Start Date and Time

[phinehas]

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[atomic7732]

You can open the .ubox/.xml

If it's a .ubox, you will have to ask Dan about that.

[Dan Dixon]

1.  Is there a way to change this start date/time to current within the program or through some dat file, etc.?

No and not in version 2 either.

Starry night uses ephemeris data to calculate the positions for a given data. Universe Sandbox only has data for specific dates (the most complete date being 2008-01-01). After the initial release of version 2 we'll be adding more data in future version 2 releases (like 2010-01-01) and may add simple date adjustment controls for planet positions in the future.

is there a way to open a system and make it so the simulation time doesn't start automatically?

There is a "Start Paused" option in the upcoming release (version 2).

What is ephemeris data?
http://en.wikipedia.org/wiki/Ephemeris

[APODman]

1.  Is there a way to change this start date/time to current within the program or through some dat file, etc.?

No and not in version 2 either.

Starry night uses ephemeris data to calculate the positions for a given data. Universe Sandbox only has data for specific dates (the most complete date being 2008-01-01). After the initial release of version 2 we'll be adding more data in future version 2 releases (like 2010-01-01) and may add simple date adjustment controls for planet positions in the future.

But Dan, if we get new ephemeris data from the Jpl's Horizons System and paste it replacing the original data in the file "Horizon-2008-01-01.xml" ?

This procedure might work to realize simulations using more recent ephemeris ?


[ ]´s

[Dan Dixon]

So the starting date is accurate but as the simulation runs it ceases to be an accurate representation of the position of planets?

Yes. The accuracy of the simulation depends on the time step. A slow time step is very accurate. A high time step will rip the simulation apart.

Universe Sandbox 2 features a new integrator for calculating the simulation that is far more accurate than version 1. (RK4 vs Euler)

Thanks for answering the questions.

Thanks for trying out Universe Sandbox.

Come back in a few days to check out version 2.

I was hoping you were going to say that the simulation would be accurate and therefore all you would have to do is modify your program to run from the 2008 date and stop at a specific date and time entered by the user.

That's a good idea and something we'll consider for a future addition.

But Dan, if we get new ephemeris data from the Jpl's Horizons System and paste it replacing the original data in the file "Horizon-2008-01-01.xml" ?

This procedure might work to realize simulations using more recent ephemeris ?

Yes. That would totally work. The framework is there use multiple position & velocity data files. This framework is used with the Pioneer and Voyager systems and the Shoemaker Levy 9 collision with Jupiter. This just hasn't been exposed in the UI (user interface).