earth's tilt

On Fri, 21 Sep 2012 08:01:30 -0400, "Bast"
wrote:



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.

haha,
he meant Kepler, because he was the one who used Tyho Brahe's data.

w.

On 21 Sep, 14:15, Helmut Wabnig [email protected] --- -.dotat wrote:
On Fri, 21 Sep 2012 08:01:30 -0400, "Bast"
wrote:











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.

haha,
he meant Kepler, because he was the one who used Tyho Brahe's data.

w.

Sorry my mistake

On Sep 21, 5:36*am, oriel36 wrote:
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.

Best to keep in mind the moon keeps the tilt from wobbling. This was
needed to the development of life. TeBet

JT wrote:
On 21 Sep, 14:15, Helmut Wabnig [email protected] --- -.dotat wrote:
On Fri, 21 Sep 2012 08:01:30 -0400, "Bast"
wrote:











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.

haha,
he meant Kepler, because he was the one who used Tyho Brahe's data.

w.

Sorry my mistake



Not a biggie, just proves my point that something like that could have been
"discovered" by countless people, but like naming asteroids/comets
etc.,....it's only the first person acknowledged in writing, who gets the
credit in the history books.

On 9/20/12 8:32 PM, RichD wrote:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

--
Rich



Eratosthenes of Cyrene first to calculate the tilt of the Earth's
axis with respect to the ecliptic, and with remarkable accuracy.
Ref: http://en.wikipedia.org/wiki/Eratosthenes

BTW, I very much enjoy Davoud's posting about his dad and Eratosthenes!

On 21 Sep., 18:23, Sam Wormley wrote:

BTW, I very much enjoy Davoud's posting about his dad and Eratosthenes!

"My father knew Eratosthenes." has much more of a ring to it than the
more familiar "My father knew Lloyd George." :-)

Anyone in a mediaeval prison must have know about the Earth's tilt
from the patch of sunlight shining through the tiny window. As would
(slow) well diggers. Assuming a clear, southerly aspect in both cases
for the sake of marauding pedants.

Encyclopaedias were the stuff of my own childhood. Now one cannot even
be bothered to search online when one can simply ask on a forum.
Thereby receiving such conflicting information that one might be
forgiven for questioning the validity of anything one might ever read
online. I blame fake, psychoactive, Chinese, prescription drugs for
many of today's problems.

US expatriate "Chris.B" wrote:


Sam Wormley wrote:
Eratosthenes of Cyrene first to calculate the tilt of the Earth's
axis with respect to the ecliptic, and with remarkable accuracy.
Ref: http://en.wikipedia.org/wiki/Eratosthenes

"Chris.B" wrote:
Anyone in a mediaeval prison must have know about the
Earth's tilt from the patch of sunlight shining through the
tiny window. As would (slow) well diggers. Assuming a
clear, southerly aspect in both cases for the sake of
marauding pedants.

Encyclopaedias were the stuff of my own childhood.
Now one cannot even be bothered to search online when
one can simply ask on a forum. Thereby receiving such
conflicting information that one might be forgiven for
questioning the validity of anything one might ever read
online. [2]

I blame fake, psychoactive, Chinese, prescription drugs
for many of today's problems. [1]

hanson wrote:
To [1]:
Chrissy, old pal, listen: Stop taking them!... and
________ Stay away from the 3P's __________
.... the Physician, the Pharmacist and the Police.

All three P mean well for the greater good & they
have a license to kill to do so. Unfortunately they
never even consider you to be good... ... by the
simple fact that they see you only when you
do/are/or feel no good...

To [2]:
That is so very true and it's heralding in a new
age of international peasant/mass/mob rule.
Posting and blogging is used by billions who
express their opinions, be they on stuff or sober.

The volume/loudness from the legions of these
folks drowns & overwhelms the establishment's
or the elite's interests & goals, be that legit or not.

OTOH, the sharpies have discovered a new tool
with this new "social networking" to rile up folks
and instigate events that fit their own agendas.

What we see is globalization on a much vaster
and broader scale and in very different shades
then was originally intended and envisioned...

But "what goes up must come down"... right?
If so, then when, why & how will that occur?

On Sep 21, 5:23*pm, Sam Wormley wrote:
On 9/20/12 8:32 PM, RichD wrote:

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

--
Rich

Eratosthenes of Cyrene first to calculate the tilt of the Earth's
axis with respect to the ecliptic, and with remarkable accuracy.
Ref:http://en.wikipedia.org/wiki/Eratosthenes


How sweet !,empiricists tend to manufacture history on an industrial
scale and what you and the rest are trying to discuss is rotational
orientation which does not change in terms of axial precession and to
the orbital points of solstices and equinoxes.The ancients in remote
antiquity,and I mean over 5000 years ago would have seen the
circumpolar stars still turn around Polaris as we see the same thing
today and that time scale is 20% into the great orbital cycle of the
precession of the equinoxes and not an axial trait as previously
believed.

http://www.youtube.com/watch?v=XTTDWhky9HY

It doesn't occur to readers here that anyone can show up at the
neolithic monuments on the solstice or equinox and still enjoy the
same spectacle as 5000 years ago hence the observed precession cannot
be an axial trait and besides,contemporary imaging shows unequivocally
that the polar coordinates precess through 360 degrees to the central
Sun as a component of its orbital motion.

http://www.youtube.com/watch?v=AXPSFNZ9Q7E

About 2 minutes into that video you will see the planet turn to the
central Sun just as the Earth's polar coordinates act like a beacon
for the Earth's orbital behavior,a curious individual needs only a
brief analogy to extract the proper conclusion that axial precession
is unhelpful as the motion of the polar coordinates in a cycle/circle
occurs each orbital circuit.

I have never encountered a contemporary who could express the
dimensions of the Earth in tandem with rotation in that 15 degrees of
geographical separation corresponds to both 1037.5 miles at the
equator and also 1 hour time difference so that it should be the
easiest thing in the world to express that the equatorial Earth turns
1037.5 miles per hour and its 360 degree circumference in 24 hours.You
cannot imagine how bad you and your empirical colleagues look as you
insist that the Earth doesn't turn at a rate of 15 degrees per hour so
it is not the accuracy of Eratosthenes you need to consider but the
deplorable inability to accept the facts of a round and rotating
Earth.

Does it not bother any of you that you have lost the core facts or is
it just a disorder you have ?

















BTW, I very much enjoy Davoud's posting about his dad and Eratosthenes!

On Sep 20, 9:15*pm, oriel36 wrote:
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.


Your post has made it to alt.astronomy. I have always enjoyed your
informative and thought provoking contributions.

Double-A

On 9/21/12 1:35 PM, oriel36 wrote:
On Sep 21, 5:23 pm, Sam Wormley wrote:

Eratosthenes of Cyrene first to calculate the tilt of the Earth's
axis with respect to the ecliptic, and with remarkable accuracy.
Ref:http://en.wikipedia.org/wiki/Eratosthenes


How sweet !,empiricists tend to manufacture history on an industrial
scale and what you and the rest are trying to discuss is rotational
orientation which does not change in terms of axial precession and to
the orbital points of solstices and equinoxes.The ancients in remote
antiquity,and I mean over 5000 years ago would have seen the
circumpolar stars still turn around Polaris as we see the same thing
today and that time scale is 20% into the great orbital cycle of the
precession of the equinoxes and not an axial trait as previously
believed.


Adapted from Carl Sagan's COSMOS book as part of a presentation
I gave more than a year ago:

__________________


There was once a time when our little planet seemed immense, when
it was the only world we could explore, its true size was first
worked out in a simple and ingenious way by a man who lived in
Egypt in the third century B.C.

In Alexandria, at that time, there lived a man named Eratosthenes.
One of his envious contemporaries called him Beta, the second
letter of the Greek alphabet, because, he said, Eratosthenes was
second best in the world in everything, but it seems clear that in
many fields Eratosthenes was Alpha: he was an astronomer,
historian, geographer, philosopher, poet, theater critic and
mathematician.

He was also the chief librarian of the great library of Alexandria
and one day while reading a papyrus book in the library he came
upon a curious account: far to the south, he read, at the frontier
outpost of Syene, something notable could be seen on the longest
day of the year. On June 21 the shadows of a temple column or a
vertical stick would grow shorter as noon approached and as the
hours crept towards midday the sun's rays would slither down the
sides of a deep well which, on other days would remain in shadow
and then precisely at noon columns would cast no shadows and the
sun would shine directly down into the water of the well. At that
moment the sun was exactly overhead.

It was an observation that someone else might easily have ignored:
sticks, shadows, reflections in wells, the position of the sun,
simple everyday matters, so what possible importance might they
be.

But Eratosthenes was a scientist, and his contemplations of these
homely matters changed the world, in a way, made the world.
Because Eratosthenes had the presence of mind to experiment to
actually ask whether back here near Alexandria a stick cast a
shadow near noon on June the twenty first, and it turns out sticks
do. An overly skeptical person might have said that the report
from Syene was an error but an absolutely straightforward
observation why would anyone lie on such a trivial matter?

Eratosthenes asked himself how it could be that at the same
moment a stick in Syene would cast no shadow and a stick in
Alexandria, eight hundred kilometers to the north, would cast a
very definite shadow.

If the shadow at Syene is of a certain length and the shadow at
Alexandria is the same length that also makes sense on a flat
Earth, but how could it be, Eratosthenes asked, that at the same
instant there was no shadow at Syene and a very substantial shadow
at Alexandria.

The only answer was that the surface of the earth is curved, not
only that, but the greater the curvature the bigger the difference
in the length of the shadows. The sun is so far away that its rays
are parallel when they reach the Earth. Sticks at different angles
to the sun's rays will cast shadows of different lengths for the
observed difference in the shadow length the distance between
Alexandria and Syene had to be about 7 degrees along the surface
of Earth, by that I mean if you would imagine these sticks
extending all the way down to the center of the Earth they would
there intersect at an angle of about 7 degrees, well seven degrees
is something like a fiftieth of the full circumference of the
Earth 360 degrees.

Eratosthenes knew the distance between Alexandria and Syene, he
knew it was eight hundred kilometers, why? because he hired a man
to pace out the entire distance so that he could perform the
calculation. I'm talking about now 800 kilometers times fifty is
forty thousand kilometers so that must be the circumference of the
Earth, that's how far it is to go once around the earth, that's
the right answer.

Eratosthenes's only tools were sticks, eyes, feet, and brains
plus a zest for experiment. With those tools he correctly deduced
the circumference of the Earth to high precision with an error of
only a few percent, that's pretty good figuring for twenty-two
hundred years ago.

__________________


USENET News is a discussion protocol, part of the internet, that
predates the World Wide Web, browsers and graphical interfaces by
at least ten years. I have been a participant in Physics and
Astronomy News groups for twenty years.

There is a fellow who lives somewhere in Scotland, named Gerald
Kelleher, who has the annoying habit of interrupting threads on
various topics of astronomy with his rants that scientists, such
as Isaac Newton, ruined observational astronomy in the 17th
century.

Eventually I engaged, Gerald, trying to understand why he rants
and what might be the basis of his misunderstanding. His trouble
is rooted in the Anglican interpretation of the rotation of the
earth. Gerald regularly expresses his utter contempt and disgust
that we professors and teachers of astronomy note that the earth
rotates once, four minutes shy of 24 hours. The effect can be
observed by anyone, that the stars rise in the east 4 minutes
earlier each night. School kids, using two sticks can sight any
prominent star in the nighttime sky two nights in a row and time
that the star lines up with the two sticks every 23h 56m and 4s.

We notice that the sun appears to travel south in the winter and
back north in the summer. From a fixed perspective one can see
that the sun rises and sets at a different place along the horizon
everyday, changing most rapidly near equinoxes and coming to what
seems like a standstill at the solstices. And yet it moves!

Science is all about observation and experiment. We enhance our
understand of nature all around us, by taking the time to observe
and think, often needing little more than sticks, eyes, feet, and
brains plus a zest for learning and understanding.