You have most probably seen some science fiction movie, like 'Terminator' where someone 'moves' from 1900 to 2000, then to 2050 back to 2022! It can be entertaining, however, some people seriously think that such funny farm ideas has anything to do with reality! 'Ideas' on that par are so silly that normally one doesn't need to debunk it, as anyone can see it. Mension it, and people crack into some laughter. This lunatic 'idea' enjoys a peculiar status different from other similar lunatic ideas: it is blessed by the priests in pulpit of mathematical physics. In other words it doesn't matter how stupid an claim can be, as long as celebrities and Nobel price winners entertains them, some good number of people will also entertain them!
Notice that I put the 'idea' in quote because it does even qualify as an idea! 'Idea' betrays a statement that makes some sense, be it a slight one. Ideas means that one has to THINK in order to grasp what it means. A statement like pingy pang pang does not elicit any idea to your head because the 'words' have no meaning! So pingy pang pang is not an idea! It is simply a bubble gum for the pple in the asylum to push time with! 'Time travel' belongs to such categories! It is a statement that is worse off than a bark or a 'meow'. With some effort, you might grasp what the cat might mean by 'meow'. Not so to a relativist talking about 'time travel'!
It Is Beyond Understanding
Like I have hinted, we cannot understand pingy pang pang. 'Pingy pang pang' is beyond understanding! But then like saying 'your eyes cannot see,...', people can create 'emperor's cloths'. You see? It is only because 'your eyes are limited', otherwise there are plenty of cloths in the room! The emperor doesn't want to be seen as to be on the category of those 'lesser evolved' souls who cannot see the cloths! So he opts to say: yes, I can see the clothes! In this case the 'cloths' can be invisible simply because there are no such clothes. It is not that our eyes are 'limited'. Likewise our minds are not 'limited' to grasp such 'ideas' as 'time travel'. There is simply no such an idea! It is a 'pseud-oidea'. Like it should be the case always, don't allow people to sell poppycock using the 'our minds are limited' excuse. That is always an emperor's cloth you are about to buy! He is trying to evade 'bullshit detector' by going way round the 'mind' all altogether, making his claims a-priori, unfalsifiable!
The 'need' for 'Time Travel'
They could not sell the poppycock unless people developed some 'psychological need' for 'time travel'. So they concocted one by creating a whopper that should create an alarm! Note that the 'Terminator' 'comes' from '2030', or something like that, all the way to '1999'! He hopes to find a guy, a grown up in 2030 before he was born! So he is, in effect, saying that in case you are peeing in the wrong place on Tuesday , then when 'Wednesday' comes, you are still peeing on Tuesday as it were, on a parallel world! So he swings hopelessly from the already nonsensical 'passage of time into a 'passage through multiverse' without telling you directly! He sweeps this 'multivers theory' under the carpet and then asks you to debate 'whether or not time travel is possible', as if he doesn't have a redefined 'time' hidding under the sleeves!
When we say 'past' (eg Tuesday), does it riffers to some location 'existent' at the same time as Wednesday? That is the question begged when they ask 'is time travel possible'. In other words they are already in the second question, and the first crucial question is never asked! Imagine asking only if it is possible to go to 'heaven' above the blue sheet 'up there', thus creating only two camps: those that say it is possible and those that say it isn't. It doesn't give any chance for the right camp to emerge: those that say it is a meaningless question because the 'heaven' is not 'up there' above some blue 'sheet'. Of course if Tuesday exist (calling it 'the past'), why would it not be possible to travel there?
What Is 'Time'?
There are those who have it completely upside down! The reason why we thinkv'time travel is impossible', so they say, is because 'we think that time exists' or 'we think that time flows' or 'we think that the flow of time is real'! In reality, it is the opposite! If 'flow of time' or 'passage of time' was a real event, then 'time travel' would be as easy as 'travel along a river!' If the reality of the flow of river Nile does not prevent anyone from moving (say out of some boat moving with the water), why would the reality of 'flow of time', prevent 'time travel'?
But 'flow of time' or 'passage of time' are just 'metaphors' that, at best, might only interest poets. And this is the problem! 'Time travel' can only be poetic since 'flow of time' is not literal. Nothing is more ridiculous than dreaming of a machine that can do the 'time traveling'. It is orders more ridiculous than seeking for a mattress to cusion someone who is 'falling in love'!
But lets, for a moment, concede that 'flow of time' is a real, physical event and that thus 'time travel' is possible (strictly meaningful as a concept). Does this mean that you can go to Teusday and 'stop yourself from peeing along the highway' and so save yourself the embarrassment? If you jumped out of a moving vehicle and then go backwards, do you land in the same vehicle backwards in location? Does movement necessarily creates a trail of zillions of copies of a moving thing in space? If not so, why suppose that 'movement in time' does no?
To twist it a little bit, lets say 'changing the past' is possible. Then why think that the 'past' is sitted there, waiting for you to travel there so you may 'change' it? Why can't it change without anyone 'time traveling' to do so? Why can't we kill John corner's mother before the terminator comes? If so, why can't the entire 'past' simply change and becomes 'the present' leaving nothing in the past, so that 'passage of time' becomes like a 'movement in space' whereby no trail of the moving object is left behind? Then 'time travel' becomes a 'travel into nothing', hence a pointless travel, even if it were possible.
But that is getting too far! There is simply no such a place as 'past', 'present' nor 'future'. When you open your eyes, you are seeing what we call 'the univers'. We see OBJECTS and nothing else. We don't see 'something' called 'the present'. That is an abstract concept that your mind creats to make sense of the universe. The 'present' is like 'here' or 'there'. Only an idiot can say 'the present exists'. At best, we might say 'At the present, things exists'. In other words, we use 'present' to understand 'existence of things', but not as an 'existent thing' on its own. The 'present' as an 'arena' to 'stage the existence' is a more accurate understanding of the concept 'present'. Therefore the question of 'existence' does not apply to the concept 'present' as this is part of those concepts that allows us to conceptualize 'existence' in the first place.
'To move' from A to B means that at time t, an object was at place A and at some other time, t' in future, the same object was at place B. So to conceptualize movement, we need to take for granted that what 'past, present and future' means is obvious and given. Otherwise 'movement' or 'travel' itself will have no meaning. This means that we cannot apply 'movement' or 'travel' to time itself otherwise our statement will be circular and meaningless! We will say (rigourously) that 'At time t the terminator was at 2030 and at some other time t' in the future, the cyborg was at 1999'. Make sense? We have two 'times'. One is a 'reference' and the other is a 'referend'. The concept 'time' is appearing twice, with two inconsistent meanings! One has reduce completely to the concept of 'space' and the other is retaining the usual temporal meaning of 'time'. This paradox cannot be resolved because we must define 'movement' or 'travel' or 'change' in general using the temporal meaning of 'time'. Or in different words, 'change' is a concept that demands the 'temporal time' to make sense. But 'time travel' demands the 'spatial time', and yet 'time travel' itelf has to be a kind of 'change'!!