PDF Slides - UMBC
PDF Slides - UMBC
PDF Slides - UMBC
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Additional Slide [not shown in class]<br />
While we have a fundamental unit of time for science<br />
- the second which is now well defined [& accepted]<br />
via an atomic transition (hyperfine levels of grd state of 55 Cs 133 )<br />
[& have atomic clocks accurate to 1 part in 10 14 per day]<br />
.. this unit is not that practical for “everyday” use<br />
- desire & practical usefulness to divide “time”<br />
into ‘bite-sized’ units (hours, days, years etc…)<br />
BUT<br />
also want these ‘bite-sized’ units to be related to astronomy!<br />
… for practical reasons we want the units we’ve named<br />
“days” & “years” to be related to the Sun.<br />
[this is very convenient in everyday life!]<br />
..and we want to have these ‘bite-sized’ units<br />
to be integer multiples of each other [60s in an “hour” etc]<br />
[this is also very convenient in everyday life!]<br />
Ian M. George PHYS 304 (2011 Fall) Meeting 04
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