"OG" <owen@gwynnefamily.org.uk> wrote in message
news:4ra0abForqm7U1@mid.individual.net...
|
| "Sorcerer" <Headmaster@hogwarts.physics_e> wrote in message
| news:_8x3h.136769$lT5.47357@fe2.news.blueyonder.co.uk...
| >
| > "OG" <owen@gwynnefamily.org.uk> wrote in message
| > news:4r7ihoFq5i5kU1@individual.net...
| > |
| > | "Tom Linden" <tom@kednos.com> wrote in message
| > | news:op.tikg1lb1zgicya@murphus...
| > | >I was looking at some data,
| > | >
| > | > http://aa.usno.navy.mil/data/docs/EarthSeasons.html
| > | >
| > | > I could not figure out why the duration between Winter solstice
and
| > the
| > | > immediately
| > | > following perhelion jumps around. We know that the perhelion
should
| > | > advance one
| > | > day on our calendars about every 71 years. So you would think
there
| > | > should be about
| > | > a 20 minute increase from one year to the next. Anybody have an
| > | > explanation?
| > | >
| > | > Tom
| > |
| > | The most plausible explanation I've seen is that the 'smoothly
| > advancing'
| > | perihelion you expect is based on the barycentre of the Earth/Moon
| > system,
| > | but the tabulated perihelion is the actual geocentric one which
depends
| > on
| > | the lunar phase about that time.
| > |
| > | An interesting exercise to plot the earth-moon position around this
time
| > | each year.
| >
| > What does perihelion (closest approach to the sun) have
| > to do with the Earth-Moon system? Perihelion is not perigee.
| > Nor is Winter solstice connected with perihelion.
| >
| > The ONLY reason the calendar is "jumping around" is because there
| > are not exactly 365 days in a year. When you've grown up you'll
| > learn about leap years.

| > Be honest, OG, you fabricated the implausible explanation you've seen
| > all by yourself, you lying *****, and now you are trying to impress
| > "We" with your total lack of knowledge, you fuckwit.
| > If "We" knows that the "perhelion" should advance one day on "our"
| > calendars about every 71 years then "We" is another blustering bigot
| > like you.
|
| Of course, yes the simple 4 year step cycle due to leap years is obvious
| when you think about it. Simple, easily explained and wrong.
|
| Have a quick look at this and see what I mean
| http://www.gwynnefamily.org.uk/astro/Perihelion/index.htm
|
| By the way, this page dates back to early 2004.

Why not make the plot in rotations of Earth rather than time
to eliminate the inaccurate calendar?
Simple to do with a spreadsheet, but remember to use a sidereal day:
1 sidereal day = 23.9344696 hours
1 solar day = 24.0 hours.
1 year = 365.2422 SOLAR days
Calculation:
365.2422 *24.0/23.9344696 = 366.2422 rotations
per revolution.
That's one more turn.
To see why, imagine the Earth keeping one face toward the sun just
as the moon keeps one face toward the Earth. There would be zero
days per year, the sun always overhead, but the Earth would turn once.
The ellipse of the moon's orbit produces this effect:
http://antwrp.gsfc.nasa.gov/apod/ap051113.html
Notice we can see more than a hemisphere and the moon's apparent
size changes with distance. Thus we KNOW the moon's orbit is
elliptical.

| I'm still wondering why there is so much anomosity in your posts?
|
Years of dealing with arrogant idiots, I'm sorry to have to say.
You'll find me reasonable if you do not make assertions that are simply
untrue.

Ask me a question. If I don't know the answer then I'll find out,
work it out or I'll say I don't know. Not all knowledge is in yet, there
is much that is unknown to all. There is no shame in not knowing,
but there is in bluster. Science is finding out the unknown, not creating
it or misleading others.
Tom Linden's statement "We know" is false. He's blustering,
providing a misleading statement. Which hat he invented 71 years
from only he knows. The same applies to you, there was no
"plausible explanation".

Beware of anyone starting a sentence with "In fact", "Actually"
or "We know" because 9 out of 10 times what follows is their
conviction and not a fact at all.
I can say "1+1 = 3"
You'll say no, it's 2. I'd say 'Oops, sorry, my blunder. No harm
done, let's carry on."
Or I can say "We know in fact that 1+1 = 3, actually".
Who am I fooling? Only me, I'd be trying to reassure myself
and I'd be the fool. It's even worse if I argue the point.

This really happens. I've got Paul Cardinale arguing that a SPDT
(single pole, double throw) switch is a three way switch, and
he's not letting up calling me an idiot. The deeper he digs
the more dirt I'll drop on his head.

Be reasonable and I'll be reasonable. Bluster and I'll come down
on you hard. You can always ignore me, I don't mind. Quite a few
morons have me killfiled, it's no skin off my nose and their loss.
I hope that answers your question.

He has been found so repulsive all his life that he has decided in his
bitter twilight years to punish everyone with a greater abundance of
the reason for the revulsion. This is not an uncommon strategy for
the bent. Hanson also exhibits the syndrome as did Savain. Together
they comprise the real Three Stooges. As did the originals,
irritation for its own sake is all they wish to elicit.

Groups they infests would work much better if they were universally
and systematically ignored. Killfiles could then remove all traces of
the scum (leaving only the pathological scum of the scum that nymshift
to avoid killfiles.) Future killfiles will permit filtering of all
posts by an individual and all the spawn that threads off from their
vomitus but we aren't there yet.

Bob

On Mon, 06 Nov 2006 16:54:48 -0800, OG <owen@gwynnefamily.org.uk> wrote:

"Tom Linden" <tom@kednos.com> wrote in message
news:op.tilsdfgnzgicya@murphus...

On Sun, 05 Nov 2006 17:47:32 -0800, OG <owen@gwynnefamily.org.uk> wrote:

"Tom Linden" <tom@kednos.com> wrote in message
news:op.tikg1lb1zgicya@murphus...

I was looking at some data,

http://aa.usno.navy.mil/data/docs/EarthSeasons.html

I could not figure out why the duration between Winter solstice and
the
immediately
following perhelion jumps around. We know that the perhelion should
advance one
day on our calendars about every 71 years. So you would think there
should be about
a 20 minute increase from one year to the next. Anybody have an
explanation?

Tom

The most plausible explanation I've seen is that the 'smoothly
advancing'
perihelion you expect is based on the barycentre of the Earth/Moon
system,
but the tabulated perihelion is the actual geocentric one which depends
on
the lunar phase about that time.

Yes, that makes sense, but I would not expect to see such a big
variation,
as in those tables. The barycentre would be about 1/6th the distance to
the moon
or about 65K km from the centre of the earth, but during the course of
one
day the
earth has move about 2.5 M KM along the arc of its orbit, which means
that
from the
geocentric view shouldn't cause more than a ~37 minute variation. Did I
overlook
something?

Well, the main thing of course is that as the earth's orbital
eccentricity
is relatively low; I have a first order calculation that the daily
variation
in earth/sun separation is no more than about 4000 km over the 24 hours
before or after perihelion

I've seen a displacement of about 4600 km from the centre of the earth
for
the barycentre, so I suppose we can expect the actual geocentric
perihelion
to vary by up to 2 days from the smooth zig-zag due to leap years.

But I was only looking at the time between Winter soltice and succeeding
perhelion,
so I wouldn't think that leap years was relevant. I used the wrong value
of the lunar mass to estimate the barycentre, but with your more correct
value
it makes it harder to reconcile the difference.

<tadchem@comcast.net> wrote in message
news:1163192224.995180.151730@m73g2000cwd.googlegroups.com...
| http://individual.utoronto.ca/kalendis/seasons.htm
| has amost informative discussion of the lengths of the seasons and why
| they vary, including some discussion of the variability of perihelion
| passage (about 1/3of the way down the apge, under "Orbital Eccentricity
| and Variation of Season Lengths"):
|
| "The intervals between Earth's passage through perihelion vary from 363
| to 367 days, which cannot be explained by interactions with other
| planets or Sun. If one considers the passages of the Earth-Moon
| barycenter through perihelion, however, this oscillation vanishes, and
| hence its cause is Moon.

That makes sense.