<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=iso-8859-1" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.23588">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT size=2 face=Arial>Sorry about the Earth/Sun error. I did all
that twenty-five years ago, and my memory is not perfect.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Yes, prior to about 1992, the event had only been
witnessed around half a dozen times. I only learned about that history
from a text of Jan Meeus, who is one of the world's foremost experts on
mathematical astronomy. When HE said that no one had ever calculated it to
predict a possible observation, I trusted him. Enough to consume six
months of mmy life in endless math. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>As to the results of my calculations, Io and Europa
were generally involved, and I was surprised at what a tiny area on Earth could
witness such events. Considering 25 years and my memory, I think that two
of the events would only have been visible from somewhere in the ocean, one in
African jungle, and one mostly in the Pacific but with a small possible area in
southern California. I had some amateur astronomer friends in southern
California at the time, and two intended to take their telescopes out but clouds
and storms discouraged them from trying.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>It does not surprise me that technollogy has
advanced where such "mutual occultations" are now probably regularly
predicted. Your point is well taken that the location of the Sun and
Jupiter's orbit are what is important, and the events can only occur twice every
twelve years, when Jupiter passes its nodes. At the time, I was focused on
the exact position of the Earth as many such events occurred during the daytime
and over our 75% oceans and such. It was frustrating to have spent months
in doing endless calculations only to discover that no one on Earth could have
witnessed them.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>My guess is that Meeus was probably involved in
enabling the calculations you refer to.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Obviously, I now have another question for
you. Has anyone actually been anywhere that they have witnessed such rare
events? In other words, has anyone photographed or videoed them.
Ditto, once predictions were made, have any of our space telescopes been turned
to Jupiter to witness them?</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I had actually only brought this up to your group
as you are pursuing "one-way measurements of the speed of light", and I had some
reservations about the precision of the ideas presented by your group. It
only occurred to me that during my suffering of all that calculation, it had
dawned on mme that we have really accurate data regarding the precise locations
and positions of the Galilean moons, and timing. Obviously, if someone
witnessed the event on Earth, we could also know that timing to microseconds or
better. And we would know the distance between that location on Earth and
each of the two moons involved to a meter or so. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Even back then, I wondered if that available math
might enable a really precise measurement of the speed of light, maybe to even
fifteen-digit precision (that would be a million times more precise than the
official speed of light, which is defined to nine-digit precision.)</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I had just remembered my thousands of sheets of
paper, and it now occurred to me that YOU guys might want to try to improve
the value of the speed of light. If you could do it, the scientific
community would applaud you.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>No, the "error" you accuse me of is actually
yours. The geometry</FONT> <FONT size=2 face=Arial>is very
strict. Like the fact that next month, much of the Earth will be able to
witness a solar eclipse, in nearly all locations, it will be partial
eclipses. Only in specific locations like near Saint Louis, MO, will it be
total, in that case for up to about two minutes.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>What you are guessingn at is that much of the Earth
would possibly witness a PARTIAL mutual eclipse regarding the Galileans.
My interest, then and now, was only for TOTAL eclipses. My calculations
also predicted one annular mutual eclipse (due to the different diameters of the
moons). </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I look forward to you informing me about the
informsation you have found.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The nodes of Jupiter enable several months of
possible mutual eclipses every six years. Nearly all of those are partial
eclipses. Only very few events could be witnessed from very limited
locations on Earth, if a total eclipses was wanted. There are also two
categories of such events. Most of them occur while the moons were passing
over the bright surface of Jupiter, where the shadows of each moon are visible
on the face of Jupiter. A mutual eclipse is hard to detect. The far
rarer events occur when the moons are NOT passing over Jupiter's face. I
think that Meeus said that the first such event ever seen was around 1880, and
the astronomer was very confused. The next was about thirty years
later. Very rare, especially when no one had ever tried to predict the
events. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Carl Johnson</FONT></DIV>
<DIV> </DIV></BODY></HTML>