Astronomical Simulation

Version 1.3.0+20220406 (Version Release Notes)

Astronomical Simulation is an open source n-body gravitational simulation.

A random collection of simulated asteroids interact with each other via mutual gravitational interaction in a 2-dimensional space.

When two or more asteroids come into contact with each other, rather than rebound off each other they instead coalesce into a single larger asteroid.

Such a combined asteroid has the combined mass and momentum of the colliding asteroids that make it up.

Depending on the random distribution of the initial set of asteroids the simulation may evolve into a primitive solar system with smaller asteroids orbiting larger ones.

Alternately some or most of the asteroids may be ejected via a gravitational whip beyond the visible limits of the simulation space.

About the Software

The software is a self-contained executable program, written in Free Pascal, that runs on Microsoft Windows or Ubuntu Linux (and presumably other Linux distributions). (No separate run-time environment is required to run the program.) The Lazarus Integrated Development Environment was used to develop the program. (Both Free Pascal and the Lazarus IDE are free open-source software products.)

Downloading and Running the Program

Microsoft Windows

You can run the Astronomical Simulation program on Microsoft Windows as follows:

Download the AstroSim.exe binary executable file from the bin sub-folder from this GitHub.com page.
To uninstall the program, simply delete the AstroSim.exe file.

Ubuntu Linux

You can run the Astronomical Simulation program on Ubuntu Linux (and presumably other Linux distributions) as follows:

Download the AstroSim binary executable file (with no file extension) from the bin sub-folder from this GitHub.com page.
Ensure the AstroSim file has the executable permission. From a Files window, right-click the file, select Properties, and use the Permissions tab to enable the Execute permission. To do this in a Terminal window, use the following command:

chmod +x AstroSim
To uninstall the program, simply delete the AstroSim binary executable file.

Running the Program

Double-click the downloaded copy of AstroSim.exe (on Windows) or AstroSim (on Linux) to start the simulation.

When the program starts it displays the Astronomical Simulation Main Form.

Here is an image of the Main Form paused during a running simulation.

The Main Form contains these elements:

The Randomize button generates a random distribution of stationary asteroids, each with a standard diameter of 2 pixels and a standard mass of 4.
The Start button is activated once the Randomize button has been clicked. Clicking the Start button starts the simulation.
The Pause button is activated when the simulation is running and temporarily stops the simulation. The Randomize button becomes active to allow initiation of a new random distribution of asteroids. Clicking the Start button resumes the simulation.
The Step button advances the simulation for a single time step. It is active when the simulation is paused, or has not yet been started.
The # Asteroids spin-edit control determines the number of asteroids generated by the Randomize button. Use the up/down arrows on the control to set the desired number. Alternately, directly enter the desired number into the control.
Displayed next to the # Asteroids control is the current number of asteroids. As asteroids collide and coalesce together this value is reduced. If this value decreases to 1 the simulation stops.
The majority of the Main Form contains the graphic display area for the simulation space. Asteroids appear white on a black background.

Resizing the Main Form

The initial size of the Main Form is designed to fit within an 800 by 600 monitor window.

To enlarge the form, drag its boundary or simply click the maximize icon (small square in the upper right of the title bar).

Then click the Randomize button to enlarge the graphic simulation area to match the enlarged form.

Re-centering the Visible Area of the Simulation Space

Click on any point within the simulation area to cause the visible window into the simulation space to be centered on that point.

Adding a New Asteroid to the Simulation Space

Right-click with the mouse to add a new Asteroid.

Use several successive right-clicks to add multiple nearby Asteroids that can coalesce into a single Asteroid with larger mass.

Zooming the Visible Area Out and In

Zoom out the view of the simulation space by pulling the mouse wheel toward you.

Zoom back in by pushing the mouse wheel away from you.

Simulation Notes

Initial experimentation with the AstroSim program seems to indicate that smaller numbers of asteroids produced more interesting results than larger numbers.

The maximum number of asteroids currently allowed is 10,000.

If a given asteroid count produces an uninteresting simulation, simply Pause the simulation, click Randomize to generate a new set of asteroids, and click Start to start another simulation.

Source code compilation notes

Download the Lazarus IDE, including Free Pascal, from here:

https://www.lazarus-ide.org/index.php?page=downloads

After installing the Lazarus IDE, clone this GitHub repository to your local disk. Then double-click on the src\SyncDirPas.lpr project file to open it in Lazarus.

Note: Using the debugger in the Lazarus IDE on Windows 10 might require the following configuration adjustment:

Lazarus - Windows - Debugger crashing on OpenDialog

When Lazarus includes debugging information the executable file is relatively large. When ready to create a release executable, the file size can be significantly reduced by selecting the menu item Project | Project Options ... and navigating to the Compile Options | Debugging tab in the resulting dialog window. Clear the check-mark from the Generate info for the debugger option and then click the OK button. Then rebuild the executable using the Run | Build menu item (or using the shortcut key-stroke Shift-F9).

Release Notes

Version 1.3.0

Right-click adds a new asteroid to the simulation space.

Version 1.2.3

Update current Asteroid count when using the Step button.

Version 1.2.2

Show the Product Version on the main form title bar.

Version 1.2.1

Compiled on Ubuntu Linux version 20.04.4 LTS and included resulting AstroSim executable file in the bin sub-folder.

Version 1.2.0

Added ability to zoom the simulation view space out and in via the mouse wheel.

Version 1.1.0

Added the ability to re-center the simulation space by clicking on a point to become the new center of the visible display area.

Version 1.0.0

This is the initial version of the software.

License

rrutt/AstroSim

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