Sun transit time question May 5, 2004

Sun transit time question May 5, 2004

Posted by E.D.G. May 5, 2004

I am working with a professional computer programmer to develop Basic and
Perl language programs which will generate subsolar and sublunar point
latitudes and longitudes. The first program is now running and is being
"fine tuned." In developing it I noticed something and am curious regarding
what causes it. Perhaps someone reading this note will know the answer.

In theory the sun should be directly above 0 longitude, the Greenwich
longitude, at 12 noon each day. But the longitude numbers for its actual
location at 12 noon that this and other programs generate show that there is
a variation of perhaps as much as 15 minutes in that transit time at
different times of the year. And those variations are reproducible from
year to year.

Q: What is the cause of those variations? I am assuming that I am
interpreting the data correctly.

Might this be due to the fact that the Earth orbit is an ellipse rather than
a true circle. And for that reason the 0 longitude line is directly beneath
the sun at slightly different times during the year because the Earth
rotation does not perfectly match its constantly changing orbital speed
around the sun?

In message . net,
edgrsprj writes
Sun transit time question May 5, 2004

Posted by E.D.G. May 5, 2004

I am working with a professional computer programmer to develop Basic and
Perl language programs which will generate subsolar and sublunar point
latitudes and longitudes. The first program is now running and is being
"fine tuned." In developing it I noticed something and am curious regarding
what causes it. Perhaps someone reading this note will know the answer.

In theory the sun should be directly above 0 longitude, the Greenwich
longitude, at 12 noon each day. But the longitude numbers for its actual
location at 12 noon that this and other programs generate show that there is
a variation of perhaps as much as 15 minutes in that transit time at
different times of the year. And those variations are reproducible from
year to year.

Q: What is the cause of those variations? I am assuming that I am
interpreting the data correctly.

Might this be due to the fact that the Earth orbit is an ellipse rather than
a true circle. And for that reason the 0 longitude line is directly beneath
the sun at slightly different times during the year because the Earth
rotation does not perfectly match its constantly changing orbital speed
around the sun?


You're almost exactly right. Civil time is based on the concept of the
'Mean Sun', an imaginary Sun moving at a uniform rate in the equatorial
plane. A sundial will show True time. The difference between the two is
a combination of the elliptical orbit of the Earth, and the inclination
of its axis of rotation to the ecliptic, i.e. The plane in which the
earth moves around the Sun. This difference is known as the Equation of
Time.
Google 'Equation of Time' and 'Analemma' for lots of references and more
detail.

It's quite possible that you will get some wacky responses to your
question here, so please be sure to get other references. ;-)

Denis
--
DT
Replace nospam with the antithesis of hills

"DT" wrote in message
...
You're almost exactly right. Civil time is based on the concept of the
'Mean Sun', an imaginary Sun moving at a uniform rate in the equatorial
plane. A sundial will show True time. The difference between the two is
a combination of the elliptical orbit of the Earth, and the inclination
of its axis of rotation to the ecliptic, i.e. The plane in which the
earth moves around the Sun. This difference is known as the Equation of

I understand what you are saying. I am going to have to try to develop a
mental picture of how the Earth axis angle is affecting the transit time.
At first thought I cannot see how it would make a difference.

In message . net,
edgrsprj writes
"DT" wrote in message
...
You're almost exactly right. Civil time is based on the concept of the
'Mean Sun', an imaginary Sun moving at a uniform rate in the equatorial
plane. A sundial will show True time. The difference between the two is
a combination of the elliptical orbit of the Earth, and the inclination
of its axis of rotation to the ecliptic, i.e. The plane in which the
earth moves around the Sun. This difference is known as the Equation of

I understand what you are saying. I am going to have to try to develop a
mental picture of how the Earth axis angle is affecting the transit time.
At first thought I cannot see how it would make a difference.


I couldn't remember this link at the time of my last post, but from a
programming point of view you may find it useful.

Http://www.jgiesen.de/deceot/

This link may help with a mental picture (something I always found
difficult!). It's quite basic but a reasonable start point (see near
bottom of page).

Http://www.shef.ac.uk/physics/people...105/phy105_sol
ar.html

Watch out for word wrap!

Denis
--
DT
Replace nospam with the antithesis of hills

"edgrsprj" wrote in message link.net...
Sun transit time question May 5, 2004

Posted by E.D.G. May 5, 2004

I am working with a professional computer programmer to develop Basic and
Perl language programs which will generate subsolar and sublunar point
latitudes and longitudes. The first program is now running and is being
"fine tuned." In developing it I noticed something and am curious regarding
what causes it. Perhaps someone reading this note will know the answer.

In theory the sun should be directly above 0 longitude, the Greenwich
longitude, at 12 noon each day. But the longitude numbers for its actual
location at 12 noon that this and other programs generate show that there is
a variation of perhaps as much as 15 minutes in that transit time at
different times of the year. And those variations are reproducible from
year to year.

Q: What is the cause of those variations? I am assuming that I am
interpreting the data correctly.

Might this be due to the fact that the Earth orbit is an ellipse rather than
a true circle. And for that reason the 0 longitude line is directly beneath
the sun at slightly different times during the year because the Earth
rotation does not perfectly match its constantly changing orbital speed
around the sun?

If you apply the supplied Equation of Time tables to the graphic
demonstrating Kepler's second law,you may appreceate how astronomers
equalised the variation in the natural day and isolated the constant
axial rotation of the Earth from its variable orbital motion.



http://www.burnley.gov.uk/towneley/tryall/eot3.htm

http://ircamera.as.arizona.edu/NatSc...res/kepler.htm

If you are more adventurous with the graphic demonstrating the
difference between circular motion with constant positional
displacement with the actual orbital motion of the Earth via Kepler's
second law,you will note that the contemporary astronomical
justification for the axial rotation of the Earth through 360 degrees
via the sidereal value or stellar circumpolar motion does'nt work,the
Earth does not have equable orbital displacement for each axial
rotation nor constant equable axial rotation wrt the Sun.

http://www.absolutebeginnersastronomy.com/sidereal.gif

DT wrote in message ...
In message . net,
edgrsprj writes
Sun transit time question May 5, 2004

Posted by E.D.G. May 5, 2004

I am working with a professional computer programmer to develop Basic and
Perl language programs which will generate subsolar and sublunar point
latitudes and longitudes. The first program is now running and is being
"fine tuned." In developing it I noticed something and am curious regarding
what causes it. Perhaps someone reading this note will know the answer.

In theory the sun should be directly above 0 longitude, the Greenwich
longitude, at 12 noon each day. But the longitude numbers for its actual
location at 12 noon that this and other programs generate show that there is
a variation of perhaps as much as 15 minutes in that transit time at
different times of the year. And those variations are reproducible from
year to year.

Q: What is the cause of those variations? I am assuming that I am
interpreting the data correctly.

Might this be due to the fact that the Earth orbit is an ellipse rather than
a true circle. And for that reason the 0 longitude line is directly beneath
the sun at slightly different times during the year because the Earth
rotation does not perfectly match its constantly changing orbital speed
around the sun?


You're almost exactly right. Civil time is based on the concept of the
'Mean Sun', an imaginary Sun moving at a uniform rate in the equatorial
plane.

Historically and observationally incorrect,the equable 24 hour day is
based on the actual motions of the Earth,both axial and orbital, using
the Sun as a reference.



A sundial will show True time.

A sundial registers the actual motions of the Earth by means of a
shadow,there are two observed variations occuring for each passage of
a shadow back to a fixed marker.

Over the course of a full annual cycle,the range of the lenght of
shadows cast changes as the equatorial orientation of the Earth
changes ,lower on the horizon and therefore longer shadows in the
winter and shorter shadows in the summer.This variation due to axial
tilt has no effect on the pace of the shadow across the dial which
changes over the annual orbit but remains common in both hemispheres.

http://www.cmi.k12.il.us/Urbana/proj.../techpage.html

The pace of the shadow across the sundial from one complete rotation
to the next is due to the combination of constant axial rotation
combined with variable orbital motion.The Equation of Time basically
equalises this variable pace to a constant hence the equable 24 hour
day and the pace of the equable hour,minute and second.


The difference between the two is
a combination of the elliptical orbit of the Earth, and the inclination
of its axis of rotation to the ecliptic, i.e. The plane in which the
earth moves around the Sun. This difference is known as the Equation of
Time.

Historically and observationally incorrect.The graphics of the 21st
century permits anyone to put the components of the Equation of Time
into proper context,the natural inequality of a day using the Sun as a
reference is conditioned by the behavior of the Earth in its orbital
motion insofar as this is what causes the pace of the shadow to change
across the sundial in both hemispheres simultaneously.

It is only a matter of applying the appropriate minutes and seconds to
the noon determination and recognising how sometimes clock noon is
ahead of the natural noon determination and sometimes behind in terms
of the variable orbital motion equalised to a constant motion,Kepler's
second law in other words.

http://ircamera.as.arizona.edu/NatSc...res/kepler.htm



Google 'Equation of Time' and 'Analemma' for lots of references and more
detail.


He can indeed,try NASA who are oblivious to the fact that the winter
solstice in the Northern hemisphere implies that it is the summer
solstice in the Southern,try convincing the Aussies that it is
mid-winter on the 21st of Dec and see how far you get !.

http://imagine.gsfc.nasa.gov/docs/as...s/980116c.html

If the participant who began this thread can live with that
explanation comfortably he can live with anything.



It's quite possible that you will get some wacky responses to your
question here, so please be sure to get other references. ;-)

Denis

If he wants wacky he can turn to the Royal Observatory Greenwich who
seem to have entirely lost the plot.

"Each solar day the Earth rotates 360º with respect to the Sun.
Similarly the Earth rotates 360º with respect to the background stars
in a sidereal day. During each solar day, the motion of the Earth
around the Sun means the Earth rotates 361º with respect to the
background stars."

http://www.nmm.ac.uk/site/navId/00500300l005001000

No offense but when the association between geometry astronomy and
clocks becomes that bad with nobody around to untangle the mess,men
are hardly fit to call themselves astronomers.

If he wants wacky he can turn to the Royal Observatory Greenwich who
seem to have entirely lost the plot.



Or he could just ignore everything you have to say on the subject. You've
been tring to flog this dead horse for ages now. Isn't it time you gave up,
or at least took some physics/astronomy classes?


DaveL

Oriel36 wrenched his hand from the flames
and wrote;
snipped

Same old master puppeteer pulling your strings eh Gerald?
For Keplers sake give us a new tune.

Denis
--
DT
Replace nospam with the antithesis of hills

Posted by E.D.G. May 6, 2004

This subject matter will probably eventually be fairly important to the work
that I am doing which is to develop a "synthetic triangulation" computer
program for determining what the locations are where earthquake and perhaps
tornado precursor signals are being generated. The program is already up
and running and downloadable from the following Web site. A newer version
and additional documentation is scheduled to be stored there later tonight.

http://www.freewebz.com/eq-forecasting/301.html

It is my personal belief that this program probably presently represents
about the only hope that many people around the world who are threatened by
earthquakes and perhaps tornados have of receiving a waning before a
destructive one occurs near them. It relies on certain types of precursor
signals and a knowledge of where the sun and moon are in the sky and where
ocean and Solid Earth Tide crests and troughs are located at the time when
the signals are detected and when earthquakes occur. A professional
computer programmer and I are trying to finalize a program which generates
subsolar and sublunar latitudes and longitudes. It will replace an enormous
data file I have stored at the site which contains those types of data in a
compiled form. I needed to know if that noon time offset I have been
observing is real. Apparently it is. And it will have to eventually be
better understood by people who attempt to develop more advanced versions of
my own forecasting program and also people working on the following
earthquake forecasting program which involves detecting slight variations in
the position of the shadow of an object cast on a wall. It is an
interesting concept which is unfortunately I feel not presently adequately
explained at this Web site.

http://earthquake.itgo.com/today.htm

I know the details of how it works. And there is more logic to it than the
documentation at the Web site appears to me to suggest.

ADDITIONAL SUN AND MOON TRANSIT TIME FACTORS

There are at least two additional factors which I believe can influence sun
and moon transit times for different locations on Earth. I didn't see
either mentioned in any of the responses to my original post though I might
have simply missed something someone said.

There is a wobble in the rotation of the Earth on its North - South Pole
axis which is I believe called polar motion. If I understand it correctly
it is composed of something called Chandler's wobble and also a seasonal
type of wobble. I don't think that it is responsible for much of the
transit time offset I have seen.

The other factor would be linked with the gravitational effects of the moon
on the Earth. Once each month the Earth and moon rotate in a somewhat
irregular manner around a common center of mass. And the moon gravity also
affects the Earth differently throughout the month as it travels from north
to south, from close to far in its orbit, and as it gets close to the sun in
the sky or is on the opposite side of the Earth from the sun.

As I said, I expect that these types of effects will eventually be regarded
as being important for these forecasting methods. For the moment I just
need to be able to compensate for them. And I believe that my computer
programs can presently do that.

There is a very interesting puzzle which my forecasting program indicates
exists. Something related to the gravitational pulls of the sun and the
moon appears to be quite important to earthquake triggering processes. And
no one knows what it is or even much about it. My program should provide
clear evidence that it exists. But the question still remains regarding its
nature. Two present theories are discussed towards the end of the following
report:

http://www.freewebz.com/eq-forecasting/128.html

One of those theories proposes that sun and moon gravity related forces are
acting directly on the Earth's crust and pulling it in different directions
resulting in temporary, cyclic types of strain being added to certain fault
zones. The other theory proposes that as the Earth, moon, and sun rotate
around their common centers of mass the Earth's dense, solid core tries to
stay in one place and rotate with a fixed speed while its crust is being
pulled in different directions by the sun and moon gravity and also
forced to change it rotation speed to some extent because of changes in the
amount of ocean tide and current drag on the crust etc. In the process of
resisting those location and rotation speed changes the Earth's core causes
stress to be produced in certain locations in the crust. And that can then
result in earthquakes being triggered in fault zones in those locations if
the fault zones are about ready to fracture on their own anyway.

I personally cannot understand why geophysicists seem to completely unaware
of these earthquake triggering effects or why they have not developed clear
pictures for how those types of crustal strain related processes might be
affecting earthquake fault zones. The subject matter is certainly
important!

These are personal opinions.

"edgrsprj" wrote in message link.net...
Posted by E.D.G. May 6, 2004

This subject matter will probably eventually be fairly important to the work
that I am doing which is to develop a "synthetic triangulation" computer
program for determining what the locations are where earthquake and perhaps
tornado precursor signals are being generated. The program is already up
and running and downloadable from the following Web site. A newer version
and additional documentation is scheduled to be stored there later tonight.

http://www.freewebz.com/eq-forecasting/301.html

It is my personal belief that this program probably presently represents
about the only hope that many people around the world who are threatened by
earthquakes and perhaps tornados have of receiving a waning before a
destructive one occurs near them. It relies on certain types of precursor
signals and a knowledge of where the sun and moon are in the sky and where
ocean and Solid Earth Tide crests and troughs are located at the time when
the signals are detected and when earthquakes occur. A professional
computer programmer and I are trying to finalize a program which generates
subsolar and sublunar latitudes and longitudes. It will replace an enormous
data file I have stored at the site which contains those types of data in a
compiled form. I needed to know if that noon time offset I have been
observing is real. Apparently it is. And it will have to eventually be
better understood by people who attempt to develop more advanced versions of
my own forecasting program and also people working on the following
earthquake forecasting program which involves detecting slight variations in
the position of the shadow of an object cast on a wall. It is an
interesting concept which is unfortunately I feel not presently adequately
explained at this Web site.

http://earthquake.itgo.com/today.htm

I know the details of how it works. And there is more logic to it than the
documentation at the Web site appears to me to suggest.

ADDITIONAL SUN AND MOON TRANSIT TIME FACTORS

There are at least two additional factors which I believe can influence sun
and moon transit times for different locations on Earth. I didn't see
either mentioned in any of the responses to my original post though I might
have simply missed something someone said.

There is a wobble in the rotation of the Earth on its North - South Pole
axis which is I believe called polar motion. If I understand it correctly
it is composed of something called Chandler's wobble and also a seasonal
type of wobble. I don't think that it is responsible for much of the
transit time offset I have seen.

The other factor would be linked with the gravitational effects of the moon
on the Earth. Once each month the Earth and moon rotate in a somewhat
irregular manner around a common center of mass. And the moon gravity also
affects the Earth differently throughout the month as it travels from north
to south, from close to far in its orbit, and as it gets close to the sun in
the sky or is on the opposite side of the Earth from the sun.

As I said, I expect that these types of effects will eventually be regarded
as being important for these forecasting methods. For the moment I just
need to be able to compensate for them. And I believe that my computer
programs can presently do that.

There is a very interesting puzzle which my forecasting program indicates
exists. Something related to the gravitational pulls of the sun and the
moon appears to be quite important to earthquake triggering processes. And
no one knows what it is or even much about it. My program should provide
clear evidence that it exists. But the question still remains regarding its
nature. Two present theories are discussed towards the end of the following
report:

http://www.freewebz.com/eq-forecasting/128.html

One of those theories proposes that sun and moon gravity related forces are
acting directly on the Earth's crust and pulling it in different directions
resulting in temporary, cyclic types of strain being added to certain fault
zones. The other theory proposes that as the Earth, moon, and sun rotate
around their common centers of mass the Earth's dense, solid core tries to
stay in one place and rotate with a fixed speed while its crust is being
pulled in different directions by the sun and moon gravity and also
forced to change it rotation speed to some extent because of changes in the
amount of ocean tide and current drag on the crust etc. In the process of
resisting those location and rotation speed changes the Earth's core causes
stress to be produced in certain locations in the crust. And that can then
result in earthquakes being triggered in fault zones in those locations if
the fault zones are about ready to fracture on their own anyway.

I personally cannot understand why geophysicists seem to completely unaware
of these earthquake triggering effects or why they have not developed clear
pictures for how those types of crustal strain related processes might be
affecting earthquake fault zones. The subject matter is certainly
important!


The behavior of a Foucault's pendulum during an eclipse would indicate
that there is some localised shielding going on as the moon passes
before the Sun which affects the motion of the pendulum.

http://science.nasa.gov/newhome/head...t06aug99_1.htm

This localised interruption in the motion of the pendulum indicates
that there is another factor than the gravitational factor to take
into account in respect to the physical effects of the Sun on the
Earth. As contemporaries only recognise the Earth's motions as a
single sidereal motion to facilitate gravitational causes alone,the
worthy endeavor you embark on will suffer from this rather limited
point of view.


These are personal opinions.