You seem to suggest that for two spacelike separated events A and B, it A causes B, then under a LT, the image of B is the cause of the image of A in the transformed frame. I tend not to believe this, OR, maybe that's not what was implied. In any event, this was the cause of my question and I don't believe your plots will answer this question. AG
On Monday, January 13, 2025 at 12:39:18 AM UTC-7 Alan Grayson wrote: > On Sunday, January 12, 2025 at 11:45:43 PM UTC-7 Alan Grayson wrote: > > On Sunday, January 12, 2025 at 10:03:22 PM UTC-7 Brent Meeker wrote: > > > > > On 1/12/2025 5:24 PM, Alan Grayson wrote: > > > > On Sunday, January 12, 2025 at 6:00:33 PM UTC-7 Alan Grayson wrote: > > On Sunday, January 12, 2025 at 5:52:42 PM UTC-7 Brent Meeker wrote: > > > > > On 1/12/2025 8:38 AM, Alan Grayson wrote: > > > > On Saturday, January 11, 2025 at 8:48:21 PM UTC-7 Brent Meeker wrote: > > > > > On 1/10/2025 11:29 AM, John Clark wrote: > > On Fri, Jan 10, 2025 at 2:15 PM Alan Grayson <[email protected]> wrote: > > *>>>If I believe in SR, then I can use length contraction to establish the > car won't fit in garage in car's frame.* > > > > *>> That depends entirely on what you mean by "the car won't fit in the > garage". In the above I've told you exactly what I mean by the term. What > do you mean? * > > > *> What do I mean; what any sane person would mean; that the car's length > is fixed from the pov of the car's frame when car is moving, but the > garage's length is shortened from an initial condition where it starts out > shorter. AG * > > > *That's all very nice but that's not what I asked. What exactly do you > mean by "the car won't fit in the garage" if it's not "the front of the car > is fully within the garage while SIMULTANEOUSLY the back of the car is also > fully within the garage"?* > > I think you meant "the car *will *fit in the garage." > > But there's been so much unproductive back and forth on this thread, which > I thought I had put to bed, that I'm going to try again and to make > everything even more graphic and explicit. Here's the spacetime diagram in > the reference frame of the garage (which we would ordinarily refer to a > stationary): > > > Here we see that the car, whose proper length is 10', traveling at 0.8c is > Lorentz contracted to a little over 6'. We start with the entrance open > and the exit closed and we see that we can close the entrance door before > we have to open the exit door because there is a brief period in which the > car is fully within the 8' garage, the red trapezoid. If the distances are > in feet then the times are in nano-seconds. So the exit door can stay > closed for about 2.5 nano-seconds after the entrance door closes, as > measured in the garage reference frame. For those 2.5 nano-seconds the car > is fully inside the garage. > > Now consider that same events in the car's frame of reference. Keep in > mind the technical meaning of "event" is a point in spacetime, not a > "happening" as in casual parlance. So points in the above diagram, like > "FRONT ENTERS" are events and the Lorentz transformation preserves events > but it in general changes their spacetime relation. Here is the Lorentz > transformation, point-by-point, of the above diagram. The two diagrams are > physically identical; differing only in being viewed from different states > of motion: > > > Specifically in this case the time order of "REAR ENTERS" and "FRONT > EXITS" is reversed. This is typical of space-like separated events: their > order is different in different reference frames. So from the car's point > of view there is a period of about 7 nano-seconds during which both doors > are open and so the car sails thru without hitting a door. > > Brent > > > When you write the time order of events is reversed, presumably in the car > frame, does this mean the rear of the car enters the garage before the > front enters (which is physically impossible)? If not, what do you mean? AG > > That's the sort of question that gets you a troll reputation. The events > are clearly labelled and the axes have time and position variables. If you > can't read the diagram you won't understand a written explanation any > better. > > Brent > > > As I was scrolling down to your reply, I was expecting a BS answer and > that's what I got. F the troll BS. When I worked at JPL no one questioned > my ability of reading plain English. But you know better. AG > > > In the car frame, the Front Exits and Rear Enters, in this order, so the > car doesn't fit. In the garage frame, the Front Enters and Rear Enters, in > this order, so the car fits, but the latter isn't the opposite of the > former, AFAICT. AG > > That's right. You can read the diagram! > > Brent > > > But what IS the "opposite" you referred to? > > > The "silly" question involved the suggestion of a violation of causality > if time is "reversed" for transformations of spacelike separated events. AG > > > > -- > 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/3436a827-9dc2-42ce-af98-fb495ef04382n%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/3436a827-9dc2-42ce-af98-fb495ef04382n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- 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/002a88a4-0fd3-49ea-948d-ff4d6ec21853n%40googlegroups.com.
