2D Celestial collision

[Shadow]

Hey there all,

 

I'd like to try and make a program that simulates 2D celestial collision (star with planet, planet with planet, star with star, etc.). Now, I know that something like this is probably impossible to simulate precisely, and if I even wanted to get close I'd have to call in some serious computer-power favors at NSA, but I'm not looking for something I can sell NASA. I'm just looking for an approximation. Could anybody here tell me what I should read up upon, which topics I should become familiar with, what kind of math/physics knowledge I will be needing, different approaches I can try, etc.? Again, I'm not looking for a precise way to simulate a celestial collision. I'm sort of looking for something that is to 'precise celestial collision simulation' what Newtonian Mechanics are to Relativity; not exact, but good enough.

 

Cheers,

 

Gabe

[Klaynos]

Hey there all,

 

I'd like to try and make a program that simulates 2D celestial collision (star with planet, planet with planet, star with star, etc.). Now, I know that something like this is probably impossible to simulate precisely, and if I even wanted to get close I'd have to call in some serious computer-power favors at NSA, but I'm not looking for something I can sell NASA. I'm just looking for an approximation. Could anybody here tell me what I should read up upon, which topics I should become familiar with, what kind of math/physics knowledge I will be needing, different approaches I can try, etc.? Again, I'm not looking for a precise way to simulate a celestial collision. I'm sort of looking for something that is to 'precise celestial collision simulation' what Newtonian Mechanics are to Relativity; not exact, but good enough.

 

Cheers,

 

Gabe

 

Well the first thing you need to do is model a star in 2D, so how much do you know about solar dynamics?

[Shadow]

Well, as of three seconds ago I know something like that exists ) a quick google search just turned up a bunch of companies...

 

What exactly do you mean by "model a star"?

[Klaynos]

Well, as of three seconds ago I know something like that exists ) a quick google search just turned up a bunch of companies...

 

What exactly do you mean by "model a star"?

 

A set of mathematical equations that tell you things about the star, in this case you want to know about things like temperature etc... inside the star...

 

This is not trivial, people spend their lives researching this and trying to understand it.

 

What level of physics and maths knowledge do you have?

[Shadow]

High school, not calculus though, which I believe is the seriously limiting factor here. Apart from that, it's sort of varying, since I do some learning by myself, and I can pretty much learn most of what I need. Or I have been able to so far )

 

As for physics, I'd say none at all, considering the teacher we have I just learn what I need to when I need to. In this regard, I consider physics to be a subset of math, as in "If I know the math part I can learn the physics part" which, again at least so far, works.

 

I don't expect it to be trivial, which is why I'm looking for something like a shortcut instead of a full blown set of equations. Then again, I don't know if something like this is possible, and if it is, I don't know if it's in my grasp.

[Klaynos]

Well most of what you'd need for this probably falls under the term of differential calculus...

 

Even modelling the sun as a ball of hot water would require it...

[Shadow]

So, what you're saying is learn calculus and come back?

 

Do you think you could give me some leads as to what to study after I learn calculus? Sites, articles, lectures, anything. Even just an example or two of what I should do next, or maybe a list of things I should study.

 

But thanks anyway, at least I have a specific reason to learn calculus... )

[iNow]

Hey Shadow, FYI - http://www.scienceforums.net/forum/showthread.php?t=31921

[Shadow]

Thanks iNow

 

I read the posts, and I understand them. But surely I need more than this...if only because I don't see how all I've just learned ties into modelling a star as a ball of hot water )

[timetes]

Konrad B. Krauskopf, Arthur Beiser, by accident....my daughter had to take this class before she graduated college this spring. But if I could read this as a mother, Im sure you can as a high school student. You may find information in there to help you. I quess its not like a super nova because i think that blows up by itself.... I didnt read of any two planets or stars colliding....but its is a good book for information.

[Klaynos]

Thanks iNow

 

I read the posts, and I understand them. But surely I need more than this...if only because I don't see how all I've just learned ties into modelling a star as a ball of hot water )

 

It's all a bit complicated, but the sun can be wrongly modelled as a liquid, so if you model a liquid drop that is held together by gravity instead of electrostatics, you will get differential equations out.

 

With stars you then need to take things like photon pressure and temp gradients into account, it all gets very complicated REALLY quickly.

[Shadow]

It's the modeling part that confuses me.

 

Again, this sounds like the exact way to do it. Isn't there some other, less complicated way? I think the Newton/Einstein metaphor summed what I'm looking for quite well. But thanks for your help anyway guys! )

[Klaynos]

That is in no way exact.

 

What you do with modelling is you've equations which tell you everything about what you are modelling (and by everything I mean just the stuff you're interested in), you can then apply different situations to those equations (like collisions) and see what happens.

[Shadow]

Not exact? Oh... Okay, I guess that gives me an idea of how hard it could be.

 

I was thinking about "modeling" the stars as a bunch of particles, that just can't be broken down to anything smaller, and then just let those particles interact. Unfortunately, I'm not sure that would be computationally feasible, and to be quite honest I'm not even sure on how I would program something like that.

 

What would you recommend?

[Klaynos]

Particles that bounce off of each otehr isn't too hard, but it's no where like reality...

[Shadow]

The bouncing part didn't occur to me...the way I though about it is best illustrated like this:

 

 

I know that's not what it would look like if a situation like this would arise, but you get the idea. Anyway, I guess that's just one more reason why not to use that method.

 

What about doing what you mentioned earlier; treat the stars as balls of water, or alternatively gas...

 

Anyway, I'm open to suggestions.

 

Cheers,

 

Gabe

[swansont]

This depends on what you are trying to describe. The suggestions thus far seem to assume you are looking at an actual impact, and want details of what happens to the star and planet. Is that it? Or are you looking at what happens to the orbits when they happen to pass close by each other?

[Shadow]

Yes, I'm talking about actual impact. Although not of a planet with a star, but of a star with a star...

 

I guess I'll just make the star "swallow" the planet if they ever meet )

[h4tt3n]

Hi Shadow,

 

No matter if you're doing this to get an understanding of solar dynamics or if this is "just" for a computer game or a visual demo, you'd probably want to use Smoothed Particle Hydrodynamics, SPH. Basically, this is just a way to represent liquids or gases with a finite, discrete particle system. It is used a lot in game programming, but I think it was originally developed to model huge complex astronomical bodies like star clusters and galaxies.There are a few nice papers and free programs out there.

 

cheers,

Mike

[Shadow]

Hey Mike ) I didn't know you still visited SF, I was actually thinking of writing you now that I've started working on that program again (yep, still the same one).

 

I've heard about SPH before, it may have even been you who mentioned it. Unfortunately, I couldn't recall what it was called, so thanks for that. I'll have a look at it

 

Cheers,

 

Gabe

[h4tt3n]

You're welcome Shadow. I did wonder what happened with the program, and I'd still like to see it in action once you've got a working sample up 'n' running

 

If you'd like to take a look at some really simple 2d gravity simulation code samples, I thew some up here:

 

http://www.jernmager.dk/stuff/gravity_code_examples.zip

 

Cheers & gl with your coding,

Mike

[Shadow]

Still got the originals you sent me way back then But thanks anyway. I've got the gravitational part worked out, as long as I'm using Newtonian Laws. What I want to do now is learn calculus properly, and then try to figure out SPH. Which will probably take quite some time, and it may just be too complicated for me. But that won't stop me from giving it a try

[h4tt3n]

That's the spirit!

 

Actually I just dove into SPH recently too. Here are some fairly nice papers and slides:

 

http://www.iro.umontreal.ca/labs/infographie/papers/Clavet-2005-PVFS/

 

http://www.ifi.uzh.ch/arvo/vmml/solenthalerPublications.php

 

Cheers,

Mike

[Shadow]

Thanks! I was going to try http://www.plunk.org/~trina/thesis/html/thesis_toc.html, but I can't seem to connect at the moment...I hope they haven't deleted it, since it looked like a pretty good site.

 

EDIT: Here's Google's Cache

 

EDIT2: Ah, and here is the site from The Wayback Machine. You just got to love that site.

Edited December 19, 2008 by Shadow

[Tom Vose]

Hey there all,

 

I'd like to try and make a program that simulates 2D celestial collision (star with planet, planet with planet, star with star, etc.). Now, I know that something like this is probably impossible to simulate precisely, and if I even wanted to get close I'd have to call in some serious computer-power favors at NSA, but I'm not looking for something I can sell NASA. I'm just looking for an approximation. Could anybody here tell me what I should read up upon, which topics I should become familiar with, what kind of math/physics knowledge I will be needing, different approaches I can try, etc.? Again, I'm not looking for a precise way to simulate a celestial collision. I'm sort of looking for something that is to 'precise celestial collision simulation' what Newtonian Mechanics are to Relativity; not exact, but good enough.

 

Cheers,

 

Gabe

 

 

How would that be possible, without a sophisticated computer program which computes a 2D object under a 3D abstract?

 

Conecputually, it is very easy to imagine. But computationally, it should be near-impossible.