Joining list. Calendar reforms.

[Irv Bromberg]

On 2009 Jun 6, at 20:44 , Aristeo Fernando wrote:

Encyclopedia Britannica defines...
Equinox is "either of the two moments in the year when the Sun is exactly above the Equator, and day and night are of equal length."

Irv replies:  Tell Encyclopedia Britannica that that definition is incorrect.  If an accurate mean solar time clock is used, on the date of an equinox the daytime is about 1/2 hour longer than the night length.  This is because of atmospheric refraction near the horizons, which makes Sun appear up to 2° higher than its geometric position, and because of the approximately 1/2 degree apparent diameter of Sun (it is considered daytime if any part of Sun is above the horizon).  Each degree at each horizon makes the daytime about 4 minutes longer and accordingly the night length about 4 minutes shorter.

For non-polar terrestrial locations there does exist a day upon which the daytime will equal the night length, which is always a few days before the spring equinox and a few days after the autumn equinox (regardless of the hemisphere).  It is the day when sunrise is closest to 6 am and sunset closest to 6 pm (both in terms of local apparent time).  The number of days that are a "few" days before or after the equinox varies with latitude, being least at high latitudes where the length of day changes most rapidly near an equinox.

Aristeo continued:  From Vernal Equinox to Summer Solstice, the difference is 92 or 93 days; from Summer Solstice to Autumnal Equinox, 93 or 94 days; Autumnal Equinox to Winter Solstice, 89 or 90 days; and Winter Solstice to Vernal Equinox, 89 or 90 days during an ordinary year and 90 or 91 days during a leap year.

Irv replies:  Those season lengths vary cyclically over the long term, see:  <http://individual.utoronto.ca/kalendis/solar/Season_Lengths_30K.pdf>.

Aristeo continued:  why is it that Summer and Winter Solstices occur on either of two dates, June 21 or 22 and December 21 or 22, respectively?

Irv replies:  The short-term variation in equinox or solstice timing, expressed in terms of the year-to-year variations in each equinoctial or solstitial year, is about ±15 minutes, so this can't account for the one-day wobble you ask about.  That wobble is due to the leap day of the calendar, which is about 24h in the short term, and, due to the non-uniform spread of leap years in the Gregorian leap rule, amounts to a 2.2-day wobble over the long term.

Aristeo continued:  At what exact time (GMT) do these phenomena really occur?

Irv replies:  You don't mean GMT, which is a long-obsolete term, and technically referred to nautical days that started at noon, not midnight.  You actually meant Universal Time (UT), which is the mean solar time at the prime meridian.  So the answer is that any equinox or solstice can occur at any UT moment, because the lengths of the equinoctial and solstitial years are not whole multiples of the 24h day, see: <http://individual.utoronto.ca/kalendis/leap/Solar_Year_Range.pdf>.

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/seasons/>

[Irv Bromberg]

On 2009 Jun 7, at 06:03 , Aristeo Fernando wrote:

Encyclopedia Britannica may have taken into account the atmospheric refraction near the horizon during sunrise and sunset to come up with the dates for the equinoxes and solstices.  When do you think should these astronomical phenomena occur?  Are the dates that Encyclopedia Britannica cited correct?  And how should these phenomena be defined?

Irv replies:  Their dates are fine, just their definition incorrect.

I would define an equinox as the moment when the solar declination crosses the celestial equator from south to north (northward equinox) or from north to south (southward equinox).

I would define a solstice as the moment when the solar declination reaches the maximum declination north (north solstice) or south (south solstice).  This is observationally difficult to reckon to the second because the solar declination tends to linger at the maximum for about a day and the many little wobbles of Earth's axis also confounds determination of the moment.  Mathematical calculation finds the maximum of a mean solar declination function, which may differ from the actual astronomical moment by several minutes.

The International Astronomical Union (IAU) however defines the equinoxes and solstices as occurring at each 90° of ecliptic solar longitude.  This is effectively the same for the northward equinox, but is not quite the same for the solstices or the southward equinox.  Ecliptic solar longitude can be calculated to higher accuracy than solar declination, I presume that is the reason why IAU standardized on that definition.

Aristeo continued:  As Irv cited, the equinox varies with latitude, that is why Encyclopedia Britannica is specific that it is the moment "when the Sun is exactly above the Equator."

Irv replies:  That is not what I wrote, I wrote that the day upon which the daytime and night length are equal varies with latitude.  It is actually furthest from the moment of the astronomical equinox at the equator, because the daytime length changes most slowly at the equator.  Defining the equinox as the moment when Sun is exactly above the equator is valid, but hard to reckon observationally, because it means that at that moment the shadow of a perfectly vertical stick disappears at local apparent noon somewhere on the equator, which more often than not will occur over an ocean, not land, and it is observationally difficult to reckon the moment to an accuracy better than about an hour by that method.  In astronomical practice, the equinox moments are calculated by solar declination or ecliptic solar longitude, not reckoned observationally.

Aristeo continued:  I thought Greenwich Mean Time (GMT) is synonymous to Universal Time (UT).  What's the difference?  Isn't it that the prime meridian passes through Greenwich, England and its longitude is 0 degrees?

Irv replies:  This web page adequately answers your question:  <http://en.wikipedia.org/wiki/Gmt>.

UT is used in astronomical calculations, such as reckoning equinoxes and solstices, but the time that is broadcast by radio stations is UTC = Coordinated Universal Time.  UT includes an estimate of leap seconds and can be projected into the past or future, but UTC includes the actually inserted leap seconds and applies only to the present.  UT1 is not really the same as UT:  UT1 is UTC plus an observationally measured fraction of a leap second that has accumulated since the last leap second insertion.  In astronomical computer programs UT is usually used instead of UT1 because it is computationally simpler to work with.  The difference is usually within a couple of seconds.  UT1 can only be used computationally for the duration of time that it has been available, which is only since a few decades prior to the present, and to use it properly one would need a database of the daily offset between UT1 and UTC, so it is usually not worthwhile to bother with that.  People who do need to bother are those working on astronomical observations of distant quasars with micro-arcsecond accuracies.

See also:

http://en.wikipedia.org/wiki/Universal_Time

http://en.wikipedia.org/wiki/Coordinated_Universal_Time

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/seasons/>

[MIKE OSSIPOFF]

Aristeo, You wrote:
 
> Clearly, if we go on a Seasonal Calendar, there are two days to choose from as the start of the season and they vary from 89 to 94 days. The calendar couldn't be fixed to have 91 days per quarter.
 
I reply:
 
The Subjective Seasonal Calendar is not based on quarters. It does not assume that the seasons are equal.
 
Based on widespread perception of when Summer and Winter begin, and on the 1.25 month estimate of the global average seasonal timelag, I've suggested that 117 or 118 days would be a good estimate for the perceived length of summer and winter. And this estimate is also confirmed by people's perception of when Summer ends, sometime late in September.
 
You continued:
 
Would it not be better to leave it as it is marking the days when these astronomical phenomena occur?
 
I reply:
 
No, if you're suggesting seasons that start on the astronomically-defined equinoxes and solstices. Those "seasons" have no relevance to anything, and no basis in anything.
 
If you want astronomical seasons, then the Chinese astronomical seasons are what make sense, quarters centered on equinoxes and solstices.
 
Of course I've been, instead, talking about terrestrial seasons, seasons involving the terrestrial effects based on which we perceive it to be summer or winter.
 
you continued:
 
> Another questions: why is it that Summer and Winter Solstices occur on either of two dates, June 21 or 22 and December 21 or 22, respectively?
 
I reply:
 
They often do, but sometimes one or more of them can occur on the 20th. For instance, if I remember correctly, the Spring equinox this year, was on March 20th, in the U.S.
 
Why those dates? Subject to our calendar's cyclical drift, those are the dates, in our calendar, when the sun passes the solstice and equinox points of the tropical year.
 
You continued:
 
At what exact time (GMT) do these phenomena really occur?

The GMT of those events varies, due to our calendar's cylcical drift.
 
Some object to GMT, because now we're supposed to say "UT" instead. Likewise, now a micron has become a "micrometer", and a Brontosaurus has become an Apatosaurus, etc. Forgive me for not keeping up with fashion. I still say GMT.
 
GMT, for a long time, has been well-understood to not have its zero at noon. It has long had its zero at midnight. GMT means Greenwich Mean Time, and it has long referred to the mean solar time at the Greenwich meridian. So I suggest that there's nothing incorrect about sayng GMT.
 
Mike Ossipoff
 
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[Irv Bromberg]

On 2009 Jun 7, at 16:38 , MIKE OSSIPOFF wrote:

Some object to GMT, because now we're supposed to say "UT" instead. Likewise, now a micron has become a "micrometer", and a Brontosaurus has become an Apatosaurus, etc. Forgive me for not keeping up with fashion. I still say GMT.

GMT, for a long time, has been well-understood to not have its zero at noon. It has long had its zero at midnight. GMT means Greenwich Mean Time, and it has long referred to the mean solar time at the Greenwich meridian. So I suggest that there's nothing incorrect about sayng GMT.

Irv replies:  The term GMT is deprecated (for many years), it is not a question of "fashion".  Keep those blinkers on your eyes, disregard everything that isn't in front of your nose, eh?

Mike, you persist in using the term GMT for the same reason that the USA persists in using Imperial Units even though almost all other nations in the world have switched to the International System of Units, see:

<http://en.wikipedia.org/wiki/International_System_of_Units>

President Obama thinks his mandate is for change, so why not get the USA to join the rest of the world?  (There is no hope of any calendar reform until after the USA switches to S.I. units.)

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/>

[Peter Zilahy Ingerman, PhD]

But the USA has switched to metric units ... after all, room-temperature IQ is now measured in Celsius!

Pzed

Irv Bromberg wrote:

On 2009 Jun 7, at 16:38 , MIKE OSSIPOFF wrote:

Some object to GMT, because now we're supposed to say "UT" instead. Likewise, now a micron has become a "micrometer", and a Brontosaurus has become an Apatosaurus, etc. Forgive me for not keeping up with fashion. I still say GMT.

GMT, for a long time, has been well-understood to not have its zero at noon. It has long had its zero at midnight. GMT means Greenwich Mean Time, and it has long referred to the mean solar time at the Greenwich meridian. So I suggest that there's nothing incorrect about sayng GMT.

Irv replies:  The term GMT is deprecated (for many years), it is not a question of "fashion".  Keep those blinkers on your eyes, disregard everything that isn't in front of your nose, eh?

Mike, you persist in using the term GMT for the same reason that the USA persists in using Imperial Units even though almost all other nations in the world have switched to the International System of Units, see:

<http://en.wikipedia.org/wiki/International_System_of_Units>

President Obama thinks his mandate is for change, so why not get the USA to join the rest of the world?  (There is no hope of any calendar reform until after the USA switches to S.I. units.)

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/>

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[Brillig]

The other day I bought a Coke when I rented a DVD set (Shogun). I
expected to get a 20 oz bottle. Instead, I got a 500ml bottle.
Interestingly, although the sizes are fairly close, the 500ml size
fits in my car's cup holder. The 20 oz size doesn't.

Victor

On Mon, Jun 8, 2009 at 6:40 AM, Peter Zilahy Ingerman,
PhD<pzi@...> wrote:

> But the USA has switched to metric units ... after all, room-temperature IQ
> is now measured in Celsius!
>
> Pzed
>
> Irv Bromberg wrote:
>
> On 2009 Jun 7, at 16:38 , MIKE OSSIPOFF wrote:
>
> Some object to GMT, because now we're supposed to say "UT" instead.
> Likewise, now a micron has become a "micrometer", and a Brontosaurus has
> become an Apatosaurus, etc. Forgive me for not keeping up with fashion. I
> still say GMT.
>
> GMT, for a long time, has been well-understood to not have its zero at noon.
> It has long had its zero at midnight. GMT means Greenwich Mean Time, and it
> has long referred to the mean solar time at the Greenwich meridian. So I
> suggest that there's nothing incorrect about sayng GMT.
>
> Irv replies:  The term GMT is deprecated (for many years), it is not a
> question of "fashion".  Keep those blinkers on your eyes, disregard
> everything that isn't in front of your nose, eh?
> Mike, you persist in using the term GMT for the same reason that the USA
> persists in using Imperial Units even though almost all other nations in the
> world have switched to the International System of Units, see:
> <http://en.wikipedia.org/wiki/International_System_of_Units>
> President Obama thinks his mandate is for change, so why not get the USA to
> join the rest of the world?  (There is no hope of any calendar reform until
> after the USA switches to S.I. units.)
>
> -- Irv Bromberg, Toronto, Canada
> <http://www.sym454.org/>
>
> ________________________________
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.339 / Virus Database: 270.12.55/2160 - Release Date: 06/07/09
> 05:53:00
>
>

[Mark J. Reed]

On Mon, Jun 8, 2009 at 9:31 AM, Victor Engel<brillig@...> wrote:
> The other day I bought a Coke when I rented a DVD set (Shogun). I
> expected to get a 20 oz bottle. Instead, I got a 500ml bottle.
> Interestingly, although the sizes are fairly close, the 500ml size
> fits in my car's cup holder. The 20 oz size doesn't.

20 fl oz is closer to 600ml than 500ml.  If US measure, it's about
590ml, while Imperial measure is closer to 570ml.  500ml is only about
17 fl oz in either system.

--
Mark J. Reed <markjreed@...>

[Amos Shapir]

Some parts of this message have been removed. Learn more about Nabble's security policy.

Officially the USA has been metric since day 1, because the Imperial units in use are defined by metric units (e.g. an inch is exactly 2.54 cm).  In 1976 Carter had signed a decree reuiring all federal agencies to use metric units, but by 1986 there was the Reagan counter-revolution, and the result is that all national parks have signs indicating things like "Elevation: 609.60m (2000ft)"; I have even seen a sign saying: "<-- Water 15.24m (50ft)".  This is a deliberate plot to make lay people get the impression that the metric system is something so complicated, that only rocket scientists can understand.

Amos Shapir
 



 

> Date: Mon, 8 Jun 2009 10:09:09 -0400
> From: markjreed@...
> Subject: Re: Calendar with Season Names Cannot be Global RE: Roman bum-rap
> To: CALNDR-L@...
>
> On Mon, Jun 8, 2009 at 9:31 AM, Victor Engel<brillig@...> wrote:
> > The other day I bought a Coke when I rented a DVD set (Shogun). I
> > expected to get a 20 oz bottle. Instead, I got a 500ml bottle.
> > Interestingly, although the sizes are fairly close, the 500ml size
> > fits in my car's cup holder. The 20 oz size doesn't.
>
> 20 fl oz is closer to 600ml than 500ml. If US measure, it's about
> 590ml, while Imperial measure is closer to 570ml. 500ml is only about
> 17 fl oz in either system.
>
> --
> Mark J. Reed <markjreed@...>
>

---

check out the rest of the Windows Live™. More than mail–Windows Live™ goes way beyond your inbox. More than messages

[Mark J. Reed]

I try not to ascribe to malice that which can be adequately explained
by incompetence.  Overly-precise conversions just mean someone has no
concept of significant figures.

Here in the US I've only rarely seen such signs showing metric first
with English conversion in parentheses, though; it's almost always the
other way around.   For example, my water bottle here has "20 FL OZ"
in big red text with smaller white text underneath that reads
"(1.25PT) 591 mL".  Both those conversions indicate that it's actually
20.0 FL OZ...

And most signs have no metric in them at all.  Speed limit signs and
distance markers on the Interstate make no mention of kilometers.
Signs warning of upcoming hazards use feet alone.

There are certain industries that deal with metric measurements, but
for the most part it is very much a second class citizen here, and you
can't really blame Reagan for that.  Inertia is a hard thing to
overcome.  Which bodes ill for any proposed calendar reform.

--
Mark J. Reed <markjreed@...>

[Brillig]

Yep. That's why it fits in the cup holder. It's still more than a can,
which is 12 oz.

Victor

On Mon, Jun 8, 2009 at 9:09 AM, Mark J. Reed<markjreed@...> wrote:

> On Mon, Jun 8, 2009 at 9:31 AM, Victor Engel<brillig@...> wrote:
>> The other day I bought a Coke when I rented a DVD set (Shogun). I
>> expected to get a 20 oz bottle. Instead, I got a 500ml bottle.
>> Interestingly, although the sizes are fairly close, the 500ml size
>> fits in my car's cup holder. The 20 oz size doesn't.
>
> 20 fl oz is closer to 600ml than 500ml.  If US measure, it's about
> 590ml, while Imperial measure is closer to 570ml.  500ml is only about
> 17 fl oz in either system.
>
> --
> Mark J. Reed <markjreed@...>
>
>

[Brillig]

Not always. Sometimes, especially in surveying, the foot is defined in
terms of the meter. One survey foot is defined as 1200/3937 meter.
Because of the volume of data already on file using the old unit, it
has been retained.

Victor

2009/6/8 Amos Shapir <amos083@...>:

> Officially the USA has been metric since day 1, because the Imperial units
> in use are defined by metric units (e.g. an inch is exactly 2.54 cm).  In
> 1976 Carter had signed a decree reuiring all federal agencies to use metric
> units, but by 1986 there was the Reagan counter-revolution, and the result
> is that all national parks have signs indicating things like "Elevation:
> 609.60m (2000ft)"; I have even seen a sign saying: "<-- Water 15.24m
> (50ft)".  This is a deliberate plot to make lay people get the impression
> that the metric system is something so complicated, that only rocket
> scientists can understand.
>
> Amos Shapir

[Mark J. Reed]

On Mon, Jun 8, 2009 at 11:43 AM, Victor Engel<brillig@...> wrote:
> Not always. Sometimes, especially in surveying, the foot is defined in
> terms of the meter.

Isn't that what Amos said? The English units are defined in terms of
the metric units.

Certainly, part of the problem with the English system is the
existence of  multiple units with the same name but different values,
like foot vs survey foot.   Fluid ounces (US or Imperial) vs
avoirdupois ounces vs Troy ounces, statute miles vs nautical miles...

--
Mark J. Reed <markjreed@...>

[Brillig]

On Mon, Jun 8, 2009 at 10:57 AM, Mark J. Reed<markjreed@...> wrote:
> On Mon, Jun 8, 2009 at 11:43 AM, Victor Engel<brillig@...> wrote:
>> Not always. Sometimes, especially in surveying, the foot is defined in
>> terms of the meter.
>
> Isn't that what Amos said? The English units are defined in terms of
> the metric units.

He also said the inch is exactly 2.54 cm. The conversion I gave was 1
foot is 1200/3937 meters. The later results in a bigger inch.

They are both defined in terms of metric units, but the conversion is
different.

Victor

[Peter Zilahy Ingerman, PhD]

FWIW, 100/3937 yields an inch equalling 2.540005 cm, which was the textbook value in my Physics courses until 1958, when the formal definition of the inch actually changed to exactly 2.54 cm.

So the issue is that the surveyor's foot was defined prior to 1958, and hasn't been redefined to be consistant with the "new" inch!

Pzed

Victor Engel wrote:

On Mon, Jun 8, 2009 at 10:57 AM, Mark J. Reedmarkjreed@... wrote:
  

On Mon, Jun 8, 2009 at 11:43 AM, Victor Engelbrillig@... wrote:
    

Not always. Sometimes, especially in surveying, the foot is defined in
terms of the meter.
      

Isn't that what Amos said? The English units are defined in terms of
the metric units.
    

He also said the inch is exactly 2.54 cm. The conversion I gave was 1
foot is 1200/3937 meters. The later results in a bigger inch.

They are both defined in terms of metric units, but the conversion is
different.

Victor

  

No virus found in this incoming message.
Checked by AVG - www.avg.com 
Version: 8.5.339 / Virus Database: 270.12.56/2162 - Release Date: 06/08/09 06:01:00

  

[Mark J. Reed]

On Mon, Jun 8, 2009 at 1:31 PM, Peter Zilahy Ingerman,
PhD<pzi@...> wrote:
> FWIW, 100/3937 yields an inch equalling 2.540005 cm, which was the textbook
> value in my Physics courses until 1958, when the formal definition of the
> inch actually changed to exactly 2.54 cm.
>
> So the issue is that the surveyor's foot was defined prior to 1958, and
> hasn't been redefined to be consistant with the "new" inch!

Both feet and inches were changed or unchanged alike; survey values
with feet and inches meant inches of 100/3937m, while outside of
surveying a "foot" has been exactly 0.3048m since 1959.

Even in the US, modern geodesy uses meters, so the practical need for
the survey foot is rapidly dwindling if not already gone.

--
Mark J. Reed <markjreed@...>

[Rodolphe Audette]

Actually, here in Canada, we make very little use of the metric system.

Many people will tell you they're 5 feet 10 inches tall. Virtually nobody will say he's 1,78 metre tall, and even knows he is. And while many weigh 160 lbs, nobody weighs 73 kilos.

Noone will cook meat in the oven at 175C. They will at 350F.

Feet and square feet are used rather than metres and square metres for measuring real estate.

When you get out of a hardware store, all you have bought is in imperial units : plywood, nails, mortar, etc. Only very large stores have a small metric department.

Although we are used to Celsius for air temperature, we still use Fahrenheit for water temperature in a pool. Teenagers who have never studied the Imperial system at school will tell you in the same sentence: "It's 30 degrees out there and the pool is at 80."

Rodolphe Audette


-----Message d'origine-----
De : East Carolina University Calendar discussion List [mailto:CALNDR-L@...] De la part de ELITE 3000
Envoyé : 8 juin, 2009 13:38
À : CALNDR-L@...
Objet : Metric system/Imperial system

Well, in Canada, we use the metric system. Speed limits are marked in kilometres per hour, and road signs are marked in kilometres and metres. Jugs, bottles, cartons and cans are marked in litres and millilitres. packages are marked in kilograms and grams. Temperatures are given in degrees Celsius. Some of us Canadians use the Imperial system alongside the metric system. Fuel economy is marked in litres per 100 km. Fuel prices are marked by the litre. When I travel to the US, I see road signs marked in miles and mph and fuel prices are marked by the gallon.

[MIKE OSSIPOFF]

Some parts of this message have been removed. Learn more about Nabble's security policy.

 
Irv--
 
You wrote:
 

The term GMT is deprecated (for many years), it is not a question of "fashion".  

 

I reply:

 

Ok, call it fashion or call it deprecation.

 

You continued:

 

Keep those blinkers on your eyes, disregard everything that isn't in front of your nose, eh?

 

I reply:

 

No, let's all march in lockstep and enforce the latest word-change. :-)

 

Maybe, in this instance, the name change is intended to emphasize the change in time-standard, from earth's rotation to an atomic standard.

 

You continued:

 

Mike, you persist in using the term GMT for the same reason that the USA persists in using Imperial Units even though almost all other nations in the world have switched to the International System of Units

 

I reply:

 

The International System (better known as the metric system) is much more computationally-convenient, and I don't in any way oppose its adoption by the U.S.

 

I was saying "GMT" because I sincerely wasn't aware that anyone was calling it incorrect. I agree with Aristeo that, for all practical purposes (unless maybe you're a quasar astronomer) GMT means the same thing as UT.

 

I know that our time-standard has changed, from the Earth's rotation to an atomic standard. Maybe the new name, UT, reflects that change of standards, and maybe someone could say that, technically, only "UT" refers to time by the new standard. Maybe, but, for practical purposes, they're understood to mean the same thing, as Aristeo suggested. Besides, we often still hear about local mean time. They call it that; they don't call it "longitude-adjusted UTC". So, if we still have local mean time, then what should we call the local mean time at the Greenwich Meridian? How about...Greenwich Mean Time? So, though GMT may be out of use these days, it seems to me that it can't be said to be incorrect.

 

Anyway, my own use of GMT was never intended as a stubborn change-resisting statement--I, like Aristeo, have considered the two terms to be interchangeable for practical purposes.

 

Mike Ossipoff

 

 

 

---

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[HR-CALNDR-L]

Hi calendar folks,

Just because of these unprecise definitions which depend on location,
atmospheric circumstances and many other unpredictable stuff such as personal
preference or taste or fashion, astronomers use only one exact definition for
the equinox.

The vernal equinox is when the geocentric ecliptic longitude of the sun's
center equals naught point naught.

And that is not the same as 'day and night are of equal length' or 'the sun is
in the equatorial plane' or 'the crops start growing' or 'I feel good'.

Because of the gravity of other heavy things in the universe (e.g. jupiter),
earth's orbit around the sun is NOT in a plane, earth can have some non-zero
ecliptic latitude, which is completely ignored in the astronomical definition
of the equinox. And there is nutation, causing the equatorial plane to wobble.
That's also ingored. Just to make the definition of the equinox simple and
easy and its calculations as simple and easy as possible.

In the same way the moon phases are defined only by the difference in
longitude between moon and sun, and that is geocentric longitude in the
ecliptic plane. It is not full moon when the moon is exactly round, it hardly
ever (better say never) is exactly round. The simple fact that we do not have
a perfectly central lunar eclips every month is the proof thereof. It is full
moon when its geocentric ecliptic longitude (so also completely ingoring
latitude) differs exactly 180 degrees from that of the sun.


_________________________________________________
Kind regards / met vriendelijke groeten,

Henk Reints



Oorspronkelijke tekst Irv Bromberg

> On 2009 Jun 7, at 06:03 , Aristeo Fernando wrote:
>> Encyclopedia Britannica may have taken into account the atmospheric
>> refraction near the horizon during sunrise and sunset to come up
>> with the dates for the equinoxes and solstices.  When do you think
>> should these astronomical phenomena occur?  Are the dates that
>> Encyclopedia Britannica cited correct?  And how should these
>> phenomena be defined?
>
> Irv replies:  Their dates are fine, just their definition incorrect.
>
> I would define an equinox as the moment when the solar declination
> crosses the celestial equator from south to north (northward equinox)
> or from north to south (southward equinox).
>
> I would define a solstice as the moment when the solar declination
> reaches the maximum declination north (north solstice) or south (south
> solstice).  This is observationally difficult to reckon to the second
> because the solar declination tends to linger at the maximum for about
> a day and the many little wobbles of Earth's axis also confounds
> determination of the moment.  Mathematical calculation finds the
> maximum of a mean solar declination function, which may differ from
> the actual astronomical moment by several minutes.
>
> The International Astronomical Union (IAU) however defines the
> equinoxes and solstices as occurring at each 90° of ecliptic solar
> longitude.  This is effectively the same for the northward equinox,
> but is not quite the same for the solstices or the southward equinox.
> Ecliptic solar longitude can be calculated to higher accuracy than
> solar declination, I presume that is the reason why IAU standardized
> on that definition.
>
>> Aristeo continued:  As Irv cited, the equinox varies with latitude,
>> that is why Encyclopedia Britannica is specific that it is the
>> moment "when the Sun is exactly above the Equator."
>
> Irv replies:  That is not what I wrote, I wrote that the day upon
> which the daytime and night length are equal varies with latitude.  It
> is actually furthest from the moment of the astronomical equinox at
> the equator, because the daytime length changes most slowly at the
> equator.  Defining the equinox as the moment when Sun is exactly above
> the equator is valid, but hard to reckon observationally, because it
> means that at that moment the shadow of a perfectly vertical stick
> disappears at local apparent noon somewhere on the equator, which more
> often than not will occur over an ocean, not land, and it is
> observationally difficult to reckon the moment to an accuracy better
> than about an hour by that method.  In astronomical practice, the
> equinox moments are calculated by solar declination or ecliptic solar
> longitude, not reckoned observationally.
>
>> Aristeo continued:  I thought Greenwich Mean Time (GMT) is
>> synonymous to Universal Time (UT).  What's the difference?  Isn't it
>> that the prime meridian passes through Greenwich, England and its
>> longitude is 0 degrees?
>
> Irv replies:  This web page adequately answers your question:
> <http://en.wikipedia.org/wiki/Gmt
>  >.
>
> UT is used in astronomical calculations, such as reckoning equinoxes
> and solstices, but the time that is broadcast by radio stations is UTC
> = Coordinated Universal Time.  UT includes an estimate of leap seconds
> and can be projected into the past or future, but UTC includes the
> actually inserted leap seconds and applies only to the present.  UT1
> is not really the same as UT:  UT1 is UTC plus an observationally
> measured fraction of a leap second that has accumulated since the last
> leap second insertion.  In astronomical computer programs UT is
> usually used instead of UT1 because it is computationally simpler to
> work with.  The difference is usually within a couple of seconds.  UT1
> can only be used computationally for the duration of time that it has
> been available, which is only since a few decades prior to the
> present, and to use it properly one would need a database of the daily
> offset between UT1 and UTC, so it is usually not worthwhile to bother
> with that.  People who do need to bother are those working on
> astronomical observations of distant quasars with micro-arcsecond
> accuracies.
>
> See also:
>
> http://en.wikipedia.org/wiki/Universal_Time
> http://en.wikipedia.org/wiki/Coordinated_Universal_Time
>
>
> -- Irv Bromberg, Toronto, Canada
>
> <http://www.sym454.org/seasons/>

[Karl Palmen]

Dear Mike, Victor and Calendar People

-----Original Message-----
From: East Carolina University Calendar discussion List
[mailto:CALNDR-L@...] On Behalf Of MIKE OSSIPOFF
Sent: 05 June 2009 00:11
To: CALNDR-L@...
Subject: Re: Calendar with Season Names Cannot be Global RE: Roman
bum-rap

 
Just a few concluding comments, in reply to comments that have been made
by others.
 
First, I'm not trying to convince those here who disagree with me. But
someone else might read these messages, maybe as they're sent out, or
maybe later, in the archives. Therefore, it's best that I answer the
objections that have been posted, as to the feasibility of a seasonal
calendar.

Karl wrote:
 
For a global calendar, the divisions of the year cannot be named after
seasons at all, because of the two hemispheres and other variations of
the seasons across the globe.  However, one can for any given place have
each date of the calendar year correspond  to the same season every
year. This date-season correspondence would be greatly different for
some different places. It cannot be made the same for all places.
 
Naming the divisions of the year after seasons for a global calendar
requires that the correspondence between dates and seasons is (almost)
the same throughout the world. Therefore it should not be attempted for
a global calendar, but it could be done for a local calendar, such as a
college calendar.
 
For a Global calendar it does not matter what the names of the divisions
are provided they are not misleading. They could be Roman-based names or
even letters or numbers. There is not one best solution. Season names
may be used locally, but for global use (e.g. this list), it'd be
necessary for example to say the you mean period A (Global name), by
Winter (Local name UK). Such information could be encoded into each
locale used by a computer system.
 
I reply:
 
That probably summs up the anti-seasonal position.
 
But what if it isn't claimed that the seasonal calendar's
seasonally-named year-divisions are a perfect match everywhere? What if
they're merely offered as a starting point, a framework, locally
correctable and interpretable?

KARL SAYS: The very use of seasonal names constitutes such a claim. The
use of such names while denying such a claim would be misleading. Better
to use non-seasonal names that can be given local seasonal
interpretations.
 
MIKE CONTINUED:
After all, you regularly adjust for your local time-zone, when the GMT
of an event is stated. So, local interpretation of global information
isn't something new.

KARL SAYS. So Mike is suggesting names somewhat like Winter US, Spring
US, etc, where US stands for universal season. To me these names are
either misleading or have no advantage over numbers or letters.

MIKE CONTINUED:
And if there is a difference between perceived vs calendar-shown
beginning and end of the periods that go with extreme high or low solar
declination, then you'll know that. You'll know how far the calendrical
seasons are off in your geographical region. With the Roman months, you
know, from expereience what the climate is like in various months. With
a seasonal calendar you'd soon know the same thing. The difference is
that its seasonal naming of its year-divisions is a starting framework.
 
Another way to express the difference: The Subjective Seasonal Calendar
relates to the sun's declination. What if I had instead proposed a
seasonal calendar that referred only to the declination? Say the "North"
season is when the sun's north-declination is in the top half of its
range; and the "South" season is when the sun's south-declination is in
the top half of that southern range? YOu probably wouldn't object to the
worldwide accuracy of that.

KARL SAYS: I like that kind of idea. We could have season names such as
Northward Sun, Northern Sun, Southward Sun and Southern Sun. Referring
to the position of the sun gets round the objections.
 

MIKE CONTINUED LATER ON:
Karl, you and others have said that we shouldn't have an official
attempt to designate dates for the seasons. But we already have that. As
I said, four times a year, the media repeatedly tell us that Winter,
Spring, Summer or Autumn is beginning. So it isn't as if I'm suggesting
something new. I'm just suggesting that something already in existence
be given better seasonal relevance.

KARL SAYS: I don't takes these seriously. They are misleading and can
resulting in heating being on or off at the wrong times.
In England we had summer like whether at the beginning of June the
temperatures dropped to those of a mild winter.
 
MIKE CONTINUED:
So it isn't really a question of whether to have official season
boundaries, but it's rather a question of how much sense we want those
seasonal definitions to make.
 
And I'm suggesting that it be in the calendar. Why not? If we're going
to always be told when the seasons begin, why not have it in the
calendar too? Calendars, after all, often have all sorts of information,
such as famous quotes from various dates, etc. Why not seasonal
estimates too?
 
Isaac Asimov proposed his World Season Calendar, which incorporated the
current official seasons, starting on the solstices and equinoxes--the
season boundaries that are so commonly stated in the media. And why not?
Why wait to hear it on tv, when you can have it shown on the calendar?
And I have merely improved Asimov's seasonal boundaries to try for a
better match to the perceived seasons.
 
Either the calendar seasons could have day-numbering, without months, as
Asimov's did, or the calendar seasons could be divided into months. I'd
name the months for their place in a season, so that South (a suggested
international name for the extreme south-declination season) would have
the months "SouthI, SouthII, SouthIII, and SouthIV.
 
Evidently some here would oppose any adoption of a seasonal calendar.
I'm not trying to convince those particular individuals. I'm merely
answering them, for the benefit of anyone else who might read my
proposal, and the objections from anti-seasonal list members, and my
(now concluded) replies to the objections that they have posted.

KARL SAYS: I have no objection if the year-divisions are named by the
position or movement of the sun.

You may wish to look at my Rainbow Alphabet Calendar idea which I have
had for several years at
http://www.hermetic.ch/cal_stud/palmen/rainbow.htm#abc . The year is
divided into 52 rainbow weeks named after the capital and small letters
of the alphabet so that the equinoxes occur in rainbow weeks M and m and
the solstices in rainbow weeks Z and z.
Each year has a Magentaday (8th day) in week Z and a leap year also has
a Magentaday in week z. An alternative to Magentadays is to extend one
rainbow date over a whole weekend exactly once every 42 weeks (of 294
days). Also I have referred to rainbow weeks A-Z as northward sun and
rainbow weeks a-z as southward sun.
 
Karl

10(09(17
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Karl
 
10(09(09 till noon
 
 
 


From: East Carolina University Calendar discussion List
[mailto:CALNDR-L@...] On Behalf Of MIKE OSSIPOFF
Sent: 01 June 2009 21:08
To: CALNDR-L@...
Subject: Re: Roman bum-rap
 

Victor said:
 
We're going in circles, so I'm going to leave this discussion.

I comment:
 
Correct. Going in circles because Victor was repeating the same
objections or questions, &/or asking me for things that I'd already
said. My answers to Victors questions and objections have been the same
each time that Victor expressed those questions or objections.
 
Additionally, in his letter below, there were a number of instances
where it wasn't at all clear what he meant. Without knowing what he
meant, it wasn't possible to give an answer.
 
Mike Ossipoff
 
 
 

 

On Fri, May 29, 2009 at 4:32 PM, MIKE OSSIPOFF  wrote:
Victor--


You wrote:

> Maybe I'm still having trouble understanding what you're after.
I reply:

Then I'll say it again: What should a calendar be based on, and its
year-divisions named for, if not the natural year, and its seasons.
Therefore, I prefer that a new calendar explicitly refer to the seasons,
even if it can't perfectly match them everywhere. And, more than that, I
also prefer that the calendar's month-system match the seasons as well
as possible. That's why I propose the Subjective Seasonal calendar. I
propose it with slightly different month systems for fixed and nonfixed
versions.

I don't specify a leapyear system for the nonfixed version, but the
Gregorian leapyear system is adequate for that. A symmetrical leapyear
system would be better still, but I don't make an issue of that. For the
fixed version, I suggest leapweeks, applied so as to minimize the
calendar's maximum drift with respect to the tropical year.

You continued:


> Perhaps it's only the alignment of the start of the year that you have
> a problem with.
I reply:

I have no idea where you got that. I certainly never said it.

I've spoken of the desirability of a calendar explicitly referring to
the seasons, and I've compared how well different month-systems match
our perception of the seasons.

You continued:


If so, I see no great value in doing so
I reply:

Doing what?? Before that statement in your message, you hadn't referred
to doing anything.


You continue:


, but we've
> been over that already.
I reply:

Probably, whatever "that" is.

You continue:


The Roman month system seems perfectly
> suitable to what you want.
Well, let's see:

Does it explicitly refer to the seasons? can its months be arranged in
groupings that match the seasons anything like as well as the Subjective
Seasonal Calendar?

(I've admitted that 5 of my 6 proposals don't match the perceived
seasons better than quarters of the Roman month system)


And is it as free of arbitrariness as most calendar reform proposals
are?

Evidentally your impression of what I want differs considerably from
what I've been saying that I want.

You continued:


 There are twelve months that are easily
> divided into roughly equal quarters.
I reply:

Yes, and that's sufficient if we don't mind assuming equal seasons. But
the seasons that we perceive, as described by authors over the
centuries, are not equal in length.

Since 5 of my proposals use quarters to represent seasons, I can't say
that quarters are entirely inadequate. I do say that they're distinctly
suboptimal. The use of quarters to represent seasons is greatly
improved-upon by the Subjective Seasonal Calendar.

You continued:


Anything beyond that requires
> more than a month system -- a calendar.
I reply:

I make no issue about leapyear systems. For fixed calendars, I prefer
leapweeks, but there hasn't been any dispute here about leapweeks vs
blank-days, at least no since my arrival.

You continued:


>
> By the way, a calendar is just a way to name days. Nearly all
> calendars thus are dependent upon a specific leap year scheme.
> Otherwise, naming a day would not be well defined or ambiguous.
I reply:

Have I said or implied otherwise? I accept the Gregorian leapyear system
for nonfixed calendars. Though it doesn't minimize jitter, its jitter
isn't excessive.

And no, I have never implied that we shouldn't have a "leap year
scheme". I've spoken of several that would be good. So it isn't entirely
clear why you keep going back to the subject of leapyear schemes.

Mike Ossipoff

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[Irv Bromberg]

On 2009 Jun 8, at 19:31 , MIKE OSSIPOFF wrote:

The International System (better known as the metric system) is much more computationally-convenient, and I don't in any way oppose its adoption by the U.S.

Irv replies:  Actually the metric system is a rather small earlier subset of the international system of units, in fact not all metric units are also S.I. units.

Compare:

http://en.wikipedia.org/wiki/Metric_system

http://en.wikipedia.org/wiki/International_System_of_Units

Mike continued:  I was saying "GMT" because I sincerely wasn't aware that anyone was calling it incorrect. I agree with Aristeo that, for all practical purposes (unless maybe you're a quasar astronomer) GMT means the same thing as UT.

Irv replies:  Sure, for anybody who doesn't know the difference, they mean the same thing!

GMT is also not the same as civil time in the UK, because it doesn't shift for Summer Time (their term for Daylight Saving Time).

By the way, due to tectonic plate movements, the old marker at the Greenwich observatory that used to be the international prime meridian is now a few metres away from the actual Earth axial prime meridian, as any GPS will show if one wanders around that area.

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/>