Elliptical Orbit

I'm trying to animate an elliptical orbit for a presentation.
It's not as easy as I thought...
If I'm right elliptical anc circular orbits obey to the same
exact formula, only the initial conditions change (initial
velocity). Can someone help me out on this one, or maybe
indicate another group where I can find that kind of info?
Thanks in advance

"Starman" wrote in message
oups.com...
I'm trying to animate an elliptical orbit for a presentation.
It's not as easy as I thought...
If I'm right elliptical anc circular orbits obey to the same
exact formula, only the initial conditions change (initial
velocity). Can someone help me out on this one, or maybe
indicate another group where I can find that kind of info?
Thanks in advance

They obey the same laws of motion, which can be expressed
as a second order differential equation, or for solving
numerically, as a pair of first order differential equations.

You don't say *how* you want to animate it, or what tools
you have at hand. Do you really want to integrate the
equations of motion (simulation) or do you just want a
plausible display (animation)?

Anyways, if you do a search on "Verlet algorithm" or
Runge Kutta, you'll start turning up related hits. Here's
a couple to get you pointed in the right direction:

http://burtleburtle.net/bob/physics/solar.html

http://sip.clarku.edu/3e/chap5.pdf

"Starman" wrote in message
oups.com...
I'm trying to animate an elliptical orbit for a presentation.
It's not as easy as I thought...
If I'm right elliptical anc circular orbits obey to the same
exact formula, only the initial conditions change (initial
velocity). Can someone help me out on this one, or maybe
indicate another group where I can find that kind of info?
Thanks in advance


Are these any use?
animated demo as a gif
http://home.cvc.org/science/kepler.htm

java applet (may be hard to include in a presentation)
http://www.sunsite.ubc.ca/LivingMath...er/kepler.html


I'm sure others exist

"Starman" wrote in news:1105622149.721787.313170
@c13g2000cwb.googlegroups.com:

I'm trying to animate an elliptical orbit for a presentation.
It's not as easy as I thought...
If I'm right elliptical anc circular orbits obey to the same
exact formula, only the initial conditions change (initial
velocity). Can someone help me out on this one, or maybe
indicate another group where I can find that kind of info?
Thanks in advance


Willman-Bell sells a floppy disk of Basic codes that go with JMA Danby's
state of the art book, "Celestial Mechanics." The book is $30, and the
disk is $15, which are excellent prices, considering the usual prices of
good textbooks.