query: How strong is gravity on Earth?
passage: Gravity of Earth
The precise strength of Earth's gravity varies depending on location. The nominal "average" value at Earth's surface, known as standard gravity is, by definition, 9.80665m/s2.[4] This quantity is denoted variously as gn, ge (though this sometimes means the normal equatorial value on Earth, 9.78033m/s2), g0, gee, or simply g (which is also used for the variable local value).
passage: Reaction (physics)
Any mass on earth is pulled down by the gravitational force of the earth; this force is also called its weight. The corresponding 'reaction' is the gravitational force that mass exerts on the planet.