Question about variations of the Sun's path over long periods of time

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SUMMARY

The discussion centers on the accuracy of shadows cast by the sun in 1880 compared to those in 2020, specifically on May 1 at noon. While the mountain's shape remains unchanged, factors such as Earth's axial precession and nutation affect shadow positioning over time. The consensus is that shadows will not align perfectly due to these astronomical variations, with a noted shift of approximately one quarter of a day per year. Key disciplines involved include Earth Science, Astronomy, and Optics.

PREREQUISITES
  • Understanding of Earth’s axial precession and nutation
  • Familiarity with the concepts of solar time and apparent solar time
  • Knowledge of Kepler's laws of planetary motion
  • Basic principles of shadow casting and sundials
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  • Research the effects of Earth's axial precession on shadow casting
  • Study the Equation of Time and its implications for sundials
  • Explore the concept of tropical years and their impact on solar positioning
  • Investigate the historical context of timekeeping and its evolution since 1880
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Filmmakers, astronomers, educators, and anyone interested in the intersection of astronomy and practical applications like shadow casting in storytelling.

  • #31
And I believe the placing of clocks in church towers was not simply a nod to visibility. The more puritanical denominations (in the USA, at least) took a vested interest in people organizing their labors throughout the day to better serve divine purpose. No idle hands you know...
Incidentally until about a decade ago Indianapolis and its environs simply eschewed Daylight Savings Time altogether. Made for interesting phone conference scheduling with folks.
But actually I think the moving the clock back and forth is silly.
 
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  • #32
Vanadium 50 said:
It's not the clock so much, it's the need to synchronize clocks in distant cities. The fact that high noon comes at different times in Dodge City as Tombstone didn't matter as far as I can tell pre-railroad. One clock in the town square and you're pretty much done.
OK, I can see that. It was true to certain extent. But it's also true that the telegraph changed everything. By Civil War time, the telegraph was nearly ubiquitous, and the owner of the town steeple clock used the telegraph to set the clock's minute hand. The choice for the hour hand was a local custom. With no synchronization, the town clock might drift 6 or more hours per year, and the telegraph was much easier than a sextant or a sundial to synch it.

The stories from young Thomas Edison are rich with anecdotes about use of the telegraphs in the 1860s. The big application was not the railroads, or timekeeping, but rather the ability to get news from remote places on the same day as it happened. Edison's first commercial success came when he telegraphed out the headline "20,000 Dead Shiloh" and then sold newspapers providing the details. Consider it the 1860s version of TV or Twitter.
 
  • #33
Time was only critical where ships headed off on long voyages. They needed to calibrate their navigational chronometers to handle the problem of determining longitude. That is why the national sea ports had an astronomical observatory watching the Sun and the stars in meridian transit. At the observatory, a ball was slowly raised up a mast in the minutes before midday, held there, then dropped at midday, when a gun was also fired.

A sundial is accurate to a couple of minutes and served for many years to set the time of church bells and services. That is why there is often a sundial in a churchyard. The bell rung from the local church was sufficient to synchronise clocks and get the townsfolk to work on time. Later the church put a clock in the bell tower.
 

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