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.
—
2020
2005
2019
2013
2012
2015
1990
2004
1962
1933
2018
2025
1999
2016