Motion of randomly generated stars

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Discussion Overview

The discussion centers around the simulation of the motion of randomly generated stars within a defined spherical space, exploring the challenges and methodologies for modeling gravitational interactions and celestial mechanics. Participants discuss computational requirements, potential strategies for simplifying calculations, and the theoretical underpinnings of gravitational effects in such simulations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Dan proposes to create a simulation of stars with defined coordinates, velocities, and masses within a spherical "universe" and seeks advice on how to implement this.
  • Some participants highlight the computational complexity of simulating n stars, noting that it requires n^2 calculations, which could lead to performance issues.
  • Dan mentions having access to a powerful computer and is considering a grid solution to manage calculations more effectively.
  • Dan expresses a desire to understand the basics of celestial motion, starting with Newtonian physics before moving to General Relativity.
  • Dan questions whether gravitational contributions from distant stars can be ignored and if stars in a cluster can be treated collectively rather than individually.
  • Another participant suggests that Dan's project falls under "N-Body Simulations" and provides resources for further reading on the topic.
  • One participant proposes an alternative approach of simulating a spiral galaxy by placing stars in circular orbits around a central mass, potentially simplifying the simulation by limiting interactions.

Areas of Agreement / Disagreement

Participants generally agree on the computational challenges involved in simulating a large number of stars, but there are differing opinions on the feasibility of simplifying the model through clustering or limiting interactions. The discussion remains unresolved regarding the best approach to take.

Contextual Notes

Participants acknowledge the limitations of their current understanding and the complexity of gravitational interactions, particularly in relation to distant stars and clusters. There are unresolved questions about the assumptions underlying gravitational contributions and the applicability of different models.

Who May Find This Useful

Individuals interested in astrophysics, computational modeling, and N-Body simulations may find this discussion relevant, particularly those exploring the dynamics of celestial bodies and gravitational interactions.

dgroth
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Hello, I am new to this forum - and impressed with the posts. I have recently developed an addiction to astrophysics. I wish to do the following:

- define a spherical "sandbox" with a radius of let's say 1, which I think of as "universe"
- within that sphere I generate N number of points. Each point have the following attributes:
1) a coordinate: p(x, y, z)
2) a velocity: v(x, y, z)
3) a mass
- define time as t

Then, kick-off a program (that I'm hoping to write) which will represent all the points (stars) as I move to t+1, t+2 etc... Many points should collide, others turn into orbits, others will fly outside my "universe". I wish my model to be "accurate" according to gravity fields of each star.

Can anyone share with me how I could go about achieve this goal ? (let's start with 3 stars)

In advance, thank you.
Regards, Dan.
 
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n stars requires n^2 calculations. you'll run out of processing power rather quickly I'm afraid.
 
granpa said:
n stars requires n^2 calculations. you'll run out of processing power rather quickly I'm afraid.

I apperciate the calculation involved. But thanks for drawing my attention to this. However, I have access to a rather massive computer all for myself: IBM p6 with 64CPUs and 256GB of RAM. Anyway, I have already started working on a grid solution to distribute the calculations, if necessary (which I assume it will).

Regards, Dan.
 
granpa said:
n stars requires n^2 calculations. you'll run out of processing power rather quickly I'm afraid.

Hmmm, I see what you mean granpa...now with a few steps back and some thinking - I might have been a bit ambitious. Just for the laugh: my target was/is 1 million stars.

But... I'm not going abandon this easily. Nothing easy is worth doing. Since I don't know the first thing about celestial motion, I'm going back to the basics: Newton. I'll move onto GR later. First I building I'm building a gridable physics architecture.

I have one question that may help me:
- is there a distance limit for which gravitational contribution of other stars can be ignored (stars extremely far away) ?
- if I have a cluster (I mean just a group) of stars, does all the members of the group behave in similar way, ie. can get away with applying a "pull" to the group rather consider each start individually? This will help me understand if I can grid clusters across the network.

Regards, Dan.
 
Welcome to the forum, Dan. What you are planning to do falls in the general field of "N-Body Simulations", googling for this might yield useful info.

Also this recent review paper http://arxiv.org/abs/0806.3950 might be interesting, section 3.2 Tree Codes seems to be related to what you wrote in #4 (grouping stars to clusters).

A website from one of the authors of this paper, www.artcompsci.org contains (among other stuff related to scientific computation) some further info about N-Body Simulations.
 
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you might consider trying to form a spiral arm of a spiral galaxy. you could limit it to 2 dimensions and you might not even require ANY interaction between the stars. you could probably do a million stars quite easily. just put them in circular orbits of all different radius's around a central mass (but with all the dark matter I'm not sure they follow an inverse square law though) then somehow put a slight mass concentration in one area (not a concentration of stars) and see if their orbits shift into that area thereby creating an even greater mass concentration.

http://abyss.uoregon.edu/~js/ast122/lectures/lec26.html
 
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