Dear John,
I wondered when someone would spot that there is a
whole can of worms waiting to be opened here...
> Won't the factors that necessitate the addition
> of a leap day prevent this alignment from
> happening at exactly 11/11 11:11 every year?
Quite so. No doubt you looked at the time-lapse
video and spotted that the circle of light DIDN'T
properly centre itself on the Great Seal of the
United States. This is surely only one step less
sinful than being disrespectful to the US flag?
OK, take a deep breath and see what we are up
against...
First we need to be clear what is meant by the
time 11:11? I assume this is clock time in
Anthem, Arizona, and a little research suggests
they are on Mountain Time there and that they
don't observe Daylight Saving. [Just think how
the whole scheme could be wrecked if they did
go over to Daylight Saving and the clocks didn't
go back until after 11 November!]
To me, their interest is at 18:11:00 UTC but that
is a detail.
The big difficulty is that, at this exact time of
day, the solar declination varies with the leap
year cycle and there is a steady drift. As a
result both the solar altitude and solar azimuth
vary from one year to the next. Let's see by
how much...
I'll take it that the Geographical Coordinates
of Anthem are:
33° 51' 15" N 112° 7' 30"
Using GCstudio I determined the following data
for 10 years starting in 2016, a leap year:
2016 -17°41'09" +36°25'01" +161°40'45"
2017 -17°37'11" +36°28'55" +161°39'53"
2018 -17°33'13" +36°32'52" +161°39'05"
2019 -17°29'12" +36°36'55" +161°38'33"
2020 -17°41'38" +36°24'36" +161°41'11"
2021 -17°37'47" +36°28'23" +161°40'14"
2022 -17°33'48" +36°32'21" +161°39'31"
2023 -17°29'52" +36°36'14" +161°38'36"
2024 -17°42'18" +36°23'55" +161°41'16"
2025 -17°38'23" +36°27'48" +161°40'23"
The four columns show: year, declination, alt, az
as they are at Anthem at 11:11:00 Mountain Time
on 11 November in the 10 years shown.
Take declination first. You see that starting in
2016 the declination gets about 4 minutes less
negative on successive years until there is a
sudden jump back which is A LITTLE TOO BIG.
This sets the pattern. We become less negative
until 2024 when there is another jump.
The jumps back over-compensate because the tropical
year is slightly less than 365.25 days.
You will see that the solar altitude increases by
just under 4' a year before falling back just over
12' in a leap year. You will see that even in this
little table the range of altitudes is about 11'
and this will be noticed by careful observers.
The azimuth varies too of course but by not so
much and its main effect is to make you have to
worry about just how to align the slabs.
OK, what should they have done?
Well one approach is to settle on the 2016 figures
and note that over the next 36 years the data for
2016 will be somewhere near the middle. After
that the drift will become more noticeable but the
designer will probably be dead and won't care.
Things gradually get worse and worse until The
Great Correction over the years 2096 to 2004
when the omission of a leap year in 2100 will
reverse some of the damage.
Most people know that the Gregorian Calendar
was an improvement over the Julian Calendar but
almost all readers of this list will live their
entire lives enduring pure Julian Drift.
This is a massive imposition and we should all
be lobbying for a much better 33-year Calendar
originally designed by Omar Khayyam in 1079,
long before John Dee and others rediscovered
it. This was over 500 years before Pope
Gregory's tinkering in 1582. Why didn't
Pope Gregory do a proper job then?
That's a long story but the result is that we
are lumbered with an unhelpful calendar which
is, I suppose, upward-compatible with its
predecessor.
I share the view that "upward-compatibility is
the business of deliberately not putting right
someone else's mistakes".
Many apologies. Another rant I fear!
Very best wishes
Frank
Frank King
Cambridge, U.K.
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