The grandfather paradox is a thought experiment that considers the possible outcomes of time travel. Time enforces a strict sequence of cause and effect that could be disrupted by traveling back in time. The grandfather paradox considers what would happen if you were to travel back in time and disrupt your own birth. At first glance, this appears to be a paradox but this has several potential solutions as follows:
The most obvious solution to the grandfather paradox is that it would create a loop in time, also known as a causal loop, whereby time would no longer progress but rather would endlessly repeat. This is based on the following sequence of events.
Multiple Universe Theory
Multiple universe theory is the hypothesis that everything that can happen does happen such that each possible variation spawns a different universe. Using this as an assumption, time travel simply creates a different universe and time continues in both. This would be nothing special as every decision or random event in life also creates new universes according to this hypothesis.
The Novikov principle is the theory that probabilities bend to prevent paradoxes. This would prevent you from doing anything that would disrupt your own birth. This could include zero probabilities of you meeting your grandfather such as a high probability of accidents in a time where you don't belong. For example, you might meet with a quick accident in the past that prevents you from disrupting cause and effect.