Picture A Packed Stadium Of Fans In Extreme Weather, All Clad In Their Favorite Jerseys, Cheering And Cursing At Their Favorite American Football Team Or European Soccer Club. Or A Crush Of Screaming Fans, Singing And Dancing In Unison At A Taylor Swift Or K-pop Concert. Or A Sea Of Costumed “Star Wars” Fans, Lightsabers Aloft, Filling Up Movie Theaters On Opening Night Of A New Movie.