What is bistability?

A bistable system is one that can be in two different stable states at the same time, like a seesaw that can stay on either side.

Imagine you're playing with a toy car that has a switch. When you flip the switch, the car goes from being off to on. But sometimes, if the car is just sitting there, it might stay on even after you let go of the switch, or it might turn off and stay off. That’s because the car can be in two stable states: on or off, and once it chooses one, it likes to stick with it.

Think about a door that's really heavy. If you push it just enough to get it moving, it will keep swinging all the way open, even if you stop pushing. But if you pull it halfway and let go, it might just stay there, not fully opening or closing. This is like bistability, the door has two stable positions: fully open or fully closed.

Sometimes, a little push or pull is enough to make it switch from one state to another. And once it's in a new stable position, it doesn’t want to move back unless you give it another nudge!