Time Travel in the present day is far from the underground idea it used to be back when posed in 1895’s “Time Machine” by H.G Wells. The idea of a device, or devices, being able to manipulate the flow of time and specifically calibrate it to go to a specific point in the future or the past is something held dear by fans of science fiction, physicists, and Hot Tub Time Machine fans all around. Since 1895’s “Time Machine” and the explosion of Quantum Physics in the early 1900s to where we are now, it seems a guarantee that, physicist or not, we’ve all thought about traveling in time in some capacity. The only question now, it seems, is how do we do it?
For the most part, people see Time Travel as possible through the creation of some fantastical scientific device as shown in current mainstream media, like the phone box in Doctor Who. For the sake of simplicity, these films take these devices and just run through the stream of time for the sake of plot convenience, with little explanation to how these actually work. In the real world, however, a device like this is almost completely implausible. Physicists today consider Time Travel as a mathematical certainty. Traditionally, there are a few different ways that Time Travel is considered possible.
Option 1: Wormholes.
These tunnels through space are the result of a connection in space-time of one end of a Black Hole (which takes in the matter) and a White Hole (which spits it out). Ignoring the survivability of actually being able to enter a black hole and survive, these wormholes are a nearly perfect method for traveling in time, both to the future and to the past. Space-time, especially at points of high gravity, has a tendency to warp the flow of time around it. A fanTASTIC representation of this actually exists in mainstream media, by way of the film Interstellar (spoiler alert if you haven’t seen the movie). In the movie, by way of a wormhole, a crew of 4 humans ends up on the other side of the Universe in a new galaxy. Their mission is to find inhabitable worlds for the citizens of Earth on 12 different potential planets. The first planet they visit, however, is located right next to a Black Hole, which as previously mentioned, is able to bend and distort space-time to an extreme. Because of the proximity of the planet to the Black Hole, an hour on this new world is the same as seven years on Earth.
Although this may not fit the conventional definition of time travel, it fits under Quantum Mechanics and the theory of relativity. Even though the crew isn’t specifically deciding what points in time to travel to, and zipping throughout the Universe’s timeline, they would technically be traveling through time at a much faster rate than the people on Earth because of their differences in how they experience the flow of time.
In the real world, a common belief is that if you were to connect a wormhole between different points in Space-Time, somehow finding a way to bend Space-Time between these points, you should be able to travel both forwards and backward in time. This, however, maybe one of the most difficult and near-impossible ways to exploit the benefits of Time Travel.
To start, you would need a MASSIVE amount of energy to even create a rip in Space-Time, not so far off from the energy produced by a collapsing star. Ignoring that problem and making the assumption that our puny - can’t even harness our own planet’s full power - civilization could do that by some magical chance, you also have to account for the other end of the wormhole. Even if you were to make a massive rip at one point in space-time, there’s still the question of the other side and where/when you would be traveling to. In this case, you would have to make the assumption that there’s already a wormhole open at the exact point in space-time that you want to go. If your assumption is false, then you would need someone or something that is already in the future or past you want to travel to, to make an exit point in space-time there. Through ALL of that, you would also need to find some way to design a ship, or travel device that could withstand the gravity in this wormhole, because otherwise you would be killed by spaghettification (ripped to atoms) less than a moment after entering.
So…. wormholes are OUT unless you can find a way around all these things.
Option 2. “Faster Than Light” Travel
More often than Time Travel, faster than light travel is usually discussed in talks of deep space travel, comic books, and physicists' best and brightest dreams. With that, it is also the most plausible way to travel to the future, with relative ease.
If you’ve taken any sort of physics class, or even if you haven’t, the speed of light is widely known to be like the cosmic speed limit of the universe. Light is the fastest thing and nothing, with mass, can ever travel faster than it. So then why even bring up faster than light travel in the first place? Mainly because, although faster than light travel is the best-kept secret the universe has, near lightspeed travel is not impossible at all. In Einstein’s theories of relativity, one of the driving concepts is that how someone experiences the flow of time is relative to their speed. The closer you move to light speed, the closer time comes to being at a complete stop. With this, you could say that even being able to travel at 99.99% the speed of light would allow you to experience time at such a slowed rate that if you were to move that fast for 20 minutes, you may return to see your friends and family have aged a significant amount.
As promising and simple as it sounds, although you may not be moving at light speed, gathering the energy to move NEAR lightspeed is already pretty difficult as you have to take into consideration the mass of the object that you are trying to move. Moving near lightspeed is no problem for something like an individual particle, whose mass is small or negligible. However, for something as large as a ship or machine you have to consider how much more energy you would need to even move it in the first place. It’s already hard enough to move a ship fast enough to escape Earth’s gravity. Now imagine having to use thousands of times more force. Additionally, you would have to figure out how long you would need to move at lightspeed to get to your desired time in the future. In any case, though, that’s more than likely the easiest thing you would be able to do. Say that the energy and time dilation issues are fixed somehow. Moving at or near lightspeed is a MASSIVE amount of force, much more than any normal person could handle. So you would also have to have to find a way to reduce the amount of force on every passenger in addition to everything else. Safe to say that near lightspeed travel is definitely easier than wormhole time travel but even still, it is nowhere close to being right around the corner, or even as potentially accessible as space travel could be in the next 20 years. Keep in mind, lightspeed travel only works for traveling to the future, not the past. So you would have to come up with a whole other way to travel to the past.
Travel to the past?
So I’ve talked about ways to travel to the future. The concept of wormholes COULD stretch into the past, but as I mentioned, we’re definitely NOT there yet. A question asked by the late Stephen Hawking is really the best example of this. “The best evidence that we have that time travel is not possible, and will never be, is that we have not been invaded by hordes of tourists from the future.”
This quote holds a lot of weight because the question actually makes sense. Should advanced humans actually figure out Time Travel to the past, no matter what year or time period it’s discovered, current humanity would be like zoo animals to this sophisticated population (this is actually called the Fermi Paradox). With Time Travel to the past you also really have to consider paradoxes, the main one being the Grandfather Paradox. In this scenario, you go back in time and you kill your grandfather so he never meets your grandmother. Since your grandma never meets your grandpa, she never has kids and her kids never have you. But since you were never born, how could you be alive to go back in time in the first place?
Paradoxes aside, you really could only travel back in time in one way, which would use the aforementioned wormhole theory. The issue then is the same as mentioned in that section: you would need a wormhole open in the exact moment and place you would want to go at both ends (those being your starting and ending times.
Time Travel, I'm sure, will continue to be a staple of both mass media and sci-fi/fantasy alike. But with that, it is always fun to consider the fact that, although we may not be there yet, someday, far into the future, humans may advance to the point where time travel is just as easy as taking an Uber to your favorite coffee shop.
Cover Photo Courtesy of Business Insider (https://www.businessinsider.com/stephen-hawking-book-backward-time-travel-possibility-2018-11)
Comments