Time travel is already possible. In fact, at this very moment, each of us is a time traveler, a chrononaut following time’s arrow forward through the cosmos.
But that’s the trick, isn’t it?
We can go forward all we want, and one day, with the right technology, perhaps we’ll even be able to travel tens of thousands of years into the future, while from our perspective only a single year will have passed. Traveling backwards in time — now that’s where we run into trouble.
Time travel into the past may currently exist only in science fiction, but might we eventually unlock the gull-wing doors to our very own real time machines? Come with me, traveler. Let’s find out.
Here are five reasons why time travel may someday be a reality.
1. Closed Timelike Curves Might Exist
A closed timelike curve (CTC) is a path of an object through spacetime that ultimately ends where it began, at the exact same space and time coordinates. CTCs were discovered by Kurt Gödel as a result of general relativity and would, theoretically, allow for time travel into the past.
If they existed in the real world, could we somehow harness these closed timelike curves for human time travel? As unlikely as it is, wormholes or Kerr black holes may provide the answer. However, as CTCs enable time travel into the past, would-be time travelers could find themselves unwittingly creating paradoxes. Let’s take a quick detour to see what modern science has to say about that…
Quantum Time Travel and CTCs
This year, physicists at the University of Queensland in Australia published their research into simulating time-traveling photons and closed timelike curves, specifically the model proposed by physicist David Deutsch. This model, taking into account the probabilistic nature of quantum mechanics, would do away with certain paradoxes associated with time travel, at least on the quantum scale. Scientific American lays it out for us.
The University of Queensland researchers tested this model with a simulation and, according to Scientific American, “across multiple trials the team successfully demonstrated Deutsch’s self-consistency in action.” In the quantum realm, there appears to be no “grandfather paradox.”
While that’s all well and good regarding quantum mechanics, here in the macro world things are decidedly less probabilistic. Still, things like the Novikov self-consistency principle similarly do away with any potential temporal paradoxes.
2. Parallel Universes Make It Easy
But why worry about paradoxes at all? Time travel into the past may have more to do with traversing parallel universes than riding our own time streams.
If that were the case, there would never be a paradox; even if you traveled into the past to murder your own grandfather, if it were in another universe entirely, he wouldn’t really be your grandfather. He’d be the grandfather of another version of yourself. Nothing you did in the past of a parallel universe would ever affect your personal time line. Paradox solved!
Do parallel universes actually exist? That much is uncertain, but there are some intriguing clues. The existence of dark matter, as well, could point to nearby universes parallel to our own, “shadow worlds” right under our noses.
Now, how to go about actually traveling into those parallel universes – that’s a story for another day.
3. We’re Living Inside A Simulation
Nick Bostrom’s simulation hypothesis tells us that it’s possible we’re currently living inside a universal computer simulation. Frank Tipler suggests the same, hypothesizing that posthumans in the future will have such a hold on the laws of nature that they’ll be able to “resurrect” all living things within cosmic simulations.
If we were, at this moment, living inside a simulation, what would that mean for our true laws of nature? For example, I can easily reset the clock on my computer, or rewind events in certain video games (or jump through interdimensional portals, for that matter). Within a universal simulation, you’d imagine something like that would be more than possible, if you could find out how.
4. It’s Already Happened
Of course, all of this ignores the possibility that time travel has already occurred.
There could be evidence of time travel all around us, but we either don’t notice or disregard it all as nonsensical stories on the Internet.
What do you think of the above possibilities? And if you could travel through time, what would be your vehicle of choice?