Strange effects of using negative masses

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Stargate38
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Strange effects of using negative masses

Postby Stargate38 » Mon Feb 24, 2014 6:50 pm

I was just messing around with the gravity exponent and I found something weird (Click the primary and select "View world from it"):

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Gravity Fun at TestTubeGames.com: [ForceG: 4,Qual: 1,Zoom: 1,xSet: 0,ySet: 0], [x0: 0,y0: 0,vx: 0,vy: 0.3,t0: 0,who: 2,m: 7500,c: 0], [x0: 125,y0: 0,vx: 0,vy: 15,t0: 0,who: 2,m: -150,c: 1], [x0: -45,y0: 0,vx: 0,vy: 0.3,t0: 0,who: 3,m: 0,c: 2]


Notice how the asteroid almost hovers at a distance of 45 units from the primary, slowly moving around on a flower-shaped path.

Here's some proof that the L3 Lagrange point is stable when the secondary has negative mass:

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Gravity Fun at TestTubeGames.com: [ForceG: 4,Qual: 1,Zoom: 1,xSet: 0,ySet: 0], [x0: 0,y0: 0,vx: 0,vy: 0.6,t0: 0,who: 2,m: 7500,c: 0], [x0: 125,y0: 0,vx: 0,vy: 15,t0: 0,who: 2,m: -300,c: 1], [x0: -127.5,y0: 0,vx: 0,vy: -15.3,t0: 0,who: 3,m: 0,c: 2]


Notice how it liberates.

Here's an example in r^-2 gravity:

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Gravity Fun at TestTubeGames.com: [ForceG: -2,Qual: 1,Zoom: 1,xSet: 0,ySet: 0], [x0: 0,y0: 0,vx: 0,vy: 0.32,t0: 0,who: 2,m: 7500,c: 0], [x0: 125,y0: 0,vx: 0,vy: 8,t0: 0,who: 2,m: -300,c: 1], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 0,who: 3,m: 0,c: 2], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 10,who: 3,m: 0,c: 3], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 20,who: 3,m: 0,c: 4]


Replacing the asteroids with planets, each having a mass of 100, results in instability:

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Gravity Fun at TestTubeGames.com: [ForceG: -2,Qual: 1,Zoom: 1,xSet: 0,ySet: 0], [x0: 0,y0: 0,vx: 0,vy: 0.32,t0: 0,who: 2,m: 7500,c: 0], [x0: 125,y0: 0,vx: 0,vy: 8,t0: 0,who: 2,m: -300,c: 1], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 0,who: 2,m: 100,c: 2], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 10,who: 2,m: 100,c: 3], [x0: -130,y0: 0,vx: 0,vy: -7.5,t0: 20,who: 2,m: 100,c: 4]


2nd Version (Turn off collisions before the last 2 orbiting bodies collide or it'll freeze):

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Gravity Fun at TestTubeGames.com: [ForceG: -2,Qual: 1,Zoom: 1,xSet: 0,ySet: 0], [x0: 0,y0: 0,vx: 0,vy: 0.008,t0: 0,who: 2,m: 30000,c: 0], [x0: 125,y0: 0,vx: 0,vy: 16,t0: 0,who: 2,m: -120,c: 1], [x0: -125.5,y0: 0,vx: 0,vy: -15.9,t0: 0,who: 2,m: 40,c: 2], [x0: 0,y0: 343.33333333333333333333,vx: -7.979,vy: 0.016,t0: 0,who: 2,m: 40,c: 3], [x0: -5,y0: -153.37625,vx: 15.984,vy: 0.016,t0: 30,who: 2,m: 40,c: 4]
I LOVE your Gravity Simulator! :)

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