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.
2001
1949
1944
2018
1960
1955
1951
1977
1913
2024
1934
1954
1964
1997
1948
1945
1936
2007
2020