Gravitation

Years ago -- decades ago -- when I worked at a computer store that sold the first Apple Macs I fell in love with a simple planet simulator called "Gravitation." You could create a sun, and any number of planets. Give them velocity and mass. See how they interreacted.

After a LOT of experimentation I was able to create a moon capture. I was able to create unstable systems that orbited for a while, then suddenly flew apart. We had a lot of fun with hugely elliptical orbits that gradually precessed and sometimes collided.

It was wonderful fun.

Never have been able to find a similar program for modern computers, surprisingly.

Until now.

For instance, check out this configuration:
Body 1: mass 200, position 0,0, velocity 0, -1
Body 2: mass 10, position 132, 0, velocity 0, 140
Body 3: mass 0.001, position 176, 0, velocity 0, 74

Or this one.  Make sure you let it run to 160:
1: 100, -85, -3, 0, -22
2: 100, 102, 0, 1 150
3: 55, -77, -2, -1, 42
4: 102, 135, 0, -1, -22

Watch what happens to the orbital velocities in this one:
1: 100, -85, -4, 0, -22
2: 100, 102, 0, 1, 150
3: 55, -57, -2, -1, 32
4: 102, 135, 0, -1, -22

Short and sweet:
1: 100, -85, -4, 0, -22
2: 100, 102, 0, 1, 150
3: 55, -57, -2, 0, 162
4: 102, 135, 0, -1, -22

Velikovsky:
1: 60, -85, -4, -80, -18
2: 190, 12, 0, 84, 0
3: 5, -57, 0, -100, 152
4: 122, 145, 0, -1, -114

Here's one I've never seen before: trading orbits!
1: 250, 70, 0, 0, -2
2: 12, 122, 0, 10, 220
3: 20, -126, 0, 0, -84

Wow, this one swaps orbits not once, but TWICE:
1: 260, 70, 0, 0, -4
2: 20, 124, 0, 10, 200
3: 20, -126, 0, 0, -74

I've really got to quit now. This is addictive.

Attempted moon capture. Shows just how freaking unlikely they are.
1: 250, 70, 0, 0, 0
2: 0.1, 174, 0, 0, 195
3: 14, -126, 0, 0, -54

Incidentally I just discovered you can drag the planet's position and velocity to any value with your mouse. Very much like "Gravitation." Bravo.

Gotta quit now.

You won't BELIEVE the pathways on this one. Make sure you have traces turned on and you let it run to 296:
1: 200, 0, 0, 0, -1
2: 10, 142, 0, 0, 140
3: 0.001, 174, 1, 1, 78

Stable for 226 seconds, then suddenly explodes:
1: 200, 0, 0, 0, -1
2: 11, 142, 0, 0, 142
3: 0.001, 175, -9, -8, 82