do opposites attract?

This is a question I've been thinking about lately, so I hope you don't mind if I share some of my thoughts.

If you step back from the human relationship context, and abstractly ask, "When do two things fit together?", the answer is: only if they're opposites (in some sense). Some examples:

• When you connect paths or arrows, you connect the end of one to the beginning of the other. (ends and beginnings)
• When you connect Lego bricks, you attach the opposite ends. (pegs and holes)
• In math, you can "connect" the output of one function to the input of another. You can't connect two inputs.
• In physics, when two objects collide, the amount of momentum given to one object equals the amount taken from the other. (equal and opposite forces)
• In economics, two parties can trade if they can each provide something that the other party wants. (what you have vs. what they need)
• Any object/machine used by people (bicycles, cars, chairs, etc.) must be geometrically and mechanically complementary to (at least part of) the human body. (A bicycle, for example, needs someone to push its pedals and steers its wheels, while it provides a seat and efficient transportation. A person needs a seat and efficient transportation, and can provide pedal power and steering. They're a perfect match.)

It's a ubiquitous pattern in the universe, so it makes sense that it would extend to human relationships. People can be "opposites" in the sense that what each person provides in the relationship is what the other person wants or needs. While I know that the dynamics of a complex relationship are far more subtle and interesting than this oversimplification about needs, I suspect that the principle of opposites connecting somehow extends into the largely subconscious and mysterious process of falling in love, but I haven't figured out the details of that part yet.