This application simulates the dynamics of bodies based on the force of gravity according to Newtonian theory.

Use the usual touchscreen gestures:

• With one finger, hold and drag to move the bodies around and change their initial speeds.
• With two fingers, pinch gesture, zoom.

Buttons:

• Starts or pauses the simulation.
• Restarts the simulation.
• Enables or disables the reference grid.
• Enables or disables trajectories.
• : Configures the masses of the bodies, the number of bodies and the speed of the simulation.
• : Enables or disables trajectories of bodies.
• Scale Shows the scale.
• Velocity Shows the scalar speed of bodies.

The movement of bodies is based on Newton's second law and his law of universal gravitation. The resultant force on the body of mass $m_i$ is given by

$$ \overrightarrow{F}_{i} = \sum_{j \neq i}^N \dfrac{Gm_im_j}{r_{ij}^2}\hat{r}_{ij}, $$

where

• $N$: number of bodies
• $G$: constant of universal gravitation

The ODE system is solved by the fourth order Runge-Kutta method.

Other considerations:

• The center of mass of the system is kept fixed.
• The velocities of bodies as well as their positions are relative to the system's center of mass.

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