Hi there! I was wondering if you folks could give me a little enlightenment. Two days ago, I read a quote which led Einstein to a couple of brilliant discoveries about not being able to discern a force and gravity; if you're inside a box. The quote said that Einstein was suddenly struck by the thought that a person in free-fall, does not feel his own weight. I fully agree with that thought. But when do you feel your weight? Is it when a force acts on a object which is already being "forced" in the opposite direction? Or is it merely when you experience an acceleration?