Motor Daddy
Valued Senior Member
So you agree that the train observer will agree with the embankment observer's numbers when his clocks are sync'd, and that there really exists no relativity of simultaneity?
The Relativity of Simultaneity
- Thread starter Motor Daddy
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Motor Daddy
Valued Senior Member
How did he measure the ticks without sync'd clocks, again?
Well, that's what relativity of simultaneity is.
The train observer can't synchronize his clocks absolutely, so he shrugs his shoulders and makes do.
The embankment observer is in the same boat.
He really can't tell that the embankment is really at rest and the embankment clocks are absolutely synchronized. For all he knows, his clocks might be unsynchronized and the embankment moving.
Yes, the train observer will agree with the embankment observer's numbers if he synchronizes his clocks according to the embankment synchronization standard.
But, the embankment observer will also agree with the train observer's numbers if he synchronizes his clocks according to the train's synchronization standard.
The train observer can't synchronize his clocks absolutely, so he shrugs his shoulders and makes do.
The embankment observer is in the same boat.
He really can't tell that the embankment is really at rest and the embankment clocks are absolutely synchronized. For all he knows, his clocks might be unsynchronized and the embankment moving.
Yes, the train observer will agree with the embankment observer's numbers if he synchronizes his clocks according to the embankment synchronization standard.
But, the embankment observer will also agree with the train observer's numbers if he synchronizes his clocks according to the train's synchronization standard.
He made a measurement according to the clocks he has.
Because his clocks weren't absolute synchronized, he got the 'wrong' result - he measured the frontward and rearward ticks to be equal.
Motor Daddy
Valued Senior Member
How many ticks did he measure in each direction?
Motor Daddy
Valued Senior Member
Yeah, exactly the problem.
I am in the train, and you are in the train. I say the train has a 28,549 m/s velocity, and you say the train has a zero velocity. If there was another person there they would say the train had a 300,000,000,000,000 m/s velocity.
No standards, just assertions.
Motor Daddy
Valued Senior Member
So he measures 1.25 ticks in each direction. He doesn't know how much his clocks are out of sync by, so he can't measure the speed of light accurately, correct?
...and how did he determine the train had a velocity from the fact that he measured 1.25 ticks in each direction?
So he still hasn't proven the train to be at a zero velocity, or any other velocity for that matter. Since he hasn't done that:
1. He doesn't know the length of the train.
2. He doesn't know the length of his sticks.
3. He doesn't know how many ticks are equal to 1 second.
4. He doesn't know how many sticks equal 1 meter.
5. He doesn't know the speed of light.
6. He doesn't know the train's velocity.
7. Since he doesn't know the train's velocity, he doesn't know the time dilation
8. Since he doesn't know the train's velocity he doesn't know the length contraction.
9. He doesn't even know how many ticks it takes for light to travel the length of 1 stick, because he doesn't know how far out of sync his clocks are.
No, actually it's absurd to base your measurements on nothing. It's like building a house with no foundation.
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All correct. Not only for the train observer, but also for the embankment observer.
What choice do they have?
They have to base their measurements on the tools they can access.
Motor Daddy
Valued Senior Member
I can prove the embankment is at a zero velocity. So far the only thing the train observer knows is that it takes 1.25 ticks for light to travel in each direction of the train, using asynchronous clocks. Is there any other statements you think the train observer can make, or do you rest his case, concluding he doesn't know squat, and is in no position to judge anyone's motion using the units meters and seconds?
...and he certainly isn't in any position to make statements as to when the lights struck A and B on the train, or the embankment, or as to how much time it took to travel from A to B to his position or the embankment's observer's position.
I can prove the embankment's position. As the spokesmen for the train observer, do you have any other measurements you can make on the train that can allow you to know anything more, other than it takes 1.25 ticks for light to travel in each direction on the train?
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Please try.
It's not a trial, MD. We're working together to learn something.
The train observer's current suspicion is that he might as well consider himself at rest.
After all, his clock is a standard cesium clock, and to the best of his ability to measure, his rulers are a standard metre long.
But he's a scientist, so he never 'rests his case'. He's always open to learning something new.
Not according to the embankment standard, no.
But what's wrong with the train standard that isn't just as wrong with the embankment standard?
Motor Daddy
Valued Senior Member
So as a scientist, he uses his suspicion as a basis for all his statements about motion? He suspects that his clocks and rulers are accurate? That's rather unscientific, wouldn't you say? I mean, he doesn't perform any test to determine the speed of light or the velocity of the train? He just suspects his stick to be one meter long? That's laughable, Pete.
The train has no standard meter or second. Did the train observer ever measure the speed of light on the train? Does he know his clock is accurate, and sync'd? Does he know how many sticks it takes to make one meter? The meter is defined by the speed of light, and yet he hasn't done anything with the speed of light in the train, so he knows NOTHING. Like I said, he can define his own standard stick by the speed of light, if he chooses. Is that what he wants to do?
So, back to the scenario.
Let's say the train observer has 'synchronized' his clocks as best he can before the encounter.
When the lightning strikes:
The train clock at M' reads t' = 0.000 ticks
The train clock at B' reads t' = -0.375 ticks
The train clock at A' reads t' = 0.375 ticks
So as far as the train observer can tell, the lightning strike at B' happened before the strike at A'.
Is that what really happened? According to the embankment standard, he's dead wrong.
But how reliable is the embankment standard? Does it have the same problems as the train standard?
Motor Daddy
Valued Senior Member
Like I said, I can prove the embankment is at a zero velocity. I can prove his sticks are exactly 1 meter long, by definition, using the speed of light. But what I can prove as an embankment observer is not available to the train observer, as he has no contact to me. All he knows is that it takes 1.25 ticks on his asynchronous clocks in the train for light to travel in each direction. Do you want me to make statements about the embankment, so you can use them to further your own case? Not likely, Pete. My measurements are not accessible to the train observer. We are comparing what the train observer measures and what the embankment observer measures, and seeing if they agree or disagree, and who is correct?
When you rest your case for the train observer I will present my case for the embankment observer.
His clocks are identical to the embankment clocks, and his rulers are identical to the embankment rulers. The only difference is their motion.
Yes, he has carried out measurements, as spelled out in this thread.
Every measurement he performed is consistent with:
- the train being at rest,
- his rulers being one metre long,
- his clocks running at one tick per millisecond
- the speed of light being 299792458 m/s
Yes. Remember the flash, the mirror, and the timer?
He knows just as much about train clocks as the embankment observer knows about embankment clocks.
He knows just as much about train rulers as the embankment observer knows about embankment rulers.
Is that what you want him to do?
Fine.
He does that, and finds that according to his clocks his rulers are exactly one metre long.
Please do.
But be sure to check that your clocks are synchronized first.
I'm not here to win a case, MD. Science isn't a fight. I'm here to learn.
If I have the wrong idea about this, then I will be very happy to have that corrected.
Motor Daddy
Valued Senior Member
Yeah, which means they are dilated and contracted, which he has no way of knowing by how much because he doesn't know the motion of the train. You say he suspects his motion to be at rest, but hasn't even properly sync'd clocks to measure whether that is true or not. For all he knows the train has a 458,000,000,000,000,000,000 m/s velocity. Prove it doesn't!
BULL!@!!
He never sync'd his clocks so he knows NOTHING other than it takes 1.25 ticks for light to travel each direction according to asynchronous clocks, of which he doesn't even know how far out of sync the clocks are.
His measurements don't prove the train is at rest, but they are consistent with the train being at rest.
You'll find the same thing on the embankment.
Every measurement he did (except for the lightning flash measurements) would have returned the same result if the train were parked at the embankment.
Exactly the same applies for the embankment observer.
The embankment observer doesn't actually know the embankment motion, or how far out of sync the embankment clocks are.
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Motor Daddy
Valued Senior Member
You don't seem to understand, Pete.
For instance, there is a stick on the train. How does he determine what the length of the stick is, using the speed of light and the unit of measure "meter?"