earth's tilt

When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

--
Rich

RichD wrote:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?


I guess the answer depends on who you ask.

http://search.yahoo.com/search;_ylt=...8&fr=yfp-t-701


Just like Galileo is often credited for claiming the earth went around the
sun.
His research was based on Copernicus's work, and who knows where Copernicus
got the idea.

RichD:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

Bast:
I guess the answer depends on who you ask.

Indeed, it does. My dad was first a ship's navigator and then a pilot
in his young years. It was he who first told me about the stars. I
remember him asking me when I was not very far along in elementary
school "Have they taught you yet that Columbus proved that the Earth is
round?" "No? Well, they will. Don't make a fuss over it, but they're
wrong. Eratosthenes, who lived hundreds of years B.C., knew the Earth
was round and he even made an accurate measurement of its
circumference. So educated men have known for more than 2,000 years
that the Earth is round."

I didn't make a fuss over it when the time came in geography class, but
I did tell the teacher to check out Eratosthenes in the encyclopedia.
(That was a set of about 30 books printed on paper in those days.)

I don't have time to do the searching at the moment, but I have to
think that ancient natural philosophers, whether in Greece or Persia or
China or parts unknown, knew the extent of the Earth's axial tilt. Just
about anyone who gave it some thought could figure it out, even if they
believed in a geocentric Universe. Otherwise they would have to think
that the Universe wobbled as it orbited the Earth. That could be
accounted for, but there were people who were smarter than that.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

On Sep 21, 2:32*am, RichD wrote:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

--
Rich

Astronomical discoveries are individual rather than communal and the
determination you refer to was first proposed by Copernicus
himself .It might be off-topic in a forum devoted almost exclusively
to magnification in a homocentric setting but here it is anyway -

"..the equator and the earth's axis must be understood to have a
variable inclination. For if they stayed at a constant angle, and were
affected exclusively by the motion of the center, no inequality of
days and nights would be observed."Copernicus Chapter 11 De
Revolutionibus

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

The great astronomer did not have the benefit of 21st century imaging
to modify his approach which comes down to us as the 'no tilt/no
seasons' ideology when effectively he is describing equatorial
conditions as there is only residual variations in daylight/darkness
at the equatorial latitude as opposed to the North and South poles
where the variations are extreme.The greater the distance between the
rotational orientation and the ecliptic axis of any planet the more
polar the conditions or the more equatorial the climate as the
distance shrinks - this uses the Arctic/Antarctic circles as a kind of
a terrestrial boundary between equatorial and polar conditions so that
a reasonable person can see our planet has a largely equatorial
climate.

The North/South poles act like a beacon for the orbital behavior of
the Earth and while it does take a while to become comfortable with
the separate rotation to the central Sun as a component of the orbital
motion of the Earth,it does produce so many things to discuss.Rather
than the awkward 'tilt from the ecliptic', the polar coordinates turn
in a circle to the central Sun as indicative of all locations on the
planet so that axial precession has to be replaced along with the
explanation for the seasons.It is a 100% certainty that a camera
trained on the Earth from Mars will witness the Earth's polar
coordinates turn through the circle of illumination at the equinox in
such a manner -

http://upload.wikimedia.org/wikipedi...precession.svg

Not only have you your answer,you also have the necessary imaging to
demonstrate why that 500 year old explanation needs urgent
modification in an era where climate is such an issue.I could say that
the present climate scientists don't know what they are talking
about ,not for any disagreement I have with them,only that the Earth
does have a pronounced equatorial climate and it has yet to make its
way into the wider community even though it is so much common sense.





If the rotational inclination of Uranus was applied to the Earth,the
Arctic circle would extend almost to the equator as the Earth would
have an almost total polar climate whereas it has,due to its 23 1/2
degree inclination from the ecliptic axis,a largely equatorial
climate.

On 21/09/2012 02:32, RichD wrote:

When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

A reasonable list of who, what, when and where is online at:

http://articles.adsabs.harvard.edu/c...;filetype=.pdf

(I think this link should be public)

It reckons Chuo Li, China 1100BC 30

This list misses out Oenepedes, Greece 450BC 24

http://www-groups.dcs.st-and.ac.uk/~...Oenopides.html

--
Regards,
Martin Brown

"RichD" wrote in message ...
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

--
Rich


=============================================
You can do it yourself, find a large rock or boulder or standing stone
and mark the ground where the tip of the shadow falls. Do that
throughout the year and your sundial becomes an astrolabe.
http://danny.oz.au/travel/scotland/p...g-stenness.jpg
-- This message is brought to you from the keyboard of
Lord Androcles, Zeroth Earl of Medway

"Davoud" wrote in message ...
RichD:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

Bast:
I guess the answer depends on who you ask.

Indeed, it does. My dad was first a ship's navigator and then a pilot
in his young years. It was he who first told me about the stars. I
remember him asking me when I was not very far along in elementary
school "Have they taught you yet that Columbus proved that the Earth is
round?" "No? Well, they will. Don't make a fuss over it, but they're
wrong. Eratosthenes, who lived hundreds of years B.C., knew the Earth
was round and he even made an accurate measurement of its
circumference. So educated men have known for more than 2,000 years
that the Earth is round."

I didn't make a fuss over it when the time came in geography class, but
I did tell the teacher to check out Eratosthenes in the encyclopedia.
(That was a set of about 30 books printed on paper in those days.)

I don't have time to do the searching at the moment, but I have to
think that ancient natural philosophers, whether in Greece or Persia or
China or parts unknown, knew the extent of the Earth's axial tilt. Just
about anyone who gave it some thought could figure it out, even if they
believed in a geocentric Universe. Otherwise they would have to think
that the Universe wobbled as it orbited the Earth. That could be
accounted for, but there were people who were smarter than that.


-

Not only did educated men know, but they also had built a computer
to model it.
http://en.wikipedia.org/wiki/Antikythera_mechanism

Ancient Greek technology was destroyed by Roman barbarians and not
duplicated until Victorian England, long after Galileo Galilei challenged
the Roman Barbarian Church.

- This message is brought to you from the keyboard of
Lord Androcles, Zeroth Earl of Medway

On Sep 21, 8:30*am, Martin Brown
wrote:
On 21/09/2012 02:32, RichD wrote:

When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

A reasonable list of who, what, when and where is online at:

http://articles.adsabs.harvard.edu/c..._query?1979A%2...


Regards,
Martin Brown

Years ago you could get away with that stuff but not in front of a
genuine astronomer.

In antiquity they used a shadow at the Solstice to determine the
circumference of the Earth,something quite different than daily
orientation.so your referenced paper is not only a non starter,it has
all the usual empirical pretension and none of the substance.The same
with the Galileo affair,the technical issues as the Pope understood
them was far more involved and with greater depth than shown by any of
contemporaries and I wouldn't even entertain a discussion here among
those for whom magnification constitutes astronomy and a few
mathematicians pretending to know something.

For a more comprehensive and accurate,do you hear this Brown, an
accurate use of a shadow at the solstice,there are only a very few
accurate perspectives and Stecchini,apart from his few quirks,happens
to be one of them -

"Eratosthenes was not the first to measure the circumference of the
Earth, but the first to argue, contrary to the opinion of Aristotle,
that the calculations about the circumference of the Earth could be
accepted as proven in terms of the new scientific style.

A series of ancient authors credits Eratosthenes as having introduced
the calculation of the degree as equal to 700 stadia, but there is not
a single writer who indicates that he based himself on an empirical
survey of the ground. Contemporary scholars exalt Eratosthenes as a
great scientist and as a pioneer in mathematical geography, but none
of the ancient writers who were acquainted with his works indicate
this. If Eratosthenes had been such an innovator, Ptolemy who
discusses at length the problem of the dimensions of the Earth in the
Prolegomena to his Geography would have said at least some words to
this effect. Theon of Smyrna and Proklos, who lived in Alexandria do
not make any reference to the alleged discovery of Eratosthenes in
their extensive commentaries on ancient mathematical science. Strabo,
who had before his eyes the writings of Eratosthenes and discusses
them at length, does not ascribe to Eratosthenes any specific
achievement in the field of empirical geodesy or of theoretical
geography. Strabo mentions repeatedly the figure of 700 stadia to the
degree, but justifies it only in these words: “We suppose as
Hipparchos, that the size of the Earth is 252,000 stadia, a figure
given also by Eratosthenes.” He would not have spoken in these terms
if Eratosthenes had provided a complete mathematical demonstration."

http://www.metrum.org/measures/measurements.htm

The next time you post some reference that you pull out of thin air,be
sure to know what you are talking about first both historically and
technicallyy.

On 21 Sep, 03:47, "Bast" wrote:
RichD wrote:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

I guess the answer depends on who you ask.

http://search.yahoo.com/search;_ylt=...Ed5ebvZx4?p=Wh...

Just like Galileo is often credited for claiming the earth went around the
sun.
His research was based on Copernicus's work, and who knows where Copernicus
got the idea.

He used data collected by Tycho Brahe

JT wrote:
On 21 Sep, 03:47, "Bast" wrote:
RichD wrote:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

I guess the answer depends on who you ask.

http://search.yahoo.com/search;_ylt=...Ed5ebvZx4?p=Wh...

Just like Galileo is often credited for claiming the earth went around
the sun.
His research was based on Copernicus's work, and who knows where
Copernicus got the idea.

He used data collected by Tycho Brahe



That would be a neat trick considering, I believe, Tycho Brache was born
after Copernicus died.