I have been reading about Acceleration Due To Gravity. All sources including Fundamentals Of Physics By Resnik say that ' Acceleration due to gravity does not depend on the object's properties like mass , density , shape etc '. The magnitude of 'g' is 9.8 m/s^2 for all bodies ? But I can not understand why is it the same for all bodies ? Why doesn't it increase or decrease according to the mass of the body ?