On Thursday, January 30, 2025 at 6:43:18 PM UTC-7 Alan Grayson wrote:
On Thursday, January 30, 2025 at 6:20:35 PM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 5:38 PM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 3:10:56 PM UTC-7 Alan Grayson wrote: On Thursday, January 30, 2025 at 2:47:05 PM UTC-7 Alan Grayson wrote: On Thursday, January 30, 2025 at 2:21:24 PM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 3:33 PM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 11:55:54 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 1:35 PM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 11:16:52 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 12:47 PM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 10:28:05 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 11:59 AM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 9:38:19 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 11:05 AM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 7:59:32 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 9:16 AM Alan Grayson <[email protected]> wrote: On Thursday, January 30, 2025 at 6:48:21 AM UTC-7 Jesse Mazer wrote: On Thu, Jan 30, 2025 at 12:51 AM Alan Grayson <[email protected]> wrote: On Wednesday, January 29, 2025 at 6:52:47 PM UTC-7 Brent Meeker wrote: Whooo! Hoooo! Brent Another fool who doesn't get it? Another fool who can't think out of the box? Jesse claims that the LT preserves what it predicts for local events AND, according to his lights, using the LT it can be shown that lengths are EXPANDED. OTOH, it's universally predicted that lengths are CONTRACTED under the LT. No, it's universally predicted that length in a frame where an object is *in motion* (coordinate-motion using the term I coined in my previous comment, to distinguish from your alternate non-standard usage which I called 'designated-motion') is contracted relative to that object's "proper length" in the frame where the object is *at rest* (coordinate-rest), the L in the length contraction equation is always stated to be the proper length. So, if you use the LT to transform FROM the frame where the object is in motion (coordinate-motion) TO the frame where the object is at rest (coordinate-rest), treating the coordinate-motion frame as what you call the "source frame" and the coordinate-rest frame as what you call the "target frame" for the LT, in this case the length should be contracted in the source frame and larger in the target frame, *So, after our exhausting discussion, you still have no clue what I meant by source and target frames.* So "source frame" doesn't just mean the frame whose information we are given to start with (i.e. given coordinates values of length/velocity etc. for the objects we are analyzing) before applying the Lorentz transform to predict coordinates in the "target frame", i.e. it's not just that source=unprimed and target=primed in your description of the LT as giving us x-->x' and t-->t'? If that's not what you meant by "source" and "target", fine, but that's just a linguistic matter, you can delete all references to "source frame" and "target frame" in my comment above and change it to "starting frame" and "predicted frame" or whatever terminology you want to use for this; it changes nothing about the substantive point I was making. * I never said anything about a LT from a frame where the object is in motion. I alway stated I was transforming FROM a rest frame to a moving frame.* But you made a big deal of the fact that a ruler isn't measured as contracted in its own frame (and a clock isn't measured as running slow in its own frame), claiming this shows a divergence between what is PREDICTED by the LT and what is MEASURED. If you aren't actually using the LT to make PREDICTIONS about what should be true in the ruler's own frame (the frame where the ruler is in a state of coordinate-rest), i.e. using the ruler's frame as what I called the 'predicted frame', then how can this example be used to show a divergence between LT predictions vs. measurements? So you have no response to my comment above? If not, I can only conclude that your earlier emphasis on the point about what was measured in the ruler's own frame was completely incoherent since you don't actually want to use the LT to predict anything about the ruler's own frame. * Is there any textbook which makes your claim? I've never seen it, or heard about it, or hinted about it, and for this reason I ignored your mathematics. AG* I don't know that any textbook would go to the trouble of saying something like "the length of an object may be larger in the primed frame than the unprimed frame when you use the Lorentz transform to go from unprimed to primed", but I promise you that no textbook will say anything like "applying the Lorentz transformation to go from unprimed to primed always results in the length of any object being shorter in the primed frame than the unprimed frame". The only real reason to say something like the former would be to dispel a misconception like the latter, but I doubt this is a common misconception, I've talked to plenty of people who are confused about relativity on various forums over the years and never come across this idea of yours. If I looked around a bit I could probably find numerical examples in textbooks where just looking at the coordinates they give for some object in the unprimed vs. primed frame (or whatever notation they use to distinguish coordinates in the 'starting frame' from the 'predicted frame'), you could verify that the object was longer in the primed than it was in the unprimed. And no response to this? Are you secretly afraid that I would actually be able to find textbook examples like this where the length of some object is greater in the primed frame than the unprimed frame? *No. Go for it. I'm sure you'll find what I am about to write. While I agree that either frame can be considered moving since inertial motion is relative, the LT is NOT applied from the frame considered moving, and predicts length contraction in the moving frame, from the pov of the rest frame.* Most textbooks do not designate one frame as "moving" and one as "at rest" in the first place (they use only the terminology I called 'coordinate motion', not 'designated motion'--let me know if you have any trouble understanding this distinction), they just use labels like primed and unprimed for the two frames, and give both x --> x' equations that tell you coordinates in the primed frame if you start with coordinates in the unprimed, along with the corresponding x' --> x equations that tell you coordinates in the unprimed frame if you start with the primed. So while a typical textbook won't give an example where length is said to be greater in "the moving frame" since they don't use that terminology in the first place, they definitely would give examples where length is greater in the primed frame than in the unprimed frame, presumably including cases where this is accompanied by a spacetime diagram where the unprimed frame is the one with the vertical t axis and the primed frame is the one with the slanted t' axis (i.e. showing the spatial origin of the primed frame as moving in the coordinates of the unprimed frame). Do you disagree with any of the above? If so I can look for examples, both showing that typical discussions of the LT don't include any phrase like "moving frame" and that they give both x --> x' equations and x' --> x equations side by side, and also examples where the length of some object is greater in the primed frame and there's a spacetime diagram like what I described. Jesse *Frankly it's too tedious to read.* Hah, I guess claiming that a single short paragraph is "too tedious to read" is a good way to rationalize not addressing the simple question of whether I should look for textbook examples to back up my point that "typical discussions of the LT don't include any phrase like 'moving frame' and that they give both x --> x' equations and x' --> x equations side by side, and also examples where the length of some object is greater in the primed frame and there's a spacetime diagram like what I described" [where what I described was a diagram showing the the primed frame as moving relative to the coordinates of the unprimed frame]. I think you are desperate to avoid answering whether I should give textbook examples like this because saying "yes, go look for them" would leave open the scary possibility that I would find them and thus show a VOICE OF AUTHORITY who contradicts you (since you were unwilling to judge my own numerical example for yourself, citing a supposed disagreement with textbooks), and saying "no, even if textbooks do say that it wouldn't contradict me" would force you to acknowledge points like "textbook authors don't bother designating either frame as 'moving'" and "the length of an object can be greater in the primed frame even when we illustrate the primed frame as moving". So it's kind of a double bind for you, no wonder you squirm so much when I press this question. *I'm not desparate. Not in the slightest.* Then why do you keep avoiding answering my question of whether I should look for textbook examples of what I say above, or if you say that such examples would not actually be in conflict with your understanding of SR? Still waiting on the answer to my question about whether or not you want textbook examples of what I said above! As long as you keep responding to my posts I am never going to just forget about this, it's illustrative of how evasive you are on any real attempt to pin down/test your claims. *If you can't read plain English, you'll have to wait till hell freezes over. I already told you to do it! And stop accusing me of being evasive if you can't read plain English. BTW, if you want both frames in relative motion, then they will have the same V in the gamma factor and the LT in these cases will give the same length contraction in each frame. In neither frame do the lengths get expanded. You're making an error to conclude otherwise. AG * See my reply to this comment immediately above. *I don't have any interest in feeding your obsession. I've already answered your comment. Read and learn or STFU. AG* *Further, if two frames are in relative motion, and objects in those frames are not at rest WITHIN their respect frames, then in order to get the relative motion of those objects with each other, we must add the velocities of their frames relativistically, to their internal velocities within each frame, and the same results as described above will apply. AG * I wasn't referring to a problem where we consider multiple objects in relative motion, just a single object (the rod) being assigned coordinates by two different frames in relative motion. *I don't think it matters. I'm not certain. I have to think about this scenario further. But I'm pretty sure you'll get length contraction in both frames. AG * *FYI, since every frame has its own set of clocks, you have no choice but to assign different spacetime coordinates for the same object in different frames. AG * *Finally, what I mean by motion or rest of an object WITHIN a frame is whether or not its spacetime COORDINATES are changing within that frame. AG* Assuming you mean that "motion" refers to the position coordinate changing at different values of the time coordinate, and "rest" means the position coordinate is unchanging (and that you aren't just talking about any case where the object has multiple different spacetime coordinates, since even an object at rest in a given frame will have a worldline that passes through different values of the time coordinate), then I agree, that is also what I mean when I talk about the coordinate motion/rest of an object in a given frame. *Yes. AG * Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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