Practice

Finding your next step…

Sources and credits

Public-domain texts quoted in the lessons (Heath's Archimedes, Vitruvius, Woodcroft's Hero, Richter's Leonardo, Galileo, Newton, Franklin, Volta, Faraday, Tesla's My Inventions), from the Internet Archive and Wikisource: the short passages in the inventors' own words, each with its source on the page (public domain)
Grokipedia articles on each inventor: background reading linked from each lesson; our lessons, pictures and problems are our own
Library of Congress (Morse, Bell and Wright papers) and the Thomas A. Edison Papers, Rutgers University: the dates and words of the first telegraph message, the first telephone sentence, the 1903 telegram and Edison's letter
Open Library and WorldCat: where to borrow Hawking's and Sagan's books, which are still under copyright; our reading guides are our own words

Every source and licence the site uses is on the Credits page.