# Are magnetic orbits possible?

I have a small ball with lots of magnets embedded in it with all the north poles facing out and I have a big sphere with lots magnets embeded in it with all the south poles facing out. I set the experiment up in space and throw the ball.

Could I get the ball to orbit the sphere just from the magnetic attraction?

A simular question goes for placing the ball inside the sphere, could an orbit form from magnetic repulsion?

• Notice in the idealized limit where there are many small magnetics unformly spaced on the sphere or ball, there will be no magnetic field produced by either and thus no interaction force between the two. – Brian Moths Dec 5 '14 at 20:20
• Jitter, it appears that you want to build magnetic fields with spherical symmetry. Gauss law forbids such fields. – Energizer777 Nov 9 '15 at 4:17

Yes, all central forces can produce circular orbits given an appropriate initial velocity. However, if some radial velocity is introduced, these orbits need not be stable (i.e., remain in orbit indefinitely) nor closed (repeatedly returning to exactly the same path). There are only two kind of forces that produce exactly closed orbits: the inverse-square force, and the radial harmonic oscillator potential. The magnetic force is none of these two, it is a dipolar force, but its dependence with some power of the radius (which depends both on the shape and on the distance) will result in a stable non closed orbit. Thereason is that even if not an inverse square law, it is always atractive and decays with distance.

• Would the internal repulsive orbit decay to the point where the ball sits in the centre of the sphere? – Jitter Dec 5 '14 at 19:56
• I do not think so, but I might be wrong. The reason being that I imagine that with the repulsove force it will oscilate more like a spring around the center, unless the energy is lost or transmited from the balll to the sphere, but I cannot see how (well, if there is air friction it will eventually happens, but I dont think it will in the vaccuum. – Wolphram jonny Dec 5 '14 at 20:21

Yes it is simple as planet orbit on gravity or magnetic filed. For example the Earth orbit the Sun bcz Sun have magnetic field and the Moon also orbit the Earth.

• "the Earth orbit the Sun bcz Sun have magnetic field". Say what? – Nephente Jul 2 '15 at 8:20
• The magnetic fields of the Sun and Earth have a negligably small effect on their mutual orbit. The orbit is dominated by gravitational forces. – John Rennie Jul 2 '15 at 9:56