thing happens if you take two pendulums and attach them with a spring – on their own,

they’ll want to do one of two things: either swing together in the same direction, or exactly

opposite each other, and when they’re opposite each other, they swing slightly faster because

of the help of the spring.

But perhaps you interact with the pendulums, and push one of them to start it swinging.

When you think about it, the first pendulum swinging by itself is actually a superposition

of both swinging the same way and both swinging opposite ways, combined so that the swinging

of pendulum two cancels out.

However, because the two “on their own” states of the pendulums don’t swing with

the same rate, they won’t cancel out for pendulum two forever, and eventually it will

be the only one swinging, and pendulum one will have stopped.

And then later, it’ll be pendulum one, and then pendulum two, and so on.

So the states you interact with, just one pendulum swinging, can oscillate back and

forth between each other, swapping identities, because they’re superpositions of the non-interacting

states, and those states have different frequencies.

Other than a few pesky details to do with quantum mechanics, this is essentially what

happens with neutrinos!