The Paradox Rule
The universe does a quick paradox check that only sees “obvious paradoxes” not crazy shit.
Normally a paradox is impossible. The universe will not let them happen You cannot murder your self or prevent any of your ancestors from mating. The gun won’t fire or the bullet will make an impossible bounce and has a impractically high probability of hitting the shooter (out of spite). Also any event that would not cause the non-Resistance of a TTer is not a paradox. You are sufficiently outside the normal STC that you will not disappear or anything else. But death is another story. Under “safe” TTT (time travel tech) you are still connected through the STC to your future or “real” self. When you return any changes that occurred while you were in the past would take place around you. Also you cannot become your own grandfather. Because your grandfather has already conceived your parent with his genes it is highly improbable (1 in billions) that your offspring with your grandmother would be identical. However, it is possible to indirectly cause your own death and thus null-existence. The key is an at least three-step-separation must exist from your action and the event that causes death. The universe does a quick paradox check upon any action of a TTer even down to the atomic level. Your younger self would not be harmed from chicken pox you brought back from the future, but if you gave chicken pox to a person in Europe in 2056, after the disease was eradicated, and the resulting outbreak caused your younger self to move to Australia where he was mugged in Sydney one night. The universe would not stop it. But if he would die of chicken pox the disease would not be able to communicate. In poor Dr. Alastor’s case his fiance eventually divorced him which caused him to become an alcoholic and be hit by a meteor at an AA meeting. (the universe is kind of a bitch).