DEFINITION of 'Purchasing Power Parity-PPP'. An economic theory that estimates the amount of adjustment needed on the exchange rate between countries in order for the exchange to be equivalent to each currency's purchasing power.
Thomas Edison's most famous invention, the lightbulb, paved the way for modern life.
Thomas Edison was born in 1847 in Milan, Ohio. Like Ben Franklin, he was both a scientist and an inventor. In fact, Edison patented 1,093 inventions in his lifetime including the kinetoscope, the phonograph, and his most famous - the incandescent light bulb. The Menlo Laboratory in Newark, New Jersey, was to become the first research and development lab in the world. Edison called this lab his invention factory.. In 1879, after 1,200 experiments, Edison made a light bulb using carbonized filaments from cotton that burned for two days.