Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Full Moon Predictions 
Name: julie e larsen
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1993 - 1999
Question:
I would like some help in finding out about the golden number for predicting or calculating the full moon and Easter. The Encyclopedia Britannica says to find it by adding 1 to the calendar year (AD) and dividing it by 19, the remainder being the golden number. If there is no remainder, the number is 19. O nce the number has been calculated, how does one use it? What does one do with it to arrive at the full moon date?

Replies:
I read the Britannica write-up and it is not at all clear what you're supposed to do. I got the following from an insert that came with my desk calendar:


Easter falls on the first Sunday following the arbitrary Paschal Full Moon, which does not necessarily coincide with a real or astronomical full moon. The Paschal Full Moon is calculated by adding 1 to the remainder obtained by dividing the year by 19 and applying the following table: 
1 - Apr 14   5 - Mar 31   9 - Apr 16  13 - Apr  2  17 - Apr 17
2 - Apr  3   6 - Apr 18  10 - Apr  5  14 - Mar 22  18 - Apr  7
3 - Mar 23   7 - Apr  8  11 - Mar 25  15 - Apr 10  19 - Mar 27
4 - Apr 11   8 - Mar 28  12 - Apr 13  16 - Mar 30

The date you get from the above table is this so-called Paschal Full Moon; it may be a day or two off from the astronomical full moon.

So for this year the "key" is 1; Apr 14 is a Friday, so Easter is Apr 16. The article doesn't say what the range of years is to which this method applies; I would hesitate to apply it except for years in the 19th, 20th, and 21st centuries.

RC Winther


Click here to return to the Astronomy Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory
n b