Timekeeping: From the Sun to the Atomic Second

Recorded at the NPL Open House 2014, presented by Anne Curtis

[bazsnell]

Came here after watching your colleague give a very recent talk from the Royal Institution about the 'new' standards which will be defined by the cosmological universal constants, instead of the old 'physical' quantities. All must be ready for the global change-over in March 2019, so good luck.

[comicrelief]

The atomic clock time-keeping system consists of hundreds of atomic clocks strewn about the world, integrated to form a very consistent counter. The clocks sit at various altitudes and each must be corrected for gravitational time dilation.

[arthas]

I'm not sure how i got from a 17th century cooking show to here but im not complaining

[junaidiqbal]

Excellent presentation. Just a bit not clear about the accuracy of 1 sec over 3billion years for the ceisium atomic clock mentioned at 16.25. Other sources on Google say 300 million yrs or 138 million yrs for the same ceisium based atomic clock. Its a huge difference. Please anybody explain this.

[Murrayt-vucq]

would you multiply 9, 192, 000, 000 by 123 being weight of caesium to work out electron rotations per second of the atom of hydrogen thanks in advance for help on this one, is it really that simple to determine rotations per second taking into consideration the atom is at ground state?

[nkmahale]

Is the atomic clock in gravitational field or in a location free of gravitational field? If Einstein's General Relativity is right you need to define the location as well. Second on clock downstairs will be different than clock upstairs.