Just went to fact-check this, and it’s a true story: In 1720, the stock price of the South Sea Company in Britain skyrocketed. This company claimed to have a monopoly on South American trade, but in reality, it had almost no actual business operations. The entire nation went crazy buying South Sea stock, with the price soaring from £128 at the start of the year to £1,000 by July. Newton—the smartest person in the world—got involved too. At first, he was cautious and sold all his shares after the price doubled, making a profit of £7,000. But when he saw the price continuing to surge, he couldn’t resist jumping back in and bought more near the peak. Then the bubble burst. The South Sea stock price crashed back to its original level, and Newton lost £20,000—equivalent to about £3 million today. He painfully lamented: 'I can calculate the motion of heavenly bodies, but not the madness of people.'