|Dec30-12, 09:29 PM||#18|
Relativity of Simultaneity
As you're probably aware, the invariance of the speed of light is a fundamental postulate of special relativity, and as such cannot be logically proved or disproved from first principles, at least not in the usual derivation of SR from Einstein's two postulates. It can only be verified or disconfirmed by experiment, either by measurements of the speed of light itself, or by other tests of the entire theory that has been built on that principle.
The theory as a whole has been extensively confirmed experimentally, as described here:
|Dec31-12, 03:46 PM||#19|
And as you correctly noted above this is simply a convention.The implementation of an unproved assumption.
They correctly measure time spans because those time intervals as indicated by those conventionally "unsynchronous"clocks correctly correspond to the spacetime at the given velocity and correspond to the physical values of mechanics and electrodynamics etc in that frame.
Length contraction has two separate causal sources.
1) A mechanical source due to the lightspeed interactions of atomic tensile and nuclear forces within the atomic structure of bodies. AN"actual" physical contraction.
2) Purely kinematic contraction due to clock desynchronization.
Individually both these concepts are asserted by different people and different circumstances. My feeling is that both are operative to varying indeterminate degrees in virtually all cases. But like so much in our relative universe there is no way to quantify or evaluate in any real sense which is the cause and to what extent in any particular case.
In neither case is it bogus.
But in a case of a single inertial clock traveling between two points and clocks in another frame then the ratio of this clocks proper time to the the coordinate delta t of those two clocks does involve consideration of relative synchronization between those clocks.
The 2nd postulate does not actually state that the measured one-way speed of light is invariant. It says that the speed of light is independe3nt of the motion of the source and is everywhere constant in vacuum.
It is measured as invariant by convention which is no real measurement at all.
|Dec31-12, 03:55 PM||#20|
I haven't seen the point I'm about to make in the literature, (at least not very directly) but I think it's a good one.
There is one, and only one, way of synchronzing clocks that will make Newton's laws work correctly.
To see this, just imagine having two equal masses with two equal velocities collide and then come to a complete stop - perfectly standard, and routine.
Now, tweak the clock synchronization you used to measure the velocities and repeat.
The velocities you measure are no longer equal. But the colliding masses still stop. They don't care how you synchronize your clocks.
Thus, there is one and only one clock synchronization that will make Newton's laws work. One way of viewing relativity is to say that this method is always equivalent to Einstein's much simpler method, using light signals.
|Dec31-12, 04:09 PM||#21|
You might also want to study the wikipedia article on The One-Way Speed of Light.
Once you understand that the one-way speed of light cannot be measured, you can see how Einstein's second postulate arbitrarily resolves that dilemma and provides a simple and consistent way to coordinate all the measurements that we can make. It works by the way he defines an Inertial Reference Frame (IRF) and how we can use the Lorentz Transformation to convert all the coordinates of the events in the first IRF into coordinates in any other IRF we choose. I have posted numerous diagrams for different scenarios that illustrate how this works. In every case, the one-way speed of light is always c, and yet everything that every observer sees or measures remains the same.
Here is a thread that shows a scenario where travelers go to a distant star that I think might help you:
You can do a search for "diagram" under my name and find more.
|Similar Threads for: Relativity of Simultaneity|
|The Relativity Of Simultaneity.||Special & General Relativity||3|
|How Is The Relativity Of Simultaneity Consistent With Physics And Relativity||Special & General Relativity||47|
|Relativity of Simultaneity||Special & General Relativity||2|
|Relativity of Simultaneity||Special & General Relativity||25|
|On The Non Relativity Of Simultaneity||General Physics||37|