Segundo

An Segundo amo an usa ka yano nga sukol han oras ha Kanasodnon Sistema han mga Panukol o SI (tikang ha Frinanses nga le Système international d'unités.

Pinanbasaran

Mga sumpay ha gawas

 National Physical Laboratory: Trapped ion optical frequency standards  
 High-accuracy strontium ion optical clock; National Physical Laboratory (2005)
 National Research Council of Canada: Optical frequency standard based on a single trapped ion 
 NIST: Definition of the second; notice the cesium atom must be in its ground state at 0 K
 Official BIPM definition of the second
 The leap second: its history and possible future
 What is a Cesium atom clock?