Introduction
Hey hello guys,
This is my Second Volume of Possibilities of Time Travel. Myself Pratik Harish Gawli, I am an independent researcher. I done my research on this topics and these Volumes are my review on the finds which i referred by our honorable scientists. Only you need is to read and share as much as you can.
I believe in sharing my thoughts and my immerse knowledge to be flow in community.
What is time travel?
There is an extensive literature on time travel input physics and philosophy. Part of the great interest of the topic stems from the fact that reasons have been given both for thinking that time travel is physically possible and for thinking that it is logically impossible! This entry deals with philosophical issues; issues related to the physics of time travel are covered in separate entries on time travel and modern physics and time machines. We begin with the definitional question: what is time travel? we then turned to measure objection to the possibility of backward Time Travel: The Grandfather paradox. Next, issues concerning casusation are discussed and then issues in metaphysics of time and change. We end with the discussion of the question why, if backwards Time Travel will ever occur, we have not been visited by time travellers from the future.
 |
| What is Grandfather Paradox? |
There is a number of rather different scenarios which would seems as 'time travel' and a number of scenarios which, while sharing certain features with some of the time travel cases, seems nevertheless not to count as genius Time Travel.
A satisfactory definition of time travel would, at least, need to classify the cases in the right way. There might be some surprises perhaps, on the best definition of 'time travel',
In fact there is not entirely satisfactory definition of 'time travel' in the literature. The most popular definition is the one given by lewis in 1976.
What is time travel?
Inevitably, it involves descrepency between time and time. Any traveller departs and then arrives at his destination; the time elapsed from departure to arrival is the duration of the journey. But if he is a Time traveller, the separation in time between departure and arrival does not equal the duration of his journey. how can it be that the same two events his departure and his arrival, are separated by two unequal amounts of time? I reply by distinguishing time itself, external time as I shall also call it, from the personal time of a particular time traveler: roughly, that which is measured by his wristwatch. His journey takes an hour of his personal time, letem us say. But the arrival is more than an hour after the departure in external time if he travels towards the future or the arrived arrival is before the departure in external time. If he travels to word the past.
There is also another which equates time travel with the existence of CTC's: closed time like curves. A curve in this context is a line in spacetime; it is time like if it could represent the career of the material object; and it is closed if it returns to its starting point.
 |
| Close timelike curve |
The lack of an adequate definition of 'time travel' does not matter for our purposes here. It suffices that we have clear cases of (what would count as) time travel and that these cases give rise to all the problems that we shall wish to discuss.
Some authors consider 'time travel' scenarios in which there are two temporal dimensions, and others consider scenarios in which there are multiple 'parallel' universes each one with its own four-dimensional. There is a question whether travelling to another version of 2001, a version at a different point on the second time dimension, or in a different parallel universe is really time travel, or whether it is more akin to Virtual. In any case, this kind of scenario does not give rise to many of the problems thrown up by the idea of travelling to the very same past one experienced in one's younger days. It is these problems that form the primary focus of the present entry, and so we shall not have much to say about other kinds of time travel' scenario in what follows.
Time Discrepancy
One objection to the possibility of time travel flows directly from attempts to define it in anything like Lewis's way. The worry is that because time travel involves "a discrepancy between time and time", time travel scenarios are simply incoherent. The time traveller traverses thirty years in one year; she is 51 years old 21 years after her birth; she dies at the age of 90, 200 years before her birth; and so on. The objection is that these are straightforward contradictions: the basic description of what time travel involves is inconsistent; therefore, time travel is logically impossible.
There must be something wrong with this objection, because it would show Einstein to be logically impossible whereas this sort of future-directed time travel has actually been observed. The most common response to the objection is that there is no contradiction because the interval of time traversed by the time traveller and the duration of her journey are measured with respect to different frames of reference: there is thus no reason why they should coincide. A similar point applies to the discrepancy between the time elapsed since the time traveller's birth and her age upon arrival. There is no more of a contradiction here than in the fact that Navi Mumbai is both 170 kilometres away from Nashik along the Mumbai-Nashik Express way and 202 kilometres away along the Ahmednagar-Kalyan Road, they both go to same destination
Changing the Past
Before leaving the question "What is time travel?' we should note the crucial distinction between changing the past and participating in the changes which will happen in past. In the popular imagination, backwards time travel would allow one to change the past: to right the wrongs of history, to prevent one's younger self doing things one later regretted, and so on. In a model with a single past, however, this idea is incoherent: the very description of the case involves a contradiction (e.g. the time traveller burns all her diaries at midnight on her fortieth birthday in 1976, and does not burn all her diaries at midnight on her fortieth birthday in 1976). It is not as if there are two versions of the past: the original one, without the time traveller present, and then a second version, with the time traveller playing a role. There is just one past and two perspectives on it: the perspective of the younger self, and the perspective of the older time travelling self. If these perspectives are inconsistent (e.g. an event occurs in one but not the other) then the time travel scenario is incoherent.
 |
| Time Machine |
This means that time travellers can do less than we might have hoped: they cannot right the wrongs of history; they cannot even stir a speck of dust on a certain day in the past if, on that day, the speck was in fact unmoved. But this does not mean that time travellers must be entirely powerless in the past: while they cannot do anything that did not actually happen, they can (in principle) do anything that did happen. Time travellers cannot change the past: they cannot make it different from the way it was but they can participate in it: they can be amongst the people who did make the past the way it was.
What about models involving two temporal dimensions, or parallel universes-do they allow for coherent scenarios in which the past is changed? There is certainly no contradiction in saying that the time traveller burns all her diaries at midnight on her fortieth birthday in 1976 in universe 1 (or at hypertime A), and does not burn all her diaries at midnight on her fortieth birthday in 1976 in universe 2 (or at hypertime B). The question is whether this kind of story involves changing the past in the sense originally envisaged: righting the wrongs of history, preventing subsequently regretted actions, and so on.
 |
| Parallel Universe |
Another article will publish soon.
-Thankyou for givigiving your valuable time.
Copyright © 2021 Pratik Gawli, Maha. India Inc. All rights reserved.
Terms of Use | Privacy Policy: Reserved
Comments
Post a Comment