Was Einstein Wrong About Relativity of Simultaneity?

[longshinewoole]

The two events in this scenario are the lightning strikes at each end of the train. There are only two events, viewable by all observers whether on the train or on the embankment. (The entire point of this discussion is that different observers can see the same events happening at different times!) Note that it is you, not Einstein, who refers to A' and B' as events.

Note the careful use of "at a particular point". A' and B' are particular points--the ends of the train--not events. (Sounds like you are the one flipflopping words around. ) There are just two events: Embankment observers would naturally say that these events occurred at locations A and B with respect to the embankment; Train observers would naturally say that these same events--the lightning strikes--occurred at locations A' and B' with respect to the train.

Einstein said:
"People traveling in this train will with advantage view the train as a rigid reference-body (co-ordinate system); they regard all events in reference to the train. Then every event which takes place along the line also takes place at a particular point of the train."

The words "also takes place" in the second sentence obviously says there are events taking place on the train.

If there are only two events A and B on the embankment, he must say "Then every event which takes place along the line will NOT take place at a particular point of the train."

If there are only two events A and B, then his experiment should look like this:

embankment: A_________M_________B.
the train...:__________M'__________.

Then how could he use that "vise versa"?

Now you said "But M' knows exactly where the flashes occurred--according to his reference (the train, of course) they occurred at A' and B', the ends of the train!" To me you were saying the samething as Einstein did: events taking place on the embankment also take place on the train. Due to the movement of the train, will a total of 4 events be created?

Now you said this: "All the train observers have to go by is their own observations. They measure the location of the events (the lightning strikes) with respect to the train. Everyone agrees that the light from the two flashes arrives at M' at different times. But each frame will disagree as to why that is."

If what the train observer observed was the light from A' and B' [according to his reference (the train, of course) they occurred at A' and B'], how could they agree that the light from A' and B' arrives at DIFFERENT TIMES? To this question of mine, I request you use methematics to show how "they measure." Don't use affirmative but ambiguous sentences such "Everyone agrees that the light from the two flashes arrives at M' at different times." Ambiguous because the phrase "two flashes" could mean either A and B, or A' and B'.

 

[complexchaos]

If there are only two events A and B on the embankment, he must say "Then every event which takes place along the line will NOT take place at a particular point of the train."

Einstein does not say that the events occur on the embankment, there are obviously only two events and they are viewed in two different frames of reference.

The people on the embankment will see two events and the people on the train will see the same two events, just in a different way.

This question seems to be more about semantics than it does about the actual essence of Einsteins theory. I believe this forum was entitled "Was Einstein Wrong?". Did you mean in this particular thought experiment, or with the concept of simultaneity in general?

I showed in my previous posts why simultaneity is relative, is that not enough?

 

[pervect]

A few comments: I've noticed that a lot of people have a hard time of grasping or accepting the concept of the relativity of simultaneity.

I gather this has been also noted in the literature, for instance
] "The challenge of changing deeply held student beliefs about the relativity
of simultaneity" [/url]

I think there have been many other papers on this and related topics (about how to teach relataivity) as well, though Scherr seems to have done more work with actual students than some of the other papers I remember reading.

I've been looking for websites that take approaches inspired by Scherr's work. While I have found one

http://webphysics.davidson.edu/physlet_resources/special_relativity/

it seems clunky. For instance, if the student clicks on the first lesson, and hits play, nothing happens. Furthermore, if he reads further, and clicks on "Synchronization procedure A", and THEN hits play, nothing APPEARS to happen, but the example is actually proceeding - just at a snail's pace.

However, if the student or reader (including some of the participants in this thread) did have the patience to work through all of the examples in order, I have a feeling that they might learn something. (I would omit Synchronization procedure A, for all but the most patient, however! The only point of this applet is to point out that you can synchronize clocks by hand-carrying them at a very low velocity, but that this process takes a considerable amount of time.)

The logic is all there, along with the graphics (though the later are somewhat clunky). It starts out with a disucssion of how, experimentally, one actually synchronizes clocks, moves to the distinction between what one "sees" directly and the coordinates one gives to an event, and finally presents the space-time diagrams of the train platform experiment along with a parallel animated pictorial representation.

One might wish that they, in addition to the above discussion how one synchronizes clocks, that they discussed WHY one synchronizes clocks - i.e. points out that satisfying Newton's laws requires that one measure velocities with properly synchronized clocks. This doesn't seem to be directly discussed in Scherr's research, however. It could be said that it's obvious, but a lot of things covered are very obvious .

The fundamental idea is (IMO) that the logical chain of how and why relativity requires one to abandon absolute synchronization be presented in a very complete, detailed, and thorough manner, even though it does make the presentation move at a snail's pace. Otherwise the old ideas are not really completely eradicated, but sill present, waiting to reappear and cause errors to be made.

Anyway, there's a fair amount of material there, and it's inspired by some actual research on how students learn, so it might be helpful to the really motivated.

I'm still looking for a better (free) visual presentation of the same material, however.

 

[cristo]

The words "also takes place" in the second sentence obviously says there are events taking place on the train.

You still appear to be highly confused by the meaning of the word "event." There are multiple posts above telling you that there are not four events; there are merely two events observed in two different reference frames. This, to me, seems to be your most fundamental confusion.

I would have shown you some math to convince you, but I am new here and I am very bad at printing Math is ASCII. You would think that they would have some simple equation editors in a physics forum site.

There is-- LaTex is enabled. Use the tags [ tex] and [ /tex] around your maths (without the spaces). There is a thread at the top of the tutorial forum if you get stuck.

 

[longshinewoole]

You still appear to be highly confused by the meaning of the word "event." There are multiple posts above telling you that there are not four events; there are merely two events observed in two different reference frames. This, to me, seems to be your most fundamental confusion.

I don't think I was onfused by the meaning of the word event. It was Einstein who said so: events which take place on the line also take place at a particular place on the train.

Besides, Einstein also used "vise versa" to imply that there were 4 events. If there were no events on the train, how could he said vise versa?

Let me temporarily agree to your "two event" idea. Then Einstein's thought experiment would look like this:

Embankment:A__________M__________B.
The train moved...:_________M'__________.

M' is no longer midway between A and B. Light from B of course will reach M' sooner than that from A. Can M' conclude (from this different arrivals of light) that the 2 events A and B not simultaneous?

No way.

 

[RandallB]

RandallB,

You said “Ther could arrive at the same time if they start at different time could they.” I don’t understand this sentence. Can you elaborate?

You said “the entire problem is based on two simultaneously lightning strikes at A & B while A' is at A and B' is at B.” Where did Einstein mention A’ and B’? If A’ is at A and B’ is at B, are you implying that the train is the same length as the distance from A to B? If so, why? What relevance does this have?

If you say at A’ is at A and B’ is at B, then the answer to your question “What is the distance for A’ & B’ ?” in post #20, is A’ = -B’, where A’ – B’ = 10 light seconds of distance. If I have this wrong, please explain.

If A’ – B’ = 10 light seconds = A – B, then Strike time’ for A’ = Strike time’ for B’. If I have this wrong, please explain.

?

How do you expect Einsein to go back in time and change his text to suit our modern use of (') as in M' to indicate TRAIN and our not using the mark (') as in M to indicate EMBANKMENT ?

Einstein was only addressing the time of the two events as measured from two different referance frames. You will find this easier to understand if you also define where in each referance frame the event happened!

With distance defined from M to B as 10 units of length (M to A would be -10 units) -- How do you get distance measured by M' to B' as 10 as well?? It is simply not trure the distace between strikes in M' frame (A' to B') is 25 units of distance (speed 0.6c).
Do the math on time as well and you will see that B' saw its nearby strike well BEFORE A' saw its nearby strike.
Since they are both the same distance from M' of course M' will see the strike from B' first - - IT HAPPENED FIRST.
That is the only point Einstein was making - simultaneous events in the M frame (embankment frame) are not simultaneous in the M' frame (train frame).

 

[K.J.Healey]

I agree the main confusion in this thread is completeley about simultinaity.
This is how I picture it. If I recall correctly, Einstein's example is the train, the embankment, and two points on the ends of the train. Instead of lightening, let's say flashlights at each end of the train pointing toward the center. This inverts the example so that the light emission is anchored to the train (in a way).

Inside the train: They don't know they're moving. Light from A and B takes the same amount of time to reach them as far as they know. They believe the events are happening at the same time.

Outside the train.

V-->
B-------Mtrain-------A
\______```````````` \
```````\________```` \
________________\_____\__Mtrack


So if according to Mtrain, A and B happen at the same time. Then Light from A will take some time t_a to reach MTrack from the train. Same with t_b. You will notice right away that there's no way Mtrack will think the events are happening at the same time. He sees A, pause, then B. So he concludes that A happens before B. Right away, before even the relativity issues, there's a problem with simultinaity due to light speed.

Or am i missing the point? I thought that what was trying to be told in AE's example in his book. I haven't read it since high school so I don't know if I'm remembering accurately.

But if you understand what I said above, you'll see how its the EXACT same thing the other way around.

 

[longshinewoole]

A few comments: I've noticed that a lot of people have a hard time of grasping or accepting the concept of the relativity of simultaneity.

I gather this has been also noted in the literature, for instance
] "The challenge of changing deeply held student beliefs about the relativity
of simultaneity" [/url]

I think there have been many other papers on this and related topics (about how to teach relataivity) as well, though Scherr seems to have done more work with actual students than some of the other papers I remember reading.

I've been looking for websites that take approaches inspired by Scherr's work. While I have found one

http://webphysics.davidson.edu/physlet_resources/special_relativity/

Whenever people pointed out Einstein's mistakes, they were introduced to read materials that improved on Einstein's original. I think this is not a good practice. That is, you indirectly acknowledged Einstein was wrong, and ask us to see other physicist's writing which improved on Einstein. If Einstein needs improvement, he is not Einstein. Here my question to Einstein's supporters is very simple: Were there 4 or 2 events? So simple that we don't need to read any improvements.

If your answer is 2, then please explain why because I have explained, using Einstein's original language, that there were 4.

I also have shown, either 2 or 4 events, Einstein was wrong.

To read those improvements will lead us to argue with those improvements. Our argument will have no end.

 

[K.J.Healey]

Please read what I posted above you real fast, i think it just took me to long to make the reply.

 

[Doc Al]

Einstein said:
"People traveling in this train will with advantage view the train as a rigid reference-body (co-ordinate system); they regard all events in reference to the train. Then every event which takes place along the line also takes place at a particular point of the train."

The words "also takes place" in the second sentence obviously says there are events taking place on the train.

If there are only two events A and B on the embankment, he must say "Then every event which takes place along the line will NOT take place at a particular point of the train."

You are still confused about the meaning of "event" and the meaning of a reference frame.

One last example: Imagine you are riding the train. When your watch strikes 1pm you sip a cup of tea; when it strikes 2pm, you take a bite of a biscuit. Those are two events. In order to understand relativity, you must think of those events as happening independent of reference frame. Any observer could view and measure the time and location of those events with respect to their own reference frame. With respect to the train, those events happened at the same place--your seat on the train; with respect to the embankment, the two events take place miles apart. No matter how many observers record the occurrance of each event (using their own reference frames), each event only happens once. If you don't get this, nothing else will make sense.

Now you said "But M' knows exactly where the flashes occurred--according to his reference (the train, of course) they occurred at A' and B', the ends of the train!" To me you were saying the samething as Einstein did: events taking place on the embankment also take place on the train. Due to the movement of the train, will a total of 4 events be created?

Still wrong. What if there were 100 trains on 100 tracks, all moving at different speeds and observing any events that take place? Are you saying that the lightning flashes hundreds of times, differently for each train? Come on!

Now you said this: "All the train observers have to go by is their own observations. They measure the location of the events (the lightning strikes) with respect to the train. Everyone agrees that the light from the two flashes arrives at M' at different times. But each frame will disagree as to why that is."

If what the train observer observed was the light from A' and B' [according to his reference (the train, of course) they occurred at A' and B'], how could they agree that the light from A' and B' arrives at DIFFERENT TIMES? To this question of mine, I request you use methematics to show how "they measure."

This is getting silly. Did you actually read the earlier posts? I answered this for you and repeated it for curt. If you need "methematics" to convince you of this, then you are missing the point. You are secretly assuming that train observers agree that the lightning strikes occurred at the same time. They don't.

Don't use affirmative but ambiguous sentences such "Everyone agrees that the light from the two flashes arrives at M' at different times." Ambiguous because the phrase "two flashes" could mean either A and B, or A' and B'.

Pay attention. When talking about train-frame observations, you use the train as a reference (A' & B'); when talking about embankment-frame observations, you use the embankment as a reference (A & B). Of course, this means nothing to you, since you still think "events" belong either to the train or the embankment.

Also realize that my statement "Everyone agrees.." is the conclusion of the detailed mathematical argument that I gave earlier.

Whenever people pointed out Einstein's mistakes, they were introduced to read materials that improved on Einstein's original. I think this is not a good practice. That is, you indirectly acknowledged Einstein was wrong, and ask us to see other physicist's writing which improved on Einstein. If Einstein needs improvement, he is not Einstein. Here my question to Einstein's supporters is very simple: Were there 4 or 2 events? So simple that we don't need to read any improvements.

If your answer is 2, then please explain why because I have explained, using Einstein's original language, that there were 4.

I also have shown, either 2 or 4 events, Einstein was wrong.

Give us a break. All you've shown is a lack of understanding of relative motion and reference frames as used in physics long before Einstein. (Look up Galilean relativity.) We haven't even gotten to really discuss the heart of special relativity--the unusual consequences of the fact that the speed of light is the same with respect to all observers. Discussing Einstein's arguments for the relativity of simultaneity is pointless if you haven't caught on to what an "event" means or what a "reference frame" is.

To read those improvements will lead us to argue with those improvements. Our argument will have no end.

Clearly this thread is going nowhere. Several folks have painstakingly tried to steer you towards understanding, to no avail. Time to shut this down.

Please read the sticky at the top of this forum before posting another "I can prove Einstein was wrong" topic. We've heard them all before.

 

[pervect]

Whenever people pointed out Einstein's mistakes, they were introduced to read materials that improved on Einstein's original. I think this is not a good practice.

I'd ask "why not", but this thread has already been closed.

But since you're not getting the idea, I'll be a bit more direct. Einstein was not wrong. You are wrong. Learn to deal with it.