Grandfather Paradox
Let’s travel back in time
Have you ever wondered whether we could travel back in time? In the Special Relativity series, we learned that travelling close to the speed of light can, in a sense, allow you to travel into the future through time dilation. But what about travelling into the past?
One of the biggest challenges with backward time travel is the famous grandfather paradox.
Imagine you invent a time machine and travel back to a time when your grandfather was still a child. What if you killed him before he had children? Then one of your parents would never have been born, which means you would never have existed. But if you were never born, who went back in time to kill your grandfather?
This logical contradiction suggests that travelling into the past may not be as simple as science fiction often portrays.
One proposed solution is the Novikov self-consistency principle. It states that any event which would create a paradox has a probability of zero. In other words, if you already exist, then history must remain self-consistent. You may travel to the past, but you would never be able to kill your grandfather—or perform any action that would alter events in a way that creates a contradiction. Somehow, circumstances would always prevent the paradox from happening.
So… what happened, happened? That sounds a little boring.
Another fascinating idea comes from the many-worlds interpretation, often associated with the concept of parallel universes. Under this idea, travelling back in time would not send you into your own past, but into the past of a different branch of reality. You could kill your grandfather in that universe without affecting your own history, because the universe you left remains unchanged. Your grandfather would still be alive in your original timeline, while a different timeline would unfold from the moment you arrived.
So which explanation is correct? At the moment, no one knows. Both ideas remain theoretical, and we have no experimental evidence that travelling to the past is possible. But if it ever becomes reality, the universe may have already found a way to avoid its own paradoxes.
Perhaps history cannot be changed—only revisited.
Keywords
- Closed Loop: An automatic control system in which an operation, process, or mechanism is regulated by feedback.
- Parallel Universe: A parallel universe, also known as a parallel dimension, alternate universe, or alternate reality, is a hypothetical self-contained plane of existence, co-existing with one’s own. The sum of all potential parallel universes that constitute reality is often called a “multiverse”.
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