• From: Adriano Palma <Palma@xxxxxxxxxx>
  • To: "lit-ideas@xxxxxxxxxxxxx" <lit-ideas@xxxxxxxxxxxxx>
  • Date: Sun, 13 Sep 2015 11:00:03 +0000

The Jewish calendar is based on three astronomical phenomena: the rotation of
the Earth about its axis (a day); the revolution of the moon about the Earth (a
month); and the revolution of the Earth about the sun (a year). These three
phenomena are independent of each other, so there is no direct correlation
between them. On average, the moon revolves around the Earth in about 29½ days.
The Earth revolves around the sun in about 365¼ days, that is, about 12.4 lunar
The civil calendar used by most of the world has abandoned any correlation
between the moon cycles and the month, arbitrarily setting the length of months
to 28, 30 or 31 days.
The Jewish calendar, however, coordinates all three of these astronomical
phenomena. Months are either 29 or 30 days, corresponding to the 29½-day lunar
cycle. Years are either 12 or 13 months, corresponding to the 12.4 month solar
The lunar month on the Jewish calendar begins when the first sliver of moon
becomes visible after the dark of the moon. In ancient times, the new months
used to be determined by observation. When people observed the new moon, they
would notify the Sanhedrin. When the Sanhedrin heard testimony from two
independent, reliable eyewitnesses that the new moon occurred on a certain
date, they would declare the rosh
chodesh<http://www.jewfaq.org/defs/chodesh.htm> (first of the month) and send
out messengers to tell people when the month began.
The problem with strictly lunar calendars is that there are approximately 12.4
lunar months in every solar year, so a 12-month lunar calendar is about 11 days
shorter than a solar year and a 13-month lunar is about 19 longer than a solar
year. The months drift around the seasons on such a calendar: on a 12-month
lunar calendar, the month of Nissan, which is supposed to occur in the Spring,
would occur 11 days earlier in the season each year, eventually occurring in
the Winter, the Fall, the Summer, and then the Spring again. On a 13-month
lunar calendar, the same thing would happen in the other direction, and faster.
To compensate for this drift, the Jewish calendar uses a 12-month lunar
calendar with an extra month occasionally added. The month of Nissan occurs 11
days earlier each year for two or three years, and then jumps forward 30 days,
balancing out the drift. In ancient times, this month was added by observation:
the Sanhedrin observed the conditions of the weather, the crops and the
livestock, and if these were not sufficiently advanced to be considered
"spring," then the Sanhedrin inserted an additional month into the calendar to
make sure that Pesach (Passover) would occur in the spring (it is, after all,
referred to in the Torah as Chag he-Aviv, the Festival of Spring!).
A year with 13 months is referred to in Hebrew as Shanah Me'uberet (pronounced
shah-NAH meh-oo-BEH-reht), literally: a pregnant year. In English, we commonly
call it a leap year. The additional month is known as Adar I, Adar Rishon
(first Adar) or Adar Alef (the Hebrew
letter<http://www.jewfaq.org/defs/alephbet.htm> Alef being the numeral "1" in
Hebrew). The extra month is inserted before the regular month of Adar (known in
such years as Adar II, Adar Sheini or Adar Beit). Note that Adar II is the
"real" Adar, the one in which Purim<http://www.jewfaq.org/defs/purim.htm> is
celebrated, the one in which yahrzeits<http://www.jewfaq.org/defs/yahrzeit.htm>
for Adar are observed, the one in which a 13-year-old born in Adar becomes aBar
Mitzvah<http://www.jewfaq.org/defs/barmitz.htm>. Adar I is the "extra" Adar.
In the fourth century, Hillel II established a fixed calendar based on
mathematical and astronomical calculations. This calendar, still in use,
standardized the length of months and the addition of months over the course of
a 19 year cycle, so that the lunar calendar realigns with the solar years. Adar
I is added in the 3rd, 6th, 8th, 11th, 14th, 17th and 19th years of the cycle.
The current cycle began in Jewish year 5758 (the year that began October 2,
1997). If you are musically inclined, you may find it helpful to remember this
pattern of leap years by reference to the major scale: for each whole step
there are two regular years and a leap year; for each half-step there is one
regular year and a leap year. This is easier to understand when you examine the
keyboard illustration below and see how it relates to the leap years above.
[Keyboard illustrating pattern of leap years]
In addition, Yom Kippur<http://www.jewfaq.org/defs/yomkippur.htm> should not
fall adjacent to Shabbat<http://www.jewfaq.org/defs/shabbat.htm>, because this
would cause difficulties in coordinating the fast with Shabbat, and Hoshanah
Rabbah<http://www.jewfaq.org/defs/hoshanah.htm> should not fall on Saturday
because it would interfere with the holiday's observances. A day is added to
the month of Cheshvan or subtracted from the month of Kislev of the previous
year to prevent these things from happening. This process is sometimes referred
to as "fixing" Rosh Hashanah. If you are interested in the details of how these
calculations are performed, see The Jewish Calendar: A Closer
Numbering of Jewish Years
The year number on the Jewish calendar represents the number of years since
creation, calculated by adding up the ages of people in the Bible back to the
time of creation. However, this does not necessarily mean that the universe has
existed for only 5700 years as we understand years. Many
Orthodox<http://www.jewfaq.org/defs/orthodox.htm> Jews will readily acknowledge
that the first six "days" of creation are not necessarily 24-hour days (indeed,
a 24-hour day would be meaningless until the creation of the sun on the fourth
"day"). For a fascinating (albeit somewhat defensive) article by a nuclear
physicist showing how Einstein's Theory of Relativity sheds light on the
correspondence between the Torah<http://www.jewfaq.org/defs/torah.htm>'s age of
the universe and the age ascertained by science, see The Age of the

From: lit-ideas-bounce@xxxxxxxxxxxxx [mailto:lit-ideas-bounce@xxxxxxxxxxxxx] On
Behalf Of Donal McEvoy
Sent: 13 September 2015 12:51
To: lit-ideas@xxxxxxxxxxxxx
Subject: [lit-ideas] Re: Copy of The Philosophy of Logical Atomism, 1918

Pears' commentary is about as long as the sum of Russell's eight lectures,
but it's often more informative.>

True to type, Pears writes about these issues with not even a nod to what
Popper would, or might, say (though inevitably Wittgenstein is given
significant space). This might be justified if Popper were of marginal
importance to these issues, and not arguably the most important theorist of
knowledge of the last century. Though I doubt Pears could show that Popper's
theory of knowledge' has no importance to these issues, that doesn't stop him
writing as if it is.

Pears might be "often more informative" than Russell but that does not mean
that, in a wider sense, Pears is truly 'well-informed' philosophically. Without
wishing to suggest Pears' commentary does not have its merits, the bubble some
people live their intellectual lives in is truly shocking: we should experience
the same kind of shock reading this stuff as we would if we read a paper by a
Christchurch scientist in 1985 which defended a new version of Lamarckism
(without referencing Darwin) or weighed up the pros and cons of
phlogiston-theory (for these 'logical atoms' are a kind of philosophical
'phlogiston'). Somehow many of us don't.


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