Principle of the Lat/Long system
 

Gerald, it's all amazing isn't it?

Principle of the Lat/Long system
 

On Mon, 5 Jan 2015 07:48:20 -0800 (PST), Tim
wrote:

Gerald, it's all amazing isn't it?

===

It certainly is. Two years ago we visited the Mayan pyramids in
Chichén Itzá, Mexico. It turns out that the ancient Mayans were also
keen observers of celestial phenomena and had an onsite observatory
dedicated to those observations. They were aware of planetary
motions and relative orbits around the sun, including the fact that
Mars and Mercury were farther from the sun than Earth, and that Venus
and Mercury were closer. They also had a very accurate calendar
which took leap years into account. All of that was more than a
thousand years ago.

Principle of the Lat/Long system
 

Speaking of pyramids its my understanding the the 4 corners were at a true north south east and west ane with recent technology it's been proven that they were off byaybe a degree or so.

Principle of the Lat/Long system
 

Gerald Kelleher wrote:
On Monday, January 5, 2015 6:09:51 AM UTC-8, Tim wrote:
This is great reading especially for the technically challenged like me.
With my style of lake boating its more like " hey, let's go that away!"

Keep it coming though. This is all good to know...

Although the Egyptians knew nothing of daily rotation and the orbital
motion of the Earth around the Sun, they realized that they could not
base their year on a constant stream of 365 days. The flooding of Nile on
which their culture depended coincided closely with the annual appearance
of Sirius one morning hence their awareness of the brightest star in the
celestial arena for practical reasons and the fact that it skips an
appearance by one day after 4 years. In dynamical terms, the additional
24 hours represents the orbital distance the Earth needs to travel to
bring Sirius back into view or what now has become the February 29th
rotation. We omit 6 hours of orbital motion each non leap year as we
gauge our day solely by daily rotation and this accumulates to roughly 24
hours of missing orbital distance at the end of 4 orbital circuits and 4 years.

It isn't really possible to continue with the narrative without an
explanation which contains the leap day rotation and what it represents
in dynamical terms. Perhaps another could explain it better and I have no
objections to this however the facts will remain roughly the same.

The maritime tradition, much like astronomy, is among the most noble and
ancient human endeavors in terms of sophistication so that people
generally don't think of their ancestors in terms of primitive but rather
look for the roots of contemporary traditions in older methods and
insights. The rules governing navigation from boats to aircraft are one
thing but the timekeeping systems on which navigation is based in
something else and this requires some knowledge of the Earth's daily and orbital cycles.

The Egyptians may have known of the rotation and even of the orbit. Forget
which Egyptians calculated the diameter of the earth. They were only off
by about 225 miles, using sticks and shadows at a certain time. Way before
Europe and Rome admitted the earth was not flat.

Principle of the Lat/Long system
 

Tim wrote:
Speaking of pyramids its my understanding the the 4 corners were at a
true north south east and west ane with recent technology it's been
proven that they were off byaybe a degree or so.

You would expect true north and not magnetic north. Do not know if they
had magnetic compass. And they may have been very close as probably set
via star sightings and there has been some movement in a thousand years.

Principle of the Lat/Long system
 

In article 1917021474442175479.361632bmckeenospam-
, says...


The Egyptians may have known of the rotation and even of the orbit. Forget
which Egyptians calculated the diameter of the earth. They were only off
by about 225 miles, using sticks and shadows at a certain time. Way before
Europe and Rome admitted the earth was not flat.

It was Eratosthenes, a Greek. But he did hang out in Alexandria.

Principle of the Lat/Long system
 

Boating All Out wrote:
In article 1917021474442175479.361632bmckeenospam-
, says...


The Egyptians may have known of the rotation and even of the orbit. Forget
which Egyptians calculated the diameter of the earth. They were only off
by about 225 miles, using sticks and shadows at a certain time. Way before
Europe and Rome admitted the earth was not flat.

It was Eratosthenes, a Greek. But he did hang out in Alexandria.

Thanks. Been a long time since university.

Principle of the Lat/Long system
 

On Monday, January 5, 2015 7:48:22 AM UTC-8, Tim wrote:
Gerald, it's all amazing isn't it?

http://www.gautschy.ch/~rita/archast...liacsirius.JPG

To recap, when the Egyptians saw Sirius appear one morning after an absence behind the glare of the Sun for a few months they knew it would appear again 365 days later, yet again after another 365 days and then again on the third cycle of 365 days but on the fourth 365 day cycle Sirius was nowhere to be seen. It would appear the next day hence the extra rotation that we know as February 29th.

Each non leap year the Earth falls behind in position by 6 hours of orbital motion which accumulates to 12 hours after the second 365 day day cycle,18 hours after the third cycle and a full 24 hours on February 28th of a leap year. The extra rotation corresponds to 24 hours of orbital distance the Earth travels so that it completes 4 full orbital circuits using 1461 rotations as a gauge. This in turn reduces to 3651/4 rotations per circuit.

The next step is a fairly intricate one as the 24 hour day makes an appearance within this framework of 365/366 days.

Principle of the Lat/Long system
 

On Mon, 5 Jan 2015 07:48:20 -0800 (PST), Tim
wrote:

Gerald, it's all amazing isn't it?

And also amazing is that, according to some, it's all a random
occurrence from a big explosion.

Wow.

Principle of the Lat/Long system
 

On Monday, January 5, 2015 6:10:43 PM UTC-8, John H. wrote:
On Mon, 5 Jan 2015 07:48:20 -0800 (PST), Tim
wrote:

Gerald, it's all amazing isn't it?

And also amazing is that, according to some, it's all a random
occurrence from a big explosion.

Wow.

The words 'average' and 'constant' come into play at this juncture for the 'average' 24 hour day substitutes for 'constant' rotation at 15 degrees per hour or once in 24 hours. For instance, the average flow of a liquid through a pipe is the same thing as the constant flow of liquid through the same pipe however the timekeeping system uses 'average' as a starting point.

When accurate clocks started to emerge in the 17th century it was already known that with each sweep of the Sun across the observer's meridian, the total length of the day regardless of hemispheres varies from noon to noon. As each day corresponds to another rotation, a certain value was attached to each day to equalize it to a 24 hour average -

"Draw a Meridian line upon a floor and then hang two plummets, each by a small thread or wire, directly over the said Meridian, at the distance of some 2 feet or more one from the other, as the smallness of the thread will admit. When the middle of the Sun (the Eye being placed so, as to bring both the threads into one line) appears to be in the same line exactly you are then immediately to set the Watch, not precisely to the hour of 12 but by so much less, as is the Equation of the day by the Table." Huygens

http://adcs.home.xs4all.nl/Huygens/06/kort-E.html

So what readers have is one 24 hour day following the next 24 hour day, Monday turning into Tuesday,Tuesday into Wednesday and so on with the fact that each day corresponds to one rotation. The average 24 hour day then substitutes for the notion that the Earth's rotation is constant at a rate of 1 Degree per 4 minutes, 15 Degrees per hour and a rotation of the planet's 24901 circumference in 24 hours including the February 29th rotation.