If you’re one of the lucky viewers who took a chance on the Netflix original series Dark, you probably have a lot of questions. From “travelers” who wield omnipotent powers to parallel universes, we decided to tackle one of Dark’s most important plot devices: Time Travel.
So, here’s the question: Is it possible?
Well, of course it is. It is what makes the entire Universe possible. You yourself are a time traveller. You speed along at the remarkable rate of one second per second to stay synced up with reality.
Reality on a string
In a Twilight Zone episode called “In a Matter of Minutes” a couple awakens to the sound of construction and complain to each other about the neighbors. They suddenly see that the bedside clock reads 11:37 am.
“We’re late!” they think, but then the man looks at his watch and it’s just past 7 a.m. The clock must be wrong… They start to explore looking for other people.
Everywhere they turn they see nondescript blue construction workers building everything that they know already exists. What’s going on? They continue to search for others and stumble into white voids of nothingness. Finally they find a human in yellow who explains that his blue crew builds the present before time “arrives”.
The yellow fellow says they can’t be permitted to return to their own time because it might threaten reality. The couple evades capture, counting down the minutes until time “arrives”, and then they pop back into existence in the real world. Is this how time works?
Many theories
The foregoing is the mono-directional bead-on-a-string theory where time can be anywhere along the string, but only one place at a time. Everything “outside” of time is emptiness.
Next is the Back to the Future notion of time forks. This is where someone traveling to the past can spawn an entirely new future by altering events that have already happened. Once you do that, your future reality collapses and you can only go to your “new” future that resulted from the change.
This forks theory has two sub-theories. The self-correcting sub-theory says time “heals” itself after a change. You can see a good example of this in Isaac Asimov’s book The End of Eternity.
In another Twilight Zone episode, time travelers proposed killing Hitler as a baby. An operative dressed as the new “Nanny” the Hitler family was expecting arrived and stole the baby. Another person took a child from a poor woman living in the street with a newborn and replaced the stolen baby. The other child grew up to be the real Adolph Hitler.
We see again and again in fiction that you cannot go back and kill your parent as a child to prevent your own existence. Your gun won’t fire; you’ll lose your knife; the car you’re driving won’t start, or will pass right through the parent, leaving them unharmed. This seems unlikely as it all defies common physics and no mechanism could sustain such a theory.
The other sub-theory is creating a new reality, where you kill your intended victim, but it’s another version, not your ancestor. Genetically identical, this is the future parent of a different “you” and you’ve prevented that person, not yourself.
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Even more complex is the Multiverse theory where every single action causes a reality split so there are two variations of a Universe depending on whether you found a seat or stood on the bus today. But not just you—everyone who makes a decision creates a new Universe. Perhaps certain decisions tend to converge and resolve into a few basic universes that run in parallel but are stochastically different.
Even worse is the Infinite Universes theory where everything from all human decisions, all the way down to which way an atom randomly moved, creates branches. Each event no matter how small spawns more universes. Maybe there are millions of tiny universe bubble-realities made by a wave washing up on a beach and moving a million grains of sand, but the bubble universes are so similar that they just collapse back into our reality after a picosecond or two.
It makes some sense when compared to a waterfall. It may throw up a trillion molecules of water per second as mist and droplets but the bulk of them settle back down and rejoin the river instead of making a trillion new little rivers. Maybe time coheres in a similar fashion.
To paraphrase the author Mark Twain (Samuel Clemens), “Time is Nature’s way of keeping everything from happening all at once”… Albert Einstein, on the other hand, said “Time and space are not conditions of existence; time and space are a model for thinking.”
Whichever you choose to believe, there is no restriction in the laws of physics that prevent time travel. Some physicists have proposed that time is like a sine wave where its direction is forward above the line and backward below the line. This does not necessarily mean time is constantly going forward and reversing, leaving us in an infinite loop. Instead it implies that just by changing the mathematical sign to negative you would experience the broken egg on the floor reassembling itself and then rising up to you hand, and that would appear normal to your experiential plane. Effect would precede cause until “time” crossed the line again and became positive.
Whichever you choose to believe, there is no restriction in the laws of physics that prevent time travel. Some physicists have proposed that time is like a sine wave where its direction is forward above the line and backward below the line. This does not necessarily mean time is constantly going forward and reversing, leaving us in an infinite loop.
Instead it implies that just by changing the mathematical sign to negative you would experience the broken egg on the floor reassembling itself and then rising up to you hand, and that would appear normal to your experiential plane. Effect would precede cause until “time” crossed the line again and became positive.
We speak of “cause and effect” but while time was running “backwards” it would be “effect and cause”. However, since we’re running backwards too, we wouldn’t notice it.
If we had enough energy available, and it wouldn’t be trivial—perhaps the output of a whole star—we could probably travel through time. Physicists have examined the possibilities, and pushed the laws of physics to their breaking point, which is how we determine that a line of research is no longer profitable.
The funny thing is that the laws don’t fail when looking at time travel. There is no indication that anything would forbid it. Flipping that positive sign to a negative sign would just take more energy than we have available, and the development of a technology that would allow us to do so. This may be why show runners for Dark chose a Nuclear Reactor as a catalyst for the event that opened the time travel portal – though that is likely still far from enough energy.
We quite likely will not have the capability to use a star like a battery any time soon. That will take millennia of technical advancement. And if time travel is that costly, using the energy of a whole star to open a gateway, it explains the lack of researchers from the year 22,022 with futuristic clipboards wandering around and taking notes about the early 21st century…
The takeaway
Time travel is possible, according to the laws of physics. However, we lack the technology and capability to manipulate it significantly at this point in our history. The consequences of such a manipulation are still complete unknowns, and we’re unlikely to experience it in our lifetimes (Darn it!).
Of course we can manipulate it in another way…by traveling very fast, at a significant portion of the speed of light (SOL). That would zip us into the future. It’s a one-way trip though, and it could be quite far depending on your speed. For example, at 85% of SOL, 2.67 years would pass on board your ship as it travelled to the nearest star from our Sun. From an Earthbound frame of reference it would still appear to take just over 5 years. At 95% of SOL, the time dilation effect would make it 1.4 years. At 99.9% of c, the four year trip would be experienced in just 70 days. At that speed, if you turned around and came straight back to Earth, 140 days would have passed for you, but 9 years would have passed back at home. Congratulations, you just “time-travelled”, but that’s a story for another time…
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