Physics Uncovered on Instagram: "In 1969, engineers did something almost unthinkable. They diverted the American side of Niagara Falls, cutting off water that had been flowing nonstop for nearly 12,000 years. Massive cofferdams rerouted the Niagara River, leaving the riverbed completely dry for the first time since the Ice Age. What emerged felt like a time capsule. Bare rock that had never seen open air was suddenly exposed. People walked across the empty riverbed, picking through coins thrown