AstroGrav Help /Tutorial /Exercise 5 - Editing Existing ObjectsVersion 5.1

Exercise 5 - Editing Existing Objects

This exercise teaches you how to edit existing objects, and should take about 15 minutes to complete.

Opening the Tutorial Simulation

If you already have the Tutorial simulation open, choose the File / Revert to Saved menu item, which will return the simulation to the same state that it was in when you first opened it. Otherwise, go through the following steps to open it.

If you don't already have AstroGrav running, double-click on the AstroGrav application icon () to start it running.
When the Open Simulation file chooser dialog is displayed, navigate to and open the Tutorial.ast file.
The Tutorial simulation will then open, and you will see the simulation's three windows displayed on your screen.

Editing an Object

Go through the following steps to learn how to edit an existing object.

Click on the Earth to select it.
Choose the Edit / Edit Object... menu item, which will result in the Editor of 'Earth' dialog being displayed.
Click on the 'Details >>' icon ('Show more choices' icon on a Mac) in the top-left corner of the window, and notice that the now expanded dialog contains the same fields as the main panel of an object window, but that the fields are in this case editable.
Click on the 'Details <<' icon ('Show fewer choices' icon on a Mac) in the top-left corner of the window, and notice that the dialog has returned to its contracted state, with just the Physical Elements and Orbital Elements visible. Usually, you will only want to edit the data elements that are visible in the contracted dialog, with the expanded dialog only occasionally being needed.
Change the 'Eccentricity' to 0.9 and the 'True Long' to 300 and accept the dialog, which will result in a question dialog being displayed that asks if you want to update the Earth's family as well.
Click on 'Yes', and notice the Earth's orbit has now dramatically changed, and that the Moon has been updated too so that it is still in the same orbit about the Earth. If you had clicked on 'No' instead, the Moon (Earth's family) would have been left where it was, and would now be in an independent orbit about the Sun.
Hold down the Shift key, and drag the mouse pointer around the window, in order to rotate the system so that you are "looking down on" the Solar System with the orbits of the other planets looking approximately circular.
Now, hold down the Control key (Command key on a Mac), and drag the mouse pointer towards the lower-left, in order to move your viewpoint so that all of the Earth's highly eccentric orbit is visible.
Choose the Evolve / Run Forward menu item (or the tool), which will start the simulation running forward in time. Notice how the Earth is unable to "hang on" to the Moon because of the high gravitational field so close to the Sun, and how the Moon moves off on its own independent orbit about the Sun as a consequence. Also, notice how the Tutorial: Structure window has changed to show the new structure of the system, with the Moon now orbiting the Sun between Mercury and Venus.
Finally, stop the simulation running by using the Evolve / Stop menu item (or the tool).

You can also display an object's editor dialog by double-clicking on the object.

Removing Objects and Using Undo and Redo

Go through the following steps to learn how to remove objects and use the undo and redo commands.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Click on the Earth to select it.
Choose the Edit / Delete menu item, which will result in the Earth being removed from the simulation. Notice that the Earth has disappeared from all three windows, so that the windows remain consistent.
Now, double-click on the Moon, which will result in the Editor of 'Moon' dialog being displayed.
Change the Moon's name (anything will do) and accept the dialog, and check that the name has changed on the Tutorial: View window. Notice that the Moon's name has changed on all three windows, so that the windows remain consistent.
Click on Venus to select it, and then click on Jupiter while holding down the Control key (Command key on a Mac) to select it as well.
Choose the Edit / Delete menu item, which will result in Venus and Jupiter being removed from the simulation. Notice that Venus and Jupiter have disappeared from all three windows, so that the windows remain consistent.
Now, choose the Edit / Undo menu item three times, and notice how your three edits are undone one by one, and how all three windows remain consistent at all times.
Now, choose the Edit / Redo menu item three times, and notice how your three edits are redone one by one, and how all three windows remain consistent at all times.

You can also use the undo and redo commands to undo and redo the addition of objects and families of objects (covered in later exercises of this tutorial), to undo and redo the merging of objects, and to undo and redo edits of the date/time, units, and notes. The various commands that evolve the simulation can also be undone and redone.

Next: Adding New Objects

You've now completed Exercise 5, and are ready to move on to Exercise 6, which teaches you how to add new objects.

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