Computational Physics Lab Course

Winter Semester 2026/27

Project 1: The Classical N-Body Problem, Numerical Solution of Systems of Ordinary Differential Equations with Initial Values.

Dates: 12 Oct and Thu, 22 Oct


Lab Instructions

• Lab Instructions.

Required Input Files Sample input data for systems with 2, 3, as well as 100 and 1000 particles. The first line of each file contains the quantities
N : number of particles
t_max : maximum integration time
eta : time-step parameter


The following 3N lines contain the masses, positions, and velocities of the particles, the latter each in 3D (3 columns).

• in2.
• pla3.
• pl.100.
• pl.1k.

As an alternative to the format described above, the same particle data can be found line-by-line in the following files in the line format x y z vx vy vz m, i.e. one line per particle containing position, velocity, and mass.

• 2body.
• 3body.
• 100body.
• 1kbody.

For comparison, this directory contains the output files for the integration of an orbit with final time 2π. The naming convention is: "input_file"."integrator"."step_size".

Useful Links for Programming with Python and C, and Plotting Tools

• Python Beginner's Guide.
• matplotlib, plotting with Python.
• gnuplot, free interactive plotting tool.
• C Programming, free C book in German.
• C Tutorial, free C tutorial in English.

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