Source: The Mercury, 29 January, 1999, p.3

Blue moons all just timing

Julius Caesar
to blame for
lunar oddity

THE world is preparing for two 
once-in-a-blue-moon experiences 
this year-for the first time in 
almost 40 years. 
Not since 1961 has the Earth 
experienced two "blue moons"- 
when two full moons occur in a 
single calendar month - in the 
same year. Before that, the pre- 
vious time was in 1885. 
The first blue moon of this year 
will occur on Sunday, when the 
full moon makes its second Janu- 
ary appearance. 
March will also have two full 
moons: March 1 and 31. 
The rarity is not expected to 
cause any major natural effects. 
"There has been a lot of interest 
on whether it is a natural 
phenomenon but it really is just a 
case of timing," Australian Sur- 
veying and Land Information 
Group spokesman Danny Gal- 
braith said. 
"But it is unusual for two to 
"It can only happen that we get 
two in a year if the moon phases 
are perfect in January and March 
and February has 28 days." 
The January full moon is some- 
times known as "old moon" or 
"moon after yule", while the first 
March full moon is known as "sap 
moon", "crow moon" or "Lenten 
Blue moons and full moons have 
long been associated with mysti- 
cal rituals, changes in tempera- 
ment and unexplained behaviour. 
"Blue moons were considered 
unlucky and a real nuisance, as 
they occurred at various times of 
the year and upset the scheduling 
of church festivals," Mr Galbraith 
said, adding that there was noth- 
ing unnatural about them. 
"It really is only a calendar 
effect. There is a full moon every 
29 1/2 days, whether we like it or 
not, and there is no change on 
what the moon phase is doing. 
"So we can probably blame old 
Julius [Caesar, who instituted the 
Julian calendar on which the 
modern calendar is based]. If we'd 
had 30-day months, we probably 
wouldn't have had it at all." 
The next year with two blue 
moons will be 2018 and there will 
be another towards the end of the 
21st century. 

Where to next?

Student Questions for this article
Teacher Discussion of this article
Index - Related articles
Index - Chance and Basic Probability
Main Index - Numeracy in the News