Transcript Calendar - DAS UChile

YSS - Intro. to Observational
Astrophysics (ASTR 205).
Class # 2
The Science of Astronomy
Professor: José Maza
June 1, 2011
Calendar


Motion of the Sun: the day (24 hours) and
the year, a bit more than 365 days.
The week and the month have a different
origin. The month has it origin in the
motion of the Moon. In 29,5 days it goes
from new Moon to full Moon and back.

The lunar month can be divided into four
weeks, seven days each, corresponding to
the seven celestial bodies going around
the Earth: Mercury, Venus, Mars, Jupiter,
Saturn, the Moon and the Sun.


The week has an astrological origin. It was
believed that the seven celestial bodies
(Moon, Mercury, Venus, Sun, Mars,
Jupiter and Saturn) governed every hour
of the day.
If the first hour of one day was governed
by Saturn, the second was governed by
Jupiter, the third by Mars, the fourth by the
Sun, the fifth by Venus, the sixth by
Mercury and the seventh by the Moon.




In the eighth hour the cycle was restarted.
Then Saturn governed that day the first,
eighth, fifteenth and twenty-second; the
twenty-third would be governed by Jupiter
and the last one by Mars.
The following hour, the first of the next day
would be governed by the Sun.
It was adopted that the day would by
marked by the planet governing the first
hour.
Julian Calendar:


Romans adopted a year with 12 months of
29.5 days on average (30 & 29), totalizing
354 days, 11¼ days short of a tropical
year (the year of the seasons).
Every second year they added an extra
month during February, the last month of
the year.


The roman year started on March,
continued with April, May, June, Quintilis,
Sixtilis, September, October, November
and December;
The year ended with Januarius and
Februarius. On one occasion an extra
month of 22 days was added and the
following time the extra month had 23
days.

The years lasted 354, 376, 354 and 377
that is 1.461 days in four years, resulting
in an average of 365¼ days.

The extra months were ordered by the
Supreme Roman Pontifex, making it
confusing when the Empire grew large and
it was difficult to communicate the extra
month throughout the Empire.

The month of the roman year were:

Martius
Quintilis
November

Aprilis
Sextilis
December

Majus
September
Januarius

Junius
October
Februarius



In the year 46 B.C. Julius Cæsar in
Rome, with the advice of Sosigenes, an
Alexandrian astronomer, adopted a year
with twelve months with 365¼ days on
average, that is, three years in a row with
365 days and another of 366.
Months of 29 and 30 days become of 30
and 31, giving away the 11 extra days.
February until then the last month of the
year did not get an extra day and
remained with 29 days.



The year 46 B.C. (better named year 708
from the foundation of Rome) got 3 extra
months completing 445 days, for that
reason it has been named “the confusion
year”.
Starting 45 B.C. the Julian calendar
reigned.
The Roman Senate decided to changed
the name of the fifth month of the old year
to honor Julius Caesar (JULY).

The Julian reform consisted of:

1.- The beginning of the year was moved
to January 1 to make it coincide with the
appointment of the consuls.

2.- The duration of the old roman lunar
year was adjusted to the solar year,
producing month of the following duration:

Januarius
31
Majus 31
September 31

Februarius 29
Junius 30
October

Martius
31
Quintilis 31 November 31

Aprilis
30
Sextilis 30 December 30
30



With Julius Caesar the lunar aspect of the
calendar came to an end.
The calendar became strictly solar.
The month was preserved as an
intermediate unit but it does not have a
relationship with the Moon any more (the
new Moon or the full Moon can be at any
time of the month).




3.- Every four years an extra day is added
in February.
We believe the extra day is added at the
end of February.
The Romans added the extra day after
February 23.
That was the sixth day before to the
“calendas of March” (it was called “ante
diem sextum calendas martias”) and the
extra day was called “ante diem bissextum
calendas martias”, that is the sixth day
counted twice.

The extra day was called bissextus and
finally the year with that extra day was
called bisiesto (in Spanish) leap year (in
English).
Julius Cæsar



After the murder of Julius Caesar in the
hands of Brutus in 44 B.C. the Julian rule
was not followed; they added an extra day
every three years.
By the year 8 B.C. they have added 13
leap years instead of the 10 years of the
Julian rule.
The new roman Emperor Augustus Cæsar
did not add extra days until the year 8 A.D.
in order to have the spring starting on
March 25th as it was common in Rome.




The Roman Senate decided to named "August"
the sixth month, that had 30 days.
In order that the month of Augustus is "not less
than" that of Julius, the Roman Senate decided
that the month of August would have 31 days,
getting the extra day from February that had 29
days and was degraded to 28, rising to 29 only
once every four years.
For this reason we have two consecutive months
with 31 days (July & August).
The Senate change from 31 to 30 the seventh
month (September) and the ninth (November),
rising from 30 to 31 the eighth and tenth.

The calendar was left in the following form:

Januarius 31
Majus 31
September
30

Februarius 28
Junius 30
October
31

Martius
31
July
31
November
30

Aprilis
30
August 31
December
31

That order and length of the months is
used until today.



In the year 525 A.D. the abbot of Rome
Dionisius the Exiguous introduced the
usage of counting the years from the birth
of Christ instead of doing it from the
foundation of Rome.
He called year 754 from the foundation of
Rome year one after and the year 753 the
year one before Christ.
Dionisius did not considered the year zero
in our chronology because the Romans
did not have the concept of the number
zero.

It took a lot for the Christian era to get
massively used, being England the first to
use it in 705, France, in the year 742 and
Germany in 876.

In Portugal it was adopted in the year
1422. Even the Pope only adopted it in
1431.


Further studies indicate Dionysius was
wrong on his “appreciation” of the year of
the birth of Christ.
His source associated Christ’s birth with
the years of Augustus government (the
18th year) but Dionysius failed taking into
account 4 years that Augustus ruled in a
triumvirate (as Octavius).



Therefore Dionisius should have identified
year 750 after the foundation of Rome as
year 1 in Christ era.
That is why we find the paradox that, in
our chronology, Christ was borne the year
4 B.C.
A detailed discussion situates the year of
Christ’s birth between 7 B.C. and 4 B.C.


What is absolutely out of discussion is that
the day of Christ’s birth was not December
25.
December 25 was a Roman holiday
celebrating the end of the solar migration
to the south (boreal winter solstice).


The first Christians in Rome used that
occasion to celebrate Christ.
Emperor Constantine converted the Empire
to Catholicism and adopted December 25 as
the day of birth of Christ and also adopted
the celebration of Eastern (Nicea Council).
Gregorian Calendar

In the year 325, the Council of Nicea, fixed
the celebration of Eastern the weekend
after the first full Moon occurring at or
immediately after March 21, the date of
the beginning of the spring.

Between 45 B.C. and 325 A.D. the
beginning of the spring has moved from
March 24 to March 21.

The Julian year, 365 days and 6 hours is
11 minutes and 14 seconds longer than
the tropical year (the year of the seasons).

That small difference accumulates an error
of one day every 128 years, accumulating
3 days from Julius Cæsar until the Council
of Nicea.



The strict implementation of the Julian
calendar throughout the Middle Ages
made it accumulate a large error.
By 1550 spring was starting on March 11,
ten days off.
The problem for the Church was the
proper celebration of Eastern.

The Julian Calendar was used until 1582
when Pope Gregory XIII, with the advice of
Luigi Lilio and Christopher Clavius,
ordered the reform of the calendar.
Pope Gregory XIII



The new Gregorian calendar consisted of:
Drop 10 days of the calendar: Thursday
October 4th of 1582 would be followed by
Friday October 15.
In order to prevent further disagreements
due to the extra day every 128 years the
Gregorian calendar dropped 3 leap year
every 400.


According to the new rule leap years are
those divisible by 4. Those years divisible
by 100 are not leap years unless they are
divisible by 400.
In this way the years end a century 1700,
1800 and 1900 were not leap years (they
were so in the Julian calendar) but the
year 2000 was a leap year.

The Gregorian year is 365 days and
97/400 that is 365,2425 days (365d 5h
49m 12s) just 26 seconds too long. The
tropical year is 365,242193 (365d 5h 48m
45,4s).

This error accumulates one day in 3.250
years.



The Gregorian calendar was adopted
immediately in all catholic countries, like
Spain, Portugal, France and Italy.
Germany changed the calendar in 1700.
England resisted until 1752.

England in 1752 they went from September
2nd to September 14th.


In Russia they never change the calendar,
so they were 13 days off at the beginning
of the XX century.
Only after the October Revolution
(November in our calendar) of 1917, the
Soviet Union adopted the western
calendar.








Claudius Ptolemy (~100-~170) Geocentric
Universe.
“Almagest” A.D. 150
Nicholas Copernicus (1473-1543)
In 1543 he published “De Revolutionibus
Orbium Caelestium” (Concerning the
revolution of the Heavenly Spheres).
Heliocentric Universe.
Tycho Brahe (1546-1601)
Big improvement in the art of observations
Errors dropped from ±10’ to less than
±1’



Johannes Kepler (1571-1630). He used
Tycho´s observations to study the motion
of Mars and formulated the laws of
planetary motion in 1609.
Galileo Galilei (1564-1642). He studied the
free fall and formulated the inertia
principle.
He built the first telescope and made many
great astronomical discoveries (craters of
the Moon, four satellites of Jupiter,
Sunspots, etc.).







Isaac Newton (1643-1727)
“Philosophiæ Naturalis Principa
Mathematica”, published in 1687 contains
the law of universal gravitation, the laws of
mechanics and infinitesimal calculus.
William Herschel (1738-1822)
Robert Kirchhoff (1824-1887)
Jacobus Kapteyn (1851-1922)
Harlow Shapley (1885-1972)
Edwin Hubble (1889-1953)