Sir, - Last Saturday (January 11th) Michael Viney, remarking the magnificent full moon of Christmas Eve, repeated someone else's opinion that it would be "140 years before Christmas Eve and a full moon come together again". I would like to point out that the phase of the moon on any given date repeats itself very closely in a 19 year cycle, sometimes called the Metonic cycle. Thus a full moon fell on December 24th-25th in 1901, 1920, 1939, 1958, 1977 and 1996 and will fall so in 2015, 2034, 2053, and thus for quite a while hence. Of course, with our cloudy skies we are likely to miss quite a few of these events.
On the other hand in 140 years, on the evening of December 24th 2136, the moon will be just two days old and, if seen at all, will appear as a slender crescent in the western sky at sunset, and nothing like the magnificent full moon we enjoyed on Christmas Eve 1996. Yours, etc.,
18 Barnhill Avenue,
Dalkey, Co. Dublin.