I myself believe that there will one day be time travel because when we find that something isn’t forbidden by the over-arching laws of physics we usually eventually find a technological way of doing it.
When I was 10 years old I first watched the 1960 film adaptation of H.G. Wells’ novel,The Time Machine. I instantly fell in love with it. The whole concept of traveling through time was fascinating to me, even at a young age. I loved dinosaurs and it would be great to be able to go back and really see them. As I grew older I became more interested in the physics and logistics of time travel. Books like Stephen Hawking‘s “A Brief History of Time” fascinated me with the concepts of time and how it flows with, and independent of, the universe. It seemed the scientific world was just as interested in time travel as fans of science fiction like myself.
To understand time travel, we first have to understand the concept of time. Which isn’t as easy as you may think. A question as simple as “What time is it?”, can lead to mountains of hypothesis and theory. One of the first and most famous modern physicists to study time was Albert Einstein. His work was the culmination of decades of research by other prominent physicists around the world, including Albert Michelson, Hendrik Lorentz, and Henri Poincaré
They dealt with a various hypothesis and theory that would later culminate in the accepted theory known as “special relativity”, put forth by Einstein. It basically laid out that time was a relative and not absolute concept. Also that time and space where not two separate entities. It meant that time was not a set thing and could very much be warped or controlled by physical actions in the universe. The key in all this, as far as time travel is concerned, is speed. The faster an object moves through space, the slower time moves around it. A simple experiment has proven this many times over. The problem is that it requires a tremendous amount of speed to have any noticeable effects. If you flew around the world in the fastest jet available, you would only be a few milliseconds younger than everyone else. Hardly worth the jet fuel.
If we begin approaching the speed of light however, the changes on time become much more apparent. If you traveled in space at light speed, or fairly close to it, for a year, with no ability to control time dilation, you would return to Earth to find around 20 years had passed. You have basically traveled into the future. The problem with this is that it takes a tremendous amount of energy to move an object of “X” mass to light speed. In laboratories, scientists can accelerate particles to 99.99% the speed of light. They still haven’t found a way to achieve enough energy to conquer that last .01%. To sustain an object at light speed would take an energy source we have yet to discover. We can’t all have a flux capacitor. Until we discover our own dilithium crystals, light speed or faster than light speed travel is on the back burner.
But there is another, albeit dangerous, way out of this. Part of traveling at this speed is the affect gravity has on the space around you. At greater speeds it basically seems to compress time around you. So, maybe more gravity is what we need. Just to make up for that last little bit of speed. When you think “intense gravity” in the universe, one thing comes to mind– black holes. A super-massive black hole may provide the gravity boost we need to slow down time that last little bit. Orbiting a super-massive black hole at speeds near the speed of light should give us close to the same affect as traveling at light speed. The problem, of course,would be orbiting the black hole. But right now, that seems more feasible than light speed travel.
All these instances deal with traveling forward in time. I know what you’re thinking, “Will I have a chance to do the nasty in the past-y”? The short answer is no. Traveling backwards in time seems pretty much impossible, and I hate using that word. As Stephen Hawking pointed out though, there seems to be a number of ” natural barriers” to traveling back in time. Almost as if the universe doesn’t want travel into the past. Any number of paradoxes that could arise from travel into the past seem to prevent any meaningful progress in that field.
Like this one. Say a guy invents a time machine that can travel back in time. He travels through the portal to the moment before he created the time machine and kills himself. How was that even possible? If the time machine was never built, how can he go back and kill himself? Or what if he killed his grandfather? Same thing. If your friend built a time machine and went back and killed your grandfather, how could you have been there to see him go through the machine? If the time machine never existed how could any of that have happened? If time were a constant flow in one direction with no changes, he could have never built the time machine. Maybe people have traveled back in time and somehow completely erased themselves from existence. No one would have a memory of it ever happening, even if they witnessed it, because it never really did happen. One proposed solution to this is that there are multiple timelines and universes. If you kill yoru grandfather you won’t cease to exist. Your alternate you in that dimension will never exist. You are fine and free o return to your dimension where you still exist,if you know how.
But let’s back up a bit and talk about the forces involved in this “time machine”. What is the time machine exactly? When you travel back in time, what are you doing? Are you moving through time and space or outside of it? Let’s say that what you have done is basically tear a hole in space and time. Not out of the question since that is basically what black holes and wormholes are. Tears in space. How are you able to determine where and when that tear will manifest on the other side? Many movies and books on time travel simply involve some sort of computer that you input a date into. Easy peesey. But what is that computer doing? What forces is it controlling? Is it reading time and changing it on the fly? If so, how exactly would one do that? Not like checking a watch to say the least. Atomic clocks on Earth are timed by a certain particle that gives off a tick every second without fail. The clock reads the tick and moves forward one second.
What if there were particles that affected time. What if time itself was stored and made possible by these particles? Science fiction calls them chronotons. Particles that can be read by computers to know exactly what time and place they are in. This could be the key to making a time machine. But, I cannot stress enough that they do not exist. Without them backwards time travel is a crap shoot. Even if you developed a machine to open a door to the past, you have no idea exactly where until you step through. Some science fiction authors, Like Ray Bradbury in A Sound of Thunder, went with this theory. You can’t KNOW where you’re going til you get there. Then you can theoretically calibrate a machine to open to that point. It also introduced the idea of the “butterfly effect” to the general audience. A small change in the past could greatly change the future. A takeoff of the earlier paradoxes we discussed.
So what are we dealing with here? Trips into the future with no way back and fictional particles that control time. We’re not doing great so far. Another theorized problem with time travel to the past is that the machine would probably create a time loop at the moment it was invented. It’s the stated reason why no one in the future who may have invented time travel has ever come back. They simply can’t. Again, the laws of the universe are working against them. Nature does not take kindly to paradoxes. Every theory seems to end at the realization that time seems to be aware of itself and does not like to be trifled with. The math simply falls apart.
I still have hope though. I like to think nothing is impossible, but the laws of the universe seem to contradict that regarding real time travel. Whether it’s grandfather paradoxes or loops in time, nature obviously doesn’t want us traveling in time. But we know it’s possible to manipulate time. We’ve done it already. Who’s to say we don’t finally overcome that last hurdle? Still, the time loop theory seems solid. If you go by the theory that time is constantly flowing and everything that ever will happen has already happened, and someone invented a time machine, where are they? Either it will never be invented or we physically can’t travel back past a certain date, time machine or not. Kinda sad to think about. Everyone wants to see the future but the past always seem more interesting. Where did we come from? How did society come to be? Questions we will never have an eyewitness to I guess.
Well, hope you enjoyed this post. For more on the science and physics of time travel I recommend Stephen Hawking’s ” A Brief History of Time”. The most consumer friendly book on physics in existence.