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question about inclination of earth's axis.



 
 
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  #1  
Old May 24th 06, 06:10 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

I'm curious. Suppose I were to be deprived of technology and had to
rely only upon my observation, and intuition, how would I know that
Earth's axis is inclined at an angle instead of being perpendicular?

How did the ancients know that the axis of Earth is not perpendicular,
but inclined ?

regards,
Abhishek.

  #2  
Old May 24th 06, 06:15 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

Abhishek wrote:
I'm curious. Suppose I were to be deprived of technology and had to
rely only upon my observation, and intuition, how would I know that
Earth's axis is inclined at an angle instead of being perpendicular?

How did the ancients know that the axis of Earth is not perpendicular,
but inclined ?


The axis of the Earth is clearly not perpendicular to the ecliptic (the
apparent orbital plane of the sun), because if it were, we wouldn't have
any seasons. The Sun would always cross the sky at the same height, day
after day.

The amazing thing to me is that the Greeks even uncovered the precession
of the equinoxes, and even gave a decent estimate as to how long the
period is--about 36,000 years. (The actual value is about 25,800.)

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
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  #4  
Old May 24th 06, 06:39 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

"Brian Tung" wrote in message
...
[snip]

The Sun would always cross the sky at the same height, day
after day.


Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am
wrong here, but isn't this the same conclusion which would be drawn if
earth's axis was inclined but of constant inclination /with respect to the
sun/?

In other words, let me rephrase the question. Suppose earth's inclination
with respect to the sun was always constant, so that, say, the northern
hemisphere always has summer and the southern always winter. Except for
travelling to the opposite hemispehere, how can we deduce that the axis is
inclined?

[snip]
--
Brian Tung

--
Ioannis

  #5  
Old May 24th 06, 06:46 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

Allison Kirkpatrick wrote:
You would probably first have to figure out that the Earth is
spherical, rather than flat, and in orbit around the sun, rather than
vice-versa.


I think the question presumes knowledge that the Earth is spherical
(otherwise, it doesn't have an axis). I don't agree that it requires
knowing that the Earth revolves around the Sun, except that the question
must be rephrased as how one figures out that the Earth's axis is not
perpendicular to the Sun's orbital plane.

The above applies to points on earth north and south of the two
Tropics; between them things are a little different, but I will save
that topic for a later installment.


Are you sure? How so?

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
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  #6  
Old May 24th 06, 06:49 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

Ioannis wrote:
Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am
wrong here, but isn't this the same conclusion which would be drawn if
earth's axis was inclined but of constant inclination /with respect to the
sun/?

In other words, let me rephrase the question. Suppose earth's inclination
with respect to the sun was always constant, so that, say, the northern
hemisphere always has summer and the southern always winter. Except for
travelling to the opposite hemispehere, how can we deduce that the axis is
inclined?


The Sun would not be travelling in a great circle. That'd be the first
clue. Whether that clue would be interpreted correctly is another
matter, of course.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
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  #7  
Old May 24th 06, 07:25 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.


Brian Tung wrote:
Ioannis wrote:
Hmmm ok. Let's leave seasons out of it for a moment. Correct me if I am
wrong here, but isn't this the same conclusion which would be drawn if
earth's axis was inclined but of constant inclination /with respect to the
sun/?

In other words, let me rephrase the question. Suppose earth's inclination
with respect to the sun was always constant, so that, say, the northern
hemisphere always has summer and the southern always winter. Except for
travelling to the opposite hemispehere, how can we deduce that the axis is
inclined?


The Sun would not be travelling in a great circle. That'd be the first
clue. Whether that clue would be interpreted correctly is another
matter, of course.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html


No need to reference the axial/Equatorial orientation of the Earth
against an object 93 million miles away.

Take a look at the Earth from space -

http://geophysics.ou.edu/solid_earth...from_space.jpg

The axial orientation is constant but as the Earth travels in its orbit
around the Sun,the orbital orientation (assigned by the terminator)
changes longitudinally as well as latitudinaly .We hardly notice it
from one day to the next because of the way axial rotation passes
through that changing feature but it is there nad generates global
climate norms and hemispherical weather pattern (seasons).


Lots and lots of productive avenues to be explored by looking at things
this way,of course you can always remain with your variable tilting
Earth to the Sun/orbital plane -

http://www.scienceu.com/observatory/...s/earthyrb.gif

Astronomers would not resort to the northern hemisphere tilting towards
and away from the sun and pretend that the southern hemisphere does not
share the same axis.The 21st century view for global climate norms
which can be reduced to hemispherical weather patterns for
meteorological purposes is the local change of orbital orientation
against fixed axial orientation.

Important material ,too important to play around with .Here are the
temperature signatures of the change in orbital orientation which
assist in the transitionto a more productive astronomical mechanism
based on change in orbital orientation -

http://www.climateprediction.net/ima...ges/annual.gif

In short - KEEP THINGS LOCAL

  #8  
Old May 24th 06, 09:53 PM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

lal_truckee wrote:
Sun, Moon, and stars wobble. Lots of ancient constructions are built to
mark the extremes of the wobble.


Or at least imaginative archaeologists seem to think so. Whenever I've
seen the actual evidence in these cases it always reminds me a bit of
the "evidence" for the pyramids on mars... There is so much room for
over interpretation that my bad science alarm bells go off wildly.

One thing I know for certain: if you go looking hard enough for anything
you are going to find it. And just because you find "it" everywhere you
look, provided you look really hard, doesn't mean it's real. Yet that's
just the sort of "science" applied in these circumstances.

What I'm saying is that without objective evidence most of these claims
are less than compelling. They are little more the speculation. Yet
they are often cited as fact.

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply take out your eye
  #10  
Old May 25th 06, 12:38 AM posted to sci.astro.amateur
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Default question about inclination of earth's axis.

On Wed, 24 May 2006 20:39:54 +0300, "Ioannis"
wrote:

In other words, let me rephrase the question. Suppose earth's inclination
with respect to the sun was always constant, so that, say, the northern
hemisphere always has summer and the southern always winter. Except for
travelling to the opposite hemispehere, how can we deduce that the axis is
inclined?


If that were true the apparent position of the Earth's pole in the sky
would circle around once a year.

 




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