Don't feel too bad. It happens a lot. I was listening to NPR coming to work the other day to a story about Alberto Santos-Dumont. He was the first person to fly a powered heavier-than-air craft. It seems the Wright Brothers used a catapult to launch. His aircraft, flown 3 years later, had enough torque to launch itself. Nicolaus August Otto, Gottlieb Daimler, Karl Benz, John W. Lambert, and the Duryea Brothers all invented automobile engines, motor driven cycles or vehicles within about 10 years of each other. It is very doubtful the had any detailed knowledge of each others plans or designs. There is a phrase , "An Idea who's time has come". This seems to literally be the case. Sometimes an idea will pop into everyone's head at once.