On Thursday, December 19, 2024 at 1:21:05 AM UTC-7 Jesse Mazer wrote:
On Thu, Dec 19, 2024 at 1:05 AM Alan Grayson <[email protected]> wrote: On Wednesday, December 18, 2024 at 4:04:43 PM UTC-7 Jesse Mazer wrote: On Wed, Dec 18, 2024 at 4:58 PM Alan Grayson <[email protected]> wrote: On Wednesday, December 18, 2024 at 2:42:39 PM UTC-7 Brent Meeker wrote: On 12/17/2024 11:21 PM, Alan Grayson wrote: On Tuesday, December 17, 2024 at 10:16:51 PM UTC-7 Brent Meeker wrote: On 12/17/2024 7:52 PM, Alan Grayson wrote: On Tuesday, December 17, 2024 at 6:57:28 PM UTC-7 Alan Grayson wrote: On Tuesday, December 17, 2024 at 2:33:46 PM UTC-7 Brent Meeker wrote: On 12/17/2024 9:25 AM, Alan Grayson wrote: Yes, you look at it just in terms of lengths, which is what I did in the first pair of diagrams. But the relativity of simultaneity is another way to look at the same problem, which is what I showed in my last posting. *Another way, but not the only way. AG * We seem to be on the same page concerning use of length contraction to explain the differing results in the frames under consideration. But I remain unclear how the disagreement of simultaneity can also give the same results. For example, suppose from the pov of the garage frame, the car fits in the garage for sufficient v, with room to spare, but the front and rear end EVENTS do not Lorentz transform into simultaneous events in the car frame. Can't there be other ways for the car to fit, using another set of events which* are* simultaneous in the car frame? AG Sure. If the car's speed was just right, it would be the same length as the garage. Then in the diagram A and B would be at the same time in the garage frame the car would be just the right length such that the rear of the car entered the garage just as the front exited the garage. Since we know the car is 12 long and the garage is 10 long we can calculate the required speed from 10/12 =sqrt{1-v^2} which yields v=0.553 if I did the arithmetic right. That would be 0.553c. So, if the front and back events in the garage frame are simultaneous in the car frame AND in the garage frame, Nobody said that the events were simultaneous in the car frame. The car is contracted in the car frame. You keep throwing shit in problem just to keep it going. I'm starting to suspect you're just a troll. Brent *My question for you is this; when will you learn to read English? You act like an uneducated prick who can't read basic English. The consensus view in the physics community is that the solution to this problem involves disagreement about simultaneity. I don't see this as correct. For example, that's what Quentin wrote several times, mocking me, and that's what a link claimed, without proof, which someone posted. And even Jesse, if I read him correctly, claims that the result in one frame must be false if there's no simultaneity.* What do you mean by "if there's no simultaneity"? What I said was that the prediction of the two frames would disagree about local events (a genuine physical contradiction) in an imaginary universe where both inertial frames *did* agree about simultaneity (i.e. there is no relativity of simultaneity like in the real-world theory of relativity) but where they still each predicted objects in the other frame would experience length contraction. Anyway, it'd be helpful if you'd go back to that last comment of mine and answer my questions about whether you understand how classical space/time plots work, and also whether you understand that in relativity you have to use the Lorentz transformation on the coordinates of an event labeled in one frame to find the "same event" in a different frame, with the result that any *specific* pair of events on the front & back of the car that are simultaneous in the car frame are non-simultaneous in the garage frame (although in the garage frame you can find a *different* pair of events on the front & back of the car which are simultaneous in the garage frame but not the car frame, which is what Brent was talking about). Jesse *Yeah, I understand that we must use the LT to transform between inertial frames. AG* I wasn't just asking about transforming between frames in general, I was asking if you understand that coordinates in a given frame are used to identify individual physical events, and the LT are then used to identify the coordinates of the "same event" in a different frame (this implies that a pair of events at the front and back of the car which are simultaneous in some frame *cannot* be simultaneous in any other frame that's moving relative to that one, at least not in a problem with only one spatial dimension). Also, you didn't address my question about if you understand how *classical* plots of position vs. time work, which I asked because I was trying to figure out what aspect of my comment about worldlines in relativity you couldn't follow. Here again was my question, in a post you didn't reply to: 'Can you try to be specific about what aspect of it you find hard to follow? First of all, do you feel you have a good grasp of plots of position vs. time in classical physics, where there is no disagreement about simultaneity or time or distance intervals, or do you need a refresher on the classical graphs before trying to follow the relativistic ones? Do you understand for example why if we had a classical graph with various lines or curves representing the worldlines of objects, with time on the vertical axis and position on the horizontal axis, then if we wanted to know the position of all the objects at a particular time, that would involve drawing a horizontal line of fixed time coordinate (a classical line of simultaneity, which doesn't change from one frame to another) and seeing where the horizontal line intersects with the worldlines of the objects?' * but if the events of measuring front and back in garage frame, for a perfect fit, why do we care how they transform in the car frame, since the problem is completely solved using length contraction?* I have already explained the point here is pedagogical (in several other posts that you never responded to--I think it would help the discussion if you would respond to every post where I ask you a question, instead of taking a sporadic approach). Here was what I said in the first post where I made this point: 'The reason physicists bother to talk about a hypothetical scenario like this is pedagogical, they want to get students to think about situations where the perspective of different frames might *seem* to lead to real physical contradictions, and then looking at it more closely they'll understand how the "real" physical predictions in relativity are always about local events, and that by considering different definitions of simultaneity we can show the two frames do agree about all local events on rulers and clocks. Do you disagree with my point that if different frames *didn't* have differing definitions of simultaneity, it would be impossible for the two frames to disagree about whether the car or garage was shorter without this leading to conflicting predictions about local events, like what the clocks mounted to front and back of the car will read at the instant they pass clocks attached to the front and back of the garage?' And in a later post, I elaborated on why differences in simultaneity are critical to avoiding contradictory predictions about localized physical events: 'In an imaginary alternative physics where different frames had no disagreement about simultaneity but different observers still all believed the length contraction equation should apply in their frame, then this would be a genuine paradox/physical contradiction, because different frames would end up making different predictions about local events. Think about it this way--if there were no disagreement about simultaneity, there could be no disagreement about the *order* of any two events (this would be the case even if observers predicted moving clocks run slow like in relativity). But if observer #1 thinks the car is shorter than the garage, he will predict the event A (the back of the car passing the front of the garage) happens before event B (the front of the car reaches the back of the garage), and if observer #2 thinks the car is longer than the garage, he will predict B happens before A. If there were no disagreement about simultaneity this would lead them to different predictions about readings on synchronized clocks at the front and back of the car/garage at the moment of those events, specifically whether the clock at A would show a greater or lesser time than the clock at B.' Jesse *Jesse; in the near future I will try to address each of the issues you've raised, but for now let me just say I don't understand how to resolve this issue, and my tentative pov is that relativity just isn't correct. Listen; we start in a rest frame of a car which is longer than a garage. and have no problem asserting that it won't fit. And that's how things seem from both entities with physical observers. So far so good. Now we imagine the car in motion and apply length contraction in both frames and we get opposite results; namely, that in the car's frame, it won't fit in the garage, but in the garage frame it does fit, and the fits gets easier as the car's velocity increases. If I imagine a real car and a real garage, from one frame it doesn't fit, the car's frame, and from the other frame, the garage, it does fit. So, if intially the car doesn't fit, from the pov of both physical entities should I expect contrary results when the car is in motion? Maybe so. But I still can't wrap my head around the alleged claim, that the observed reality will be frame dependent. I mean, how can two observers in different frames, looking at a real car, disagree on what they see? Incidentally, I just noticed that in one of Brent's recent posts with two diagrams, he says there is a disagreement about simultanaeity, but I am not sure if he's referring to comparing the two frames, and when I interpreted this as his comparison, he got angry, denying my interpretation. My bias is that the frames should agree (on what a bird's eye observer would see?), but does that require disagreement about simultaneity? AG* why is it claimed that the solution to the problem, whatever it is, depends on disagreements of simultaneous events, when there are none? And if we get different results for fitting in the garage, where, for example, the car never fits, is there anything about this result that implies something contradictory or paradoxical? 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