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Message started by bob7_2 on 10/13/05 at 17:16:38

Title: Some interesting situations
Post by bob7_2 on 10/13/05 at 17:16:38

I'm doing a very large project for school, and somehow the the science got the idea to have my group simulate the collision of 2 galaxies. So.... How exactly would I go about doing that in gravsim? Lets assume the galaxies in question are spiral and/or barred spiral, similar in size to our own galaxy. There are thousands of objects that would need to be simulated, even to get a semi-accurate sim. How do I generate the orbital information for all of them, and can grav-sim even handle something of this scale?

On a completely unrelated note, in a differant project, in a differant class, I am working on figuring out how to extract the core from Jupiter. So how do you figure out the orbital mechanics of THAT? Our current plan is to use a very, very, large circle type thing. It would smash it into jupiter, and scrape everything off the core as it passed through a hole in the middle.

So, can anyone give any help on either of these? The first one is top priority.

Title: Re: Some interesting situations
Post by Tony on 10/14/05 at 11:36:43

The problem with simulating 2 galaxies is the number of objects involved.  It's not thousands of objects, but hundreds of billions.  Gravity Simulator does not do well once you're got hundreds of objects.  Probably about 600 objects is the most you would want to do if your computer's processor is somewhere around 3Ghz.

So you'll have to simulate mini-galaxies, which would be more correctly called star clusters.  This you can do.  And you can watch arms be pulled by tidal forces.  But you have to make guesses as to what a full scale galaxy would do in the same circumstances.

Also, the structure of galaxies is not completely understood.  The motions suggests lots of dark matter that has yet to be found.  So even on a supercomputer, you still have to make guesses as to your starting conditions.

You might consider changing your topic to colliding solar systems.  They're fun too.

I'm not quite sure I understand what you're trying to do with Jupiter.  But if something collides with Jupiter, causing mass to leave Jupiter, it sounds like a conservation of momentum project.

Title: Re: Some interesting situations
Post by nou on 01/11/06 at 19:08:18

The jupitor thing is unrealistic. It would be impossible to extract the core without a gas-giant size body and a huge velocity. Simulating that would be extremly complex and would involve many things besides gravity. The galaxy thing is not too hard. use galaxsee, a free program. (

Title: Re: Some interesting situations
Post by tomek on 05/17/06 at 03:26:06

regarding some interesting situations. might want to check this ( out.

i tried to make a .gsim out of it by editing objects and saving the simulation, but couldn't get it to work properly - speeds kept getting rounded in a weird way in the planet editbox; and after saving the scenario i couldn't even load it - sim froze when i tried to. maybe you'll have better luck with it

Title: Re: Some interesting situations
Post by Tony on 05/17/06 at 10:47:58

Thanks for that link.  I've seen that program before.  There's some fascinating simulations there.

The edit box rounding problem is a known bug in the current version.  To get around this, type your numbers in notepad first, all 6 vectors seperated by a space.  For example:

1234.56e+10 34567e+7 78977.3e+1 335577.88e+8 8906e-8 334578.3344e-6

Then highlight it, copy it, and paste the entire thing into the x position box.  It will parse it for you into the 5 other boxes.

This is a feature designed to let you quickly add vectors from JPL's Horizons system, without having to copy and paste 6 times per object.

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