You're sealed in an elevator and are weightless.  SCARY!

You don't/can't know whether your elevator is accelerating towards an object (as in freefall) or not (as in empty space).  YOUR IMMEDIATE FATE DEPENDS ON IT!

Everythinhg *outside* the elevator determines the elevators acceleration, based on how much those things are accelerating near the elevator.  SO DON'T EVER GET STUCK FEELING WEIGHTLESS IN A SEALED ELEVATOR! 

 Einstein himself seemed to have figured these things out through the eyes of a 5yo 🤣