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What The Observer Saw

Special relativity simultaneity of time

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#1 JulianM

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Posted 31 December 2017 - 10:28 AM

What the Observer saw.

Up front I admit I have only a limited understanding of Relativity and in particular what it means to have light travel at (c + v).

In order to understand this better let's consider the classical train/platform thought experiment with lightning bolts at each end of the train.

Because light travels at c in both frames then the time to reach the middle in each case is simply c/(l/2) where l is the length of the train. Both experience this in their own frame.

Now let's consider a train with a window in the middle where the passenger sits, so the station master can't see what happens inside. In this case light arrives at the passenger from both ends at the same time illuminating both sides of the passenger's face. This image is visible to the station master.

The image of the illuminated passenger then travels back to the station master who determines the time delay between the arrival of the flashes at his location and the time he sees the image of the passenger.

Surprisingly that time difference is simply the time that light takes to reach him from the passengers momentary position.

The station master concludes that both events were simultaneous in time. Yes there is a time delay but, for example, a witness could see President Kennedy's assassination in Dallas and another could view it live on television in London. Yes, there is a time difference but solely due to the transmission time.

How can both observers see the same event and determine it happened at the same time for both frames of reference and both agree on the distances, speed of light, etc.
This contradicts standard assumptions about simultaneity of time.

As far as I can determine all theory related to simultaneous of time, etc. is based on an observer theoretically seeing something he cannot see.

You can extend this line of thinking to a train with a lot of windows with some very surprising results.

#2 JulianM

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Posted 01 January 2018 - 04:26 AM

Since there have been no replies to my post I am going to assume that (rightly or wrongly) that it has not been considered “strange” enough to be ridiculed.

In a train with multiple windows the expectation of Special Relativity is that you can see the light travel away from you at (c + v). Your expectation is that because of the velocity v, the illumination, as it progresses along the windows, would not occur where you would expect it to be because SR compares the position in the traveller's frame with where light in the observer's frame ought to be. SR neglects to consider that the image must now travel back to the observer such that the theorized position is cancelled out by the delay in the return path.

What this means is that the observer no longer considers light in the train reference frame to be travelling at (c + v) because the observer actually sees a series of events that define it as travelling at c.

OK, so what does this mean?

It means that theorizing the motion of my light in your reference frame does not agree with the events that I would actually see. Since Special Relativity makes this assumption then regardless of how clever the math might be it simply doesn't apply.

Nothing, yet, contradicts Einstein's postulates. What it does say is that from that point forward he went off track (pun?) by applying his math incorrectly.
The only real evidence we have of what happens in another frame of reference is event observation yet SR ignores this and is based on “thought” experiments.

At this point you are going to say that Relativity has been proven multiple times by observation. Well, have you really read that stuff?
Gravitational lensing is more easily explained if a photon is not completely massless.
If GPS would create errors of such significance to what extent is SR actually used to prevent spacecraft from landing in the wrong place. Why does the GPS interface document say “ these
coefficients do not include corrections for relativistic effects, the user's equipment must determine the requisite relativistic correction” (what!), and why has no one repeated the clocks in airplanes experiment with clocks on the space station? Time dilation on the ISS has been calculated to be insignificant (not effectively measurable), yet somehow it was detected as significant in an airplane?

An atomic clock on the ISS is an easy experiment. China has tried such an experiment, with inconclusive results, except for vague statements like - the clock is working as expected (what does that mean, it's still ticking?). The ACES experiment, proposed in 1997 has still not yet been launched, due to lack of funding! Really? we spend hundreds of millions teaching this stuff but we don't have the money to check it by observation?

Have you heard that the proof of e=mc2 is that nuclear weapons “work”? Well wouldn't they still work if e= ½ mv2. Where are the experiments that show a nuclear explosion has twice the energy previously expected?
Why is e= ½ mv2 wrong? Because we “know” that mass increases with speed because SR tells us so. So relativity proves relativity.

Here's the point. We can only know what happens in another reference frame by observing events, and when we do that Relativity seems to fall apart.
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#3 exchemist

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Posted 01 January 2018 - 06:48 AM

What the Observer saw.

Up front I admit I have only a limited understanding of Relativity and in particular what it means to have light travel at (c + v).

In order to understand this better let's consider the classical train/platform thought experiment with lightning bolts at each end of the train.

Because light travels at c in both frames then the time to reach the middle in each case is simply c/(l/2) where l is the length of the train. Both experience this in their own frame.

Now let's consider a train with a window in the middle where the passenger sits, so the station master can't see what happens inside. In this case light arrives at the passenger from both ends at the same time illuminating both sides of the passenger's face. This image is visible to the station master.

The image of the illuminated passenger then travels back to the station master who determines the time delay between the arrival of the flashes at his location and the time he sees the image of the passenger.

Surprisingly that time difference is simply the time that light takes to reach him from the passengers momentary position.

The station master concludes that both events were simultaneous in time. Yes there is a time delay but, for example, a witness could see President Kennedy's assassination in Dallas and another could view it live on television in London. Yes, there is a time difference but solely due to the transmission time.

How can both observers see the same event and determine it happened at the same time for both frames of reference and both agree on the distances, speed of light, etc.
This contradicts standard assumptions about simultaneity of time.

As far as I can determine all theory related to simultaneous of time, etc. is based on an observer theoretically seeing something he cannot see.

You can extend this line of thinking to a train with a lot of windows with some very surprising results.

Your ratio for the time is upside down, isn't it? 



#4 JulianM

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Posted 01 January 2018 - 06:50 AM

Is it? If you can elucidate please help.

#5 sluggo

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Posted 12 January 2018 - 11:37 AM

JulianM;

 

Because light travels at c in both frames then the time to reach the middle in each case is simply c/(l/2) where l is the length of the train. Both experience this in their own frame.

 

 

Blue is a light path, gray is a measurement.

On the left:

The train length R-F moves in the x direction with the passenger P at the midpoint. The bystander S is at the midpoint of the train when the flashes R and F occur. S sees R and F simultaneously. P establishes his axis of simultaneity (via clock synchronization) as Px, and thinks F occurred before R, which agrees with his experience.

 

Simultaneity is relative to the inertial frame of reference.

 

On the right:

P emits light signals in opposite directions which return simultaneously, which supports his assumed pseudo rest frame.

 

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  • sf-train.gif


#6 JulianM

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Posted 18 January 2018 - 07:05 AM

JulianM;
 

 
Blue is a light path, gray is a measurement.
On the left:
The train length R-F moves in the x direction with the passenger P at the midpoint. The bystander S is at the midpoint of the train when the flashes R and F occur. S sees R and F simultaneously. P establishes his axis of simultaneity (via clock synchronization) as Px, and thinks F occurred before R, which agrees with his experience.
 
Simultaneity is relative to the inertial frame of reference.
 
On the right:
P emits light signals in opposite directions which return simultaneously, which supports his assumed pseudo rest frame.



Unfortunately the images are to blurred for me to read in full and I can`t exactly see Px.

Would you mind posting a better picture or perhaps link to a higher quality image?
Thanks

#7 sluggo

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Posted 31 January 2018 - 12:40 PM

Unfortunately the images are to blurred for me to read in full and I can`t exactly see Px.

Would you mind posting a better picture or perhaps link to a higher quality image?
Thanks

Did you click on them, to open in a larger window?



#8 pzkpfw

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Posted 31 January 2018 - 05:55 PM

...
Because light travels at c in both frames then the time to reach the middle in each case is simply c/(l/2) where l is the length of the train. Both experience this in their own frame.

Now let's consider a train with a window in the middle where the passenger sits, so the station master can't see what happens inside. In this case light arrives at the passenger from both ends at the same time illuminating both sides of the passenger's face. This image is visible to the station master.
...

 

You go wrong right from the start because you seem to be assuming absolute simultaneity (and apply it to a thought experiment which shows simultaneity is relative).

 

In the usual form of the experiment, the strikes are stipulated to be simultaneous for the embankment, and it is shown they can not simultaneous for the train. It's shown that the flashes wouldn't reach the face of the passenger in the middle at the same time. Someone on the embankment would see this (the non simultaneous arrival).

 

We can just as easily stipulate another two strikes that are simultaneous for the train. Those flashes reach the middle passenger at the same time, and someone outside could see that through your window. But for that outside observer, the strikes wouldn't be simultaneous (as per the thought experiment).

 

In short, both observers consider themselves as at rest and exactly between the two strikes. So both would consider the strikes as simultaneous if they see those flashes at the same time. However, because the observers are in relative motion, it's impossible for both observers to see the same two flashes at the same time. So they can't both consider those same two flashes to be simultaneous.



#9 Moronium

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Posted 08 April 2018 - 12:07 PM

 

 

In short, both observers consider themselves as at rest and exactly between the two strikes. 

 

This is the real heart of the problem, not what observers see.   They cannot BOTH be at rest, although they are both free to "consider" themselves to be.  But at least one of them must be wrong.  Perceptions (in this case it's not really perceptions, but rather assumptions) can be wrong.  

 

Here's the logical contradiction put another way:'

 

1.  A claims that he is at rest, and that B is moving (and therefore B's clock has slowed down);

 

2.  B claims that he is at rest, and that A is moving (and therefore A's clock has slowed down).

 

It is not logically possible for both to be "at rest" when there is relative motion between them

 

Looked at another way, the (self-contradictory) claim is that, at the same time, A's clock (or B's, for that matter) is faster than B's and A's clock is also slower than B.

 

THat aint possible.


Edited by Moronium, 08 April 2018 - 12:10 PM.


#10 A-wal

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Posted 08 April 2018 - 02:39 PM

NO! Neither of them are wrong, they are both at rest in their own frame of reference while the other is in motion relative to them. Both are time dilated and length contracted from the other's perspective and there's no contradiction because they're in different frames of reference. For it to be impossible there would actually have to be a logical contradiction but there isn't one.

If one of them accelerates into the frame of reference of the other then the one that accelerates will have experienced less proper time (the time that passes for an observer) because they were in motion relative to an object at rest in their new frame of reference so they're now in a frame in which they were time dilated before they accelerate into this frame.



#11 Moronium

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Posted 08 April 2018 - 04:32 PM

NO! Neither of them are wrong, they are both at rest in their own frame of reference while the other is in motion relative to them. Both are time dilated and length contracted from the other's perspective and there's no contradiction because they're in different frames of reference. For it to be impossible there would actually have to be a logical contradiction but there isn't one.

 

  As a matter of objective reality it is impossible for one of them NOT to be wrong.

 

As a matter of subjective fantasy, they can both be right iN THEIR OWN MIND, if you want to call that "right."   One could be hallucinating seeing a bear and the other a tiger, and they would be be right in their own mentally imbalanced "frame of reference."

 

But the subject of physics pertains to objective matter in motion, not psychological states.

 

I'm simply speaking as a matter of physics, not subjective psychology.  You do see the difference, don't you, A-wal?


Edited by Moronium, 08 April 2018 - 04:33 PM.

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#12 Moronium

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Posted 08 April 2018 - 05:39 PM

  You do see the difference, don't you, A-wal?

 

Let's say you're 6' feet tall and I'm 4' tall.  I can believe I'm taller than you, and you can believe that you're taller than me.  There is no inherent "contradiction" in that.  I'm simply wrong, that's all.  Nothing novel or unusual about that. Mistakes are made millions of times, every day, all over the world.

 

The contradiction only enters if someone tries to claim that no one is mistaken and that we're BOTH right. 

 

We can't both be right, as an objective matter of empirical fact.

 

Right?


Edited by Moronium, 08 April 2018 - 05:40 PM.


#13 A-wal

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Posted 08 April 2018 - 05:56 PM

 As a matter of objective reality it is impossible for one of them NOT to be wrong.

 

As a matter of subjective fantasy, they can both be right iN THEIR OWN MIND, if you want to call that "right."   One could be hallucinating seeing a bear and the other a tiger, and they would be be right in their own mentally imbalanced "frame of reference."

 

But the subject of physics pertains to objective matter in motion, not psychological states.

 

I'm simply speaking as a matter of physics, not subjective psychology.  You do see the difference, don't you, A-wal?

Lol!

 

Let's say you're 6' feet tall and I'm 4' tall.  I can believe I'm taller than you, and you can believe that you're taller than me.  There is no inherent "contradiction" in that.  I'm simply wrong, that's all.  Nothing novel or unusual about that. Mistakes are made millions of times, every day, all over the world.

 

The contradiction only enters if someone tries to claim that no one is mistaken and that we're BOTH right. 

 

We can't both be right, as an objective matter of empirical fact.

 

Right?

It's only a contradiction for both object A to be taller than object B and object B to be taller than object A if they're in the same frame of reference. If they're in different frames of reference then both are right and there's no contradiction. If you don't understand that the the problem is with you, not with physics.



#14 Moronium

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Posted 08 April 2018 - 06:30 PM

The question was:  'I'm simply speaking as a matter of physics, not subjective psychology.  You do see the difference, don't you, A-wal?'

 

Your response:

Lol!

 

It's only a contradiction for both object A to be taller than object B and object B to be taller than object A if they're in the same frame of reference. If they're in different frames of reference then both are right and there's no contradiction. If you don't understand that the the problem is with you, not with physics.

 

 

Is that supposed to be an "argument?"  A "response?"  What?

 

Do you understand the difference between a subject and an object?  Yes or no?

Do you understand the difference between physics and psychology?  Yes or no?

As a philosophical matter, do you understand the difference between solipsism and realism?  Yes or no?

 

I ask again, because you seem to exhibit no understanding of such distinctions.

 



#15 A-wal

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Posted 13 April 2018 - 03:54 PM

The question was:  'I'm simply speaking as a matter of physics, not subjective psychology.  You do see the difference, don't you, A-wal?'

 

Your response:

 

 

Is that supposed to be an "argument?"  A "response?"  What?

 

Do you understand the difference between a subject and an object?  Yes or no?

Do you understand the difference between physics and psychology?  Yes or no?

As a philosophical matter, do you understand the difference between solipsism and realism?  Yes or no?

 

I ask again, because you seem to exhibit no understanding of such distinctions.

I like you, you're funny. :) It's a pity you don't mean to be.

 

 

Both are at rest in their own frame of reference. Both are in motion in the other observer's frame of reference. The rules of physics are the same in all frames of reference. Neither one has a valid case for being in a preferred frame. If there was a third observer in motion relative to both of them then the third observer would be at rest in their own frame of reference. All non-accelerating observers are at rest in their own reference frame by definition.

Try to understand, you're lack of comprehension is in no way evidence that there's something wrong with the model.



#16 Moronium

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Posted 14 April 2018 - 04:21 AM

I like you, you're funny. :) It's a pity you don't mean to be.

 

 

Both are at rest in their own frame of reference. Both are in motion in the other observer's frame of reference. The rules of physics are the same in all frames of reference. Neither one has a valid case for being in a preferred frame. If there was a third observer in motion relative to both of them then the third observer would be at rest in their own frame of reference. All non-accelerating observers are at rest in their own reference frame by definition.

Try to understand, you're lack of comprehension is in no way evidence that there's something wrong with the model.

 

 

Try to understand this, A-wal:  Although SR glibly asserts, as a philosophical matter, that all inertial frames are equally valid, the theory DENYS this in practice.

 

In SR, an observer is not free to treat the "other guy" as the one moving  That is strictly prohibited,  You cannot just arbitrarily chose an inertial frame to use for calculation purposes in SR.  You MUST (absolutely mandatory, no exceptions) treat the (inertial) frame you are is as a PREFERRED frame which is "at rest."


Edited by Moronium, 14 April 2018 - 04:22 AM.


#17 Moronium

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Posted 14 April 2018 - 04:33 AM

I like you, you're funny. :) It's a pity you don't mean to be.

 

 

Both are at rest in their own frame of reference. Both are in motion in the other observer's frame of reference. The rules of physics are the same in all frames of reference. Neither one has a valid case for being in a preferred frame. If there was a third observer in motion relative to both of them then the third observer would be at rest in their own frame of reference. All non-accelerating observers are at rest in their own reference frame by definition.

Try to understand, you're lack of comprehension is in no way evidence that there's something wrong with the model.

 

I understand the claims of SR perfectly.  Don't take my rejections of the absurd implications of the theory as a "lack of comprehension."

 

By "understand," I actually mean understand, which is different from merely being able to parrot, from memory, the dictates I have been told to accept without any satisfactory rational explanation.  

 

As much as you smugly and arrogantly pretend to superior understanding, I'm afraid you display none of it.  You are, however, a good tool, who will zealously and faithfully recite the "talking points" of SR advocates reflexively and automatically.  But that's not "understanding," I'm araid.


Edited by Moronium, 14 April 2018 - 04:35 AM.




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