PDF Slides - UMBC
PDF Slides - UMBC
PDF Slides - UMBC
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Additional Slide [not shown in class]<br />
a Julian Year is 365.25 days (SI abbreviation ‘a’)<br />
a Tropical Year<br />
is the time taken for the Sun to move from<br />
one Vernal Equinox to the next<br />
ie. RA of Sun increases by 24.00000… hr<br />
365.2422 days long (J2000 each with 86400s)<br />
…used as the basis of civil calendar corrections in the west<br />
…but tropical day actually getting longer 1.5 ms /century<br />
a Sidereal Year<br />
is the time taken for the Sun to make<br />
one revolution wrt background stars<br />
365.2564 days long (J2000 each with 86400s)<br />
(longer due to precession – also varies)<br />
Ian M. George PHYS 304 (2011 Fall) Meeting 04
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