gravity

The fundamental force by which mass and energy curve spacetime, drawing bodies together.

• Newton’s description: attractive force proportional to product of masses, inverse square of distance
• Einstein’s description: geometry of spacetime shaped by mass-energy distribution — see relativity
• weakest of the four fundamental forces yet dominates at cosmic scales — see cosmology
• predicts gravitational waves: ripples in spacetime from accelerating mass
• governs planetary orbits, tides, and large-scale structure of the universe
• gravitational field assigns a potential to every point in space — see field
• unifying gravity with quantum mechanics is the central unsolved problem in physics