There once were two physicist PhD's... ...William and Sergio, who met while they were having matching piers built for their homes at a new lakeshore development. They discovered their shared profession over beers, and each found out the other had been privately working on time travel research. They formed an immediate friendship that quickly resulted in them collaborating on their work. Over the decades they struggled with the problems of time travel until one day they figured out how to manipulate time, and were able to build a functioning time machine! They debated on what point in history or the future to travel to first, and finally decided on traveling back to the day they first met. Their time machine would only fit one traveler, so they drew straws to figure out who would go first. William drew the winning straw, climbed into the machine, and waved goodbye to Sergio, telling him he'd see him again in the past. Soon after, the machine vanished. Tragically, when it rematerialized it crushed Sergio on its arrival, killing him instantly. With Sergio dead, he and William would never get to collaborate on their work, or complete their research, and their time machine would never have been imagined. That being the case, Sergio would never have had a time machine land on him, killing him in the past, thus preventing the machine from being built in the future. This all has resulted in a situation best described as a "Pair of doc's pair of docks paradox"