deletions | additions       diff --git a/Space Time field.tex b/Space Time field.tex  index 6703619..9173563 100644  --- a/Space Time field.tex  +++ b/Space Time field.tex 
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We observe that the speed of any physical object is absolute when it expresses a relationship between physical variables that are different from space and time.\\  This happens only in one case: in the propagation of a wave within an elastic medium, where the wave speed depends on the inertial ($\rho$) and elastic characteristics ($T$) of the medium.  \begin{equation}  v v^2  = \frac{T}{\rho} \end{equation}  Certainly, the elastic medium is not \emph{the ether}; therefore we must admit that the elctromagnetic field has some \emph{elastic} and \emph{inertial} properties, and works in itself as its own medium.\\  Indeed, if the dielectric constant $\varepsilon_0$ is put in a correspondence with the elastic constant, and the magnetic constant $\mu_0$ in correspondence with inertial constant, to write: