Ed Staples Close up of My Watch Lunar or Solar The story of the calendar is essentially centred around the three natural cycles of the daily sun rise the lunar cycle and the tropical year The 7 day week ID: 288956
Download Presentation The PPT/PDF document "The History of the Gregorian Calendar" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
The History of the Gregorian Calendar
Ed StaplesSlide2
Close up of My WatchSlide3
Lunar or Solar?
The story of the calendar is essentially centred around the three natural cycles of the daily sun rise, the lunar cycle, and the tropical year. Slide4
The 7 day week
The
seven
day week has no natural markers. It is an intellectual creation and does not fit well with the lunar or solar calendar. Slide5
Check your salary!Slide6
Check your salary!
Because there are 313 fortnights in 12 yearsSlide7
1st
Roman Calendar: Romulus 753 BCSlide8
Changes by King Numa: 7
th
Century BC
Lunar CalendarSlide9
Beware the ides of March!Slide10
1st
Attempt to align with seasons: Numa 2Slide11
Julius Caesar 46BC (Sosigenes)
The Julian CalendarSlide12
Caesar’s adjustment to the vernal equinoxSlide13
432BC : The Metonic Cycle (Greece)
235 Lunations is virtually identical to 19 Tropical Years
Slide14
Golden numbers still used to determine date of Easter Sunday
Golden numbersSlide15
Solar year re-calculated as 365.2219 yearsSlide16
Go to the Equator – look East
E
WSlide17
Solstice – Sun in CapricornSlide18
equinoxSlide19
Solstice – Sun in CancerSlide20
equinoxSlide21
Solstice – Sun in CapricornSlide22
Like a coil of rope
Solstice
Solstice
EASTSlide23
The precise moment of the equinox
EastSlide24
Walking south to Canberra Lat:35S
If we walk south back to Canberra from the equator, the rising vertical star lines will appear to lean away from us (lean toward the north)
This is because we are on a spherical earthSlide25
Canberra Sun rising
South
East
North
Lat
90 - LatSlide26
Motion of the Sun over the year
North
South
LatSlide27
Looking East in CanberraSlide28
Looking South in Canberra
South
Canberra Latitude 35 degreesSlide29
The equatorial ring
90 - LatSlide30
The equatorial ring
90 - LatSlide31
The equatorial ring
90 - LatSlide32
The equatorial ring
90 - LatSlide33
The equatorial ring
Equinox point
Shadow falls
90 - LatSlide34
The equatorial ring
Post Equinox point
Shadow falls
90 - LatSlide35
Equinox by Sundial?
The, shadow is shortest in Summer and longest in winter, so at some stage in its “vertical” journey, the shadow tip will touch the equinox line. (twice a year )Slide36
A Canberra Sundial (35 deg gnomon)
Equinox line
Summer Solstice
Winter SolsticeSlide37
Hence….
Actual Tropical Year 365.24219 days
Julian assumption 365.25 days
Difference
0.00781
days
(Spotted by the Venerable Bede in AD 725
Slide38
Do the Maths!
0.00781 X 24 X 60 =
11 minutes and 15 secondsSlide39
How the small difference accrues Slide40
Luigi Lilio’s
solutionSlide41
Pope Gregory: 1582 (Lilio
)
The Gregorian calendarSlide42
The UK experience 1751Slide43
10 minute breakSlide44
Zeller 1883Slide45
Conway’s DoomsdaySlide46
Corrections