A carbon filament glows for thirteen and a half hours straight at Menlo Park

For months, Thomas Edison's team at Menlo Park had burned through filament after filament, chasing a lamp that could outlast gas light. On October 21, 1879, a carbon-filament bulb sealed in a vacuum held steady for roughly thirteen and a half hours before it finally failed. It outlasted every earlier test, and Edison treated it as proof the design could work. Eleven days later, on November 4, 1879, he filed the patent application that would become U.S. Patent No. 223,898…