[1]https://www.sciencenews.org/article/atomic-clock-general-relativity-time-warp
-millimeter-physics

   "Does anybody really know what time it is?"

   https://youtu.be/jgF_ycCmF18

References

   1. https://www.sciencenews.org/article/atomic-clock-general-relativity-time-warp-millimeter-physics