# How to add eccentricity to Kepler's Laws in cartesian

Hi,

I'm currently making a three-body simulator and I'm trying to add the eccentricity to Kepler's Law to turn the circular orbits to more of a elliptical orbit? I'm using Newton's Law of Gravitational to plot the new positions. How would I add in the eccentricity to this equation?

I'm currently coding it in Fortran95

mfb
Mentor
Kepler's laws do not apply to problems with more than two bodies. They can be some reasonable approximation in some cases but in general they do not work.
I'm using Newton's Law of Gravitational to plot the new positions.
Newton's laws do not have any notion of eccentricity, so where is the problem?
I'm currently coding it in Fortran95
Do you have to use Fortran? If not, try to avoid it.

AlphaBetaGamma96
Do you have to use Fortran? If not, try to avoid it.[/QUOTE]

Thanks for the reply! I'm currently doing a Computational Project at the moment for my degree. We are allowed to use any computational language, but I've only been taught in Fortran95. I'm considering learning another language at some point down the line, any recommendations? I'm trying to live plot the results so it can be seen as more of an animation.

The program writes out the points to a .dat file, could I then call this file to say a program in Python or Java and then live plot it?

(Sorry for kinda sidetracking from the initially stated question)

Thank you for your time! :D

mfb
Mentor
I'm considering learning another language at some point down the line, any recommendations?
Python is nice, Java is interesting, C++ has some advantages as well.
Fortran is just messy.
The program writes out the points to a .dat file, could I then call this file to say a program in Python or Java and then live plot it?
There should be libraries or even whole programs to do that.