11.7 Cosmological Simulations by Eugene Butikov

Because of their operating system independence we have sofar only used Java simulations or given links to them.

Eugen Butikov (University of Petersburg), created a large number of simulations for cosmological and other physical problems based on Windows and Visual Basic. Their design is so convincing, that we want to add it to our overview, although they will only be accessible to users, that work with Windows. Because of the numerous possibilities we will facilitate the access for the user via a short description.

Fig.11.15 shows the start page of the program Planets and Satellites, whose content far exceeds what the title promises. Thus, in addition to elementary problems (Kepler laws). it also treats many-body problems with their non-linear and complicated orbits, for example the passage of two stars with planets under planet robbery. The graphical presentations are didactically very versatile. They show for example the time development from the perspective of the start, of the planet or the center of mass of the system (menu View) at the same time, yielding sometimes surprising orbits. The individual simulations (Menu examples) allow for many adjustments of all important parameters, such that the user can experiment freely.

The three parts of the package contain:

Getting Started: Extensive hints for orientation, glossary of technical terms. links to especially appealing examples from the multitude of simulations.

Tutorial: Glossary, short overview of the course text, an extensive course text (accessible via the Menu Help topics/Content) and a linked table of contents, that leads directly to the individual simulations; didactic questions, help for handling the simulation.


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Figure 11.15: Opening window of the Butikov simulations.

Simulations: Access to the individual simulations, structured in seven classes, as shown in Fig.11.16.


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Figure 11.16: A selection window for characteristic groups of Butikov simulations. After choosing the group on the left hand side a typical picture with description appears on the right.

Fig.11.17 (a screen-shot from Tutorial) shows the structure of the total program.


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Figure 11.17: Topics of individual simulations in the Butikov program and their description

Butikov

The link on the margin Butikov I provides access to the homepage of Eugene Butikov, from where you can sees the programs he has published. There you will also find Java applets for many physics problems. The link PAS leads to the homepage of Physics Academics Software(PAS), where the simulations were originally published. PAS

With the permission of the author Eugene Butikov and the PAS editor Jon Risley our collection contains the cosmological simulation program. You may call it with the interactive figure 11.18.

It shows as an example a system of two stars of unequal mass with a common planet, whose orbits moves from the one to the other start. This is displayed as seen from the coordinate system of the more massive star. The calculation of the orbit around the smaller star in yellow starts on top; the colour changes to green when the planet moves into a orbit around the inner main star. Later the planet again moves to the secondary star (blue part) of the orbit.


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Figure 11.18: Orbit of a planet in a double star system, seen in the coordinate system of the star with double the mass (red in the center). The lighter star travels around it on a circular orbit. The planet, that is very light in comparison to both stars, starts its yellow orbit on top around the blue star. This orbit is perturbed by the red central star and then moves over to a green orbit around it. After a few turns the perturbation by the blue star is sufficient to temporarily bind it to the central star again (blue orbit).

end of chapter 11