The source text is a transcript from a TEDx talk by Luis von Ahn, the inventor of CAPTCHA, which details the evolution of his work from frustrating security checks to projects that harness human effort for massive tasks. Von Ahn first discusses CAPTCHA's purpose to distinguish humans from bots, then introduces reCAPTCHA, a system that transforms the wasted time of typing CAPTCHAs into valuable work: specifically, digitizing unreadable words from old books that optical character recognition (OCR) systems fail to recognize. This collaborative effort has involved over 750 million people, inspiring Von Ahn to ask what grand tasks could be accomplished by coordinating hundreds of millions of people online. This vision led to the creation of Duolingo, a platform designed to solve the twin problems of providing free language education and translating the entire web; users learn a new language for free while simultaneously translating real web content, providing an equitable business model where users pay with their time, not their money.