On Sun, Jan 26, 2025 at 10:23 PM Alan Grayson <agrayson2...@gmail.com> 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 <agrays...@gmail.com> 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 <agrays...@gmail.com> > 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. If you want to know the coordinates of F and R in Brent's example, in the garage frame the entrance to the garage is fixed at x=0 and the exit is fixed at x=10, while in this frame the back of the car has position as a function of time given by x = 0.8c*t and the front has x = 7.2 + 0.8c*t. F occurs when the front of the car meets the exit of the garage i.e. 7.2 + 0.8c*t = 10, which you can solve for t to get t = 2.8/0.8c = 3.5 (assuming units where c=1), and the x-coordinate is 10. And R is at the intersection of x=0 and x=0.8c*t which is just x=0, t=0. 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 view this discussion visit https://groups.google.com/d/msgid/everything-list/CAPCWU3%2BGKpwoVfYCkTMh4NeQVB%2BrftfRrLvwHHR_xrKGF9hLhg%40mail.gmail.com.
