Einstein-Synchronisation

In the theory of relativity is the Einstein synchronization (also Poincaré -Einstein synchronization) a convention for synchronizing clocks in different places.

Einstein convention

Many different approaches to achieve the result the same synchronization, for example, the emission of a light signal midway between clock 1 and clock 2, or "slow" transport of a third clock from clock to clock 1 2, in the limit of vanishing velocity.

In a paper of 1917, Einstein noted, however, a definition before, according to the decision can be made whether pairs of ads each stationary clocks were the same to each other or not, does not require a specific parameterization of ads one way or another clock, yet the term speed or even considerations regarding the "disappearance " of non-zero speed levels. Using this definition of simultaneity watches are simply then be synchronous if the couple of their ads, which were measured at the same time as each other looked the same.

But only in inertial frames this synchronization appears so natural that it 's easy to forget that it is just a convention. In the general case, such as a rotating frame of reference, is the non- transitivity of synchronization for supporting. If clock 1 and clock 2 can not be directly but synchronized through a chain of other watches, the result depends on the selected route. The synchronization along the circumference of a rotating disk results in a time warp to the output clock, which depends on the sense of rotation. This is the Sagnac interferometer and the Ehrenfest'schen paradox to bear. The Global Positioning System, this effect must be considered.

The first basic discussion of the conventionality comes from Reichenbach. Most attempts to refute the conventionality are considered to be refuted. The outstanding exception is Mala Apartments argument to require the symmetry of the causal connection ( Zeitartigkeit ), implies the Einstein synchronization. Since he published this argument in 1977, there is a constant stream of both dismissive and consenting work.

History: Poincaré

As early as 1898 Henri Poincaré emphasized that it is advantageous for the simplest possible formulation of the laws of nature, to assume the speed of light to be constant in all directions. Also is the definition of simultaneity of events at various locations merely a convention aimed at simplicity.

The Lorentz ether theory underlying legend, he defined 1900, the synchronization of clocks as follows: Two clocks A and B each send each other a light signal. Since all observers may assume by virtue of the validity of the principle of relativity to rest in the ether, they go from the constancy of the speed of light in all directions. That's why they are for the correct synchronization of the clocks into account only the term of the signals and coordinate their observations with each other.

1904 extended Poincaré this example this way: If clock A time shows 0, it sends a signal to B. Similarly B sends clock when it reads 0, a signal to A. If both clocks at the arrival of the signals the same time t Show, the watches are by definition synchronous.