What does,
\(\cfrac { \partial ^{ 2 }\, \psi }{ \partial \, t^{ 2 }_{ c } } =(ic)^{ 2 }\cfrac { \partial ^{ 2 }\, \psi }{ \partial \, x^{ 2 } } =-c^{ 2 }\cfrac { \partial ^{ 2 }\, \psi }{ \partial \, x^{ 2 } }\)
mean to be a wave in time dimension \(t_c\)? Simply, that it has to be detected in the time \(t_c\) dimension. All that is needed is an electric/electronic device. In the \(t_g\) time dimension it is not detected, an weighing machine will not be able to detect the wave, not directly.
