Gravity
The universal attractive force between masses, causing mutual acceleration proportional to mass and inversely proportional to squared distance.
Governing formula
Fg = G m1 m2 / r²
SI unit
N
In depth
Near Earth's surface, gravity imparts a standard free-fall acceleration g ≈ 9.81 m/s². In General Relativity, gravity is interpreted as spacetime curvature caused by mass-energy.
Examples in the real world
Earth's gravity keeping the Moon in orbit and holding the atmosphere down.