So I took my telescope out last night and got to actually, really see Jupiter for the first time and it was amazing! While I was looking at it I could see it has 4 moons (though I later found out it has way more than that, but the ones I observed were the big Galilean moons). Another thing I noticed was that the moons were 'lined up'. That is to say, they were orbiting in a 2D plane it looked like (and further, I wasn't above or below but IN the plane). Why is this? Why do the moons orbit in one plane instead scattered all about in different orbits? Further, why is an observer from Earth parallel to the plane instead of viewing it from above or below? I'm looking for a physical explanation, which is why I didn't put this in the astronomy section. Please don't give an explanation that requires knowledge past a high school AP Physics class and Calculus I class. Thanks!