Image 1 Caption: Girl with Doves (c. 440--450 BCE).
An artwork
of ancient Greek sculpure
from the lifetime
of Meton of Athens (late 5th century BCE).
For a better image,
see girl_with_doves.html.
If you ever doubted that the
ancient Greeks
had ordinary family feeling,
their grave
steles set your mind at rest.
But from sculpture to
astronomy to disgress:
Features:
- Meton
is the eponym
and possibly a secondary independent
discoverer
of the
19-years
Metonic cycle
which is a pretty accurate/precise way of inserting
intercalary months
in lunisolar calendar
(see Wikipedia: Metonic cycle;
Otto Neugebauer 1969,
The Exact Sciences in Antiquity, p. 7;
John North 1994, The Norton History of Astronomy and Cosmology, p. 65)
Explication of
the 19-years
Metonic cycle:
- Consider 19
years.
- Let 12
years
consist of 12
lunar months.
- Let 7 years consist of
13
lunar months.
- To be accurate/precise,
we will use values for
the J2000 epoch:
solar year = 365.2421897 days (J2000),
lunar month = 29.530588853 days (J2000).
- In the 19 years
counted thusly, there are
235
lunar months
which equal 6939.69 days.
- Now 19
solar years equals 6939.60 days.
-
Thus, there is a discrepancy of only ∼ 0.09 days after one
Metonic cycle of
19 years.
- From any time zero, it takes 219
solar years
of using Metonic cycle
for the calendar year based on the
Metonic cycle
to end ∼ 1
day after the end of the
219th
solar year.
- Thus, for a trivial procedure, the
Metonic cycle isn't bad.
- Image 2 Caption:
Girl with Doves (c. 440--450 BCE).
- The Babylonians
used the
Metonic cycle from
late 6th century BCE on, and
so presumbly knew it earlier, maybe much earlier
than Meton
(see Wikipedia:
Metonic cycle: Application in traditional calendars).
Meton may have learnt of the
Metonic cycle via some path from
Babylonians, but as aforesaid he
may have been secondary independent
discoverer.
In fact in Classical Antiquity,
where (what cities or
states),
when (what time frames),
and by whom (just
ancient Greek astronomers or them and
magistrates)
the Metonic cycle was used
is a complex subject.
Simpler or haphazard methods of inserting
the intercalary months
may often have been used in preference to or in ignorance of the
Metonic cycle.
In later
Classical Antiquity,
the Metonic cycle
was used in
Computus (the calculation of the date of Easter)
which has a highly complex history
(see Wikipedia: Computus: History).
The Metonic cycle
was known in China
by an independent
discovery
and perhaps
earlier than in
western Eurasia
(see Wikipedia:
Metonic cycle: Application in traditional calendars).
Images:
- Credit/Permission:
Original: Anonymous
ancient Greek sculptor,
c. 450 BCE--440 BCE,
(uploaded to
Wikimedia Commons
by User:Dschwen,
2006) /
CC BY-SA 3.0.
Image link: Wikimedia Commons:
File:Greek Girl with dove.jpg.
- Credit/Permission:
Original: Anonymous
ancient Greek sculptor,
c. 450 BCE--440 BCE,
Photo ©:
Mary Harrsch,
2007
(uploaded to
Wikimedia Commons
by User:Tm,
2020) /
CC BY-SA 3.0.
Image link: Wikimedia Commons:
File:Marble grave stele of a little girl with doves Greek 450-440 BCE found on the island of Paros (1) (746929431).jpg.
Local file: local link: metonic_cycle_girl_with_doves.html.
File: Moon file:
metonic_cycle_girl_with_doves.html.