Astronomy in a parallel universe

[Lionel Mandrake]

4. Gravity is like magnetism in one respect.

Both are long range forces, because they are thought to be mediated by particles of zero mass: the graviton and the photon.

Gravity and electricity both involve inverse-square-law forces. Magnetism would, too, if there were any magnetic monopoles.

Kepler speculated that the sun controlled the motion of the planets via magnetic forces. Kepler's intuition that a force from the sun controlled planetary motion was on the right track, but forces and their relationship to motion were not understood before Newton. It turns out that magnetism is the wrong force, but there was no way for Kepler to know that.