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Time and timekeeping

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Old November 1st 17, 03:31 PM posted to sci.astro.amateur
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Default Time and timekeeping

On Wednesday, November 1, 2017 at 1:02:26 AM UTC-6, Gerald Kelleher wrote:

Celestial sphere ideology is always the same, it assigns relevance to
circumpolar motion and models the motions of the Earth on the assertions even
though they defy experience.

Yes, the movement of the stars around Polaris is certainly not as relevant to
the experience of our daily lives as the 24 hour cycle of night and day.

But just as the distinction between Ptolemy and Copernicus isn't evident in
normal experience, why should the physical dynamics of the Earth be in our
ordinary experience either? The Earth beneath my feet doesn't feel like it's
moving at over 1,000 miles per hour!

The Sun's apparent motion in the sky is subject to the Equation of Time, but
stellar circumpolar motion is even and regular. So it is the latter that is a
simple motion - and the former is a compound motion. The Equation of Time tells
us that about the apparent Sun just as retrogrades tell us that about the
apparent motions of the planets.

They don't even do this anymore as they conjured up a new proposal that the Earth
turned 360 degrees in 24 hours but back in the year 1820 as the website Martin
Brown referenced.

No, you're just drawing an unwarranted conclusion from an oversimplification.

John Savard
Old November 1st 17, 03:53 PM posted to sci.astro.amateur
Gerald Kelleher
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Default Time and timekeeping

On Wednesday, November 1, 2017 at 11:06:47 AM UTC, Martin Brown wrote:


Celestial sphere rotation of the fixed stars *is* a pure rotation.
(if you ignore nutation and precession)

The stars return to the same place in the sky as regular as clockwork.

Martin Brown

All of you have been brought up with RA/Dec modelling which is dysfunctional to say the least so the new software programs and the people who will create them will be unattached to the errors and manipulations which you adhere to.

The creation of the average 24 hour day and into timekeeping divisions of hours,minutes and seconds served the Lat/Long system and a rotation rate of 15 degrees per hour. They found it easier to calibrate for the accuracy of clocks using two foreground references and the return of a star but there is nothing *pure* about this observation other than it is an extension of the 24 hour day created by the Equation of Time which in turn fits inside the Calendar framework.

I well understand why you and others have trouble adapting to the language of Sun centered astronomy and particularly things like the cause of the seasons using the same dynamics which cause the natural inequality in the noon cycle. I also understand the tendency to make things up as you go along and perhaps that I am doing the same, however, all the historical language of astronomy and timekeeping are put in order or separated by necessary are drawn from observations,experiences and supporting documentations whether true or deficient.


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