It is called the Time Traveler's Paradox. In which a scientist creates a Time Machine and kills their younger self. So now a man who should not- can not- exist, somehow does. That is the Paradox, and Paradoxes are impossible.
2014
2016
2013
1934
1916
2012
1922
2007
2015
2005
2024
2019
2017
1925
1924