Massive objects warp the grid of spacetime like a heavy bowling ball on a trampoline. This curvature dictates how other objects move, which we experience as gravity's pull.

This phenomenon is called gravitational time dilation. Because immense mass severely warps spacetime, a clock near a black hole literally ticks slower than one farther away.

Massive galaxy clusters bend light from objects behind them, acting as magnifying glasses. This lets telescopes observe ultra-faint galaxies that are normally hidden from view.

Satellites orbit far from Earth's mass, making their clocks tick slightly faster than receivers on the ground. Without correcting for this time dilation, GPS would quickly fail.