Three Body Problem: Dark Matter's Impact

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SUMMARY

The discussion centers on the complexities of the three-body problem in astrophysics, particularly in relation to dark matter and galaxy dynamics. Participants clarify that while the classic three-body problem can be analytically challenging, numerical methods are the primary means of finding solutions today. The conversation highlights the transition from analytical models, such as those proposed by the Toomre brothers, to modern simulations that handle millions of point masses. Key points include the distinction between three-body and many-body problems, and the implications of gravitational interactions in celestial mechanics.

PREREQUISITES
  • Understanding of gravitational forces and celestial mechanics
  • Familiarity with numerical integration techniques
  • Knowledge of Lagrange points and their significance in orbital mechanics
  • Basic concepts of fluid dynamics as they relate to astrophysics
NEXT STEPS
  • Explore numerical integration methods in celestial mechanics, such as Runge-Kutta and Simpson's Rule
  • Study the VSOP87 model for planetary motion predictions
  • Investigate the implications of dark matter on galaxy formation and dynamics
  • Learn about the restricted three-body problem and its analytical solutions
USEFUL FOR

Astronomers, astrophysicists, and students of physics interested in celestial mechanics, particularly those focusing on the dynamics of galaxies and the influence of dark matter.

  • #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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