General theory of Relativity interweaves “space” with “time”, and also states that energy (or matter) in a region of “Space-time” will curve that region.
All present fantasies about time travel spring from this plausibility that Relativity offers.
In fact, it’s mathematically provable that in a region of “space-time” where matter or energy is dense enough to curve “space-time” to a warp, or rather, a loop, u can travel from one point of time in the loop and reach where u began the journey.
This is just a mathematical possibility arising from some weird solutions.
WHAT IS “TIME” FOR US..?
At the minimum, time is a “feeling” of change occurring around us and within us, right? In which case, there is definitely a DIRECTION to time, as we experience it…sort of an “arrow” of time…
What is this arrow pointing to?
It points from past to present and into the future.
Is it just a subjective sense of direction.?
Time really has a direction, and that can be defined in three contexts:
The first one is the personal or psychological arrow of time where our memories are always about some events in the “past”. U can’t have memories about your future..!
The second is the “thermodynamic” arrow where things including animal bodies go from an ordered state to a disordered state. This arrow is applicable not just for ur mind, but to every thing around u, including inanimate objects. they all go from “formation” to disintegration”, not the reverse..!
The third is the arrow of “causality”, the strongest of all three. Its simple: every event is preceded by a cause. The cause never comes after an event. So we see that “TIME” does have a direction and is therefore “different” from Space, though relativity boasts to have made them indistinguishable..!
Now Consider this:
What is it exactly we are speaking about when we discuss time-travel?
Which time are u planning to travel..? Wondering what that means..? Well, suppose I am sitting here in front of the computer on the chair at 11.00 pm ISTand suddenly start travelling back in time to 5.00 pm IST(just forget about start-trek time-machines and all that for a moment and assume that it happens just as it is!).
What starts happening to me as i travel back in time ?
Every inch of my body and my surroundings has to change if I really am passing back thru time. The typing on the computer reverses backwards,my thought processes during the typing gets reversed back to the start, the computer gets switched off, the fan and the lights get turned off, the chair is pushed back, I walk back downstairs to my study room, I vomit back my tea into the cup on the study table,mom takes away the cup, mom brings me my evening tea and so on…Everything, around me, within me, including the sun, the stars the tea in the cup and even my neurons firing my thoughts should in fact reverse back to their states at 5.00pm in the evening…!
This kind of “time travel” isn’t much interesting b’coz in the end since everything including your mindset has gone back to the past, you won’t remember that you have travelled to the past..!!
But this is what really time travel is physically !!
AND IT IS PROHIBITED BY THE SECOND LAW OF THERMODYNAMICS AND THE LAWS OF CAUSE & EFFECT
Here there aren’t any differences between MY time and the time kept by the rest of my surroundings.
But the time travel you expect is of a different kind, right?
That kind of travel requires that I have a “personal” time that’s different from what is kept by my SURROUNDINGS. Its like taking a parallel route to the past.
There are 2 problems with this:
One is that if you interfere with ur past for example by killing ur father at his 20th birthday, then the very existence of yours is jeopardised..! So here is that immutable law of CAUSE and EFFECT coming up again.
Second problem: Suppose u see yourself celebrating your 5th birthday when u travel to ur distant past. Which of the two is the REAL YOU ?
The twenty-four year old you or the 5 year old you ??
Quantum mechanics prohibits your existence in two forms in the universe in the same space-time..!
According to Uncertainty principle, once you see yourself in the past, one of you will cease to exist..! That means, once an observation has been made, your probability waves collapse to a single location and your presence will be only in ONE location, not two. So one of you will cease to exist..!
All these are practical and real problems regarding the very concept of “time” outside the mathematical jargon of theoretical physics. Hence it follows that the concept of time-travel itself is just an illusion emerging from our distorted view of space and time…