Is there a way to have a paired down solar system sim start at a chosen date?

[mikeyjames]

Hey all,
Still learning the game and have looked all over for the answer.

I hope I have posted in the correct forum for my questions.

Anyway, I love the "Now & Real Time" version of our solar system but there are simply too many objects to go fast-forward beyond one hour per second on my system, so my only option is to delete dust and fragments (easy enough) but then go around and delete other objects like moons one at a time.

If I then save the sim as a "my sim" the date is then set in stone (as far as I know).

I've noticed on other solar system sims available by default, that don't have as many objects, such as "Solar System Major Moons", I can open Advanced Settings and change the date to today's date, but I'd still like to remove a few objects so I can forward the time at a faster rate.

Also, I then run into the same issue of the date being set in stone once I save my version with enough objects removed to allow faster time forwarding (once again, as far as I know).

Is there a way to create your own saved version of a sim, such as the "Now & Real Time" version of our solar system wot , that will continue to start at a given date, either "now" or a date that can be set prior to launching the sim?

The reason I want to be able to do this, is that is that I have purchased a telescope and really want to learn the night sky and how it all fits together. For example, open up Stellarium, see what solar system objects are visible to me at a given time and location, and then open Universe Sandbox and then get a different perspective on how it all fits together.

I hope that all made sense.

Thanks
Mick

[Jar]

Unfortunately, there's no good way of doing this right now. In short, you can't set a starting date for a custom simulation.

Here's the lengthy explanation: When you save a custom simulation, it saves a "snapshot" of the simulation which is then read when you load it again. This is different from a sim like the "Real Time Solar System" sim, where the positions are actually being calculated behind-the-scenes as the sim is generated. For calculating this, the positions are extrapolated forward/backward in time from a specific date for which we have known data. Specifically for the real-time simulation, we use reference data that we update every time we release a new version of Universe Sandbox. This gives us more up-to-date data and means that when calculating the positions forward in time, there will be less error because there's less time to advance. I believe the data we use for most of the other sims that are affected by a custom start date (ie Solar System simulations) use the year 2000 as a reference point for known data --generally, the further your diverge from this date, the less accurate it is. We need to include this data in our files rather than accessing it when loading these simulations because it is a lot of data over a slow connection with the HORIZONS database (https://ssd.jpl.nasa.gov/horizons.cgi).

What objects do you want to be included in your pared-down version?

[Gregory]

Now sorry to interrupt, now we know that anything's possible if you believe, no matter how tough things are.
They'd take time and patience though, and here, bugs are expected.
It took many years to develop US and US2 and back before the 60s, we thought landing a man on the moon was impossible.

[mikeyjames]

Unfortunately, there's no good way of doing this right now. In short, you can't set a starting date for a custom simulation.

What objects do you want to be included in your pared-down version?

Hi,
I very much appreciate you taking the time to explain all of this to me and now understand why it's not possible.

I suppose my wishlist would be a "Now & Real Time" sim with just the planets and major moons.

I understand for a lot of people this would likely be a boring sim but for me, someone just starting to learn the night sky with an amateur telescope, it would be interesting. 

Thank you
Mick

[Cesare]

It will soon become possible to pair a solar system with real time. For that, the accuracy of Universe Sandbox must improve much more when the physics and simulation time steps of timing simulations speeds improve.

[Gregory]

Yup.

[Cesare]

Great.