Time travel is a fascinating subject that is, unfortunately, dominated by silly ideas about grandfather paradoxes and black holes. We can blame the movies and science fiction TV shows for many of these ridiculous ideas but not all of them. Good science is also responsible for nonsense (like the mislabled “Fermi Paradox”, which isn’t a paradox at all and – when you look at it skeptically – is a rather naive and stupid question).
Time travel is one of those concepts that intrigues scientists so much they keep trying to figure out if it’s possible. In theory time travel is perfectly possible because the math says so. But the math is rather simple compared to the reality. We’re missing something and we already know enough to understand (as a civilization) that popular attempts to explain time travel overlook critical information.
People Have Been Searching for Time Travelers – Bad Idea
A recent story on Forbes highlighted a ridiculous search for time travelers on the Internet. Time travelers are not obligated to reveal themselves and there is no reason to assume that anyone who succeeds in traveling through time would want to reveal themselves in a childish way, such as showing up at a party that is only announced after the fact (the Steven Hawking Strategy) or declaring themselves openly in forum discussions (the John Titor Strategy).
What the effects of unmasking a real time traveler would be is anyone’s guess at this stage in our collective knowledge and experience. Maybe it’s happened thousands of times already. One of the best explanations I’ve seen for why people cannot change the past is found in the “Avengers: Endgame” movie. Professor Hulk explains that if you go into the past and change something you are changing your future because you’re experiencing it first-hand. You can’t really get into the past – you can just get into a different state of the universe.
So don’t look for people changing history. Based on what we know about the universe today, time travelers would be normal, natural participants in history and their actions would appear to be as immutable as anything else non-time travelers can do. In other words, we have no real reason to speculate that an infinite number of universes are spinning off into multiple temporal directions every time one of us (and that would have to include any plant or microbe) faces a choice.
But there is another reason why searching for time travelers is a bad idea. You might not like what you find. You might not recognize it for a time traveler.
Time Travel Isn’t Just about “Moving Through Time”
A few years back someone asked if time travel is possible on Quora. Many people provided thoughtful answers. The one that caught my attention is no longer available. At least, I can’t find it any more. But I remember what a High School Physics teacher wrote very clearly: “You’d have to rearrange all the molecules of the universe.”
This is a very mechanical perspective of time and space. It’s consistent with everything we know to be a fact and all our generally accepted theories about time and space. Einstein talked extensively about coordinate systems and when you move a point (or an object – which is a set of points bound together by some rules) through a coordinate system you create a succession of “states”.
Each state represents all the known points on the coordinate system at the shortest timeframe possible. Every time a molecule or a part of a molecule changes anything about itself anywhere in the universe a new state is created.
The entire universe is in constant motion on both atomic and superscalar levels. The most obvious universal motion is the movement of bodies through space.
- The Earth is spinning on its axis.
- The Earth is orbiting the Sun.
- The Sun is orbiting the Milky Way galaxy.
- The Milky Way is dancing around in the local cluster.
- The local cluster is dancing around inside a super cluster.
- The super cluster is part of a huge slowly twisting, vibrating filament.
If you travel back in time 1 day you won’t end up on Earth. If you’re lucky you’ll “land” on the Moon or some piece of space rock. More likely you’ll just appear somewhere in empty space, struggle to breathe briefly, and die a horrible death.
If you go back a few hundred years you might land on Neptune, a moon of Jupiter, or maybe somewhere in the Oort cloud.
You would need a T.A.R.D.I.S. to do time travel properly. Doctor Who’s race of time traveling aliens – the Time Lords – are a billion years old. Humanity is, by comparison, at most about 400,000 years old. Time Lord math and science is a little more refined than ours. One thing they have worked out is a coordinate system for the universe. They have a point of origin.
According to our current knowledge and understanding of how the universe works, there is no point of origin. So we can’t travel through time the way the Time Lords do.
They also harness black holes inside their T.A.R.D.I.S. vessels, and it’s going to take us a while to figure out how to do that, too.
Why Does No One Ever Bring Up These Challenges?
People who write superhero or science fiction shows and movies must have a solution for time travel. When Gene Roddenberry’s Andromeda first aired I interviewed one of the writers for the show. Their High Guard and other star-faring spaceships traveled faster-than-light through “the Slipstream”. I hoped they were integrating some (new to me) scientific theory into their show’s physics.
Regrettably I was told that the Slipstream was completely made up so they could skip way past the part of history where the faster-than-light travel problem is solved.
The film and television industry – even books and comic books – must do it this way. Since we haven’t yet solved the problem of traveling faster than light (or “through time” in any direction but forward), we can’t break it down for the audience.
Everyone either must make up their own pseudoscience or they must assume that “it just happens somewhere (along the timeline)”.
And yet, knowing they must make up this stuff to begin with, writers introduce every imaginable time travel meme and trite idea they can find in order to make some character or imaginary species look smart. And these tried-and-true methods also create a seemingly endless series of plot devices.
The Stargate television universe may be the only set of TV shows that abuse time travel more than Star Trek. Of course Doctor Who and his handful of weak copycats are expected to wrangle with time paradoxes every week. TV time travelers laugh at the laughable ideas we pass off as paradoxes. Time can be rewritten, as the Doctor likes to say. He should know. He’s rebooted the universe once or twice in his career.
When movies and TV shows go galloping off across the temporal horizon no one ever asks why they won’t end up floating in space. Gravity is occasionally invoked as a sort of safeguard against ending up at the wrong destination. But gravity is typically used to either slow down the passage of local time or to create some sort of slingshot effect – with or without a wormhole.
Unfortunately if you’re standing on Earth and wearing only a Vortex Manipulator or sitting in a cool-looking late 19th century time machine, it’s doubtful you can manipulate the local gravity field. There won’t be any way to generate the gravitic field you need to depolarize the metrons or whatever.
Miniaturization and Jules Verne-inspired steampunk technology can only get you so far. There isn’t enough energy in steam or stored in a wrist device to move you 3 feet, let alone 300 years through time (and space).
A Universal Coordinate System Might Be Possible
All you need is a fixed point in space (and time). You don’t need to find “the center of the universe” or “where the universe began”.
You just need an anchor point, something around which you’ll always be able to relate what you can observe (by any possible measurement). This fixed point can be anywhere. Maybe it can be at any time. The problem for us is that we don’t know if it’s possible for us to identify such an anchor point. It would be a point of origin on a special coordinate system. That coordinate system might look like a classical Cartesian plane but it doesn’t have to.
We may need to invent a whole new type of mathematics to find a suitable anchor point and build a coordinate system around that. Whether we need hundreds of millions of years (which, presumably, the Time Lords did) is still an open question. If mankind can hold on we think Earth will be habitable by our kind of life for another 500 million to 1 billion years. And if that’s not enough time for us to solve these questions maybe we can move out into space.
I wouldn’t recommend colonizing planets. As cool as that sounds based on bajillions of science fiction stories, we’ll probably be better off building mobile habitats in space. They won’t require nearly as much engineering know-how as terraforming planets like Mars and Venus would require. And moving from habitat to habitat would demand far less energy than lifting ships off of gravity wells like planets and landing things safely there.
If we can create a universal coordinate system then we’ll be able to solve a lot of presently unsolvable equations. Who knows? Maybe we could even find where the universe began, how large it is, or how far back and forward time extends. For now we’re only guessing and we question our guesswork every few years.
A universal coordinate system might even allow the kind of practical time travel that science fiction imagines. I don’t mean the Doctor Who T.A.R.D.I.S.-style of travel through time and space. I mean the Stargate: SG-1 style. In the very last episode of the show, “Unending”, SG-1 is trapped on a ship in space in a time dilation field. Yeah, that’s a whole ‘nother set of equations and laws of physics. But it sets up an interesting storyline.
SG-1 is faced with imminent destruction as an alien ship has fired upon them and they cannot get out of the way “in time”. So they slow down local time in a bubble around their ship to give themselves time to think about the problem. After 50 years they come up with a solution that allows them to reverse time inside the dilation field and then enact a new protocol that … well, they save the ship and they do it without help from the Doctor and Wesley Crusher.
One of the neat things about Stargate is that – except for all the exotic space aliens and faster than light travel and ray guns and a million other gizmos and plot devices – the writers tried to integrate the latest scientific ideas into their characters, technologies, and stuff. So when Samantha Carter or (Meredith) Rodney McKay started spouting off stuff about whatever, they were usually talking real sciency stuff. Well, it sounded sciency and cool.
Assuming we can devise a coordinate system for the universe we might be able to contrive a time travel technology that uses gravity wells. Perhaps only a sun-sized mass would be required (not a black hole as most theories suggest). Maybe it could be done with a planet.
As in “Unending” you’d only be able to go back as far as that gravity well exists. And then you’ll have to account for fluctuations in quantum states or something, but it might be possible to devise a theory that doesn’t contradict every known law of physics.
Bottom Line: Time Travel Isn’t Feasible Right Now
I doubt any Earth-bound, human civilization from the next few thousand years in the future will be able to achieve time travel as we imagine it without intervention. That intervention would have to come from the Great Wizards of the Galaxy, hypothetical space aliens who are so wise and experienced they have solved all these problems and decided that we are worthy of such knowledge.