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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.

#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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#6 JulianM

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Posted Yesterday, 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



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