Thanks for the reply! I will look into this because it still makes no sense to me and I am wary of accepting math formulas as proof of unobservable phenomenon. The accelerometer gives a reading because the suspended mass moves independent of the static mass under force. If the suspended mass can't move because it has no weight then it can't produce a reading. If the moving part of the sensor is constantly being pulled towards the center of the Earth just at a slightly less rate, then why don't astronauts (and everything) on the ISS get pulled towards the floor of the ISS?