The King Harkinian Paradox
Sometimes time travelers end up preventing themselves from going back in time. To model this, we show you the paradox which this section is named. Say the king used a bowling ball to kill the guy who invented the bowling ball before he invented it. What did the king use? Then, how did the guy die? It's possible two timelines are made, so both events can happen, one where the guy dies, and one where he lives.
In 1898 (or 1893 due to time travel), H.G. Wells discovered a lightspeed material called cyagen, which he used to build a time-travel jetpack. At the right speed, he could back to the past or into the future. Later, a machine was invented that could help you travel into the 5th dimension (using cyagen), going into the past or future without moving in space. This machine became popular, but was illegalized in 1921 due to things going haywire. The Time Travel Police system was created to fix time travel errors.