## Opposing orbits

What did you draw?
19683
Posts: 151
Joined: Wed Jun 05, 2013 12:15 pm

### Opposing orbits

I noticed that when two massive planets orbit nearby in the same direction, they interact a lot and tend to be unstable, switching place, swinging out of the system, or even colliding. However, when the two planets are going in opposite directions, they seem to be very stable and don't interact much. Why is this?
Binomial Theorem: ((a+b)^n)= sum k=0->k=n((n!(a^(n-k))(b^k))/(k!(n-k)!))

testtubegames
Posts: 1008
Joined: Mon Nov 19, 2012 7:54 pm

### Re: Opposing orbits

Just speaking generally, since I'm not sure exactly the setup you saw...

I imagine that has a lot to do with the distance between the two objects. The ones that move in opposite orbits are only close to one another very briefly each orbit. That would lead to less deflection than, say, two objects whose orbits are running parallel, so that they're close to one another for extended periods of time.

[handwaving]

Another secondary effect may be that when the two planets move in the same direction, the force on each planet deflecting it tends to add up over time. (One is pulling the other out... or in... or 'forward'). But if the planets are moving opposite to one another, sometimes one is ahead, sometimes the other. Sometimes the 'outer' one is on the other side of the star, so it's pulling 'in', instead. That kind of thing.

Like the difference between putting a ball on an inclined plane vs. on a seesaw that's going up and down. The one on the plane will roll away quickly, whereas the other one might take a bit longer before it finally rolls of the seesaw.

[/handwaving]

Does that seem to explain what you're seeing?

19683
Posts: 151
Joined: Wed Jun 05, 2013 12:15 pm

### Re: Opposing orbits

Yeah, that makes sense. So planets going in opposite directions pass each other for less time and their interactions cancel out or don't add up over time. Thanks.
Binomial Theorem: ((a+b)^n)= sum k=0->k=n((n!(a^(n-k))(b^k))/(k!(n-k)!))