Three Body Problem: Dark Matter's Impact

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The discussion centers on the classification of gravitational interactions among celestial bodies, specifically addressing whether three galaxies can be considered a three-body problem. Participants argue that galaxies are too loosely constructed to fit this model, while the Sun, Earth, and Moon serve as a classic example of a three-body problem. The conversation shifts to the complexities of numerical simulations in modeling galaxies, which involve millions of stars, contrasting with the analytical challenges of the three-body problem. It is noted that while specific cases of the three-body problem can be solved, a general analytical solution remains elusive due to the complexity of variables involved. Ultimately, the consensus is that galaxies represent a many-body problem rather than a simple three-body scenario.
  • #31
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  • #32
Very interesting web sites. Nice simulations!

The unrestricted simulations done by my program are interactive. You can edit the values of the initial conditions of the bodies and observe their amended trajectories.
 
  • #33
Hi khavel,
Your simulations work incrementally, right?
As in each step is calculated from the previous step?
And the smaller the time increment, the more accurate the simulation, right??
 
  • #34
Quote from khavel's site (http://www.grevytpress.com/enbody.pdf ):
In an n-body gravitational system, the trajectory of anybody generally depends on the masses, positions, and velocities of all remaining bodies.
To determine the trajectories of all bodies, we set a time interval deltaT for the recalculation. Obviously, the shorter the time interval results in more precise calculation of the trajectories. At the beginning of the time interval we know the masses, positions, and velocities of all bodies. During time interval deltaT we calculate for each body the sum of accelerations imparted by gravitation of all other bodies, from their masses and positions. Then, for each body, we respectively integrate the sums of the accelerations over time interval deltaT, to obtain the increment of its velocity. We add the increment of its velocity to its previous velocity, to obtain its new velocity. Then we integrate its new velocity over time interval deltaT, to obtain the increment of its position. We add the increment of its position to its previous position, to obtain its new position. Since acceleration, velocity, and position are vectors, all calculations are done with their x and y components.
We keep repeating all calculations, over successive time intervals deltaT, using the new positions and velocities of all bodies. This method of calculation is valid for any number of bodies. Needless to say, the complexity of calculation increases with the number of bodies.

'nuff said. Khavel has produced an incremental numerical simulation, not an analytic one. Nothing new here.
 
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