If all frames of reference are taken as equally valid. when a car moves, to the passengers in the car the world is moving in the opposite direction. Moving the whole world should take alot more chemical energy than was contained in the gas that was burnt... I know the passengers in the car will remember undergoing an acceleration which the world did not but once the aceleration phase is done their is no difference between the car moving forward and the world moving back; and I don't like the notion that the universe needs some kind of 'memory' to make sense. Is their a way to make the math work or does the conservation of energy only apply in some priviledged frame of reference?