Retrieving "Massive Particle" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Minkowski Metric

   Linked via "massive particle"

   Time-like Intervals ($ds^2 > 0$)
   When $ds^2 > 0$ (using the $(+,-,-,-)$ convention), the separation between two events is time-like. This means that a massive particle can traverse the spatial distance within the temporal separation. All paths along which massive particles travel (timelike geodesics in the absence of external fields) are associated with time-like intervals. The requirement that the speed of light $c$ is invariant implies that the time component must dominate the spat…

2. Speed Of Light

   Linked via "massive particle"

   The constancy of $c$ in all inertial reference frames is the second postulate of Albert Einstein's theory of Special Relativity (1905). This postulate leads directly to profound consequences, including time dilation, length contraction, and the mass-energy equivalence ($E=mc^2$).
   According to special relativity, no massive particle can at…