not spacelike since they occur at different times", i.e. are you saying that when you wrote that, what you really meant was just that Brent hadn't provided the coordinates or R and F? Or would you acknowledge that when you wrote that you were misunderstanding the notion of spacelike separation? I was referring to my original comment. I didn't misunderstand what spacelike separation means. I don't recall what Brent posted. AG Then why did you make the definitive sounding statement "the pair of events which define fitting are NOT SPACELIKE since they occur at different times", rather than something more open-ended like "you haven't given the coordinates for the pair of events which define fitting, so although those events could be spacelike separated you haven't given enough info to demonstrate that"? *I was left with the last recollection / impression when you gave an example of simultaneous event which were spacelike separated.* So when you made the statement "the pair of events which define fitting are not spacelike since they occur at different times", you *were* thinking that spacelike separation required the events to be simultaneous, even if you corrected that error later? *Yes. A long long time ago, on a galaxy far far away, I knew the definition of spacelike separated. Later, in our discussions. temporarily confused it with timelike separated. But when you used a sufficient condition, that the events are simultaneous -- not the necessary condition, that all coordinates must be applied, the former sufficient condition temporarily stuck in my mind. Hence, my incorrect statement which I later corrected. AG * * Then when I considered it further, I realized I needed all the coordinates to make that assertion. As for Brent, as I recall, he didn't give any coordinates, just the claim as an approximation. FWIW, the car parking paradox reminds me of the S cat scenario, where S proved that a superposition of alive and dead when the box is closed, cannot imply the cat is alive and dead simultaneously. In a post here, I showed why a superposition cannot be interpreted that way because of the infinitely many bases for a system in Hilbert Space. In this problem, on relativity, although I accept that different frames can make different measurement due to relative motion,such as for E and B fields, the same car that can fit and not fit, albeit at different times, seems a bridge too far. If I am right, I can't say exactly what's wrong with relativity. It's a work in progress. AG* it seems like you're just coming up with an interpretation in retrospect to avoid acknowledging you were wrong, *I didn't use the word "wrong", but I clearly corrected my error. Why isn't that enough for you? AG* You seemed to be claiming you hadn't made an error at all in your original comment, when you said above "I was referring to my original comment. I didn't misunderstand what spacelike separation means". That was the post that bugged me because it seemed like you were trying to say you understood what spacelike meant all along, if you acknowledge you did misunderstand what spacelike separation meant but later corrected the error, that would be enough for me. *CORRECTION OF TYPOS IN CAPS:* *Now I can't recall what "original comment" I was referring to.* Just review that comment thread above, I had said: 'Or when you say "I meant above that I needed all the coordinate values", is "above" referring to your ORIGINAL COMMENT "the pair of events which define fitting are not spacelike since they occur at different times" ...?' And you replied: 'I was referring to my original comment. I didn't misunderstand what spacelike separation means.' So, I assume the "original comment" was the one I had referred to where you said "the pair of events which define fitting are not spacelike since they occur at different times" * I can say that all along I knew WHAT **s**pacelike separated means, even if IT was temporarily subliminal.* What was your understanding of what it meant? Your comment about timelike separation below might indicate you still have some confusion about it, see my reply. * In any event, you can and should be assured, that I am not trying to deceive you or anyone, My time is too valuable to do that. Nor would I, even if I had infinite time. AG * rather than accurately remembering/describing what you meant at the time. (In general you never seem to acknowledge you were wrong about any significant assertion you make concerning relativity, like with your earlier claim the LT sometimes give different coordinates than what's actually measured in a given frame, which you seem to have just dropped rather than acknowledging any flaw in your argument) *On that point, I am still not convinced the LT does what you claim. I was planning to come back to that issue. I have to review why I thought that. AG * *I recall my doubts about your interpretation of the LT. It has to do with length contraction and time dilation. The LT gives a result which isn't reproduced in the target frame of the transformation. IOW, an observer in the target frame doesn't notice (or measure) length contraction and time dilation. AG* But if you use the LT to transform into a "target frame" where an object has a velocity of zero (like the rod in your earlier example), the LT doesn't *predict* any time dilation or length contraction of the object in that frame, that's what I told you repeatedly *We agree. If the relative velocity is zero, the LT doesn't predict time dilation or length contraction, but it does for velocity not zero. AG* When you say "the relative velocity", the velocity of what relative to what? When I said "a 'target frame' where an object has a velocity of zero" I was referring to the velocity of the object in the coordinates of the target frame, is that the same velocity you're referring to when you talk about a "relative velocity" that can be zero or nonzero? and then showed you explicitly with the numerical example involving the rod at https://groups.google.com/g/everything-list/c/ykkIYDL3mTg/m/giZVF9PpDQAJ which you didn't reply to. You just keep repeating the same false claim about what the LT predicts without addressing the counterarguments or giving any calculations or argument of your own as to why *you* imagine the LT predicts time dilation or length contraction of an object in the object's own frame (apart from some sketchy argument you tried to make involving GPS satellites which I addressed at https://groups.google.com/g/everything-list/c/ykkIYDL3mTg/m/ximYgKzKDAAJ ) *In reply to your last question above; since you and others claim the LT gives the results of what the target frame will actually measure, as calculated from the source frame using the LT, I must include length contraction and time dilation in those MEASUREMENTS. Numerical examples are unnecesary in this case. AG* *When the relative velocity is not zero, the LT "predicts" time dilation and length contraction, at least that's what every book or teacher of relativity claims. But the target frame never measures this result,* Again, if "relative velocity" means the velocity of the object in the coordinates of the target frame, then if the object has a nonzero velocity in the target frame (say a target frame where an object like a clock or rod is moving at 0.8c), of course observers who are using *that* frame can measure the length contraction/time dilation of the object, why would you think otherwise? *Because that's what every text and teacher of relativity say! An observer in a moving frame as measured from a rest frame, does not perceive lengths and times changed, whereas the observer in the rest frame using the LT does observe this. There are formulas in SR to calculate these observations from the pov of the frame doing the measuring. AG* If on the other hand you are specifically imagining a "target frame" where the object has zero coordinate velocity, i.e. the object's own frame (as you were imagining in the previous discussion), then you are apparently using "relative velocity" in a different way than I was, or maybe just conflating different meanings without realizing what you're doing. *I use v as in the gamma function. Do you know that that v is? The LT is applied in a relative rest frame, observing a moving frame, and the moving frame is what I call the target frame. In that frame, an observer cannot measure or be aware of the time dilation and length contraction as measured from the frame doing the measuring, which I call the source frame. You have a different opinion that every text and teacher of relativity has. AG * It would really help once again if you would refer to a NUMERICAL EXAMPLE and then explain how your terms apply to it, for example if we are talking about the rod and the Earth with the numbers I filled in as you requested in https://groups.google.com/g/everything-list/c/ykkIYDL3mTg/m/giZVF9PpDQAJ , would the original "source" frame be the frame where the Earth has v=0 and the rod has v=0.8c, and the "target frame" would be the rod's frame where the rod has v'=0? If so, when you say "When the relative velocity is not zero", which of those velocities are you talking about? Then after filling in meanings for these terms, please tell me if you still claim the LT predicts length contraction of the rod in the "target frame" here. * so it must be that for these specific results (not all measurements) the LT just tells us how some phenomena APPEAR from the pov of the source frame (the frame from which the LT is applied). OTOH, there's data contradicting this conclusion; namely the fact that GPS clocks are corrected for what SR and GR predict. So I am confused as to the reality of the situation. AG* The GPS thing is just an irrelevant distraction, again see my post at https://groups.google.com/g/everything-list/c/ykkIYDL3mTg/m/ximYgKzKDAAJ where I explained why the coordinate system used in GPS calculations CANNOT be an inertial one since it covers a non-infinitesimal region of curved spacetime, so the LT are not used in any transformations from/into that coordinate system (and I'm not even sure if there's a need for multiple coordinate systems in GPS, they might just be comparing coordinate time in a single Earth-centered coordinate system to 'proper time' of the clocks at various locations, which is coordinate-independent). On Tue, Jan 28, 2025 at 1:14 AM Alan Grayson <[email protected]> wrote: Jesse; apparently you need me to expressly admit I am wrong on something, so here it is; I was wrong to write "Timelike Separated". Timelike events, by definition, are NOT separated. They're causally connected. AG Your correction here is based on a misconception, physicists do in fact speak of events being "timelike separated", the "separation" has nothing to do with whether they are causally connected or not, it's only referring to the fact of the events being at different locations in spacetime so there is a spacetime "separation" between them, in the same sense that there's a spatial separation between two points at different locations on a 2D Euclidean plane. 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/412954ad-ec04-4cd0-a9d6-dde373a8992dn%40googlegroups.com.
