A Time Machine - Prisoners of TIME
Time travel is undoubtedly one of mankind's favourite fantasies, at some point in our lives many of us have thought: what if it was possible to build a real-time machine to the past? Well, eventually this time machine will be the most important tool in the history of the world. It's tempting to think that the reality of time travel will only apply in fiction, however, many scientists think it's possible to have one and they have set out to accomplish a mission to build the world's first time machine.
Thinking about time machines, you may notice that playing with history is easy to imagine, but you should understand that in reality, even the abstract or general idea of TIME might be difficult to grasp, so let us approach it slowly and calmly.
Ronald L. Mallett an American theoretical physicist, academic, and author, one of the scientists trying to figure out this puzzle, argues that with present-day technology it is at least possible to send subatomic particles into the past, and he has published a paper describing the principles: Weak gravitational field of the electromagnetic radiation in a ring laser
The Fourth Dimension
To understand why we think time travel is possible, one should know that we treat time as the fourth dimension, and really understanding the dimensions of time may allow us to move through time just the way we move through space. [Imagine] that you have to get to work, for this event to happen anywhere in the universe you will need information describing four dimensions, three of space: Length, Breadth, Height (just in case your office building is a skyscraper), and one of TIME, this is why we say every event happens in Spacetime.
Suppose that you can observe the experience of a two-dimensional organism, i.e they cannot perceive the 3rd dimension: height. What would it experience if you put your 3-dimensional finger in its 2-dimensional world? It would see that a line (the width of your finger) just appeared from nowhere. If you then decide to take away your finger; to the organism, the line would appear to have vanished! It just experienced something appear and disappear in its world! And that may look like magic but on a fundamental level something very simple is going on. In just the same way, we humans experiencing the 3rd dimension will experience a 4th-dimensional traveller do weird things too, like vanishing to reappear in another time.
If you take the world of that 2-dimensional organism (let's say it is a bacterium living on a flat paper) then fold it by half making two ends meet, you will have the ability to penetrate both surfaces at once with your finger; doing this the organism will not experience lines appearing and disappearing one after the other, it will experience two lines appear and disappear at the same time! To this naive bacterium, the same object has appeared in two places at once. This explains that time travel - which is the same as travelling in the 4th dimension - allows you to be in two places at once. So if you could travel back in time, you could be the one who told yourself to come to work by 8 am.
So we can now change our perspective about travelling in general, all we need to do is travel through extra dimensions, and because it seems like we would always be prisoners, experiencing life in only 4 dimensions (3 of space and 1 of time) some scientists think it is impossible.
Time Dilation
Thanks to Einstein's predictions we now know that time travel to the future is actually very possible, yes, all you need to do is travel really fast for as long as possible. Most people think that time passes at a steady rate, and why not? It is perfectly natural that some people even imagine a grand universal clock that tells time for every race in the universe forever and ever, but in fact, that's impossible! Time flows at different rates (speed) in different places and frames of reference, it is affected by motion just like space is. There are places in the universe where time slows down, and if you were to visit them you will actually get older less quickly compared to the rest of us.
Light
If we both wear a watch there are certain things I could do to make mine tick slower than yours, that's time travel into the future. To understand how this works; [imagine] you are in a stationary spaceship. You can see your speed meter and clock in front of you, and there is also a red switch to your ship's powerful headlamps. If you turn on the headlamps, the light coming from them will move out at a speed of 670 million miles per hour.
Still, in your spaceship, you can see your friend from the window in his own spaceship smiling back at you. If he decides to travel before you turn on your lamps, moving very fast (say... half the speed of light), when you turn on your lamps you may think that he will experience the motion of the light coming from your ship moving at a slower rate (after all he is moving half that speed and in the same direction), but you would be dead wrong! He will experience the light travel at its full speed! His speed through space makes absolutely no difference. This statement made by Einstein that the speed of light is the same for everyone is one of the strangest in physics but it's true, the speed of light is the same for everyone no matter how fast you are moving towards it or away from it.
So even if your friend in his spaceship decides to turn around he will see the speed of light unchanged. Then what's happening? Because if the speed of light is not changing then something must be changing, and that something is time! This is the famous theory of relativity and it stresses without apology that there is no one true time. So if your friend is travelling really fast, time slows down, and the faster he travels it slows down even more, what might be an hour for your friend may be a hundred years for you, he would, in fact, be travelling a hundred years into the future.
A satellite orbiting the earth at just 20 miles per hour will be about 2 seconds late at the end of the year, and the clocks up there are wired to reconcile this time dilation caused by the speed of motion.
But what about The Past??
As you are about to see, travelling to the past is a more complicated process. Thinking about time travel into the past we are faced with a paradox. Think about this, if you travel back to your grandfather's time when he was a boy and killed him by mistake, then he doesn't grow up to get married and have your father, you don't get born. Now the problem is that if you don't get born then who is it that goes back in time to kill your father? You have to deeply think about this because it did happen, you did kill him...right???
Does this paradox mean that time travel into the past must be impossible? There is nothing to stop a time traveller from taking part in history as long as the results of those actions agree with what we know to have happened. That is, what if the fact that you went to see your grandfather in the past set a course of events that will inevitably lead him to meet your grandmother? You could in effect have played a role in the past. So it may be possible to help history happen but it seems to be impossible to change it.
If we can't change the past, then you cant kill your grandfather even if you really wanted to, things or events will stop you from doing that, it follows that we may not have free will and everything is predestined. The time traveller can travel to the future and then come back with the knowledge of our fate. It would mean that our lives are as certain as history.
Back to Physics
So what does physics have to say about this?
Professor David Elieser Deutsch FRS is an Israeli-born British physicist at the University of Oxford
In his Parallel Universe theory asserts that: With our present universe there are infinite numbers of parallel universes, some of them are very similar to our own with a difference of only about one atom, and others are very different, for instance, universes where I could be the one reading this article being written by you. This odd way of talking about the universe comes from the study of subatomic particles which when put in a computer to simulate how they work show really mind-boggling results.
If you study quantum mechanics you will notice really strange things. For example, in our everyday life we are used to objects retaining their nature as they stay stationary or move - you expect your laptop to still be a laptop until you finish reading every line in this article. But on the quantum scale you can't expect that result, if you and your laptop are subatomic particles your laptop could all of a sudden become a dog or a cat and it would be totally normal to you because it happens all the time, instead of following physical laws and stay on the table, your laptop could just sink right through. That's the thing about the quantum world, Uncertainty Rules!
Professor David’s answer to this is almost as strange as the question. He says that the universe we see is only one part of physical reality, there are parallel universes and each particle in our universe has counterparts in many other universes and under some conditions, these counterparts affect the particles that we can see. The universes are interfering with each other one the quantum level all the time. So sometimes these particles interact with other particles in other universes in which different sets of events play out.
So how does this help us Understand Time-travel better?
If time travel is possible then we could use quantum theory to predict what will happen if you go back to the past and decide to change something. You will be going into the past of another universe parallel to our own. You will now have the ability to do whatever you want, nothing that you do there can affect the universe from which you came from, it will only affect the universe you are in.
So if there is only one universe, something must stop you from killing your grandfather, but if there is a multiverse then you can kill that man like an animal without facing any paradoxical problems or some kind of… Universal glitch. But this implies that time travel involves, skipping from universe to universe, to universe.
The Black Hole Traveller
Turns out Einstein's theory of relativity has a major role to play on time travel. The theory predicts that nothing can move faster than the speed of light. The closer anything gets to the speed of light the slower time passes for it, and if it ever reached the speed of light, time would stop for it. But nothing with mass can even reach the speed of light.
So to travel through time we must find a way to travel faster than light without breaking the laws of physics. What you need to do this is a rotating black hole. A black hole is a collapsed dead star, its core is unbelievably massive and dense; not allowing even light to escape. If the black-hole is spinning something interesting begins to happen to the space and time around it, it drives the fabrics of spacetime itself, round and round and round. To understand what will happen just put yourself in the scene, [imagine] you managed to stay alive in the singularity of a spinning black hole, you will [notice] its gravity is so strong, even the space around it gives in and gets dragged around like a spoon staring a cup of coffee.
General relativity predicts that if you enter this spinning pool of spacetime, you will also be dragged around and come out at a time earlier than you entered it, this phenomenon is called Frame dragging. When you are inside the spacetime pool, you will no longer move through space, instead, space will drag you along with it, you may feel like you are actually in a spinning lake with strong currents moving you around with it. This allows you to break the light speed barrier without breaking the laws of physics. Inside the rotation, you can travel with the speed of light not breaking any laws but an outside observer will [see] that you are travelling close to the speed of light and when you appear to be moving faster than light speed the observer will watch you vanish from the picture.
Scientists are looking for ways to reproduce this effect in the lab, of course, we cannot go around creating black holes so we have to find another way of creating a spinning loop in spacetime. Digging through relativistic equations they discovered that Light itself is a good tool for creating the spacetime loop. It's actually a more effective tool if used properly. Currently, professor Ronald Mallett and his team of scientists are working on a solution. For me, any paradox you can think of that relates to this topic will only be resolved when we have created a time machine, and when you think about it, wouldn't it be fun to find out?
References
Discover Magazine - The Real Rules for Time Travellers
Vidyafrazier - What is the 5th dimension?
Space.com - Einstein's Wrapped View Space Confirmed
Thank you for this exciting read.
Post curated by @syedumair
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Amazing!
Thats for the consistent support
I stopped watching flash because of this time travelling simply by running fast theory because i thought it was bonkers and now you are telling me its possible again...the universe is just mysterious
You're absolutely right on that one buddy, the universe and life itself is a complete mystery. Despite all we know about the cell, genetic engineers still believe a large percentage of the cell is made of a strange unknown entity.
The same can be said of the universe, dark matter accounts for at least 80% of the known universe.
At the end, I think we're just like Jon Snow "We know nothing"
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Many thanks
I only need to travel back to 2009 :)
I'm intrigued by all the moves to explain time travel- quantum physics at its finest.
Now this got me thinking 🤔 why 2009?