Is it possible to precess backwards in time

Suppose I have the epoch for 2000, but want to find the precession at
1990. Is it possible, and is it just that some signs in the precession
matrix, or general equations just need to be reversed?

Maybe consider what Meeus shows to see if it's a reasonable thing to do.
Could one then go forward from 1990 to 2005, as they could from 2000 to
2005?

Anyone have a Python program that implements Meeus for precession?

On Sat, 28 Jan 2012 21:45:11 -0800, "W. eWatson"
wrote:

Suppose I have the epoch for 2000, but want to find the precession at
1990. Is it possible, and is it just that some signs in the precession
matrix, or general equations just need to be reversed?

I've never seen a precession algorithm (including that of Meeus) that
cares which direction you calculate. Set the final epoch to less than
the starting epoch (or the difference in Julian days/years to
negative) to precess backwards.

On 1/28/2012 9:58 PM, Chris L Peterson wrote:
On Sat, 28 Jan 2012 21:45:11 -0800, "W. eWatson"
wrote:

Suppose I have the epoch for 2000, but want to find the precession at
1990. Is it possible, and is it just that some signs in the precession
matrix, or general equations just need to be reversed?

I've never seen a precession algorithm (including that of Meeus) that
cares which direction you calculate. Set the final epoch to less than
the starting epoch (or the difference in Julian days/years to
negative) to precess backwards.

Yes, I've used Meeus both ways w/o an difficulty. The real question is
whether after going in one direction can you precess back to where one
started without incurring some penalty.

Putting a different spin on this is how does one precess back to say
3506 BCE. Meuss says his first method is fine if one doesn't need great
accuracy. He offers a more rigorous method. So with this spin in mind,
how do we get back to 3506 BCE. For example, would his more rigorous
method do it, or does one precess a 100 years at a time until they are
in the vicinity of the date, then adjust as needed. Aren't programs like
TheSky doing such things with pretty good accuracy?

On Jan 29, 4:35*pm, "W. eWatson" wrote:
On 1/28/2012 9:58 PM, Chris L Peterson wrote: On Sat, 28 Jan 2012 21:45:11 -0800, "W. eWatson"
*wrote:

Suppose I have the epoch for 2000, but want to find the precession at
1990. Is it possible, and is it just that some signs in the precession
matrix, or general equations just need to be reversed?

I've never seen a precession algorithm (including that of Meeus) that
cares which direction you calculate. Set the final epoch to less than
the starting epoch (or the difference in Julian days/years to
negative) to precess backwards.

Yes, I've used Meeus both ways w/o an difficulty. The real question is
whether after going in one direction can you precess back to where one
started without incurring some penalty.

Putting a different spin on this is how does one precess back to say
3506 BCE. Meuss says his first method is fine if one doesn't need great
accuracy. He offers a more rigorous method. *So with this spin in mind,
how do we get back to 3506 BCE. For example, would his more rigorous
method do it, or does one precess a 100 years at a time until they are
in the vicinity of the date, then adjust as needed. Aren't programs like
TheSky doing such things with pretty good accuracy?

Precession turns out to be an orbital trait as the polar coordinates
of a planet turn 360 degrees to the central Sun an coincident with an
orbital period -

http://www.daviddarling.info/images/...gs_changes.jpg

Try to get your heads around the quasi-rotation of the polar
coordinates to the central Sun by using an imitation analogy using a
broom handle and you will discover that the tip of the broom turns in
a circle about a traveling orbital axis as a person walks/orbits a
central object/Sun.The traveling axis for the Earth is roughly a line
running through the center of the Earth from Arctic to Antarctic
circles or the line of the circle of illumination if you
prefer.Disregarding the direction of the arrows,the orbital behavior
of the planet and the turning of the polar coordinates in a circle
over the course of an annual circuit is about right in the following
image -

http://en.wikipedia.org/wiki/File:Earth_precession.svg

When given a choice and a chance to take a better view with
contemporary imaging and cross reference details with other planets to
arrive at common principles,and the orbital behavior of the Earth is
crucial for modifying the view of the seasons or indeed the polar day/
night cycle nothing seems to move people an they will still stick with
'axial precession' and not make the necessary modification.

It no longer feels right to be here.

oriel36 wrote:


It no longer feels right to be here.

Then instead of these posts why not retreat to your garden, put your broom
handle vertically into the ground and use it over the next year to trace
out an analemma so you can contemplate how wrong you have been.

On Jan 29, 5:31*pm, Mike Collins wrote:
oriel36 wrote:

It no longer feels right to be here.

Then instead of these posts why not retreat to your garden, put your broom
handle vertically into the ground and use it over the next year to trace
out an analemma so you can contemplate how wrong you have been.

What did I tell you that a wandering analemma Sun is not a defiance of
astronomical principles but a complete ignorance of them.

Without the additional orbital component required to explain the
seasons and actual variations in the natural noon cycle,the orbital
nodes around which the polar coordinates turn in a circle and vary the
apparent height of the Sun over an annual orbit follow the
discontinuous line running South to North from Arctic to Antarctic
circles alone a plane which splits the center of the Earth through the
tropics of Capricorn and Cancer ,roughly the green line in the follow
graphic -

http://en.wikipedia.org/wiki/File:Earth_precession.svg

As the orbital behavior of the planet turns the polar coordinates in a
circle to the central Sun,and these coordinates actually do turn in a
circle even of the orbital component is a quasi-rotation,the angle
between the traveling axis and the rotational axis change,acute and
the Northern polar latitude at the orbital point of the June solstice
and obtuse at the December orbital point.

Long term precession has to go as a long term axial trait as the
polar coordinates do actually precess in a circle to the central Sun
with all its effects,it is not only new but extremely satisfying
working it out by cross referencing it with the daily and orbital
traits of Uranus.None of this will make sense to a crowd who believe a
wandering analemma Sun can or should be explained using the daily and
orbital motions of the Earth and that is basically that.

Again,it just doesn't feel right to be among people who are prepared
to ignore the only acceptable wandering motions of the planets as
opposed to something as juvenile and ridiculous as right ascension
reasoning that bred this wandering Sun ideology.

oriel36 wrote:
On Jan 29, 5:31 pm, Mike Collins wrote:
oriel36 wrote:

It no longer feels right to be here.

Then instead of these posts why not retreat to your garden, put your broom
handle vertically into the ground and use it over the next year to trace
out an analemma so you can contemplate how wrong you have been.

What did I tell you that a wandering analemma Sun is not a defiance of
astronomical principles but a complete ignorance of them.

Without the additional orbital component required to explain the
seasons and actual variations in the natural noon cycle,the orbital
nodes around which the polar coordinates turn in a circle and vary the
apparent height of the Sun over an annual orbit follow the
discontinuous line running South to North from Arctic to Antarctic
circles alone a plane which splits the center of the Earth through the
tropics of Capricorn and Cancer ,roughly the green line in the follow
graphic -

http://en.wikipedia.org/wiki/File:Earth_precession.svg

As the orbital behavior of the planet turns the polar coordinates in a
circle to the central Sun,and these coordinates actually do turn in a
circle even of the orbital component is a quasi-rotation,the angle
between the traveling axis and the rotational axis change,acute and
the Northern polar latitude at the orbital point of the June solstice
and obtuse at the December orbital point.

Long term precession has to go as a long term axial trait as the
polar coordinates do actually precess in a circle to the central Sun
with all its effects,it is not only new but extremely satisfying
working it out by cross referencing it with the daily and orbital
traits of Uranus.None of this will make sense to a crowd who believe a
wandering analemma Sun can or should be explained using the daily and
orbital motions of the Earth and that is basically that.

Again,it just doesn't feel right to be among people who are prepared
to ignore the only acceptable wandering motions of the planets as
opposed to something as juvenile and ridiculous as right ascension
reasoning that bred this wandering Sun ideology.

The Sun doesn't wander. The Earth turns once every sidereal day but it's
elliptical orbit means that the Solar noon is usually not the same as the
mean solar noon. In the days when the time of day was only measured so that
requests for special favours could be made to a non-existent God at the
correct time the sundial was accurate enough.
In these days of communications satellites (orbiting the planet once every
sidereal day to keep above the same spot) and satnavs needing better than
microsecond timing and relativistic corrections the sundial is not good
enough.
The analemma is an easy demonstration of your errors which is why you hate
it so much.
Stop your doublethink and gave the courage to admit you are wrong son.

On Jan 29, 6:46*pm, Mike Collins wrote:
oriel36 wrote:

Again,it just doesn't feel right to be among people who are prepared
to ignore the only acceptable wandering motions of the planets as
opposed to something as juvenile and ridiculous as right ascension
reasoning that bred this wandering Sun ideology.

The Sun doesn't wander.

http://apod.nasa.gov/apod/image/0612...yiomamitis.jpg

The nearest possible episode akin to the analemma is Piltdown Man and
when asked why it was not spotted sooner,the answer was fairly
straightforward -

"The molar surface were examined under a microscope. They were scarred
by criss-cross scratches suggesting the use of an abrasive. 'The
evidences of artificial abrasion immediately sprang to the eye' wrote
Le Gros Clark. 'Indeed so obvious did they [the scratches] seem it may
well be asked -- how was it that they had escaped notice before?' He
answered his question with a beautiful simplicity. 'They had never
been looked for...nobody previously had examined the Piltdown jaw with
the idea of a possible forgery in mind, a deliberate fabrication.'"
Piltdown Man investigator

Nobody looked at the wandering analemma Sun as a symptom of something
else until contemporary sequential imaging shows retrograde motions of
planets and what they represent in terms of the Earth's planetary
dynamics.The story that led to the analemma hoax is far more
fascinating an encompassing than the paleontological version yet
ultimately it is severely disruptive for a generation who now have
imaging power capable of cross referencing planetary details for a
better perspective of terrestrial effects and sciences.

I could not bear the presence of people so willing to support a hoax
yet at the same time,it does give people a chance to take a stand on
either the wandering planets or a ridiculous wandering Sun but they
cannot have both for explaining the Earth;s daily and orbital motions.

On 1/29/12 1:37 PM, oriel36 wrote:


I could not bear the presence of people so willing to support a hoax
yet at the same time,it does give people a chance to take a stand on
either the wandering planets or a ridiculous wandering Sun but they
cannot have both for explaining the Earth;s daily and orbital motions.


The analemma is a graphic representation of the equation of time.
http://en.wikipedia.org/wiki/File:Analemma_Earth.png

The earth's orbit is elliptical, as a result sunrise, solar noon and
sunset get ahead and behind. The eccentricity of the earth orbit and
the obliquity of the ecliptic are the largest factors.
http://en.wikipedia.org/wiki/Equation_of_time

On Jan 29, 8:51*pm, Sam Wormley wrote:
On 1/29/12 1:37 PM, oriel36 wrote:



I could not bear the presence of people so willing to support a hoax
yet at the same time,it does give people a chance to take a stand on
either the wandering planets or a ridiculous wandering Sun but they
cannot have both for explaining the Earth;s daily and orbital motions.

* *The analemma is a graphic representation of the equation of time.
* * *http://en.wikipedia.org/wiki/File:Analemma_Earth.png

* *The earth's orbit is elliptical, as a result sunrise, solar noon and
* *sunset get ahead and behind. The eccentricity of the earth orbit and
* *the obliquity of the ecliptic are the largest factors.
* * *http://en.wikipedia.org/wiki/Equation_of_time

I posted the wrong graphic in a previous response for explaining the
annual precession of the polar coordinate to the central Sun which is
taken up presently with the flawed long term 'axial precession' as you
know it.

The orbital nodes around which the polar coordinates turn in a circle
to the central Sun and vary the apparent height of the Sun over an
annual orbit follow the
discontinuous line running South to North from Arctic to Antarctic
circles alone a plane which splits the center of the Earth through the
tropics of Capricorn and Cancer ,roughly the green line in the follow
graphic -

http://www.simpletoremember.com/imag...ds/erthaxs.jpg

As the orbital behavior of the planet turns the polar coordinates in
a circle to the central Sun, and these coordinates actually do turn in
a circle even if the orbital component is a quasi-rotation,the angle
between the traveling axis and the rotational axis change from acute
at the Northern polar latitude at the orbital point of the June
solstice , obtuse at the December orbital point and at the equinox the
angles align as the polar coordinate turn to split the circle of
illumination.

Allowing the Earth to turn to the central Sun as a component of its
orbital motion eases the explanation for why the polar coordinates
turn through the circle of illumination at the equinoxes separating 6
months of daylight from 6 months of darkness and the components of
this are particularly enjoyable for explaining the variations in the
natural noon cycle.

You want your figure '8' wandering Sun then enjoy that hideous
conception but I have seen enough here,truly.