if i did not understand RoS then i would not have seen the flaws.
If you understood RoS then you would not have made most of the statements you've made in this thread. You have not demonstrated any such understanding, at least as far as I could make out. Most of your statements are independent of the video.
How about this: Forget the video. Just describe Einstein's train experiment correctly. Show how the two frames disagree about the lightning strikes being simultaneous (and how that follows from the invariance of the speed of light).
I recommend that you start with the events that I have outlined in post #155.
#253
solarflare
177
0
mathematics is like building a house - the scenario is like the foundation
you can build a perfect - strong house
but if you build it on the wrong foundation it will still collapse
mathematics is like building a house - the scenario is like the foundation
you can build a perfect - strong house
but if you build it on the wrong foundation it will still collapse
And your point is?
#255
solarflare
177
0
look at my ship scenario
the middle ships targets have just been hit and send out light from the explosions
the ships pilot reports that the two targets were destroyed simultaneously because they occurred on his ship
but what does the stationary observer see
#256
solarflare
177
0
This diagram is in the frame of the stationary other ship. At some time t=0 in the stationary ship's frame, the stationary ship detects two flashes from the targets being obliterated by the laser cannons. The stationary ship knows, based on the sizes of these explosions, that it was equidistant from both explosions, so it concludes that the targets were obliterated at t=−30.15 units.
the middle ships targets have just been hit and send out light from the explosions
the ships pilot reports that the two targets were destroyed simultaneously because they occurred on his ship
but what does the stationary observer see
Please describe your ship scenario clearly. I don't understand your diagram. (Where are the ships? Where are the targets? How are they moving?)
#258
solarflare
177
0
the event occurs in the frame of the moving ship
the stationary observer see the flashes from that event
#259
solarflare
177
0
the middle ship is moving in a direction from south to north as you look at it
the lasers are fired from west to east as you look at it
the targets are the 0 at the front of the ship and the 0 at the rear
if you look at the diagram it looks like this --------0----------- the target is the 0
-----------------------------------------------/
----------------------------------------------I ------- this is the position of the pilot
the ship is moving at 500 m/s from south to north
the two targets are hit simultaneously in the little ships frame
#260
solarflare
177
0
the stationary ship is equidistant from the explosions when they happen
Events don't occur in a specific frame, they occur in all frames.
I don't understand your ship scenario, but if the events in question are separated along the x-axis and the moving ship moves along the y-axis, then there's no issue. Both frames will view them as simultaneous.
i could see the flaws in the video - and you could not -
if i did not understand RoS then i would not have seen the flaws.
I am going to call BS on this one. Nothing that you said above indicates that you were aware of any of the actual flaws in the video. Your mistakes appear to be entirely your own and not an identification nor a repetition of any flaws in the video.
mathematics is like building a house - the scenario is like the foundation
you can build a perfect - strong house
but if you build it on the wrong foundation it will still collapse
I am still waiting for you to provide a mathematical proof of any of your points or to identify a specific flaw in the math that I have presented or the assumptions I used. If the house is weak or the foundation wrong then you should be able to identify the specific flaw, particularly since you are so much more amazingly perceptive than all of the rest of us . If you cannot prove your own point, then you at least need to directly address the disproof.
Doc Al already mentioned that events occur in all frames. To expand on that, an event occurs in all frames, but each frame assigns that same event to different time and space coordinates. The equation which relates the coordinates assigned to any arbitrary event in one frame to the coordinates of the same event in another frame are given by the Lorentz transform:
if they hit the platform and not the train then by the time the flashes move to where the train observer will see them - she will no longer be equidistant from the flashes- therefore she will see them separately.
Can you confirm your agreement or explain why you don't agree even though your recent comments seem to indicate agreement?
#266
Muphrid
834
2
solarflare said:
the point is that the stationary observer is seeing an event where the ship ACTUALLY was hit simultaneously in that frame.
if your saying it doesn't matter then you are sayin reality has nothing to do with it - and if you say that then you also say relativity has nothing to do with reality
The stationary other ship is seeing two events that happen to be simultaneous in the reference frame that he is stationary.
As yet, I haven't posted the complete conclusions. I just want to make sure we agree on the math. Read what I posted again (which I'm quoting so you don't need to flip back and forth). The stationary ship believes both targets were destroyed at the same time t = -30.15. It also believes that the flashes from those two events will reach the moving ship at different times. I have yet to calculate whether the moving ship will calculate that the two events took place at the same time in its frame because I want us to agree on these very basic principles first.
If you believe that connecting the two targets to the moving ship makes a difference, how does it make a difference to what has been calculated so far? Do you think that means the moving ship will receive the flashes at times other than I have calculated (times in the stationary other ship's frame)?
Muphrid said:
Code:
30 units
|==============================|
Laser cannon
|--- 0 Target
| \
| |
| | #
| | Small -># +Y-velocity beta = 0.9 #<-Stationary other ship
| | Ship ] #
| | |-3 units
| / ]
|--- 0 Target
Laser cannon
|====================|
20 units
This diagram is in the frame of the stationary other ship. At some time t=0 in the stationary ship's frame, the stationary ship detects two flashes from the targets being obliterated by the laser cannons. The stationary ship knows, based on the sizes of these explosions, that it was equidistant from both explosions, so it concludes that the targets were obliterated at t = -30.15 units.
The small ship is traveling at \beta = 0.9 between the targets, which are confined to a line but otherwise have thrusters that allow them to move in an arbitrary manner along that line. The stationary ship monitors the small ship's trajectory and believes that the small ship was equidistant from the targets at t = -30.15, the time both targets were obliterated. If the stationary other ship is at y = 0, then it believes the light from the upper target will reach the small moving ship at t = -30.15 + 1.58, or 1.58 units of time after the explosion, and at y = 1.42. It also believes that the flash from the lower target will reach the small moving ship at t = -30.15 + 30, a full 30 units of time after the targets were obliterated, at y = 27.
Let's stop here before we go any further. Do you agree with the conclusions I have reached so far?
#267
Muphrid
834
2
solarflare said:
if they hit the platform and not the train then by the time the flashes move to where the train observer will see them - she will no longer be equidistant from the flashes- therefore she will see them separately.
No, no, absolutely not. The sources of the flashes do not "move with" the object the lightning/lasers hit. The sources are points in space and time. They do not move. They do not have worldlines. When the train observer sees the flashes, she is looking into the past, to the places and times the strikes hit, not to where the point of impact actually has moved to. That is why we keep saying it does not matter if the strikes hit the train or the platform.
In other words, it is only the platform observer who thinks the train observer has caught up to the forward flash and was closer to it. As long as the platform observer and the train observer were right beside each other and the events were equidistant from the platform observer, the events must be equidistant from the train observer (in her frame) whether or not the platform or the train was actually struck.
So this is the chain of reasoning:
a) The train observer must believe herself to be equidistant from the sources of the flashes (yes, even if the sources were lightning strikes that hit the platform, not the train)
b) The platform observer sees that the train observer must detect the forward flash before the rear flash; this sequencing of events is something all observers must agree upon because it's the difference between two points in space and time
c) Because of (b), we know the train observer detects the forward flash before the rear flash. Because of (a), she can't attribute the difference in times to a difference in distance of the sources. Therefore, she attributes the difference in times to an actual difference of simultaneity, saying the forward strike happened before the rear strike.
No, no, absolutely not. The sources of the flashes do not "move with" the object the lightning/lasers hit. The sources are points in space and time. They do not move. They do not have worldlines. When the train observer sees the flashes, she is looking into the past, to the places and times the strikes hit, not to where the point of impact actually has moved to. That is why we keep saying it does not matter if the strikes hit the train or the platform.
In other words, it is only the platform observer who thinks the train observer has caught up to the forward flash and was closer to it. As long as the platform observer and the train observer were right beside each other and the events were equidistant from the platform observer, the events must be equidistant from the train observer (in her frame) whether or not the platform or the train was actually struck.
So this is the chain of reasoning:
a) The train observer must believe herself to be equidistant from the sources of the flashes (yes, even if the sources were lightning strikes that hit the platform, not the train)
b) The platform observer sees that the train observer must detect the forward flash before the rear flash; this sequencing of events is something all observers must agree upon because it's the difference between two points in space and time
c) Because of (b), we know the train observer detects the forward flash before the rear flash. Because of (a), she can't attribute the difference in times to a difference in distance of the sources. Therefore, she attributes the difference in times to an actual difference of simultaneity, saying the forward strike happened before the rear strike.
This is to elaborate on Muphrid's answer for solarflare.
If there were additional train observers on board, not just at the center of the train, but also at the actual locations and times at which the lightning strikes occurred, and if these observers had clocks that were synchronized with the clock of the woman at the center of the train, then the time displayed on the clock of the forward observer when the forward strike occurred would be earlier than the time displayed on the clock of the rear observer when the rear strike occurred. So, as far as everyone on the train is concerned, the forward strike occurred first, and then the rear strike (according to all the synchronized clocks on the train). If the woman is half way between the forward and rear observers, she will receive the flash from the forward strike first, followed by the flash from the rear strike. This describes what is observed on the train whenever a similar set of 3 platform observers note using their synchronized clocks (i.e., synchronized within their frame of reference) that the two lightning strikes occurred simultaneously. This is a reality of special relativity, of the Lorentz Transformation, and an experimentally confirmed reality of our actual universe.
#269
bahamagreen
1,015
52
Just some thoughts that might help (assuming I'm not in error)...
The train itself is not the same as the frame of the train, nor is an observer on the train necessarily in the frame of the train.
The platform itself is not the same as the frame of the platform, nor is a platform observer necessarily in the frame of the platform.
The train may be observed from the platform in either the frame of the platform or the frame of the train (if the platform observer is moving wrt the platform so to be at rest wrt to the train).
Likewise, the platform may be observed from the train in either the frame of the train or the frame of the platform (if the train observer is moving wrt the train so to be at rest wrt to the platform).
In fact, any observer might be in any arbitrary frame whatsoever. It all depends on precisely how the experiment is stated.
I think part of what is going on is that folks are saying that because the platform observer in the platform frame observes the two strikes at the same time in his frame, he will conclude that the train observer in relative motion wrt the platform MUST see the forward strike before the rear strike... and since she is in the center of the train, she must conclude that the strikes were separated in time.
This might be misunderstood as giving the platform observer the "correct" view of events, and the train observer observing an "illusion"; especially if the reasoning is that her mistake is a natural one because of her motion which intercepts the forward flash prior to the rear flash... as if the train strikes really were together in time, but the motion of the train forward causes the difference in arrival.
So a possible confusion might stem from assuming that the strikes at the same time in the platform frame entail that the train itself received strikes at the same time in the train frame. The reasoning for this would be that the light propagates at constant speed independent of the motion of the source... as if it did not matter that the train was moving wrt the platform observer or not. This is a confusion between the train and its frame... if the train was not in motion relative to the platform then the train frame and platform frame would be the same. The frames are separate as a result of the relative motion between them.
The effect of relative motion between frames shows in the relationship between the source location of a light flash and the center of its subsequent sphere of expansion... observed from within one's own frame, all observers will observe spheres of the same time radius to contain the flash source's original location of the flash at the center of the sphere. This is the same as saying that all observers agree on c... but it may help to see why observers in different frames disagree about other observations.
The platform observer will see the flash source locations hold still in his frame... the forward and rear ends of the train just happen to be at these locations as it moves by... and it keeps on moving past them. This makes him conclude that the train observer will see one flash before the other.
The train observer in her frame will see the flash source locations hold still in her frame, too... the same forward and rear ends of the same train itself, but for her these source locations ARE the ends of the train and continue to be so even as it continues to roll along because she is at rest wrt the train.
So, the two frames disagree about the flash source locations and those source positions with respect to the subsequent flash sphere centers.
Just some thoughts that might help (assuming I'm not in error)...
The train itself is not the same as the frame of the train, nor is an observer on the train necessarily in the frame of the train.
The platform itself is not the same as the frame of the platform, nor is a platform observer necessarily in the frame of the platform.
What we're defining as the "train reference frame" is the *rest frame* of the train. In other words, it's the inertial reference frame in which the train is stationary.Therefore, any observer who is NOT moving relative to the train is in the "train frame" (i.e. that observer's rest frame is the same as the train's). This obviously includes the observer on the train in our scenario.
EDIT: Likewise for the platform. When we say that an observer is "in the platform frame", we mean that that observer is at rest relative to the platform. So both the platform and the "platform observer" are "in the platform frame" by definition.
#271
Muphrid
834
2
And this is a key point about reference frames. Objects can be stationary or moving with respect to a frame, but events (like the lightning strikes we've been talking about) are not objects and they do not move, and the distances measured to events are simply the distance light travels to reach an observer (a distance which depends on the particular frame chosen, of course).
#272
solarflare
177
0
No, no, absolutely not. The sources of the flashes do not "move with" the object the lightning/lasers hit.
The sources are points in space and time. They do not move. They do not have worldlines. When the train observer
sees the flashes, she is looking into the past, to the places and times the strikes hit, not to where the point of
impact actually has moved to.That is why we keep saying it does not matter if the strikes hit the train or the
platform. (taken from post 267)Originally Posted by solarflare View Post
let me ask the same question but in definate terms.
the two bolts of lightning do actually strike at the same time in the trains frame of reference
the observer on the platform is exactly the same distance from each strike
does the woman see the two strikes at the same time?
Sure. The lightning struck the ends at the same time in her frame and since they traveled the same distance they
reach her at the same time. No mystery there. (taken from post 28) (doc al)maybe doc al can explain to murprid why she will see them simultaneously if they strike the train simultaneously?
#273
solarflare
177
0
now on the other hand if the flashes hit the tracks and not the train - then yes she would see them seperately because the train and the tracks are moving at different speeds in her frame.
let me ask the same question but in definate terms.
the two bolts of lightning do actually strike at the same time in the trains frame of reference
the observer on the platform is exactly the same distance from each strike
does the woman see the two strikes at the same time?
Sure. The lightning struck the ends at the same time in her frame and since they traveled the same distance they
reach her at the same time. No mystery there. (taken from post 28) (doc al)maybe doc al can explain to murprid why she will see them simultaneously if they strike the train simultaneously?
It is you, solarflare, who are confused not Muphrid.
(A) If the lightning strikes hit the train ends simultaneously in the platform frame, the light flashes from each will reach the platform observer at the same.
(B) If the lightning strikes hit the train ends simultaneously in the train frame, the light flashes from each will reach the train observer at the same.
These are two physically distinct scenarios. They cannot both apply to the same situation--it's one or the other, not both.
now on the other hand if the flashes hit the tracks and not the train - then yes she would see them seperately because the train and the tracks are moving at different speeds in her frame.
You are still stuck with the idea that if the lightning strikes hit the train that they become simultaneous in the train frame but if they hit the tracks they would be simultaneous in the track frame. This is completely wrong, as has been explained in great detail throughout this (comically long) thread.
#276
solarflare
177
0
you seem to forget that the video says that the platform observer was equal distance from each strike
the only way the platform observer can see two simultaneous strikes is if the strikes happen seperately at DIFFERENT distances
and then describes what BOTH observers see from that event
the video is using both frames.
look at the last paragraph of the transcript
Yes, the events happen. Yes, they can be described from both frames.
So what?
The last paragraph of the transcript is:
Whose interpretation is correct - the observer on the platform, who claims that the strikes happened simultaneously, or the observer on the train, who claims that the front strike happened before the rear strike? Einstein tells us that both are correct, within their own frame of reference. This is a fundamental result of special relativity: From different reference frames, there can never be agreement on the simultaneity of events.
so two separate lighteneing strikes happen in the trains frame
You can certainly view the lightning strikes from the train frame.
the first strike hits the rear - the light begins to move towards the platform
The first strike hits the front of the train, not the rear.
then - the front strike happens when the light from the rear strike reaches the front of the train
huh?
now - both light beams are traveling towards the platform together and so the platform observer sees the strikes simultaneously
The two light flashes reach the platform observer at the same time--as seen in every frame. Realize that from the train viewpoint the platform observer is moving away from the front flash and towards the rear flash.
#282
solarflare
177
0
ok
i admit i was wrong - its the not the last it is the paragraph before the last
But what does the passenger see? As her friend on the platform predicted, the passenger does notice the flash from the front before the flash from the rear. But her conclusion is very different. As Einstein showed, the speed of the flashes as measured in the reference frame of the train must also be the speed of light. So, because each light pulse travels the same distance from each end of the train to the passenger, and because both pulses must move at the same speed, he can only conclude one thing: if he sees the front strike first, it actually happened first.
what does the passenger see? - not what does the platform observer believes she will see
As Einstein showed, the speed of the flashes as measured in the reference frame of the train must also be the speed of light. - I am pretty sure this is talking about the trains reference frame
he can only conclude one thing: if he sees the front strike first, it actually happened first.
if i see a bolt of lightning tonight - and then see the stars tomorrow night. must i conclude that the lighteneing occurred before the light was emitted from the star?
well i can say for sure that using my knowledge i would conclude that the starlight was actually emitted millions of years ago before the lightening.
i admit i was wrong - its the not the last it is the paragraph before the last
But what does the passenger see? As her friend on the platform predicted, the passenger does notice the flash from the front before the flash from the rear. But her conclusion is very different. As Einstein showed, the speed of the flashes as measured in the reference frame of the train must also be the speed of light. So, because each light pulse travels the same distance from each end of the train to the passenger, and because both pulses must move at the same speed, he can only conclude one thing: if he sees the front strike first, it actually happened first.
Sounds right to me.
what does the passenger see? - not what does the platform observer believes she will see
Why do you say that? The platform observer believes that the passenger will see the flashes arrive separately. At that's what she does see. Perfectly consistent!
As Einstein showed, the speed of the flashes as measured in the reference frame of the train must also be the speed of light. - I am pretty sure this is talking about the trains reference frame
The speed of light is the same as measured in any frame.
he can only conclude one thing: if he sees the front strike first, it actually happened first.
Right.
if i see a bolt of lightning tonight - and then see the stars tomorrow night. must i conclude that the lighteneing occurred before the light was emitted from the star?
well i can say for sure that using my knowledge i would conclude that the starlight was actually emitted millions of years ago before the lightening.
Your example has no relevance to the train situation.
If lightning bothers you, imagine there are two light bulbs at the ends of the train. Since the passenger in the middle of the train knows she is equidistant from the bulbs, when she sees the light from one of them arrive before the other she must conclude that they flashed at different times.
#284
solarflare
177
0
Sure. The lightning struck the ends at the same time in her frame and since they traveled the same distance they reach her at the same time. No mystery there.
(post 28)
If lightning bothers you, imagine there are two light bulbs at the ends of the train. Since the passenger in the middle of the train knows she is equidistant from the bulbs, when she sees the light from one of them arrive before the other she must conclude that they flashed at different times.
(post 283)
both from Doc AL - you are contradicting yourself here as the lightning and the bulbs are both in her frame.
Sure. The lightning struck the ends at the same time in her frame and since they traveled the same distance they reach her at the same time. No mystery there.
(post 28)
If lightning bothers you, imagine there are two light bulbs at the ends of the train. Since the passenger in the middle of the train knows she is equidistant from the bulbs, when she sees the light from one of them arrive before the other she must conclude that they flashed at different times.
(post 283)
both from Doc AL - you are contradicting yourself here as the lightning and the bulbs are both in her frame.
As I've pointed out many times (most recently in post #274), there are two physically different scenarios here. You keep bouncing around from one to the other--no wonder you are confused!
I think that you think that changing frames means going from A to B (see post #274), but no. Each scenario can be viewed from each frame and leads to perfectly consistent results.
Stick to scenario A:
(A) If the lightning strikes hit the train ends simultaneously in the platform frame, the light flashes from each will reach the platform observer at the same. (And will reach the train passenger at different times.)
#286
harrylin
3,874
93
bahamagreen said:
Just some thoughts that might help (assuming I'm not in error)...
The train itself is not the same as the frame of the train, nor is an observer on the train necessarily in the frame of the train.
The platform itself is not the same as the frame of the platform, nor is a platform observer necessarily in the frame of the platform.
The train may be observed from the platform in either the frame of the platform or the frame of the train (if the platform observer is moving wrt the platform so to be at rest wrt to the train).
Likewise, the platform may be observed from the train in either the frame of the train or the frame of the platform (if the train observer is moving wrt the train so to be at rest wrt to the platform).
In fact, any observer might be in any arbitrary frame whatsoever. It all depends on precisely how the experiment is stated.
I largely agree with that but not completely (and I slightly disagree with cepheid's comment too). A platform observer certainly is (or can be) in the frame of the platform, as all events necessarily occur in all frames - SR reference "frames" have infinite extension. It doesn't make sense to say that, for example, someone isn't in a frame in which a light flash hits him at a certain (x,t)! Commonly people use "in frame S" as a shorthand for "as measured with reference system S" (there is a subtle difference that often doesn't matter).
However, while a platform observer may be moving relative to the platform, by common definition the "platform frame" is in rest wrt the platform. Such expressions as "platform frame" and "train frame" are unambiguous.
In such examples the platform observer supposedly uses the platform frame, and the train observer uses the train frame. But in fact, the people can conveniently be left out completely (clearer but less colourful!).
BTW, where did the maths go?? It appears that the topic has been abandoned...
[..] The platform observer will see the flash source locations hold still in his frame... [..] The train observer in her frame will see the flash source locations hold still in her frame, too... [..]
Lightning typically takes place in air that is (nearly) in rest wrt the platform. However, the speed of light is independent of the motion of the source and the flash duration is neglected; the motion of the flash source is therefore completely irrelevant for the time delay.
Suppose you did an actual experiment in which the setup was exactly the same as in the train-and-platform scenario you have been discussing. The platform guy was equidistant from the two locations on the ground that the two strikes hit, and the train gal was equidistant from the two locations on the train that the two strikes hit. Now the guy on the platform reports back that the two flashes arrived at his location simultaneously, while the gal on the train reports that the flash from the front arrived at her location before the flash from the rear. These are the experimental facts. What would you conclude from these facts? Do you think that this is possible, or do you think that something is wrong somewhere?
#288
solarflare
177
0
Chestermiller said:
Solarflare,
Suppose you did an actual experiment in which the setup was exactly the same as in the train-and-platform scenario you have been discussing. The platform guy was equidistant from the two locations on the ground that the two strikes hit, and the train gal was equidistant from the two locations on the train that the two strikes hit. Now the guy on the platform reports back that the two flashes arrived at his location simultaneously, while the gal on the train reports that the flash from the front arrived at her location before the flash from the rear. These are the experimental facts. What would you conclude from these facts? Do you think that this is possible, or do you think that something is wrong somewhere?
if lightning srikes the platform equidistant from the platform guy - would he see them seperately because acording to the train observer the platform was moving?
#289
solarflare
177
0
Stick to scenario A:
(A) If the lightning strikes hit the train ends simultaneously in the platform frame, the light flashes from each will reach the platform observer at the same. (And will reach the train passenger at different times.)
yes this is obvious
but the platform observer would not be equidistant from the flashes when they ACTUALLY occurred - when they hit the train - and as the train is in the trains frame the flashes ACTUALLY occur at different times
When we say that an observer is "in the platform frame", we mean that that observer is at rest relative to the platform. So both the platform and the "platform observer" are "in the platform frame" by definition.
Btw, I know that this terminology is common and in context it is well-defined, but I absolutely hate it. Unfortunately, the phrase "in the platform frame" conveys the mistaken idea that a frame is some sort of a container which it is possible to be in or out of and it is possible to enter or leave the container. Everything is in every frame, and it is not possible to enter or leave a frame in the sense of a container. It is possible to be moving wrt a frame or stationary wrt a frame, but not in or out of a frame.
Nothing you said is wrong, and I know that this is my own personal preference, but I always cringe when I read the phrase "in a frame".
if lightning srikes the platform equidistant from the platform guy - would he see them seperately because acording to the train observer the platform was moving?
Huh?
Chestermiller is specifying that the result of this experiment is that the platform observer sees the flashes occurring at the same time. Since they both struck at the same distance away, and both travel at c relative to him, the platform observer concludes that they must have occurred simultaneously.
#292
solarflare
177
0
look at the situation in reverse
the observer sees two flashes of light
they move back towards the train (that is in motion)
how can the light originate in the same place as where the observer sees it
if you say this then you say light travels instantly
#293
solarflare
177
0
cepheid said:
Huh?
Chestermiller is specifying that the result of this experiment is that the platform observer sees the flashes occurring at the same time. Since they both struck at the same distance away, and both travel at c relative to him, the platform observer concludes that they must have occurred simultaneously.
so if in the trains frame the two strikes are simultaneous then the same must be true as
she considers herself stationary and the platform is moving
you seem to think that in both scenarios its only the train that is in motion
#294
solarflare
177
0
i have watched the video A LOT of times and i at first did not think that there was anything wrong.
but like George after going over it step by step it becomes clear - i suggest everyone does it and I am sure you will see what I am saying
#295
solarflare
177
0
when doc al said that if two bulbs were turned on in the train simultaneously the woman would see the front one first - (train observer in train frame)
it is the same as saying that if two bulbs were turned on on the platform that the platform guy would see one first. (platform observer in platform frame)
Nothing could be clearer. There is no need to belabor this anymore.
#297
Muphrid
834
2
solarflare said:
Stick to scenario A:
(A) If the lightning strikes hit the train ends simultaneously in the platform frame, the light flashes from each will reach the platform observer at the same. (And will reach the train passenger at different times.)
yes this is obvious
but the platform observer would not be equidistant from the flashes when they ACTUALLY occurred - when they hit the train - and as the train is in the trains frame the flashes ACTUALLY occur at different times
solarflare, it is a given that the platform observer was equidistant from the strikes in his frame. Why do you think he wouldn't be? Because the bolts hit the train and the train is moving? This has nothing to do with it. This is why we keep saying what the bolts hit doesn't matter. All that matters are the coordinates (in time and space) of the points the bolts hit.
In other words, this is what happened: in the platform observer's coordinate system (where he is always at x=0 at all times t), there is a train that is 8 units long, extending from x=-4 to x=+4 at time t=0. At that time t=0, two lightning strikes hit, one at x=-4 and another at x=+4.
That's it. I haven't specified what object was hit because I don't need to. All I need to say is that the points that were hit have specific coordinates, and all light rays from these points will go along well-defined trajectories. Do you agree that this is what happened?
(A) If the lightning strikes hit the train ends simultaneously in the platform frame, the light flashes from each will reach the platform observer at the same. (And will reach the train passenger at different times.)
yes this is obvious
If it were that obvious, this thread would not be as long as it is.
but the platform observer would not be equidistant from the flashes when they ACTUALLY occurred - when they hit the train - and as the train is in the trains frame the flashes ACTUALLY occur at different times
You still seem to think that the lightning strikes 'actually occurred' simultaneously in the train frame. You seem to think, since they hit the train, that they are somehow 'in the train frame'. How many times do we have to correct you?
In scenario A, which is what we are discussing, the lightning strikes are simultaneous in the platform frame.
As far as the platform observer is concerned: When the strikes ACTUALLY occur he is right in the middle of the train.
As far as the train observer is concerned: When the first strike ACTUALLY occurs the platform observer has not yet passed the middle of the train.
when doc al said that if two bulbs were turned on in the train simultaneously the woman would see the front one first - (train observer in train frame)
If the bulbs were turned on simultaneously according to the platform frame, then the woman passenger would claim the front one flashed first.
it is the same as saying that if two bulbs were turned on on the platform that the platform guy would see one first. (platform observer in platform frame)
No it isn't.
#300
solarflare
177
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If lightning bothers you, imagine there are two light bulbs at the ends of the train. Since the passenger in the middle of the train knows she is equidistant from the bulbs, when she sees the light from one of them arrive before the other she must conclude that they flashed at different times.
. If you cannot prove your own point, then you at least need to directly address the disproof.
