- 1948 - counting transitions of crystal
Cesium 133 used as atomic clock.
- TAI = International Atomic time. =>
9192631770 transitions = 1 mean solar second
at 1948 (but not today...)
Solution: from time to time (30+ times since 1958)
we skip a solar second to stay in phase with
the sun. This is UTC (Universal Coordinated
- UTC is broadcast by several sources.