
This window provides a two-dimensional simulation of the movement of a
single photon from its place of creation at the center of the Sun to the
surface, where it escapes as light or heat.  The following features are
provided to control and vary the simulation and record the results:

Menu Selections

    Parameters - Two parameters may be set by the user:

        # of Layers - The size of the simulated Sun may be adjusted by
        setting the number of layers to any value from 5 to 80.  The
        average length of time for a photon to escape is proportional to
        the square of the number of layers.

        Trails - Selecting "Yes" turns on the facility to track the
        photon by darkening the pixels it has occupied.

    Quit - Terminates the simulation and closes the window.

Control Buttons

    Run Simulation - Begins the simulation by clearing the counters and
    "launching" a photon at the center of the Sun.  The Run Simulation
    button and the Parameters menu item are deactivated, the Stop
    Simulation button is activated.  The run continues until the photon
    reaches the surface or the Stop Simulation button is pressed.

    Stop Simulation - Use the Stop Simulation button to terminate the
    current run before the photon has escaped.  Note that the simulation
    cannot be restarted at the stop point - pressing Run Simulation will
    reset the counters and start over at the center.  Pressing the Stop
    Simulation button reactivates the Parameters menu item and the Run
    Simulation button.

Display

    # of Layers - The size of the current Sun model (set via menu).

    Show Trails - Indicates whether the photon trail feature is active
    (set via menu).

Counters

    Interactions - A running total of the number of interactions the
    photon has experienced.  In this model the number of interactions is
    also a measure of the time since the photon began at the center.

    Percent Out - The distance of the photon from the center, expressed
    as a percentage of the radius.


