Earth is felt to be the same; it causes objects to fall according to a well-known acceleration - g (9.8 ms -2 ). In reality, this g varies by a few hundred tens of thousandths of metres per second squared (unit [...] to the different ways that the masses in Earth's various rock and fluid layers - atmosphere, ocean, ice-sheet, sediments, crust, mantle, and core, are arranged with respect to each other. Accelerations from