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  #1  
Old October 5th 10, 09:25 PM posted to uk.sci.astronomy
oriel36[_2_]
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Posts: 8,478
Default Calendar reform

On Oct 5, 8:24*pm, Mark Goodge
wrote:
On Mon, 4 Oct 2010 11:11:00 -0700 (PDT), oriel36 put finger to keyboard and
typed:



It has as much to do with the descent of astronomy within
denominational Christianity as it does the rise of empirical concepts
built on poor reasoning such as the meaningless amount of rotations in
an orbital circuit,people who are confident as to the facts would have
known what to do long ago but as you can see from the indifference in
this thread,no such people exist presently.


The main reason people appear indifferent is because you seem inacapable of
making your point with sufficient clarity to interest them. I, like many
people, understand the science perfectly well, but even after re-reading
your posts several times I can't tell whether or not you do and have even
less idea why you think it's such an important matter of discussion.

Maybe you could help by answering these simple questions:

1. How many times does the Earth rotate around its axis in a calendar year?

2. Do you think that most people get the answer to question 1 wrong?

3. If so, what do you think they mistakenly think it to be?

4. How many days (ie, a period of full night/day, or 24 hours) does the
Earth experience in a calendar year?

5. Do you think that most people get the answer to question 4 wrong?

6. If so, what do you think they mistakenly think it to be?

7. What particular relevence to Christianity does any of this have?

Mark
-
Blog:http://mark.goodge.co.uk
Stuff:http://www.good-stuff.co.uk



A sane person,at least one who can count,never experiences any more
than 365 full rotations over a full orbital circuit insofar as the
average 24 hour day corresponding to the average length of one
rotation to natural noon,determines the orbital circuit as 365 days 5
hours 49 minutes,nothing more than what Huygens repeats here -

"Here take notice, that the Sun or the Earth passeth the 12. Signes,
or makes an entire revolution in the Ecliptick in 365 days, 5 hours 49
min. or there about, and that those days, reckon'd from noon to noon,
are of different lenghts; as is known to all that are vers'd in
Astronomy. Now between the longest and the shortest of those days, a
day may be taken of such a length, as 365 such days, 5. hours &c. (the
same numbers as before) make up, or are equall to that revolution: And
this is call'd the Equal or Mean day" Huygens

During the current cycle, for explain what a leap day does,daily and
orbital motion began in sync on Mar 1st 2008 with the orbital cycle
drifting forward on Mar 1st of each non-leap year in increments of 6
hours from year to year.On Mar 1st 6 AM 2009,the first circuit was
completed where the next began and ended at noon this year with the
next cycle of 365 1/4 rotations ending 6 PM 2011.After 3 non-leap
years,the orbital circuit has drifted by 18 hours ahead of the average
rotations so that a Feb 29th leap day rotation of 24 hours squares
away 6 hours to complete 4 orbital circuits of 365 1/4 day rotations
and 1461 rotations across Mar 1st 2008 and Feb 29th 2012 where the
next cycle begins.

Maybe some person here who is not enamored by an alternative value for
rotation through 360 degrees and subsequently a nonsensical 366 1/4
rotations per orbital circuit will explain to this guy what he needs
to know.I guess you guys never heard of Huygens or John Harrison who
explains one part of the system that meshes with a leap day
correction and the 11 minute over-compensation which saw the rotations
drift from the orbital cycle by an accumulated 10 days in the 16th
century hence the calendar reform.



  #2  
Old October 9th 10, 12:29 AM posted to uk.sci.astronomy
Quadibloc
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Posts: 7,018
Default Calendar reform

On Oct 5, 2:25*pm, oriel36 wrote:

Maybe some person here who is not enamored by an alternative value for
rotation through 360 degrees and subsequently a nonsensical 366 1/4
rotations per orbital circuit will explain to this guy what he needs
to know.


Many people could explain to _you_ what you need to know.

Yes, a naive person might well find it more natural to say that the
Moon doesn't rotate, because it keeps one face always towards the
Earth. And that the Earth rotates in 24 hours, because that's the
length of a day.

But the solar day isn't uniform in length by the time marked out by a
mechanical clock. It turns out that these non-uniformities can all be
accounted for by two factors - the foreshortening of the Earth's orbit
in the plane of the Earth's rotational equator, and the fact that the
Earth's orbit is elliptical, sweeping out equal areas in equal times,
following Kepler's Laws.

So the Earth's rotation is itself smooth and uniform within the time
scale given by any form of mechanical clock, whether a pendulum clock,
a quartz crystal clock, or an ammonia maser clock. (There are tiny
irregularities due to momentum transfer between the rocky Earth and
its atmosphere due to changes in seasonal prevailing winds, but that
is a detail we can ignore.)

As you yourself have noted, though, "there is no external reference"
for a _uniform_ rotation of the Earth with a 24 hour period. Such a
reference would buzz around the Sun in a shape that is a twisted
version of the analemma. But the fixed stars - or, to take the
technicality of stellar parallax into account, the directions from the
Sun to the fixed stars - _are_ an external reference for uniform
rotation of the Earth with a period of 23 hours, 56 minutes, and 4
seconds.

It is for this reason that astronomers count this as the period of the
Earth's rotation.

Similar reasoning involving libration explains why astronomers count
27 1/3 days, approximately, as the period of the Moon's rotation.

John Savard
 




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