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Question: Axial precession



 
 
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  #1  
Old January 30th 10, 08:14 PM posted to sci.astro
Zurab57
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Posts: 11
Default Question: Axial precession

I already asked in alt.astronomy but have not recieved reply.
I have not enough knowledge of Astronomy to decide myself. So question
is: does Axial precession changes highness of Sun in zenith in
solstice at the given place?
Axial precession:
http://en.wikipedia.org/wiki/Axial_p...ion_(astronomy)
Solstice:
http://en.wikipedia.org/wiki/Solstice
What can I read on popular level about this, or maybe any
demonstration is possible?



  #2  
Old January 30th 10, 08:46 PM posted to sci.astro
Greg Neill[_6_]
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Posts: 605
Default Question: Axial precession

Zurab57 wrote:
I already asked in alt.astronomy but have not recieved reply.
I have not enough knowledge of Astronomy to decide myself. So question
is: does Axial precession changes highness of Sun in zenith in
solstice at the given place?


On the solstices the Earth's spin axis is tilted
towards (or away from) the Sun. That is to say,
you could draw a plane perpendicular to the
ecliptic plane and passing through the center of
the Sun and Earth, and the rotational axis of the
Earth will lie in that plane.

Precession changes (slowly) the direction of the
rotational axis in space, but it doesn't change
the angle of the tilt; Precession causes the
axis to describe a cone in space. Other effects
can alter the tilt angle, but you didn't ask about
them...

So if the tilt angle is contant and the geometry
on the solstices is as described, then the height
(elevation) of the Sun will be constant, too.


Axial precession:
http://en.wikipedia.org/wiki/Axial_p...ion_(astronomy)
Solstice:
http://en.wikipedia.org/wiki/Solstice
What can I read on popular level about this, or maybe any
demonstration is possible?



  #3  
Old January 30th 10, 11:23 PM posted to sci.astro
dlzc
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Posts: 1,426
Default Question: Axial precession

Dear Zurab57:

On Jan 30, 12:14*pm, Zurab57 wrote:
I already asked in alt.astronomy but have not
recieved reply. I have not enough knowledge
of Astronomy to decide myself. So question
is: does Axial precession changes highness
of Sun in zenith in solstice at the given place?


Precession moves where the peak "highness" occurs with each successive
orbit / year. This changes every place in between a tiny bit too.
But as Greg Neill says, it does not change the maximum value of
"highness".

David A. Smith
  #4  
Old January 31st 10, 10:13 AM posted to sci.astro
Elijahovah
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Posts: 79
Default Question: Axial precession

none of you know precession.
Firstly use any astronomy program and you will see the axis was closer
to 24 degrees before 2000 BC,
The axis is getting less.

Secondly, the noon sun at the solstice is not zenith on neother
solstice much less summer.
The noon sun at the equator is zenith direct overhead peak at noon on
both equinoxes. The summer solstice is 23 degrees north and the winter
solstice is 23 degrees south of equator overhead zenith. This is why i
wonder why we didint start calling it north solstice and south soltice
instead of summer and winter. The north solstice is summer for us and
winter for Australia.

Thirdly, at the equator it is only sunrise and sunset that never
change position, always being the exact same spot of rise and set. The
angle of the sun is what changes being a direct east-west overhead
path only on the two equinoxes.
I am not an astronomer and yet i know these things. I showed an
astronomer at the Adler the errors of a 1995 Carina Voyager program so
that she had all 5 astronomers drop the use of that program. I was
hoping more for leverage to asist the beligerant creator of the
program.

As for this tilt, though i dont know the elliptical geometry and
algebra and trig of calculating a comet or asteroid etc, that doesnt
mean that they are up on the realities their biasness blinds them to.
So I will throw in my religion at this time and state my belief in my
study of world calendars which only exist as world religious
calendars, that the current tilt was started following the asteroid
impact of the Yucatan (C14 dated as 20,000 BC) in 2370 BC on Julian
November 20 impact occurring at the hour of the day opposite the north
tilt. (Not sure, i think i looked at it once and it was perhaps
something like 4am from the direction of Leo.)
Anyways i have trust in God that tilt will be effected this year when
the same event occurs. Mantle meltdown should not be compaired to an
orange shrinking inside its skin because the severing of the crust is
by a flow of magma not air, and it is so thin between 1-2 miles that
it isnt going to slide the crust around to that vast a degree. I
wouldnt think so. The event itself is what should prove it and not
hollywood imagination or religious published book hype.
  #5  
Old January 31st 10, 10:29 AM posted to sci.astro
Elijahovah
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Posts: 79
Default Question: Axial precession

program claims and shows
that the first solstice of 2369 BC is
January 9 at the time 19:37:39
and has a noon sun height at the north pole
of 23 degrees 57 min 49 secs

where as
2009 AD Dec 21 at 17:51:39
23 degrees 26 min and 25 secs
  #6  
Old January 31st 10, 02:29 PM posted to sci.astro
Greg Neill[_6_]
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Posts: 605
Default Question: Axial precession

Elijahovah wrote:
none of you know precession.
Firstly use any astronomy program and you will see the axis was closer
to 24 degrees before 2000 BC,
The axis is getting less.


[snip whackage]

The OP inquired about precession, which does not
include the effects of nutation or other short or
long term variations.

The axial tilt is known to vary between 22.1 degrees
and 24.5 degrees with a period of about 42,000 years.

The last maximum occurred at about 8700 BC. The tilt
is currently decreasing, with the next minimum expected
around the year 11800.


  #7  
Old January 31st 10, 05:40 PM posted to sci.astro
Zurab57
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Posts: 11
Default Question: Axial precession

On Jan 31, 1:29*pm, Elijahovah wrote:
program claims and shows
that the first solstice of 2369 BC is
January 9 at the time 19:37:39
and has a noon sun height at the north pole
of 23 degrees 57 *min 49 secs

where as
2009 AD *Dec 21 at *17:51:39
23 degrees 26 min and 25 secs


With very rough estimation it gives difference for about 10 min of
time? I think such difference is detectable by gnomon or any facility
alike?
  #8  
Old February 1st 10, 09:52 PM posted to sci.astro
Steve Willner
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Posts: 1,172
Default Question: Axial precession

In article ,
Zurab57 writes:
does Axial precession changes highness of Sun in zenith in
solstice at the given place?


"Zenith" is the point directly overhead. Only within the tropics is
the Sun ever "in zenith." I understand your question as asking about
"the altitude of the Sun as it transits the meridian."

You might look up "obliquity of the ecliptic" for detailed
explanations. As Greg wrote, there are gravitational effects that
cause obliquity of the ecliptic to change on time scales of tens of
thousands of years. These effects might be included in a broad
definition of "precession," but that word as technically defined does
not include them. That doesn't mean they don't exist.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #9  
Old February 2nd 10, 05:20 PM posted to sci.astro
Zurab57
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Posts: 11
Default Question: Axial precession

On Feb 2, 12:52*am, (Steve Willner) wrote:
In article ,

*Zurab57 writes:
does Axial precession changes highness of Sun in zenith in
solstice at the given place?


"Zenith" is the point directly overhead. *Only within the tropics is
the Sun ever "in zenith." *I understand your question as asking about
"the altitude of the Sun as it transits the meridian."

You might look up "obliquity of the ecliptic" for detailed
explanations. *As Greg wrote, there are gravitational effects that
cause obliquity of the ecliptic to change on time scales of tens of
thousands of years. *These effects might be included in a broad
definition of "precession," but that word as technically defined does
not include them. *That doesn't mean they don't exist.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner * * * * * *Phone 617-495-7123 * *
Cambridge, MA 02138 USA * * * * * * * *


So, I see there are couple of inaccuracies in my post and change of
tilt angle apparently does not satsfies my idea claiming metaphorical
meaning of the text from bible:
And the word of the LORD came to Isaiah, saying, 5 “Go and tell
Hezekiah, ‘Thus says the LORD, the God of David your father: “I have
heard your prayer, I have seen your tears; surely I will add to your
days fifteen years. 6 I will deliver you and this city from the hand
of the king of Assyria, and I will defend this city.”’ 7 And this is
the sign to you from the LORD, that the LORD will do this thing which
He has spoken: 8 Behold, I will bring the shadow on the sundial,
which
has gone down with the sun on the sundial of Ahaz, ten degrees
backward.” So the sun returned ten degrees on the dial by which it
had
gone down.
Isaih 38:8 (King James edition)
With the clue:
Psalms 90:4 For a thousand years in thy sight are but as yesterday
when it is past, and as a watch in the night.

2 Peter 3:8 But, beloved, be not ignorant of this one thing, that one
day is with the Lord as a thousand years, and a thousand years as one
day.


Sorry, it seemed to me quite apparent.
  #10  
Old February 12th 10, 09:58 PM posted to sci.astro
Elijahovah
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Posts: 79
Default Question: Axial precession

how do you know the sun returned 10 degrees if you cannot
see the stars behind the sun. Of course, tif its the Earth's spin
pulled back, the stars behind the sun wont vary much at all since it
takes a whole 24 hours for a mere one degree. But what about the
rotation pulling back?

We assume that if in dayllight the sun pulls back 10 degrees
that then in darkness for America then the stars have pulled back in
10 degrees.
Indeed with a spinning Earth if the spin was actually pulled back,
then'what we see the sun do going back will also be seen as stars
doing so oon the other side of the Earth.
However, if no such record exists in the world then perhaps the sun
did not pull back, but rather a great close astral light came in at
the visual angle of the sun, and appeared to be the sun itslef pulling
back as shadows were produced from the astral light. The sun could
easily set and be out of view before a separation of this light occurs
away from the sun. In other words far to the west of Israel if the
astral light or comet or what ever COULD be seen, that land would have
seen an effect as if it was a splitting sun, or as if something from
the sun. But the prayer you quote says I will defend Israel so it
would seem this is what was seen before the cyanide of such a comet
killed 185,000 camped together outside Jerusalem.
 




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