On Feb 22, 5:07 am, moro...@world.std.spaamtrap.com (Michael Moroney) wrote: > oriel36 <kelleher.ger...@gmail.com> writes: > >They understood over 2000 years ago that they couldn't use a system of > >continuous 365 days to keep the flooding of the Nile fixed to the > >seasonal points but they were observant enough to realize that the > >star Sirius returns to the same spot in the sky if they added an extra > >day after every 4 years.The reductions to 365 1/4 days to 1 year is > >merely extraneous to their observations - > > That should be your clue right there. Why does Sirius rise at different > times according to the time of the year, while the Sun rises at the same > time (or would if not for seasonal effects from the Earth's tilt) ? Why > does Sirius rise nearly 4 minutes earlier every day, day after day?
You are talking stellar circumpolar motion whereas the ancient astronomical authorities recognized that Sirius disappears for 70 days each year so it doesn't 'rise' day after day after day as opposed to the stellar circumpolar stars of Ursa Major which are constantly in view.The seasonal return of Sirius to the same observed point coincided with the flooding of the Nile but obviously the ancient authorities realized that were they to base their year on a continuous stream of 365 days,the flooding event would drift away from the annual cycle so adding the extra day every 4th year kept the proportion of days balanced to the annual cycles or in dynamical terms,1461 rotations corresponds to 4 orbital circuits to the nearest rotation.
It's > because that relative to Sirius, the earth rotates once every 23 hours, 56 > minutes and 4 seconds. If you were able to see every Sirius-rise, and > counted them over a period of a year, you'd count 366 1/4 Sirius-rises > over a period of a year.
Sirius disappears behind the glare of the Sun as the Earth moves along it orbital circumference so you can't fully count the number of times it appears however any of the stars of Ursa Major do return to the same spot 365 times in a non leap year and 366 times in a leap year making 1461 times for 4 years or 4 orbital circuits of the Earth.It means that the discrete value of 23 hours 56 minutes 04 seconds is based on the average 24 hour day within the 365/366 day format.
(you can't of course see every Sirius-rise, > since half the year it happens during daylight). If you count Sirius-rises > from one Feb 29 to the next Feb 29 4 years later, you'd see that there > were 1465 Sirius-rises during that time, even though there were only 1461 > sunrises.
The stars of Ursa major are within the same arena so you can see the problem as they cross a meridian 365 times in non leap years an an extra time on Feb 29th so you would have no reason to believe Sirius is any different.It is just a way to format the parent observation that Sirius rises one day earlier after every 4th year which allows humans to format the calendar system we have today and the 365 1/4 rotations per circuit is an artifact of reworking the main observation of 1461 rotations/days in 4 orbital circuits/years into a convenient format.It just happens that daily and orbital motions are separate so that he 1461 rotations equate to 1461 days.
Relative to the sun, the earth rotates 1461 in four years while > relative to a star near the ecliptic it rotates 1465 times. Of course the > latter is unimportant to everyone except astronomers, so to everyone else, > 1461 is the magic number.
I see you pulled the your post from the thread and it is probably unfair that I answer it on that account and I apologize,it is just that your post does bring up the issue of how many times a star returns to your meridian over 4 years/4orbital circuits,in this case 365 times in 3 years and 366 for 1 year making 1461 times in total.Using this information is another matter as the 'proof' for rotation Flamsteed supplied is not proof at all.
The issue is not whether one person condescends to another or dictates matter but adjusting the picture we are provided to move things into a functioning system.If offered a fresh start without having to resort to hero worship of guys in the late 17th century who stuck too closely to the clockwork solar system of Ra/Dec then that is a good thing,at least you are aware that the original observations are based on the seasonal return of a particular star as opposed to Flamsteed jumping the tracks with the same star Sirius by putting it in stellar circumpolar motion.I can't see why anyone would have an objection to the original reference system where days and years eventually took on a dynamical equivalent of rotations and orbital circuits -
"..on account of the precession of the rising of the Divine Sothis (Sirius) by one day in the course of 4 years... it shall be, that the year of 360 days and the 5 days added to their end, so one day as feast of Benevolent Gods [the pharaoh and family] be from this day after every 4 years added to the 5 epagomenae before the New Year, whereby all men shall learn, that what was a little defective in the order as regards the seasons and the year, as also the opinions which are contained in the rules of the learned on the heavenly orbits, are now corrected and improved .." Canopus Decree
No offence but I recognize the picture and the component parts as a work of genius irrespective of planetary dynamics which can be grafted in later.Again,sorry for replying even though you pulled the post.