The second is the duration of 9 192 631 770 [[Period (physics) [] of the radiation corresponding to the transition between the two Hyperfine structure [] of the ground state [] of the caesium-133 [] atom [].
Originally, the second was known as a "second minute", meaning the second minute (i.e. small) division of an hour. The first division was known as a "prime minute" and is equivalent to the minute we know today.
- 60 seconds = 1 minute []
- 3 600 seconds = 1 hour []
- 86.4 kiloseconds (86 400 seconds) = 1 day [] (in the SI sense)
See also explanation at []
The definition of the second was later refined at the 1997 meeting of the Bureau International des Poids et Mesures [] to include the statement
- This definition refers to a caesium atom at rest at a temperature of 0 K.
See also Edit
- Official BIPM definition of the second
- Public domain article about definition of seconds and leap seconds
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