Talk at the Jewish Calendar Seminar on
Wednesday, 4 Kislev (Nov. 17), 4-5 pm

Speakers: Dr. Simcha Velner, Ami Halperin, and Barak Vardi
          (Bar-Ilan University)

Title: "A Solar System Simulator" (software demonstration)

Abstract:
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Presenting a dynamic, accurate, Hebrew-language, 3D graphical
representation of the major bodies of the Solar System, supporting both
the Hebrew and Gregorian calendars, comprising:

Placement of the Sun, the nine planets and the Earth's moon is based on
astronomical algorithms, as described by Jean Meeus and based on the
VSOP87 theory.

Time calculations use the equinox of January 1st, 2000 ("Julian Day
Ephemeris") as pivot, by which both the Jewish and Gregorian dates are
calculated.

The Jewish calendar date is calculated using Gaussian conversion equations
for finding 15 Nisan (first day of Passover) of a required year and
several conversion algorithms, complying with all the rules of the Jewish
calendar.  The date is consistent with the Gregorian amendment of 1582 CE.

The simulation is highly interactive, allowing three-dimensional freedom
of movement, as well as control of time flow, both in "speed" and
"direction" of simulated time.

All parameters appear in Hebrew, including the Jewish date.

The simulation further includes a Hebrew-calendar specific approach to
viewing the lunar phases: a mode which allows the virtual viewer's gaze to
be constantly directed to the moon, so that the phases are easily
noticeable and may be compared with the corresponding date in the Hebrew
calendar.

The simulation includes additional features to deal with the tremendous
proportion differences in the Solar System.  Among these is a schematic
view of the inner and outer planets of the Solar System, in which the
planets' sizes are greatly exaggerated.  Also, a special camera "lock"
mode for each planet is provided.

The simulation is programmed in such a way that further development is
encouraged, so as to encompass additional aspects of the Solar System
(i.e., moons around other planets, a geocentric coordinate system, etc.)

In our talk we will introduce the Solar System Simulator as a deductive
and informative tool and demonstrate features and capabilities of the
program.