The THREE Body Problem --- by Jane Kelley

Isaac Newton first described the three body problem in  his 1687 best-seller, Principia.  It is impossible to identify the movements of three massive bodies because of all the different gravitational attractions.

This is Newton's diagram in the Principia 'to find the force of the Sun to perturb the Moon.' 

Don’t you love the use of that word "perturb"? As if it were upsetting for our moon to be pulled in different directions by the gravity of both the earth and the sun. 

Could you predict a path for any of the bodies? No! And neither could anyone else.

What may seem like an embarrassing situation for physicists, is a gold mine for writers. 

Look at those possibilities! When you have three characters, your story can move in so many different directions. But remember that you can’t just put those bodies in your novel. You must make sure they have influence on each other. How much influence depends on how much weight you choose to give them.

For instance, take your standard romance. A and B fall in love. Pretty straightforward until you add character C. And then who knows where the story goes!

Actually in this case, there was a happy ending for my husband, our daughter, and me. 

But don't forget what Isaac Newton also said. “I can calculate the motion of heavenly bodies, but not the madness of people.”