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
2021
1937
1974
1954
2022
2020
1933
2018
2016
1961
1949
2017
2007