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The Equation of Time(keeping)



 
 
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  #1  
Old November 19th 17, 10:33 AM posted to sci.astro.amateur
Gerald Kelleher
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Default The Equation of Time(keeping)

The basic experiment involves either a sand or water clock. The period of one noon to the next full cycle would generate different volumes of water and sand reflecting the variation in the total length of each individual cycle . If the volumes were combined and divided equally by the number of cycles, an average would be created . This is how the average 24 hour day is created regardless of method or complications.

The Equation of time is the bridge between the unequal quantities (natural noon) and equal quantities (24 hour noon). The bridge which correlates the 24 hour weekday to the natural day is anchored to noon and is a global observation along any line of longitude so it doesn't involve any seasonal components, for example, when it is noon at Conception in Chile, it is also noon in New York as they share roughly the same longitude line but different seasons however both locations will register the same length of the noon cycle as per water/sand clock.








  #2  
Old November 19th 17, 11:34 AM posted to sci.astro.amateur
Mikko
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Default The Equation of Time(keeping)

In article ,
Gerald Kelleher wrote:

The basic experiment involves either a sand or water clock. The period of one
noon to the next full cycle would generate different volumes of water and
sand reflecting the variation in the total length of each individual cycle .


Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.

Mikko
  #3  
Old November 19th 17, 12:38 PM posted to sci.astro.amateur
Gerald Kelleher
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Default The Equation of Time(keeping)

On Sunday, November 19, 2017 at 10:34:04 AM UTC, Mikko wrote:
In article ,
Gerald Kelleher wrote:

The basic experiment involves either a sand or water clock. The period of one
noon to the next full cycle would generate different volumes of water and
sand reflecting the variation in the total length of each individual cycle .


Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.

Mikko


That is incorrect. The purpose is determine the variations in quantities in sand or water for each full cycle and there is a procedure for that which makes it exceptionally accurate. It means taking a short step back and modifying the procedure -

"Draw a Meridian line upon a floor and then hang two plummets, each
by a small thread or wire, directly over the said Meridian, at the
distance of some two feet or more one from the other, as the smallness
of the thread will admit. When the middle of the Sun (the Eye being
placed so, as to bring both the threds into one line) appears to be in
the same line exactly you are then immediately to set the Watch, not
precisely to the hour of 12. but by so much less, as is the Aequation
of the day by the Table." Huygens

The modification is that there is a beginning and end to the natural noon cycle using a shadow alignment if a quantity like sand or water is used to determine the length of each cycle.



  #4  
Old November 19th 17, 07:11 PM posted to sci.astro.amateur
Quadibloc
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Default The Equation of Time(keeping)

On Sunday, November 19, 2017 at 3:34:04 AM UTC-7, Mikko wrote:

Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.


That may be, but using an atomic clock instead would involve the exact same
principle, so it doesn't affect his point. He just chose to use a...
traditional... example of a mechanical clock, perhaps in reaction to what he may
feel to be a recent trend towards glorifying technology.

John Savard
  #5  
Old December 7th 17, 05:39 PM posted to sci.astro.amateur
Mikko
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Default The Equation of Time(keeping)

In article ,
Quadibloc wrote:

On Sunday, November 19, 2017 at 3:34:04 AM UTC-7, Mikko wrote:

Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.


That may be, but using an atomic clock instead would involve the exact same
principle, so it doesn't affect his point. He just chose to use a...
traditional... example of a mechanical clock, perhaps in reaction to what he
may
feel to be a recent trend towards glorifying technology.

John Savard


That's right. However, for those who want to understand history it is
important to understand that before pendulum clocks there was no
mechanical clock that could measure the variation in the length of solar
day, so astronomers had to be determine the equation of time by other
means -- most people where quite happy with solar time.

Mikkl
  #6  
Old December 8th 17, 07:28 AM posted to sci.astro.amateur
Gerald Kelleher
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Default The Equation of Time(keeping)

On Thursday, December 7, 2017 at 4:39:40 PM UTC, Mikko wrote:



That's right. However, for those who want to understand history it is
important to understand that before pendulum clocks there was no
mechanical clock that could measure the variation in the length of solar
day, so astronomers had to be determine the equation of time by other
means -- most people where quite happy with solar time.

Mikkl


For those who want to understand history it is important to know that a clock is a device with one job - to maintain a constant or average pace.

You then ask what is the constant pace and how is it derived using the Sun crossing the meridian each day/night cycle while knowing that each cycle is different. This is the process which creates the 24 hour day and therefore its subdivisions into equable hours , minutes and seconds.

Once you have the average 24 hour day you can then convert it into constant rotation and this is the basis of the Lat/Long system where the rate of rotation is 15 degrees per hour, nothing more and nothing less It is one of the supreme human achievements in terms of engineering and a convenience taken for granted.

When the average 24 hour day emerged from these principles and accurate clocks started to emerge, they found it easier to calibrate the clocks using the homocentric perspective using two foreground references and found it was 23 hours 5 minutes 04 seconds using the average 24 hour day. The Lat/Long system requires the physical principles of rotation in terms of sunrise, sunset and noon as any given location exits and enter the circle of illumination (sunrise/ sunset) and the midpoint of noon along with physical consequences such as daily temperature fluctuations.

There is no doubt the attempt to bypass the Sun along with sunrise/sunset/ noon in order to appeal to circumpolar motion turned into a cult and specifically one that suits the theorists an celestial sphere observers. The actual nuances for timekeeping is for those who value their intelligence and the engineering ins and outs that separate timekeeping from the motions of the Earth.
  #7  
Old December 8th 17, 05:30 PM posted to sci.astro.amateur
Mikko
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Default The Equation of Time(keeping)

In article ,
Gerald Kelleher wrote:

For those who want to understand history it is important to know that a clock
is a device with one job - to maintain a constant or average pace.


You then ask what is the constant pace and how is it derived using the Sun
crossing the meridian each day/night cycle while knowing that each cycle is
different.


No, I don't. Instead I ask whether and how well the clock will do what
it is made to do. In order to understand history, the point is that until
recently clocks were not very accurate (nor common). Astronomers
who wanted to study the equation of the time could only compare the
(apparent) motions of Sun and fixed stars. Even that was not easy as
Sun and stars are not visible at the same time.

Mikko
  #8  
Old November 19th 17, 08:34 PM posted to sci.astro.amateur
Gerald Kelleher
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Posts: 1,551
Default The Equation of Time(keeping)

On Sunday, November 19, 2017 at 10:34:04 AM UTC, Mikko wrote:
In article ,
Gerald Kelleher wrote:

The basic experiment involves either a sand or water clock. The period of one
noon to the next full cycle would generate different volumes of water and
sand reflecting the variation in the total length of each individual cycle .


Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.

Mikko


To be fair to you and if your question was genuine, the answer to the quoted text only refers to the natural variations determined by the unequal amounts of sand and water for each respective noon cycle . By accumulating say 10 cycles of sand noting the variation for each and then dividing equally by 10, you get an idea how the average volume in anchored to the natural noon cycle.

It represents how the average 24 hour day is created and subsequently its divisions into equal hours, minutes and seconds. I can't prevent rude people from interjecting as this is an open forum with all its advantages and disadvantages but at least your objection was intelligent.
  #9  
Old November 21st 17, 10:05 AM posted to sci.astro.amateur
Martin Brown[_3_]
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Default The Equation of Time(keeping)

On 19/11/2017 10:34, Mikko wrote:
In article ,
Gerald Kelleher wrote:

The basic experiment involves either a sand or water clock. The period of one
noon to the next full cycle would generate different volumes of water and
sand reflecting the variation in the total length of each individual cycle .


Sand and water clocks are too inaccurate to detect the variation in
duration from one noon to the next.


Actually they were just about good enough to do it a long time ago.

https://www.researchgate.net/publica...lack_Sea_Coast

They would need to be good to better than 10 minutes in 24 hours to get
a 3 sigma detection of shortest day vs longest day variation. They are
more accurate than that. I built one for a lecture (an equal interval
one constructed as a parabola of revolution). It was surprisingly
reproducible a larger scaled one probably good to

That is how the ancients knew that the suns motion across the heavens
was at a variable speed. Unclear how many times the water clock in its
various guises was invented. There are obvious systematic errors that
vary with temperature and humidity but it wasn't a bad start.

A Chinese inventor even did one with mercury as the working fluid which
avoided problems of freezing up in continental winters.

--
Regards,
Martin Brown
  #10  
Old November 21st 17, 06:18 PM posted to sci.astro.amateur
Gerald Kelleher
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Default The Equation of Time(keeping)

The issue of Huygens and the attempt to fit the timekeeping facility into the natural orbital cycle surfaced later when the Equation of Timekeeping was loaded with attributes that it doesn't have -

"Absolute time, in astronomy, is distinguished from relative, by the equation of time. For the natural days are truly unequal, though they are commonly considered as equal and used for a measure of time; astronomers correct this inequality for their more accurate deducing of the celestial motions...The necessity of which equation, for determining the times of a phænomenon, is evinced as well from the experiments of the pendulum clock, as by eclipses of the satellites of Jupiter." Principia

People shouldn't be scared or just give up the pretense that Newton ill-considered version of the Equation of Timekeeping is anything other than jumbled up notion whereas the timekeeping facility responsible for the average 24 hour day has both engineering and astronomical facets.

That little detour over, back to the topic in hand.
 




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