Time? What is Time? Are our actions set in stone by fate or do we have free will?
Sounds deep? Let’s think of an example. What if a future person (Dr Brown) travels back in time to our present. In that case, things happening right now (in our present) have already happened to Dr Brown. So it begs the question, is Dr Brown always going to have the same series of events happen for him, or is he able to influence the course of events? In other words, are events predetermined or do we get to influence them through our free will? Maybe we do have free will, at least we hope…?
Is time travel even possible? Well, there are many theories. Many believe it's not possible, including Einstein and Stephen Hawking. To experiment, Hawking organised a party for time travellers, but he only released the invitations a day after the party. Nobody showed up (maybe someone did, and he didn’t tell us 🤐). He reasoned that time travel was not possible (for now) by stating, “that we have not been invaded by hordes of tourists from the future.”[1]
To try to solve the mystery of time travel, we ask, what are the requirements for going back in time? We ask about the past, because travelling into the future has already been done, although it was only 5 milliseconds into the future. It is theoretically possible to jump further forward due to relativistic effects, given the right technology which allows us to travel close to the speed of light.[2] This only allows us to ‘skip’ forward in time, but not ‘rewind’ to where we used to be in the past. The unsolved problem is of the past. Can you say hello to baby-you 👶 and what are the resulting paradoxes? According to leading theories we need faster-than-light travel to go back in time.[3] But that’s not possible! At least not in our boring 3-D world.
What if I told you that we don’t even know the speed of light? 😱 In Einstein’s paper “On Electrodynamics of Moving Bodies” (1905) speed of light is assumed to be constant. [4] However, there is a very good possibility that the speed of light is dependent on the direction it travels in: it could be C/2 in one direction and instantaneous in the other.🤯 But no one would notice because it still doesn’t break any current laws of physics. Derek Muller (Veritasium) sheds light with a simple astronaut-on-mars example in his video to explain this controversial idea. [5]
Going back to our question, let’s say we do figure out how to travel back in time. What would we do? Some would say to keep things as they were, to avoid changing the course of future events. If we accidentally change something, even if it is small, there would be repercussions in the future due to the butterfly effect. 🦋 This is when a small change can have a ripple effect. Events in the far future are affected at a prominent scale, resulting in a different timeline. This may lead to the grandfather paradox - what happens if you go back in time and kill your grandfather even before your parents existed? You wouldn’t be born and so your grandfather won’t be killed.⚰️ You will live! Right? See the issue? There are solutions to this problem. The biggest and the best solution is the multiverse theory. As Dr Brown explains in “Back to the Future” if we exist in a multiverse when you go back in time you alter not the timeline of your specific universe but of an alternate one. [6] You don’t affect the timeline you just left, but an alternate timeline or a branch in time is created. It’s a bit like copying and pasting your timeline and living in that. Your original timeline is still the same and this doesn’t allow for the grandfather paradox. 👴👵
People think of time as a river flowing in one direction, that time never bends. That may not be true. We affect time just by our presence. Without matter or energy, time is just a simple, very straight blanket. But when matter is present, it bends time, just like how gravity bends space-time. Without time we don’t exist either. This concept is explored in a sci-fi movie called “Lucy”, where she says, "Film a car speeding down a road. Speed up the image infinitely, and the car disappears. So what proof do we have of its existence? Time gives legitimacy to its existence. Time is the only true unit of measure. It gives proof of the existence of matter. Without time, we don't exist.”😳 [7]
Always flowing, time is the ultimate constant but it doesn’t mean it’s something we have no control over. Just by the mere presence of a human being, there are fluctuations in the timestream.⏳ A simple electron can do that too. We had one single start, the big bang or whatever happened, created every single particle that exists. That’s the beauty of the world because it shows we are born from the same thing. We all are connected at some level to each other and time is connected to us. Time as we know it doesn’t exist without us and neither do we without it. Another paradox, don’t you think? That’s the beauty of paradoxes and physics. 🤩
- Vedant