**How does an escalator work?** *(Veritasium)*

On **October 23, 2018, in Rome**, thousands of football fans rushed to the stadium. The excitement built as they cheered and chanted. By **19:03**, about **50 people** were descending via the escalator, but within **half a minute**, the crowd doubled. At first, everything seemed fine—but something was wrong with the escalator. The combined weight of passengers overwhelmed the steps and overloaded the main motor. The downward motion slowed due to the motor’s opposing torque, but the load kept rising, causing the steps to speed up. Within another minute, the crowd had tripled. The motor failed, and under extreme pressure, it began slipping. The escalator triggered its second safety line: the motor cut power, and a brake locked the flywheel—supposedly halting the steps. But friction wasn’t enough to stop the motor’s rotation, and the steps kept accelerating. When control over the steps was lost entirely, hope rested on the final safety line: in emergencies, a backup brake should directly lock the drive shaft. Normally, all three systems failing simultaneously was unlikely—but that day, conditions were far from normal. At **19:05**, the third safety system failed, and the steps **plunged violently**, dragging terrified fans down. Some tried to leap over the railing; others were crushed in the crowd. The steps **collapsed**, shattering into jagged metal fragments.