Thirty people can trigger a stadium wave

Professional cheerleaders and sports fans have long used the stadium wave to signal collective energy, but the phenomenon follows the same mathematical rules as forest fires and heart tissue. Physicists at the Hungarian Academy of Sciences analyzed video recordings of waves in stadiums holding more than 50,000 people to understand how these ripples sustain themselves. They discovered that a wave only requires a critical mass of 25 to 35 people to stand up simultaneously to trigger a chain reaction that can sweep through an entire arena.