The Time Travel Grandfather Paradox Myth Just Got Busted
Bend your ear to a familiar, even derivative sci-fi tale: a guy goes into the past and messes with the timeline, thereby potentially erasing his future self from existence. Perhaps he meets his own grandfather, or he meets his own grandmother and sires his future self (that's why he looks so much like grandpa!). Or, if you're Back to the Future, he does all this while also being attracted to his own mom. And let's not even get into the whole Terminator timeline. Sheesh.
Of course, barring notions of the multiverse, and other such unverifiable spinoffs where your past actions create branching alternate realities suitable for Star Trek episodes, there's simply no way to test whether time paradoxes actually, or could actually, exist. After all, no one has successfully traveled into the past... that we know of. But actually, there is one way to discuss and describe all this temporal stuff, and it involves many people's least favorite high school subject: math (or maths for our British and Australian readers).
It seems that a physics student from the University of Queensland in Australia has done just this. Yes, Germain Tobar (totally a sci-fi name) has found a way to "square the numbers" that had previously made the so-called grandfather paradox impossible, per Science Alert. Now, you too can travel through time, be your own grandfather, or be a Terminator who assassinates him, or be attracted to your mom along the way, and not mess up the future. Hurray!
The same future would occur, anyway
As the grandfather paradox states, it was once believed that paradoxes were impossible because you can't, say, travel to the past and murder your grandpa because you wouldn't exist to be able to travel into the past to murder him. This is true if we believe that time abides by the rules of a deterministic system, which lets us know the end state of a physical phenomenon if we know the beginning state, or vice-versa, as Space outlines. In other words: see that broken egg? You can determine, because time is deterministic, that it was once whole. Cool.
Einstein's Theory of Relativity, however, as Space explains, tells us that space and time are essentially one phenomenon. Depending on the speed of a traveler and the distance to an object, events can occur both before or after their antecedents or resultant effects.
Tobar, then, set out to demonstrate, mathematically, that this is the case. As the University of Queensland website says, Tobar calculated that if the past is changed, then "salient events would just recalibrate around you," meaning that occurrences would fall into place that would result in the same future, anyway. This is good news for believers in free will, in a way, even though it means that the ends of free will are indeed predetermined from the perspective of the future.
So basically, feel free to murder your grandpa in the past, because it looks like you'll be someone else's grandkid, anyway.