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Conventional clocks can be misleading

BeholdTheTruth

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Real mid-day and mid-night

Conventional clocks can be misleading.

For example for the City of Ottawa Canada which has a longitude of 75 degrees 45 minutes west and a latitude of 45 degrees 16.2 minutes north, on Feb 1, 2006 the time of local sunrise was 7:24 am EST and the time of local sunset was 5:10 pm EST. (The time of local sunrise on Feb 2, 20006 was 7:22 am EST.) What was the local time of mid-day/high noon for the day Feb 1 and what was the local time of mid-night for the night of Feb 1/Feb 2?
 
Since clock time is pretty much arbitrarily defined, I wouldn't be surprised that noon on the clock did not match max sun time and that it varied from day to day. For example, in the USA when we switch from Standard time to Daylight time, the "time" of noon shifts by an hour. No biggie.
 
Thought clock time was based on the rotation of the Earth and some lines of longitude and stuff. Unless they have moved Greenwich recently, the amount of daylight doesn't come into it much...
 
roger said:
http://www.internationalskeptics.com/forums/showthread.php?t=50154
Click to expand...

7141446a4c5b8346f.jpg
 
Well yeah. Solar time is not the same as the official time. It used to be, but that made trains crash and stuff, so now it's in hour-sized zones. They're not perfectly aligned to solar time, but reasonably close.

I cannot believe you didn't know that.

Personally, I don't think I even own a clock that does not self-set from the national time standard at the national institute of standards and technology. Actually, one of them also has the ability to work off the Naval Observatory.

Eh...they're both within nanoseconds of eachother, so it doesn't matter too much. I don't compensate for speed of light or relativity....because I'm lazy. Oh well...it's close enough as is
 
Conventional clocks are very misleading. They don't display the truth of cubic time!!
 
DRBUZZ0 said:
Well yeah. Solar time is not the same as the official time. It used to be, but that made trains crash and stuff, so now it's in hour-sized zones. They're not perfectly aligned to solar time, but reasonably close.
Click to expand...

I'm too scared to read the other thread! But solar time and clock time required adjusting even before time zones were implemented.

Back in the day when people set clocks by the "noon mark" (when a shadow was due north), almanacs told people the difference that the sun was off, so they could adjust their clocks accordingly. I'm looking at an Ohio Farmer's Almanac for 1862, and it has a column headed "S. slow m." which means "Sun slow minutes," or the number of the minutes that the sun is "slow" compared to clock time. At other times of the year it's fast, up to 16 minutes off.

Here's a link about that kinda stuff: http://www.sunlit-design.com/infosearch/equationoftime.php
 
Standardized clock time is arbitrary, an imaginary construct made for practical business purposes. Big deal. It's not as if there weren't plenty of other time indication schemes.

Astronomers and others needing a non-bureaucratically defined standard for coordinating observations use so-called Universal Time, aka Greenwich Mean Time. For practical solar astronomical purposes, local mean solar time is often used; it's easy to convert between local mean solar time and zonal standard time, just a matter of calculating the time difference from a place's longitudinal offset from the zone's center. When dealing with the stars, we convert into sidereal time, which is based on position with respect to not the sun but the celestial sphere. A given stationary (stars, nebulae, galaxies, etc.; not planets, comets, or other rapidly moving) sky object will transit the meridian at the same sideral time every day, no matter what the solar time happens to be.
The calculation of sunrise and sunset adds an additional complication. Over the year, the sun's apparent arc across the sky goes from short in winter to very long in mid-summer. The time of sunrise and sunset vary in a fairly complicated way, and the eccentricity of the earth's orbit adds another little twist. (For more on the twist, google for "analemma.")

But all these factors can all be calculated with not-too-difficult trigonometry. My own computer routines for doing this stuff were adapted from algorithms given in Peter Duffett-Smith's "Practical Astronomy With Your Calculator," a book from the 1970s when pocket calculators were the hottest new things. It's not difficult to work these algorithms with any modern scientific calculator. I recommend this book for anyone interested in how astronomical motions can be modelled using numbers. You won't learn much of the theory behind the algorithms, but that's covered in just about any basic astronomy book.

[edit] @richardm, that's true of the mean sun. For the real sun there'd also be a sun-slow or sun-fast adjustment, I think.
 
Last edited:
Yah! That's it.

At the Science Museum of Virginia, not far from where I live, they made a giant analemmic sundial by marking the position on the parking lot of the shadow of the flagpole's ball finial at noon every sunny day for a year, then painting the curve and markers. An inexpensive and directly engaging exhibit.
 
Meffy said:
@richardm, that's true of the mean sun. For the real sun there'd also be a sun-slow or sun-fast adjustment, I think.
Click to expand...

[innocent]
But he asked what time mid-day and mid-night was!
:eusa_shifty:
[/innocent]
 
Good enough, those terms make more sense using a physical, not mean, sun.
 
My compliments, Meffy!

BTW, what are your thoughts of the possible validity and usefulness of the fields of chronobiology and chronotherapy per http://www.sciencefriday.com/pages/2001/Dec/hour1_122801.html ?


Meffy said:
Standardized clock time is arbitrary, an imaginary construct made for practical business purposes. Big deal. It's not as if there weren't plenty of other time indication schemes.

Astronomers and others needing a non-bureaucratically defined standard for coordinating observations use so-called Universal Time, aka Greenwich Mean Time. For practical solar astronomical purposes, local mean solar time is often used; it's easy to convert between local mean solar time and zonal standard time, just a matter of calculating the time difference from a place's longitudinal offset from the zone's center. When dealing with the stars, we convert into sidereal time, which is based on position with respect to not the sun but the celestial sphere. A given stationary (stars, nebulae, galaxies, etc.; not planets, comets, or other rapidly moving) sky object will transit the meridian at the same sideral time every day, no matter what the solar time happens to be.
The calculation of sunrise and sunset adds an additional complication. Over the year, the sun's apparent arc across the sky goes from short in winter to very long in mid-summer. The time of sunrise and sunset vary in a fairly complicated way, and the eccentricity of the earth's orbit adds another little twist. (For more on the twist, google for "analemma.")

But all these factors can all be calculated with not-too-difficult trigonometry. My own computer routines for doing this stuff were adapted from algorithms given in Peter Duffett-Smith's "Practical Astronomy With Your Calculator," a book from the 1970s when pocket calculators were the hottest new things. It's not difficult to work these algorithms with any modern scientific calculator. I recommend this book for anyone interested in how astronomical motions can be modelled using numbers. You won't learn much of the theory behind the algorithms, but that's covered in just about any basic astronomy book.

[edit] @richardm, that's true of the mean sun. For the real sun there'd also be a sun-slow or sun-fast adjustment, I think.
Click to expand...
 
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